Progressive Crop Consultant - January / February 2023

Page 1

Irrigation Tools and Information for Efficient Water Management in California Avocado Production Systems January / February 2023 Volume 8: Issue 1 Can Disease Suppressive Soils Hold the Key for Sustainable Agriculture? Properly Timed Foliar-Applied Urea and Phosphite Increase Citrus Yield and Fruit Size

IMPROVE EARLY SEASON DISEASE MANAGEMENT: COMBINE BIOLOGICALS WITH CHEMISTRY

Now is the time to start preparing for early season pests such as powdery mildew, Botrytis and anthracnose. These pests will quickly reduce peak yield potential if they are not carefully monitored and effectively treated.

Rotating modes of action is one of the most powerful approaches in an effective integrated pest management (IPM) program. “In addition, research indicates that combining biologicals with chemistry can improve management of problematic pests,” says Dr. Melissa Jean O’Neal, Ph.D., Senior Product Development Manager, Pro Farm Group, Inc.

BIOLOGICALS FOR MODERN-DAY TANK MIXES

Regalia® Biofungicide is one such product that is highly compatible with other crop protection products and can be incorporated into tank mix or rotational programs.

Particularly effective against powdery mildew, Regalia Biofungicide has a broad spectrum of activity against many fungal and bacterial diseases. “It is a good product to apply preventatively before disease gains a foothold,” says O’Neal.

Another product to consider is Stargus® Biofungicide with the active ingredient Bacillus amyloliquefaciens strain F727. It contains a unique strain that is broad spectrum and provides multiple modes of action, for which efficacy data appear in the grape Botrytis dataset below. This Bacillus differs from other species and strains in that it generates living spores to form a protective barrier; therefore, pathogens have a more difficult time establishing within the plant.

These two biofungicides, Regalia and Stargus, show their greatest efficacy when applied early – when conditions become conducive to disease development or at the very onset of disease.

Regalia and Stargus Biofungicides support plant health and impart overall stress tolerance for grapes by boosting a plant’s innate ability to defend itself through induced systemic resistance (ISR) and systemic acquired resistance (ISR).

Adding Jet-Ag® 5%, a peroxyacetic acid (PAA), in tank mixes or rotations is another IPM approach to improve disease management by utilizing a contact curative. “This product kills pathogens on contact and has an extremely broad spectrum of activity,” says O’Neal. Jet-Ag also tends to be widely available and is quite economical to purchase.

BIOUNITE™ PROTOCOL FOR INCREASED EFFICACY

Combining the power of biology with the performance of chemistry is called a BioUnite ™ approach by Pro Farm Group.

In summary, benefits of biologicals in an IPM program include utilizing novel modes of action that improve pest management, reducing the development of pesticide resistance, and offering cost-effective tools through new formulations.

For more information, visit the grape page at www.ProFarmGroup.com

©2023 Pro Farm Group, Inc. All rights reserved. Always read and follow label instructions. Please find labels and more information at www.ProFarmGroup.com. *Regalia®, Grandevo®, Jet-Ag® and BioUnite™ are registered trademarks of Marrone Bio Innovations. Luna® is a registered trademark of Bayer. Vanguard® and Miravis® are registered trademarks of Syngenta.

2 Progressive Crop Consultant January / February 2023 FORMERLY MARRONE BIO INNOVATIONS
Advertorial
scan
QR code to
Season Disease Management
Untreated Program with Regalia 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0%
BIOFUNGICIDE’S PERFORMANCE ON GRAPES Percent Control of Powdery Mildew Summary of 13 Studies • Pacific Ag Research, UC Davis Percentage Control 2009 2010 2010 2011 2011 2011 2015 2016 2017 2018 2018 2020 2021 PRE-CLOSE VERAISON PRE-BLOOM • Regalia 1-2 qts./A If disease is already present, tank mix with Jet-Ag as a contact fungicide for best results. • Stargus 1-2 qts./A OR • Regalia 1-2 qts./A • Jet-Ag 2-4 qts./100 gal. • Stargus 1-2 qts./A OR • Regalia 1-2 qts./A 46% 44% 42% 40% 38% 36% 34% 32% 30% Mean % Incidence Untreated Control Miravis® Prime 13.5 fl. oz./A AC | Vanguard® 10 oz./A B Luna® Experience 8.6 fl. oz./ A ABC Stargus® 2 qts./A A | Luna® Experience 8.6 oz./A BC Stargus® 2 qts./A A | Miravis® Prime 13.5 oz./A BC Stargus® 4 qts./A ABC 5/15/2020 6/15/2020 6/28/2020 TREATMENTS Pre-Bloom Pre-Close Veraison 4-16% Less Botrytis Incidence vs. Alternatives Dr. Eskalen, UCD, Clarksburg, Ca, 2020 • Variety:
or
this
download the Early
IPM Guide.
REGALIA®
‘Riesling’
January / February 2023 www.progressivecrop.com 3 IN THIS ISSUE 8 22 28 CONTRIBUTING WRITERS & INDUSTRY SUPPORT Surendra Dara Director, North Willamette Research and Extension Center Kevin Day UCCE Pomology Farm Advisor, Tulare and Kings Counties Elizabeth Fichtner UCCE Farm Advisor, Kings and Tulare Counties Katherine Jarvis-Shean UCCE Orchard Systems Advisor, Sacramento, Solano and Yolo Counties The articles, research, industry updates, company profiles, and advertisements in this publication are the professional opinions of writers and advertisers. Progressive Crop Consultant does not assume any responsibility for the opinions given in the publication. Steven Koike Tri-Cal Diagnostics Jhalendra Rijal UCCE Integrated Pest Management Advisor, Stanislaus County Mohammad Yaghmour UCCE Area Orchard Systems Advisor, Kern County UC COOPERATIVE EXTENSION ADVISORY BOARD PUBLISHER: Jason Scott Email: jason@jcsmarketinginc.com EDITOR: Taylor Chalstrom ASSOCIATE EDITOR: Cecilia Parsons Email: article@jcsmarketinginc.com PRODUCTION: design@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com Can Disease Suppressive Soils Hold the Key for Sustainable Agriculture? Irrigation Tools and Information for Efficient Water Management in California Avocado Production Systems Properly Timed FoliarApplied Urea and Phosphite Increase Citrus Yield and Fruit Size Adapting Solutions: A Novel Product for Soil Salinity Management The Agronomy of Water Phosphate vs Phosphite: Part One The Five Rs of Nutrition in the Vineyard Unwrapping the Possibility of Watermelon Grafting 4 26 28 12
Ph.D., Senior R&D
AgroPlantae
Faber UCCE Subtropical Crops Advisor,
AgroPlantae JW
CCA,
Verdesian
Professor
Davide Ciceri
Scientist,
Ben
Ventura and Santa Barbara Counties Raquel Gomez M.Sc., Research Agronomist,
Lemons
CPAg,
Life Sciences Carol J. Lovatt
of Plant Physiology, Emeritus, Dept. of Botany and Plant Science, UC Riverside
Vegetable
8 16 22 32
Cassidy Million Ph.D., Director of Ag Science, Heliae Agriculture Zheng Wang
Crops and Irrigation Advisor, UCCE Stanislaus County Dr. Karl Wyant Director of Agronomy, Nutrien; Western Region Certified Crop Advisor Board Chair

Can Disease Suppressive Soils Hold the Key for Sustainable Agriculture?

The Key to Building a Soil that Can Suppress Pathogens Naturally

When it comes to managing soilborne plant diseases, methods for reducing or eliminating the impact of pathogens have heavily relied on selecting a resistant plant variety and the use of pesticides for protection. However, the soil, and specifically the biological component consisting of microbes, can be another tool growers can leverage to help protect their crops from soilborne diseases.

Healthy soil and a healthy crop can lead to reduced disease incidence, an idea that is becoming more widely accepted across the agriculture industry. Many questions arise with this concept: How are soil health and soilborne plant diseases related? Can soil health result in less plant disease increase pressure? What are the mechanisms behind this phenomenon? In this article, we will discuss and address these questions and take a deep dive into a phenomenon known as disease suppressive soil (DSS).

Microbes Are the Key

The activity of soil microbes or communities of microbes is what gives rise to a soil’s disease suppressive properties. As you can imagine, the soil is a complex system, and understanding the mechanisms that contribute to DSS is extremely intricate. Imagine the interactions between beneficial and pathogenic microbes as a battlefield belowground. In the case of DSS, the beneficial microbes win. Just like on a battlefield, many tactics, strategies and tools are needed to overcome your opponent; and the same is true for soil microbes. Multiple mechanisms from increasing soil and plant health to directly impacting pathogenic microbes are used by soil microbes in the battle between beneficial and pathogenic.

Soil microbes play a key role in soil health and soil quality, which in return

affect the degree of disease suppression in the soil. Soil microbes have multiple ways in which they suppress disease in the soil, including the improvement of plant health, inducing natural defense response in the host plant, secreting enzymes and antibiotics, and through microbial competition.

Defining Suppressive Soils and Why They Matter

DSS are defined as soils that naturally defend against pathogenic diseases before the disease attacks a growing crop, or the pathogen can infect the crop but the disease declines with successive cropping (Figure 1). Soils can do this through reducing the establishment or growth of pathogenic fungi or bacteria due to the makeup of their microbiome (the communities of fungi and bacteria that are living in the soil.) Soils can keep disease development at a minimum even in the presence of a susceptible host and disease-causing pathogen.

DSS can be naturally occurring but may also be developed over time through cropping practices. To help clarify, we

can divide suppressive soils into two categories: general suppression and specific suppression (Figure 2, see page 6).

General suppression gives protection towards multiple pathogenic microbes. The increase in the abundance (number of microbes) and diversity (which microbes are present) of soil microbes is key in general suppression. These soil microbes out-compete pathogenic microbes, which in turn creates general suppression. Agricultural practices can impact this type of suppression with practices such as soil sterilization reducing it and good soil health practices enhancing it.

Specific suppression can occur naturally (long-standing) or be induced. Long-standing specific suppression is associated with a specific species of microbes or group of microbes and is naturally found in the soil without the presence of a plant. Induced specific suppression can be produced through monoculture of a crop, growing suscep

4 Progressive Crop Consultant January / February 2023
ContinuedonPage6
Figure 1. Disease suppressive soils are defined as soils that naturally defend against pathogenic diseases before the disease attacks a growing crop, or the pathogen can infect the crop but the disease declines with successive cropping.

OPTIMIZE

WATER EFFICIENCY

YOUR
©2023 Tessenderlo Kerley, Inc. All rights reserved. Crop Vitality® and CaTs® are registered trademark of Tessenderlo Kerley, Inc. Call: (800) 525-2803 | Email: info@cropvitality.com www.cropvitality.com
100% soluble calcium, conditions soil to improve water infiltration. Blends with most nitrogen fertilizers, including UAN and liquid urea. Easy and convenient year round application.
Improves water use efficiency.

tible crops or by mixing small amounts of a suppressive soil into a conducive soil.

So, why should we care about DSS? As we move forward in modern agriculture, restriction of fumigants and pesticides as well as the lack of available resistant cultivars will only make these soilborne diseases harder to manage. DSS are another tool growers can use to help manage difficult-to-control soilborne diseases.

Soil Microbial Battleground

Beneficial soil microbes have a direct impact on their pathogenic counterparts, but on the battlefield, the beneficial soil microbes can outcompete their pathogenic counterparts, leading to greater numbers of beneficial soil microbes. Underground, beneficial soil microbes use up the exudates and nutrients created and released by the host plant, blocking the pathogenic microbes from accessing and utilizing the resources needed to survive.

During the battle, the soil microbes can display hyperparasitism, where they infect pathogenic microbes present in the soil that pose a threat to the crops around them. Plus, the microbes can cause additional impact on their pathogenic microbial counterparts by secreting antibiotic-like enzymes and toxins in a process called antibiosis. Antibiosis is a competitive tactic that kills other pathogenic microbes and increases their ability to battle and defend themselves and the host plant from pathogens.

The health of the host plant above the ground is impacted by the soil health under the ground. The structure of the soil plays a direct role in plant health in terms of water infiltration, retention, soil compaction and access to nutrients. Soil microbes are to key to improving soil structure through increased soil aggregation, and aid in the release of mineral nutrients through a conversion process called nutrient mineralization. Soil microbes secrete exudates that can trigger disease-resistant responses for host plants. All these factors aid in im-

Figure 3. Disease triangle. For disease to occur, there must be three components, representative of the sides of a triangle. The environment side of the triangle shows the impact of soil health and microbes on the ability for disease to occur.

proved plant health and performance.

Soil Health Impact

In the soil microbe-pathogen battleground, what exactly are these microbes battling for? For the pathogenic microbes, they are battling to infect the host plant. To understand the complexity and how soil health and microbes play a role in plant disease and DSS, we need to review the disease triangle (Figure 3). For disease to occur, there must be three components (representative of the sides of a triangle):

• Susceptible host

• Conducive environment

• Virulent pathogen

If one of these sides is removed, plant

disease is not possible. The environment side of the triangle is where we need to focus as this is the side that includes soil health and holds the key to creating disease suppressive soils.

The physical and chemical properties of the soil, including pH, soil organic carbon and nutrients, provide the habitat for microbial activity. Crop management practices such as tillage, irrigation, fertilization, the addition of green manures and weed management can directly impact the soil environment and microbial activity in the soil. Many of the factors mentioned here directly impact microbial activity and communities and are the key to soil health. Many of the factors mentioned here directly impact microbial activity and communities and are the key to soil health. As we know, there are tools and

6 Progressive Crop Consultant January / February 2023
ContinuedfromPage4
Figure 2. Disease suppressive soils can be naturally occurring but may also be developed over time through cropping practices. They can be categorized by general suppression and specific suppression.

inputs to help improve soil health, meaning that if we manipulate the environment (the soil) and remove one side of the disease triangle, we can reduce plant disease infection. Therefore, improving soil health can lead to general DSS (Figure 4).

What about specific disease suppression? If we recall, longterm monocropping can be used to achieve specific suppression in some systems, which is contradictive of soil health practices. The literature has noted the ability to achieve specific disease suppression by using compost and green manures. However, increasing soil health and increasing microbial communities is the best practice to achieve and improve general suppression and increase crop productivity.

Managing the Soil to Achieve Disease Suppressive Soil

Soil microbes are key to DSS, and soil health directly impacts the makeup and activity of soil microbes. DSS can be negatively or positively impacted by cropping systems and management practices. Soil management practices that positively influence DSS include crop rotation, intercropping, minimum tillage practices, fertility or organic inputs such as manures and composts. In addition, adding liable carbon sources as a food source for microbes will increase the abundance and diversity of soil microbes, which is critical in general suppression. Crop rotation is an important factor; rotating to a non-host can aid in reducing soilborne diseases and positively impact soil microbial diversity. What we know to date is that suppressive soils are usually mediated through soil microbial community shifts overtime, so adopting practices and amendments that increase soil health and organic matter and increase the diversity and abundance of microbial activity in your soils will aid in suppressing soilborne diseases.

Battle for a Sustainable Solution to

Soilborne Diseases

DSS can be a tool for soilborne disease management. Adapting soil health practices and increasing the soil microbial activity is a sustainable agricultural practice that will be key in the coming years. Building and maintaining suppressive soils can provide a solid foundation for crops to thrive. We’ve discussed the key to DSS (microbes) and contribution to a soil’s disease suppressive properties. Focusing on the improvement of soil health and natural defense response belowground is a good first step toward the achievement of healthy crops that

are protected against soilborne disease.

Resources

Disease Suppressive Soils: New Insights from the Soil Microbiome- https://doi.org/10.1094/PHYTO-03-17-0111-RVW

Disease-Suppressive Soils—Beyond Food Production: a Critical Review- https://www.ncbi.nlm.nih.gov/pmc/articles/ PMC7953945/

Current Insights into the Role of Rhizosphere Bacteria in Disease Suppressive Soils- https://doi.org/10.3389/ fmicb.2017.02529

Plant Health Management: Pathogen Suppressive Soilshttps://doi.org/10.1016/B978-0-444-52512-3.00182-0

Fine-Tuning with Soil Health; Soilborne Disease?- https:// csanr.wsu.edu/fine-tuning-soilborne-disease/

Developing Disease-Suppressive Soil Through Agronomic Management- https://www.researchgate.net/publication/292011599_Developing_Disease-Suppressive_Soil_ Through_Agronomic_Management

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

Advertorial

Oregon State has developed an Aglime Score which is basically an efficiency rating. Particle size or mesh size is key to this rating and is the primary indicator of reactivity. Studies have shown that pulverized limestone smaller than 40 mesh (size of table salt) are considered 100% effective and are the quickest to dissolve in the soil to release calcium and adjust soil pH.

Mildly acidic water and soil conditions will dissolve finely ground limestone. For example, the pH of rainwater in California is typically around 5.7, which is enough to dissolve our aglime that is broadcast. Our pulverized limestone products average 85% passing 100 mesh (diameter of a human hair). Remember aglime quality increases when particle size decreases.

U.S. 20 Mesh U.S. 40 Mesh

January / February 2023 www.progressivecrop.com 7
Ask for it by name Blue Mountain Minerals Naturally the Best! For more information 209-533-0127x112
Figure 4, How soil health is related to general disease suppression and the agricultural practices that impact soil health leading to general disease suppression.

Irrigation Tools and Information for Efficient Water Management in California Avocado Production Systems

In California, avocados are primarily grown in southern and central parts of the state along the coast. These regions face uncertain water supplies, mandatory reductions of water use and the rising cost of water, while efficient use of irrigation water is one of the highest conservation priorities. Data on water use by avocado orchards and optimal irrigation strategies needs to be updated in light of increasing water pressure in order to achieve efficient water and fertilizer management. Moreover, due to increasing salinity in water sources, effective irrigation is more critical to ensure optimal yield and high-quality fruit as avocados are one of the most salt-sensitive crops.

An ongoing irrigation study aims to acquire relevant information on crop water consumption and develop more accurate crop coefficient curves over the season for avocados under different environment and cropping systems in southern California. Extensive data collection is being conducted in nine mature avocado sites in San Diego, Temecula, Orange and Ventura counties using combined cutting-edge groundand remote-sensing technologies. A combination of surface renewal and eddy covariance equipment (flux tower, Figure 1) are utilized to measure actual crop evapotranspiration to develop crop coefficient curves at each site. Several other sensors and equipment are being used to monitor soil and plant water status and soil salinity, and high-resolution images are being captured by unmanned aerial systems to evaluate canopy features. This article provides some avocado water management tips based on the preliminary findings of this study.

Variable Spatial and Temporal Crop Water Needs

The results from the avocado experimental sites demonstrate considerable variability in avocado consumptive water use, both spatially and temporally. The cumulative avocado consumptive water use (actual evapotranspiration or ET) across two sites in Temecula (site 1 with an elevation of 1,490 ft. above sea level) and in the San Pasqual Valley, Escondido (site 2 with an elevation of 720 ft. above sea level) varied from 28.1 in. to 38.5 in. over a 235-day period (Figure 2, see page 10). The average daily actual ET was 0.18 in d-1 in June/July at site 2, while the amount was 0.14 in d-1 at site 1 for the same period. This is a notable

A B Cdifference of actual ET between these two sites. More uniform daily crop water consumption over the summer period occurred at site 2 when compared with site 1 located at a higher elevation.

Crop Coefficient Values a Valuable Tool

To estimate crop water requirements, various crop coefficient (Kc) values of 0.64 (Grismer et al. 2000), 0.72 (Gardiazabal et al. 2003) and 0.86 (Oster et al. 2007) were reported for “Hass” avocado. K c value is greatly impacted by differences in climatic conditions, canopy features (size of crop canopy and shaded area), row orientation, soil and irrigation water salinities, and amounts

8 Progressive Crop Consultant January / February 2023
| UCCE Irrigation and Water Management Advisor, San Diego, Riverside and Imperial Counties and BEN FABER | UCCE Subtropical Crops Advisor, Ventura and Santa Barbara Counties Figure 1. a) An aerial view of the flux tower from a distance; b) a ground view of the tower; and c) a close look from the top of the flux tower demonstrates net radiometer sensor and two fine thermocouple sensors at one of the avocado experimental sites.

and frequencies of water applied. The question is, can we use a single crop coefficient the entire season that is based upon data developed decades ago that does not consider the impacts of plant density, row orientation and microirrigation? Can this value be used for different avocado regions in California?

Figure 3, see page 10 demonstrates the trend of daily actual crop coefficient values over a 235-day period at avocado site 2. More variations in water use were found during fall months when compared with spring and summer months. Average crop coefficient values of 0.77, 0.72 and 0.81 were determined for the periods of April to May, June to mid-October, and mid-October to early December, respectively. Lower crop coefficient values were obtained at site 1. It needs to be noted that these sites haven’t been under water stress and/or salinity stress most of the study period while due to the two heat waves in late June and early September, trees could experience heat stress for a while. The continuous measurements across the experimental sites will provide a comprehensive data set to update and develop more accurate crop coefficient curves for avocados at each site. These crop coefficient curves could be considered as an effective tool for irrigation management in California avocado production systems.

Soil Moisture Sensing

Understanding the effects of irrigation events on soil moisture provides critical insight for growers about the present growing environment for crops. While experienced growers have learned over seasons of observations how their soils and water interact, utilizing a soil moisture measuring device of some sort enables them to put a number on their observations and more accurately track trends over time.

The sensors allow growers to better understand the frequency and duration of irrigation events needed and to maintain adequate moisture based on the crops being grown. There are instances where irrigation cycles are occurring

January / February 2023 www.progressivecrop.com 9
Zinc-Shotgun® is a fertilizer that focuses on micronutrients to satisfy needs of customers seeking high zinc with manganese, iron and copper. The micronutrients are completely chelated with natural organic acids, amino acids, and carbohydrates that are readily bio-degradable and supply energy to the plant and soil microflora. Many soils are low in zinc and also require other micronutrients for the growth of good crops. We Are Here to Help Call: 209.720.8040 Visit: WRTAG.COM Mn Fe Zn Cu Complete, organically complexed micronutrient package containing essential elements to improve plant health and growth. Organically complexed with plant based amino acids, organic acids, and complexed polysaccharides. The nutrients are readily absorbed by the plant for a faster response. Designed to be applied both by foliar application and fertigation practices and is also e ective when applied directly to the soil. ContinuedonPage10

too often and for far longer periods than needed to achieve field capacity of the rooted volume of soil. There are also instances where the use of sensors revealed malfunctioning irrigation system components by reporting unusually dry soil in areas that should have received

ample irrigation. Soil moisture sensing is contingent on having a well-maintained irrigation system with a good distribution uniformity. Soil moisture sensors should be used as a useful tool to answer the following critical questions:

What is the water status of the soil early in the irrigation season?

When is the right time for the first and subsequent irrigation events?

Is the soil profile full after each irrigation event?

What is the length of irrigation time?

Should the irrigation practice be changed?

An example of the use of soil moisture monitoring at site 1 over a six-month period is shown in Figure 4. Half-hourly soil water tension was plotted for multiple depths (6”, 12” and 18”). The data shows that soil water was maintained at a desired level within the crop root zone at this site due to the frequent drip irrigation events. Although the average soil water tension varied over time in the top 18 in. of the soil, it never declined below 5 centibars and never exceeded 56 centibars over the period. The average values at 6”, 12” and 18” deep over the period were 20.1, 11.5 and 9.0 centibars, respectively. The soil moisture data at this site indicates that the irrigation frequency was scheduled properly while shorter irrigation runs could be considered in each irrigation event to improve irrigation efficiency.

Soil Types and Conditions, Canopy Features and Row Orientations

Avocado is one of the most salinity sensitive crops produced in California but is commonly grown in areas where poor quality is common. In recent years, salinity problems in California avocado have become increasingly common as the cost of irrigation water has risen and the availability of low salinity water for agriculture has diminished.

The source of water across the six avocado experimental sites in San Diego, Temecula and Orange counties have an EC e greater than 1.0 dS m-1 and chloride >100 ppm. Across the sites, the maximum soil EC e of the top 1 foot was measured (3.4 dS m-1) at a site with 28-yearold trees and a silty loam soil texture

10 Progressive Crop Consultant January / February 2023
in Orange County. A high chloride content ContinuedfromPage9 Figure 2. Daily actual evapotranspiration at avocado site 1 and over 235-day period (April 14, 2022 through December 4, 2022). Considering daily actual ET measured and tree spacings, the average crop water consumption during this period was determined to be 40.8 gallons per day per tree at site 2 and 20.1 gallons per day per tree at site 1. Tree spacings were different at the two sites, so per-tree use varies more than the per-area ET as mentioned above. Figure 3. Actual crop coefficient values determined at the avocado experimental site 2 in Escondido. The orchard has a south-facing slope and the dominant soil texture is sandy loam. Figure 4. Half-hourly soil water tension (centibar) measured at depths of 6”, 12” and 18” at avocado site 1 over a six-month period (March 14, 2022 through October 13, 2022).

(311.3 ppm) was also measured in the top 1 foot. A leaf chloride percentage of 0.465 was observed in early September at this orchard. Under such circumstances, yield improvement could be gained for the avocado orchard with increasing amounts of applied water to leach salt and particularly chloride from the effective crop root zone. Excess irrigation can be considered as beneficial water use for salinity management in avocado groves while the optimal leaching strategy could be different from site to site depending on soil types and salinity status, quality of irrigation water and irrigation system.

Ground shading percentage or canopy cover that provides a good estimation of canopy size/volume (Figure 5) and the amount of light that it can intercept is likely the most important driver influencing crop water needs. At the experimental sites, canopy vegetation cover percentage for each tree derived from drone-based multispectral imagery ranged from 0% (missing trees) to 100%. For instance, the canopy cover varied from 33.5% to 98.9% with tree spacings of 15 ft. × 18 ft. at site 1 versus 40.3% to 94.5% at site 2 with tree spacings of 20 ft. × 20 ft. The average canopy cover was 71.6% and 85.4% around the flux towers at site 1 and site 2, respectively. This clearly indicates that site 2 has a greater light interception, and as a result, greater crop water needs are expected when compared with site 1 (Figure 2, see page 10).

Both sites 1 and 2 have a south-facing slope orientation which means there is unlikely to be a notable impact from slope differences on the crop water use between the two sites. Avocado sites with north- and east-facing slope orientations are expected to have lower crop water needs even in a single orchard, and accordingly sometimes a different irrigation schedule is required for different zones under different orientations in an avocado orchard.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

January / February 2023 www.progressivecrop.com 11
Figure 5. Polygons RGB Mosaic of avocado trees at site 2 (top) and avocado tree centers and polygons at site 1 (bottom). Trees at both experimental sites (around monitoring stations) have a south-facing slope orientation.

Properly Timed Foliar-Applied Urea and Phosphite Increase Citrus Yield and Fruit Size

New Evidence Suggests the Underlying Mechanism

The goal of properly timed foliar-applied fertilizer is to increase the economic benefit derived from the grower’s fertilization program. In this strategy, fertilizer is applied at key stages in citrus tree phenology (the series of developmental events that result in fruit production and tree growth) (Figure 1, see page 13). Key stages of tree phenology are associated with important physiological and developmental processes. The fertilizer application is timed to stimulate a specific physiological process and achieve a plant growth regulator effect that increases flowering, fruit set, yield, fruit size or fruit quality, even when the tree is not deficient in the applied nutrient based on standard leaf or other tissue analyses. Properly timing the fertilizer application is important because the developmental stage of the target organ determines the result obtained.

Winter Applications Increase Yield and Fruit Size

The key stage of citrus tree phenology being targeted is bud determinacy, the irreversible commitment of buds that transitioned from vegetative shoot development to floral development in the fall to produce inflorescences and flowers. When a bud is determined, it can no longer revert to vegetative shoot growth. At the microscopic level, bud determinacy is identified by the initiation of sepals, the green outer leaves that cover and protect the developing floral bud (Lord and Eckard 1987). Due to an-

nual variations in temperatures and the fact that not all shoots and buds are the same age or at the same stage of development, January 1 through February 15 is an effective window within which to make foliar applications of urea or potassium phosphite to increase flowering in citrus.

Low-biuret urea (46% N, 0.25% biuret, 25 lb N/acre or a 50 lb bag of low-biuret urea per acre) applied in mid-January to target irreversible commitment to flowering in ‘Washington’ navel orange trees resulted in a net increase in threeyear cumulative yield of 17,355 lb/96 trees/acre compared to control trees receiving five-fold more urea applied to the soil. Delaying the foliar-application of low-biuret urea to mid-February resulted in a net increase in three-year cumulative yield of 13,757 lb/96 trees/ acre. In both cases, yield of commercially valuable size fruit of packing carton sizes 88+72+56 (2.7 to 3.5 inches in transverse diameter) increased as total yield increased (Ali and Lovatt 1994). Similarly, potassium phosphite as Nutri-Phite (0-28-26; Verdesian Life Sciences), which supplies P as PO3, not PO4, applied at 0.64 gal/acre in January to target irreversible commitment to flowering of Valencia orange trees in Florida resulted in an average net increase of 900 inflorescences per 12-inch square frame, a 166% increase in inflorescence number compared to untreated control trees, and produced a net increase in yield of 6,853 lb/acre (Albrigo 1991). In

a second experiment, foliar-applied Nutri-Phite (0-28-26, 0.64 gal/acre) in January resulted in a net increase in four-year cumulative Valencia orange yield of 25,247 lb/acre, an average net increase of 6,311 lb/acre/year for the four years of the experiment, with an average net increase of more than 400 lb total soluble solids per acre per year (Albrigo 1991).

Summer Applications Increase Yield

The key stage of phenology being targeted is maximum peel thickness, which marks the end of Stage I of fruit development in citrus in which fruit growth is predominantly by cell division, and the beginning of Stage II of citrus fruit development, the period of exponential fruit growth by cell expansion. At maximum peel thickness, all the cells that make up the mature fruit are present. Subsequent fruit growth is by the uptake of water into the juice sacs. The cells of the albedo, the white layer of the peel, simply stretch to accommodate the increasing size of the juice sacs; only the flavedo, the outer colored layer of the peel, continues cell division through harvest. The goal is to stimulate additional cell divisions just prior to maximum peel thickness. One additional cell division would double the number of cells in the fruit, a second cell division would quadruple the number of cells, etc. When these additional cells enlarge, fruit size is increased. Field research with navel orange, Valencia and mandarin cultivars documented the efficacy of

12 Progressive Crop Consultant January / February 2023

foliar applications of low-biuret urea or potassium phosphite made between the last week of June and mid-July.

Foliar-applied low-biuret urea (46% N, 0.25% biuret, 25 lb N/acre) in early July to target maximum peel thickness in ‘Washington’ navel orange trees resulted in a net increase in yield of commercially valuable size fruit of packing carton sizes 88+72 (2.7-3.15 inches in transverse diameter) of 4,927 lb/109 trees/ acre/year and a net increase in yield of larger fruit of packing carton size 56 (3.2 to 3.5 inches in transverse diameter)

of 3,374 lb/109 trees/acre/year compared to untreated control trees (Lovatt 1999).

To stimulate cell division prior to maximum peel thickness, Nutri-Phite was applied at 0.49 gal/acre in mid-May and again in mid-July. Nutri-Phite produced a net increase in fruit of packing carton sizes 88+72 of 5,078 lb/109 trees/acre/ year with a net increase in yield of larger fruit of packing carton size 56 of 4,158 lb/109 trees/acre/year. The Nutri-Phite treatment also increased fruit total soluble solids (TSS) by early November compared to the untreated control (P <

0.001), achieving a TSS:acid ratio of 8.1 by early November compared to 7.2 for fruit from untreated control trees ( < 0.01) (Lovatt 1999).

Application and Flowering Physiologies

It is well known that flowering in citrus is induced by low temperature (LT ≤59 degrees F day/ ≤50 degrees F, but >7 degrees F night) and by water-deficit stress

January / February 2023 www.progressivecrop.com 13
Surround® Crop Protectant and Purshade® Solar Protectant prevent damage from sunburn, harmful ultraviolet radia�on and infrared light — while allowing photosynthesis. It’s like growing your crops in the shade — in full sunlight. SURROUND is OMRI-listed for use as a crop protectant. Review website for restric�ons. Always read and follow label instruc�ons. Learn more at novasource.com SOMETIMES YOU JUST NEED A LITTLE SHADE 4-6 °F COOLER 50% UP TO LESS SUNBURN DAMAGE h20 INCREASES WATER USE EFFICIENCY UNDER INTENSE SUNLIGHT AND HIGH HEAT NovaSource®, Surround® and PurShade® are registered trademarks of Tessenderlo Kerley, Inc. OMRI® is a registered trademark of Organic Materials Review Ins�tute. Pat. novasource.com | ©2023 Tessenderlo Kerley, Inc. All rights reserved. ContinuedonPage14 Fig. 1. Key stages of citrus tree phenology, including from left to right: flowering, fruit set, fruit development (exponential fruit growth), fruit maturation, and flushes of shoot and root growth. Figure 1. Key stages of citrus tree phenology from left to right: flowering, fruit set, fruit development (exponential fruit growth), fruit maturation and flushes of shoot and root growth.

(WD ≤-2.4 MPa stem water potential) for eight weeks. Inflorescence and flower number both increase as the duration of the LT or WD period increases. Citrus is unique in the plant world. Not only does flowering increase with the increased duration of WD, but also with the increasing severity of WD (Figure 2).

In the late 80s, my lab discovered that leaf ammonium concentrations increased with the increased duration of both LT and WD and that leaf ammonium concentrations increased in parallel with the increase in both inflorescence number and flower number in response to the duration of LT or WD (Lovatt et al. 1988a, b). Since urea applied to leaves is catabolized by the plant enzyme urease to ammonia and carbon dioxide (NH3 and CO2), my lab tested the capacity of foliar-applied urea to supplement ammonium accumulation during LT and WD and increase citrus flowering. For navel orange trees exposed to a 50% or 25% shorter period of low temperature, foliar-applied low-biuret urea increased flowering 194% and 230%, respectively. Foliar-application of low-biuret urea to lemon trees maintained at a moderate WD (-2.4 MPa predawn xylem pressure potential) at the end of the 50-day stress period increased flowering 260% compared to WD-treated trees not receiving foliar-applied low-biuret urea (Lovatt et al. 1988a, b). At the level of gene transcription, new evidence suggests that LT and WD initiate flowering through overlapping genetic pathways (Tang and Lovatt 2022). Thus, WD provides a tool to increase citrus flowering in growing areas experiencing warmer, dry winters, with foliar-applied low-biuret urea or potassium phosphite able to supplement both LT and WD to increase citrus flowering.

These Different Molecules Share the Same Benefits, but How? Recent evidence suggests that both urea and phosphite increase tree nitrogen status and cytokinin biosynthesis. In both roots and leaves, nitrate and ammonium upregulate the expression of the key gene regulating cytokinin biosynthesis, IPT, the gene encoding

10 8 6 4 2 Flowers per shoot

-4 -3 -2 -1 0

Predawn Xylem Pressure Potential (PDXPP) (MPa)

10 8 6 4 2 Flowers per shoot Days after PDXPP reached -2.4 MPa 0 10 20 30 40

Fig. 2. The figure on the left illustrates that flowering in lemon trees increases as the severity of water-deficit stress increases (the numbers on the x-axis become more negative). Water-deficit stress is measured as predawn xylem pressure potential (PDXPP) in MegaPascals (MPa). The figure on the right demonstrates that flowering increases with the increased number of days lemon trees are maintained at a moderate water-deficit stress (-2.4 MPa PDXPP). After Hake (1995).

Figure 2. The figure on the left illustrates that flowering in lemon trees increases as the severity of water-deficit stress increases (the numbers on the x-axis become more negative.) Water-deficit stress is measured as predawn xylem pressure potential (PDXPP) in MegaPascals (MPa). The figure on the right demonstrates that flowering increases with the increased number of days lemon trees are maintained at a moderate water-deficit stress (-2.4 MPa PDXPP). After Hake (1995)

isopentenyl transferase, which catalyzes the rate-limiting step in cytokinin biosynthesis (Sakakibara 2006; Sakakibara et al. 2006). Nitrate taken up by roots and cytokinin synthesized in the roots move in the xylem to the shoots and leaves, where nitrate upregulates the genes for N assimilation and the IPT gene for cytokinin biosynthesis. Cytokinin and metabolites synthesized in the leaves are then transported in the phloem to the roots. Thus, N and cytokinins work together to promote and coordinate root and shoot growth, bud break and flowering. Ammonium derived from foliar-applied urea would stimulate N assimilation and upregulate cytokinin biosynthesis. Cytokinins are known to promote flowering and fruit growth.

Surprisingly, phosphite was recently demonstrated to upregulate key genes for N assimilation, resulting in increased nitrate uptake (Vereet et al. 2021) and, as predicted by the information presented above, phosphite increased cytokinin biosynthesis (Swarup et al. 2020). Phosphite supplied to roots resulted in significantly greater cytokinin concentrations one day after phosphite treatment (P ≤0.05). Root cytokinin concentrations continued to increase during the week-long experiment to a level greater than untreated control plants (P ≤0.05).

The Window for Increasing Flowering is Now

Citrus flowering is induced by LT and WD stress. WD stress of approximately -2.4 MPa stem water potential can be maintained by deficit-irrigation, and thus WD can be used to supplement LT in citrus areas with warmer, dryer winters due to global climate change. Winter prebloom foliar-applied urea and Nutri-Phite can be used to supplement LT and WD stress to increase citrus flowering and yield. In addition, summer foliar-applied low-biuret urea or Nutri-Phite can be used at maximum peel thickness to further increase fruit size and yield of commercially valuable size fruit. In light of recent research results, foliar-applied urea and Nutri-Phite likely achieve a plant growth regulator effect by increasing N assimilation and cytokinin biosynthesis.

Foliar fertilizers should be applied in sufficient water for good canopy coverage (at a final pH of 5.5 +/- 0.5), but not to run off, which is a waste of product. Pooling of fertilizers at the leaf tip can result in tip burn. The application should be like a pesticide spray with good canopy mixing and coverage of the upper and under surfaces of the leaves on the exterior and interior of the canopy and the target organ. Always follow the product label. Results cited for properly timed foliar-applied potassium phosphite reported herein are

14 Progressive Crop Consultant January / February 2023
ContinuedfromPage13

for Nutri-Phite, Verdesian Life Sciences, the only commercial product for which results appear in peer-reviewed journals.

References

Albrigo, L.G. 1991. Effects of foliar applications of urea or Nutri-Phite on flowering and yields of Valencia orange trees. Florida State Hort. Soc. 112:1-4.

Ali, A. and Lovatt, C.J. 1994. Winter application of low-biuret urea to the foliage of ‘Washington’ navel orange increased yield J. Amer. Soc. Hort. Sci. 119:1144-1150.

Hake, K.D. 1995. Regulation of Flowering in Citrus limon by water-deficit stress and nitrogen compounds. PhD Dissertation, University of California, Riverside. 149p.

Lord, E.M. and Eckard, K.J. 1987. Shoot development in Citrus sinensis L. (Washington navel orange). II. Alteration of developmental fate of flowering

shoots after GA3 treatment. Bot. Gaz. 148:17–22

Lovatt, C.J. 1999. Timing citrus and avocado foliar nutrient applications to increase fruit set and size. HortTechnology 9:607-612.

Lovatt, C.J., Zheng, Y. and Hake, K.D. 1988a. A new look at the Kraus Kraybill hypothesis and flowering in Citrus. 6th. Intl. Citrus Congr. 1:475-483.

Lovatt, C.J., Zheng, Y. and Hake, K.D. 1988b. Demonstration of a change in nitrogen metabolism essential to floral induction in Citrus. Israel J. Bot. 37:181188.

Sakakibara, H. 2006. Cytokinins: Activity, biosynthesis, and translocation. Annu. Rev. Plant Biol. 57:431-449.

Sakakibara, H. Takei, K. and Hirose, N. 2006. Interactions between nitrogen and cytokinin in the regulation of metabolism and development. Trends in Plant

Science 11: 40-448.

Swarup, R., Mohammed, U., Davis, J. and Rossall, S. 2020. Role of phosphite in plant growth and development. White paper, School of Biosciences, Univ. Nottingham.

Tang, L. and Lovatt, C.J. 2022. Effects of water-deficit stress and gibberellic acid on floral gene expression and floral determinacy in ‘Washington’ navel orange. J. Amer. Soc. Hort. Sci. 147(4):183-195.

Verreet, J.-A., Prahl, K.C., Loof, S. Birr, T. Klink, H., Cai, D. Xu, S. 2021. Phosphite plant biostimulant mode of action: gene expression, phytohormone levels, enzyme activity. Electronic Biological Inorganic Chemistry PO3 Workshop. (Christian-Albrechts-University of Kiel, Germany).

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

January / February 2023 www.progressivecrop.com 15
TALETE ® THE VALUE OF EVERY SINGLE DROP. Help your crops produce, even with water scarcity with VALAGRO’s NEW TECHNOLOGY
www.valagrousa.com

Adapting Solutions: A Novel Product for Soil Salinity Management

It is estimated that approximately 78 million acres in the western San Joaquin Valley are affected by soil salinity, with 30% of that acreage categorized as strongly or extremely saline (Scudiero et al. 2017). In soil, salinity refers to the presence of dissolvable ions like sodium, potassium, magnesium, calcium, chloride and nitrate. Salinity stress in crops occurs either from high concentration in the soil solution of specific ions like Na and Cl or mixes of several soluble salts.

Geological processes in the San Joaquin Valley (accumulation of marine coastal alluvium) and low-quality irrigation water are major contributors to soil salinity (Corwin 2003). Additionally, as crops absorb water, and water evaporates from the soil surface, salts are left behind in the rootzone. Crops growing in saline conditions experience osmotic stress, diminished growth, yield and shortened lifespan (Figure 1). With little access to high-quality irrigation water and

ongoing drought, there are few solutions to alleviate salinity. Updated management practices are required to face the situation at hand.

The most traditional method to manage soil salinity is by application of calcium in the form of gypsum (CaSO4 2H2O). As CaSO4 breaks down it yields calcium (Ca) and sulfate (SO4 2-) ions. Calcium works to desorb Na from the soil particle surface while the remaining sulfate binds the loose Na to yield sodium sulfate (Na 2SO4). In turn, the newly formed sodium sulphate can be leached and moved down the soil profile and out of the rootzone. Additionally, replacing Na with Ca flocculates the soil for improved water infiltration and pore space. However, the application of gypsum as a sole salinity manager has challenges. Gypsum may require specialized machinery and equipment to facilitate applications in water-saving drip line, and attention

should be paid to water quality or Ca may precipitate and plug the irrigation system. Finally, it is not uncommon to see Ca stratification in the soil from years of broadcast applications that have not fully dissolved or incorporated.

The standard practice for salinity management is a 0.5- to 2-ton/ac application of gypsum in the fall in anticipation of fall/winter rain. This practice has become the feel-good practice of many growers to date. However, updating such a practice becomes necessary when considering the current effects of climate change and economic circumstances. 2021 marked the driest winter months in 100 years with record lows of snow and rainfall as well as the third year of extreme drought. No rainfall and low access to irrigation water means little of the surface-applied gypsum is dissolving in the soil. With less access to surface water, more reliance on ground

16 Progressive Crop Consultant January / February 2023
Figure 1. Almond (left) and pistachio (right) foliage yellowing and leaf margins with symptoms of salt toxicity (photos courtesy R. Gomez).

water and decreasing crop prices, growers now more than ever should reassess their management practices.

Modern methods for salinity management focus on high solubility products, ease of application and efficiency. CATION-EX5 PLUS is a salinity management product formulated by AgroPlantae. It is fully miscible with water and better suited for fertigation systems than traditional gypsum and contains other important elements to help rebalance soil, improve fertility and invigorate soil microbes. CATION-EX5 PLUS is 0-0-5, Ca 10%, S 8%, Co 0.10% and Mo 0.10%.

The following are results of a three-year study on soil salinity management in California’s Tulare Basin. Treatments were designated Grower’s Standard or CATION-EX5 PLUS. The Grower’s Standard (GS) consisted of a yearly postharvest application of broadcast gypsum 95% at a rate of 1 ton/ac in an 80-acre block and multiple in-season

solution-grade gypsum applications through the irrigation system. AgroPlantae’s CATION-EX5 PLUS (CTX) was applied at 11 gal/ac over 80 acres, split into five applications over the growing season. Soil samples were taken in a predetermined area of each treatment block in 12-inch increments until 5 ft depth was achieved. Soil samples were taken in the spring before the first irrigation occurred and again in the fall after the last in-season irrigation in each year of the study. The spring sample acted as a baseline for the year while the fall soil sample showed the changes that occurred in the soil during the span of the crop growing months.

CATION-EX5 PLUS Reduces Salinity Buildup

Soil Electrical Conductivity (EC) is the measure of soil salinity. EC is highly influenced by soil texture, i.e., sand, silt and clay. For example, clay-like soils attract and retain more positive charges (cations) and have higher EC

values than other soil textures. Based on saturation percentages, the soil in both treatment blocks was determined to be clay-loam. Aside from soil texture, soil EC is also highly affected by inputs like irrigation water and fertilizer.

In this study, a greater degree of variability was seen in GS treatment when compared to CATION-EX5 PLUS (Figure 2, see page 18). In 2020, EC values were comparable amongst treatments. However, in 2021 and 2022, large increases in soil EC were seen in the GS treatment. EC increased 24%, 742% and 573% in the GS treatment for 2020, 2021 and 2022, respectively. The red dotted line represents the average EC for the soil profile. The large increase in values suggests the GS treatment is neither remediating nor alleviating water penetration or infiltration. In the CTX treated area, EC decreased on average by 14%, increased by 145% and 117% in

January / February 2023 www.progressivecrop.com 17
Protect and Nourish your crop from pests with OMRI-listed Promax® and nourish your soil with Zap® for a healthy return on your investment! www.humagro.com/PCC123 A Bio Huma Netics® Brand ContinuedonPage18

2020, 2021 and 2022, respectively. With the application of CATION-EX5 PLUS, soil is maintaining a manageable EC level and showing greater performance for managing soil salinity when compared to conventional gypsum (GS). The increases seen in the GS area call for an update to salinity management practices.

Managing Soil Sodium and Chloride

Sodium chloride (NaCl) is the most common and problematic salt in irriga-

tion water. Sodium in soil antagonizes uptake of other beneficial elements like K, disperses soil and can create chemical compaction.

At the start of the experiment in 2020, soil sodium was comparable amongst treatments (Figure 3). In the GS treatment, a clear Na increase is seen from spring to fall in each experimental year. The red dotted line represents the average Na for the soil profile. Overall, the GS increased 53%, 654% and 429% soil Na concentration in 2020, 2021 and 2022, respectively. Comparatively, in the

CATION-EX5 PLUS treated field, soil sodium decreased by 4%, increased by 162% and 82% in 2020, 2021 and 2022, respectively. An increase in soil Na cannot be avoided but it can be managed to reduce toxicity, osmotic stress and mitigate growth/yield. Additionally, in 2022 CTX treated soil is beginning to show an effect carry over rate. In 2022 CTX treated soils showed little fluctuation in soil Na. This alludes to the lasting effects of proper soil flocculation.

18 Progressive Crop Consultant January / February 2023
0 2 4 6 8 10 12 14 16 Spring Fall Spring Fall Control CTX5 Axis2020Title 1 ft 2 ft 3 ft 4 ft 5 ft 0 2 4 6 8 10 12 14 16 Spring Fall Spring Fall Control CTX5 2021 1 ft 2 ft 3 ft 4 ft 5 ft 0 2 4 6 8 10 12 14 16 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft Growers Standard CATION-EX5 PLUS Growers Standard CATION-EX5 PLUS Growers Standard CATION-EX5 PLUS 2020 2021 2022 +742% +573% +117% +145% -14% +24% Growers Standard CATION-EX5 PLUS Soil EC ( dS /m) Soil EC ( dS /m) Soil EC ( dS /m) ContinuedfromPage17 0 20 40 60 80 100 120 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft 0 20 40 60 80 100 120 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft 0 20 40 60 80 100 120 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft 2020 2021 2022 Growers Standard Growers Standard Growers Standard CATION-EX5 PLUS CATION-EX5 PLUS CATION-EX5 PLUS +654% +82% +429% +162% Growers Standard CATION-EX5 PLUS +53% -14% Soil Na + ( meq /l) Soil Na + ( meq /l) Soil Na + ( meq /l) Figure 2. CATION-EX5 PLUS effectively manages soil EC compared to the Grower’s Standard (1 ton/ac gypsum). Red dotted line shows the average EC of all depths. Figure 3. Soil sodium is effectively reduced by CATION-EX5 PLUS when compared to standard management practices like gypsum. Red dotted line shows the average sodium of all depths. ContinuedonPage20
January / February 2023 www.progressivecrop.com 19

Soil Cl is an essential element needed by plants for growth, however when too much Cl is available in the soil, toxicity occurs. Cl toxicity is common in poorly drained soil and areas being irrigated with ground water. Cl is negatively charged, so it may be leached through the soil profile with irrigation water. When irrigation water is the largest contributor of Cl, and soil Na creates an environment for poor soil drainage, management becomes more critical. When soil Cl exceeds 5 meq/L, a management protocol should be activated. In this trial, soil Cl began the experiment below the action threshold in both treatments (Figure 4). The red dotted line represents the average Cl for the soil profile. As the experiment progressed, Cl concentration built in the soil profile. In 2021, the GS increased the soil concentration about 2257% from spring to fall and about 697% in 2022. The CTX treat-

ment had lower increases of 378% and 112% from spring to fall in 2021 and 2022, respectively.

No soil infiltration measurements were collected for this study; however, the data suggest an increase in water movement and wetted area in the soil profile. This is corroborated with the reduction in Na and Cl as well as EC. CTX is improving soil structure and remediating soil salinity.

The increases in soil EC and Na seen in the GS treatment call for an update to salinity management practices. Experimental data from this long-term and large-scale trial show CATION-EX5 PLUS effectively managing soil salinity, especially when compared to the standard yearly gypsum application. Modern agriculture puts great emphasis on efficiency, precise solutions and ease of use while still demanding results. CATION-EX5 PLUS offers results, efficiency, precision and ease of use in fertigation systems like those used in California’s Central Valley.

20 Progressive Crop Consultant January / February 2023
Order from your PCA or local Ag Retailer / Crop Protection Supplier *One application of Anti-Stress 550® will remain e ective 30 to 45 days, dependent on the rate of plant growth, application rate of product and weather conditions. 559.495.0234 • 800.678.7377 polymerag.com • customerservice@polymerag.com Additional Environmental Stress Conditions that the product is useful for: Frost & Freeze • High Temperatures & Extreme Heat • Drought Conditions • Transplanting • Drying Winds Anti-Stress 550® Beat the Heat & Care for Your Crops with: Optimal application period is one to two weeks prior to the threat of high heat. A foliar spray that creates a semi-permeable membrane over the plant surface. The coating of Anti-Stress becomes e ective when the product has dried on the plant. The drying time of Anti-Stress is the same as water in the same weather conditions. What is Anti-Stress 550®? When to apply Anti-Stress 550®? When is Anti-Stress 550® most e ective? Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com 0 5 10 15 20 25 30 35 40 45 50 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft 0 5 10 15 20 25 30 35 40 45 50 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft 0 5 10 15 20 25 30 35 40 45 50 Spring Fall Spring Fall Control CTX5 1 ft 2 ft 3 ft 4 ft 5 ft Growers Standard CATION-EX5 PLUS Growers Standard CATION-EX5 PLUS Growers Standard CATION-EX5 PLUS 2020 2021 2022 +2257% +378% +697% +112% +264% +75% Growers Standard CATION-EX5 PLUS Cl( meq /l) Cl( meq /l) Cl( meq /l) Figure 4. Soil chloride is effectively reduced by CATION-EX5 PLUS when compared to standard management practices like gypsum. Red dotted line shows the average chloride of all depths. ContinuedfromPage18
salinity. Updated management practices
"
'With little access to high-quality irrigation water and ongoing drought, there are few solutions to alleviate
are required to face the situation at hand.'
Subscribe at MyAgLife.com or Download the MyAgLife App to Play in Your Vehicle Scan to Download

The Agronomy of Water

22 Progressive
January / February 2023
Crop Consultant
A water sample can help quantify your risk of negative fertilizer interactions, which can help you choose the right kinds of formulations based on your on-farm water quality (photo by Vicky Boyd.)

PLANS

Water ties all aspects of crop production together and is the largest input on most farm operations on a per-acre basis (both by volume and weight.) Aside from recent challenges with water quantity, we are also experiencing issues with quality, or the chemical and physical properties that characterize a water source. In this article, I will describe how water quality is important to five categories of farm management: nitrogen management plans, fertilizer performance, predicting salinity issues, irrigation efficiency and distribution uniformity, and interactions with crop protection products (Figure 1).

Given the long list of interactions that farm water quality can impact, I would like to make the case for the explicit consideration of what I call “the agronomy of water”, in which we are managing this input similarly to how we take soil and plant tissue tests. After reading this, my hope is to convince you of the utility derived from water sample data to help manage this important natural resource. Remember, a water sample can help inform the management strategy of the five aforementioned categories, often in the same analysis. Thus, a water sample can allow you to better manage five aspects of crop production for the price of one analysis.

Nitrogen Management Plans

All water sources contain dissolved ions in various quantities. Most often, we think of the ions that cause salinity issues and toxicities, which include sodium and chloride. However, due to recent changes in regulatory policy, we now must think about the nutrient content of water applied to field to help mitigate groundwater pollution risk. In this case, nitrate (NO3-) values can be measured in your irrigation water, converted to lbs/acre, and applied against your annual crop nitrogen budget. The benefit of a water quality analysis is that you can keep track of other important nutrients, which can help inform your overall management program. A water sample can help estimate the presence of nitrates in your irrigation water and

contribute to an improved understanding regarding in-field nitrogen management compliance.

Predictive Salinity Management

Soil salinity is often caused by the application of irrigation water that is high

in dissolved salts, particularly sodium, chlorine and boron. These ions can cause a loss in crop yield due to specific ion toxicities (e.g., boron toxicity)

January / February 2023 www.progressivecrop.com 23
ContinuedonPage24
Figure 1. Crop yield is strongly influenced by the agronomy of water and the quality of applied irrigation and sprays. Water quality can be managed to influence several different areas of crop protection, as shown above.

and, in the case of sodium, can drive a loss of soil structure, impairing drainage and impeding water penetration and infiltration. A water sample can help quantify your risk of salt damage to your fields and crops and help you formulate a proactive reclamation plan.

Negative Fertilizer Interactions

Ok, so you have the water, now you just apply it to the crop, right? Not so fast!

Ions in the water can interact with each other and form solid precipitates (chalky or cottage cheese like substances). For example, water that is high in calcium and/or has a high pH can negatively interact with the phosphate in your fertilizer program. When calcium and phosphate come together, they form a mineral called apatite that is highly insoluble. This can have a severe impact on the liquid blends you are applying to your crops. I have seen cases where

one ranch has tremendous success running a certain blend but the ranch down the road cannot use the same formulation due to interactions with local water quality. Along the same lines, when phosphate and calcium form precipitates, the nutrients are no longer available for your crop to drive yield, which is a waste of input dollars. A water sample can help quantify your risk of negative fertilizer interactions, which can help you choose the right kinds of formulations based on your on-farm water quality.

Irrigation Efficiency and Distribution Uniformity

Pacific Gro has merged with Tidal Vision, a producer of chitosan, also based in Washington. Together we are Tidal Grow AgriScience.

Crop Resilience

Biologicals restore resilience against disease and pest pressure. Crop yield and quality are best when grown in biologically rich and nutritionally balanced soil. This helps plants avoid the need for silver bullets to rescue crops.

Pacific Gro is a core biological input that helps growers improve soil health, and improve nutrient uptake for better crop performance.

Continuing with the clogging theme, fertilizer precipitates, and other minerals, can also lodge themselves in drip emitters, sprinkler heads and other types of nozzles. Once these particles clog your system, you lose irrigation system efficiency. When your irrigation system is clogged, you now must use more water and power to deliver the same irrigation set to your thirsty crops than you would if your system had higher efficiency. Furthermore, the clogging of lines can impact some parts of the field more than others, causing an issue with the distribution uniformity of your applied water. A water sample can help you understand drip system clogging risk and formulate a plan to deal with it. Further fieldwork is required to quantify changes in distribution uniformity across a field, but it can be beneficial for improving overall irrigation efficiency.

Ag Chem Efficacy

Now let’s turn to your crop protection program. An essential question to ask here is, “How good is your spray water quality?” The answer demonstrates the connection between your ag chem programs (e.g., pesticides, herbicides and fungicides) and the most common mechanism for conveyance (e.g., spray water). However, the constituents of the water can have severe impacts on the pest control capacity of your ag chem spray program (e.g., efficacy). A pesticide spray that controls a pest to a high degree per application has high efficacy. An ag chem spray that doesn’t quite

24 Progressive Crop Consultant January / February 2023
ContinuedfromPage23
www pacificgro com 503-867-4849
Plant-Available Calcium Amino Acid Nitrogen Carbon Compounds Please visit with us at the BioSolutions Conference in Reno Feb. 23 24, 2023

do the job has low efficacy. Efficacy is strongly influenced by the interaction between the active ingredient in your applied pesticide and the water it is mixed with (e.g., spray tank, chemigation, etc.)

Five main physical components of water can have a negative influence on efficacy: pH, bicarbonates, hardness, total dissolved solids and turbidity. For example, spray water that is characterized by alkaline pH (>7) can cause an issue called alkaline hydrolysis, a scenario where the pH causes the active ingredient in the crop protection product to lose its efficacy due to physical and chemical deterioration. In another example, certain ions in the spray water, called hardness, can tie up the active ingredient in your ag chem and render it unusable for pest control.

Some pesticides are more strongly influenced by these components than others, and management programs should work to improve efficacy on a case-by-case basis. A water sample can help you determine how your ag chem sprays interact with water quality and put together a water conditioning and adjuvant plan to improve the overall activity and control of your pesticide programs.

Take a Water Sample

The importance of understanding your water quality cannot be understated, and a water sampling program will help you form a solid foundation of “water” agronomy and will produce tangible benefits for your farm. Ironically, while water is often the largest farm input by volume and weight, a water sample can be one of the cheapest inputs (e.g., $/ acre) around as one water source can serve many acres on a given ranch. However, many folks do not have a regular water sampling program in place to monitor changes in water quality. Talk to a Certified Crop Advisor today about starting a water sampling program and to improve the agronomy of water on your farm operation across the five categories described above.

Resources

Irrigation Water Salinity and Crop Production, anrcatalog.ucanr.edu/pdf/8066. pdf

The Impact of Water Quality on Pesticide Performance, extension.purdue. edu/extmedia/ppp/ppp-86.pdf

Water Quality for Crop Production, ag.umass.edu/sites/ag.umass.edu/files/ book/pdf/ghbmpwaterqualityforcropprod.pdf

Agronomy of Water FieldLink (originally created by author), helenaagri.com/ fieldlink/the-agronomy-of-water/

The Agronomy of Water Series (2 CCA credits available: Soil and Water), wrcca. org/continuinged

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

January / February 2023 www.progressivecrop.com 25
Other Innovative Products* From Belchim Crop Protection: Visit:www.belchimusa.com Belchim Crop Protection USA, LLC 2751 Centerville Road | Suite 100 Wilmington, DE 19808 Phone: 855-445-7990 Email: info.usa@belchim.com • PROVIDES Uniform Penetration and Lateral Movement of Water • ENCOURAGES Improved Rooting and Nutrient Uptake • IMPROVES Distribution and E ectiveness of Soil Applied Chemicals • SAVES WATER - Reduces Irrigation Requirements by Up To 25% Other Innovative Products From Belchim Crop Protection: Visit:www.belchimusa.com Do More With Less Water! Integrate® 80+ ENHANCES WATER MOVEMENT and Gets MORE Applied Water To The Rootzone, and LESS To Run O and Evaporation.

Phosphate vs Phosphite: Part One

Phosphite has been a controversial topic for years. Its use and benefits are argued in hundreds of research papers across the world’s scientific communities. Is it a fertilizer, a biostimulant or a fungicide? These questions are discussed in multiple university research results. I believe that if we look carefully, we can conclude phosphite serves all three functions. As with everything we do with chemicals and nutrition, we need to be aware of possible negative effects. We also need to determine how we are using the phosphite materials and the results we are seeking.

First, we need to understand and differentiate between phosphate and phosphite. There is often a lot of confusion here.

It Starts with Phosphorus

Phosphorus (P) is an essential major macronutrient. It is required by all living organisms. It is a limiting nutrient that controls growth in many ecosystems. P in living systems occurs mainly in the form of inorganic phosphate as well as phosphate esters. The formation and breakdown of phosphate esters under the control of kinases and phosphatases regulates the temporal protein activity and is responsible for the generation, distribution and utilization of free energy throughout the cell in several metabolic pathways. P is a structural component of the phospholipid bilayer membranes and genetic material including DNA and RNA. In nature, most P exists in its completely oxidized

Though phosphite is not the best nutritional source of phosphorus, it can serve as a carrier and catalyst for quick nutrition supplements and responses to nutrient deficiencies.

state (valence of +5) as a phosphate anion (PO43-, Pi), phosphate-containing minerals and organic phosphate esters. Pi compounds are the only form of P utilized by the plants for their nutrition.

Modern agriculture is currently dependent on the continuous input of Pi fertilizers, produced by the mining of rock Pi. Approximately 80% of the mined P is used to manufacture Pi fertilizer.

26 Progressive Crop Consultant January / February 2023
Phosphite can fertilize like phosphate, but its other functions may be more impactful.
LEMONS
CCA, CPAg, Verdesian Life Sciences

The

Difference is An

Atom Phosphite (Phi) is a reduced form of Pi with one less oxygen atom (P valence of +3). Phi compounds have been widely used in agriculture as fungicides for controlling several plant diseases caused by oomycete pathogens including Phytophthora spp. Although Phi can be absorbed by the plant cells through the Pi transporters, plants cannot metabolize Phi, which limits its use as a fertilizer. Phi can only be metabolized naturally by certain bacteria with an enzyme called Phi dehydrogenase (PtxD), which oxidizes phosphite into phosphate, a form that can be utilized for various cellular functions, and it does not provide P nutrition to the plants. The supply of Phi attenuates the Pi starvation responses (PSRs) in plants and inhibits the growth in Pi-starved plants. The addition of Phi to plants experiencing deficiencies of P confuses the plant’s internal signal that triggers the P deficiency responses. Several studies show that too much Phi application has detrimental effects on the growth and development of various plants. Therefore, Phi compounds should not be used as a major source of P fertilizers in agriculture.

Phi is more soluble than Pi and has a smaller structured molecule, so it is more readily absorbed by plant tissue. When added with other nutrients, it can serve as an excellent carrier. For example, a Phi mix containing phosphorus and potassium, calcium or magnesium would be absorbed readily and carry the needed nutrient into the plant. This has been demonstrated in numerous trials based on Verdesian Life Sciences’ line of NutriPhite nutrient products. Because of the proven biostimulant properties of Phi and the fungicidal benefits, we have the possibility of getting multiple benefits applied with a single application.

Phosphite Not a ‘Traditional’ Fertilizer

So, though Phi is not the best nutritional source of P, it can serve as a carrier and catalyst for quick nutrition supplements and responses to nutrient deficiencies. Soil applications of Phi usually do not replace P in the soil; however, plantings the following year show the plants do better where Phi had been applied the previous season. Interest in using Phi as part of a total production package is increasing, especially for some high-value crops. Phi fertilizers, if not formulated correctly, have significant potential to be phytotoxic and induce adverse reactions with other materials in the spray tank such as microelements and pesticides. When choosing your Phi source, it would be wise to seek a stabilized formula as it is proven not to bind with other tank mix materials. Chemical bonds will create another compound that even if not phytotoxic can be completely useless and unattainable by the plant. The salt-out effect can be a potential to clog nozzles and filters and could result in a waste of dollars spent on the Phi and/or other nutrients and chemicals. By binding these up, we are losing all or most of the efficacy of an expensive input in our crop management. All fertilizers, especially Phi, should be used in close consultation with a crop consultant to meet desired production goals.

In California, it is important to recognize that research has shown foliar applications of Phi can replace Pi in citrus and avocado crops suffering from P deficiency. Phi conversion to Pi may be attributed to slow chemical oxidation or by oxidizing bacteria and fungi that have been found living on the leaves of these two crops.

In part two of this article series, we will visit the biostimulant role of Phi, which is possibly even more important than the fungicidal properties of this very diverse and very useful tool to consultants and growers.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

January / February 2023 www.progressivecrop.com 27

The Five Rs of Nutrition in the Vineyard

Whether your grapes are destined for wine, raisins, juice or the table, the job of the grapevine is to capture energy from the sun and use it to convert CO2 and H2O to carbohydrates and O2. Maximizing this process begins at budbreak and leads to larger, higher-quality crops. To have the greatest influence, a wholistic understanding of plant nutrition and crop production need to be engaged to ensure that every dime of fertilizer applied best serves its intended purpose. This is where the Five Rs of Plant Nutrition enters the decision-making process.

By combining knowledge from plant physiology, soil science, microbiology and chemistry, core principles of plant nutrition arise that affect fertilizer use efficiency, yield and quality. The Five Rs

provide this science-driven approach in a memorable way that helps to confirm or guide nutritional decisions. A series of checks, the Five Rs ensure that the applied nutrients get into the plant when and where they are needed with minimal unintended nutrient interactions or losses. When framed as a question, the Five Rs can be stated as:

For my application, is this the:

• Right Nutrient?

• Right Time/Crop Stage?

• Right Form?

• Right Nutrient Mix?

• Right Place in the Plant?

The order of the Five Rs is easily re-organized to fit a given scenario, and when focusing on a specific growth period, considering the right time/crop stage first has the most value.

Right Time/Crop Stage

Early spring is a critical period for grapevine growth and development as the foundational support components of the plant and crop (xylem, phloem, initial leaves and new roots) are created. This timing is also very challenging because the ability of the plant to obtain and move the needed nutrients from the soil is hindered by low soil temperature and low atmospheric evaporative draw.

Cold soils inhibit microbial growth and function, preventing the cycling of nutrients from plant-unavailable to plant-available forms. Similarly, mineral solubility in the soil-water solution is also reduced as soil temperatures decline.

Evapotranspiration is the primary mechanism for the movement of nutrients between the soil and the plant. When air temperatures decrease, so does the amount of moisture a given volume of air can hold as does the rate that the air can cause evaporation. Coupled with the small surface area of new growth, very low levels of evapotranspiration result.

The classical thought that soil nutrient stores alone can support optimal plant growth and development early on is brought into doubt, and other fertility decisions need to be considered. Other non-evapotranspirational mechanisms exist within the plant to mobilize and move stored nutrients but should be viewed purely as supplemental.

Right Place in the Plant

Just as important as what nutrient to apply and when to apply it is identifying the most efficient or appropriate place in the plant for the application. As addressed above, early spring conditions result in the soil being a poor nutrient source with low delivery efficiency. Yet, nearly all nutrients found in or used by the plant over a growing season were sourced from the soil via the roots. So then why is “Right place in the plant” a

28 Progressive Crop Consultant January / February 2023
Maximizing nutrient uptake and energy conversion of vines begins at budbreak and leads to larger, higher-quality crops (all photos by S. Jacobs.)

core principle? When nutrient demand timing and nutrient delivery limitations meet, the end goal of maximizing economic yield focuses less on ‘where is the nutrient found?’ and more on ‘where are the nutrients needed and what is the best way to deliver them?’ Hint: The answer isn’t always via soil application.

For most nutrients, what is found in or applied to the soil meets the volume requirements of the plant, but often soil conditions during the demand period or interactions with other nutrients limit their availability. Even in soils with perfect nutrient conditions, periods still exist where only foliar nutrient appli cations can meet the limited window of nutrient demand. Post-budbreak is such a time and pre-bloom, bud differ entiation, set and berry development, post-veraison and postharvest periods all see benefits from timely foliar ap plications. During these periods, foliar nutrient applications can achieve results that the soil cannot deliver. And to go a step further, foliarly applied nutrients can uniquely alter nutrient ratios or balances within the plant in ways that cannot be achieved economically, or

This article will not go into specifics, but generally, foliar applications dry quickly, are exposed to comparatively high oxygen concentrations and wide-ranging temperatures, and are bombarded with solar radiation. The soil, on the other hand, is very chemically and physically active at the molecular scale and is teaming with life that needs many of the nutrients for its life cycle that our plants

Nutrient products are available as various compounds that can be organized

O ce: 559-686-3833 Fax: 5 59-686-1453 2904 E. Oakdale Ave. | Tulare, CA 93274 newerafarmservice .com Helping Farmers Grow NATURALLY Since 1974 ContinuedonPage30 A combination of both foliar and soil-based applications for most nutrients will be necessary to meet the quantities and timing required for high-level production.

roughly into four formulation groups: insoluble salts, soluble salts, chelates and complexes. Ideal use scenarios can generally be defined for each formulation group, and nutrient stability and uptake performance rely heavily upon where (right place) they are applied.

The main points to understand are 1.) there is no “magic bullet” formulation possessing very high performance as a nutrient delivery vehicle in both soil and foliar applications; and 2.) something else is always competing with the plant to acquire applied nutrients or acting against the formulation of the nutrient, decreasing its availability to the plant.

Insoluble salts: carbonates, oxides, hydroxides

Nearly or completely insoluble in aqueous solutions but micronize well. Foliarly, they coat tissues like paint and

are highly effective reflectors/blockers of sunlight. As such, they are often used to prevent sunburn or sunscald of plant tissues. Foliar nutrient delivery performance is very poor. Slow conversion to plant-available forms in the soil results in poor performance.

Soluble salts: sulfates, nitrates, acetates, chlorides

Soil applications usually perform very poorly, but low cost can offset the inefficiency. Foliar performance is poor as uptake is slow, and excess accumulation of the companion anions (SO4, NO3, C2H3O2 , Cl) elicit stress responses in the plant or are otherwise problematic.

Chelates: EDTA, EDDHA, EDDHSA, citric acid, amino acids

30 Progressive Crop Consultant January / February 2023
Contact us to see how we can help! (559)584-7695 or visit us as
Serving California since 1983 ContinuedfromPage29
www.superiorsoil.com
Plant nutrient demands fluctuate over the season, and nutrient-to-nutrient ratios shift subsequently.

Synthetic, EDTA-type and similar are generally large, highly water-soluble materials that perform exceptionally well in soil applications. They are toxic to plants and soil organisms, however, and can solubilize heavy metals in the soil, causing accumulation in plant tissues. They are not great foliars.

Conversely, citric and amino acid based chelates perform well when applied foliarly and are less toxic. Stability is an issue in soil applications compared to EDTA-type chelates.

Complexes: dextrose-lactose, mannitol, glucoheptonate, lignosulfonate

Poor performers in soil applications, these naturally derived materials make average to exceptional foliar delivery vehicles. Molecular weight and size of the complex affects performance. The complexing compounds of some offer carbon skeletons that are easily assimilated by the plant once the nutrient is removed.

Right Nutrient/Nutrient Mix

While not always grouped together, the right nutrient and the right nutrient mix are closely related. Plant nutrient demands fluctuate over the season, and nutrient-to-nutrient ratios shift subsequently. Nutrient-to-nutrient inhibitions, synergies, antagonisms and stimulations exist and must be accounted for as not all nutrients work well together in the plant at the same time.

In our budbreak to pre-bloom vineyard, demand for all nutrients except potassium are high, and calcium and phosphorus are both needed early on. But Ca and P antagonize each other, decreasing application and assimilation efficiency. So, which do we apply? If we assess the right time and right place components, foliar application of Ca makes sense since it moves exclusively with the transpiration stream and as is needed in the leaves to initiate cell division and develop cell walls. P on the other hand provides the energy needed for cell division and other growth functions to occur. Under ideal circumstances,

we could apply P foliarly today and Ca foliarly in three to seven days and see the greatest benefit. Practicality doesn’t often allow for this type of application situation, and in our attempts to reduce the number of passes through the field, we must apply both simultaneously.

Tie-ups and antagonisms in real-world agriculture are inevitable and will occur in the spray tank and in the plant. But

synergies and gains in efficiency and yield will occur from a little time, effort and application of the Five Rs into your nutritional program.

YOUR YEAR-ROUND ORGANIC SOLUTION FOR WEED CONTROL & POTATO DESICCATION

With years of proven efficacy, SUPPRESS® Herbicide EC consistently provides fast and effective broad-spectrum burndown on a wide variety of post-emergent grasses and weeds. Now it is approved for use as a plant desiccant!

ADVANTAGES

Excellent tool in IPM programs

Helps break chemical resistance

No pre-harvest interval or MRLs

Low-foaming and easy-to-use

Highly effective pre-harvest desiccant

Apply early applications of SUPPRESS® for weed control and apply late season applications for desiccation.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com WESTBRIDGE

599-8855 or visit www.san-agrow.com.

January / February 2023 www.progressivecrop.com 31
IS NOW GROWING AS SAN AGROW Call (760)

UNWRAPPING THE POSSIBILITY OF WATERMELON GRAFTING

HOW GROWERS CAN USE THIS ANCIENT PRODUCTION TOOL

You will probably not surprise to see the grafting of fruit and nut tree crops and well understand the needs to do so. But when I am going to discuss watermelon grafting here, I am sure many of you may pause and ask, “Can watermelon graft? What is that? Why graft watermelons? Is it still sweet after grafting? Is it still watermelon?”

Why Graft Watermelons?

The main purpose of grafting watermelons is to deliver plant traits to farms much faster than the traditional breeding programs. It is NOT designed to replace breeding and other well-documented techniques of developing new cultivars; rather, it offers growers and consultants a quicker and unique way to solve production problems. In contrast to the traditional breeding system, a grafted watermelon seedling comes from the recombination of two different plant species into one physical (not genetic) hybrid (Figure 1). The phenotypic traits that are brought to farms after grafting include soilborne disease resistance, abiotic stress tolerance, greater nutrient and water use efficiency, higher fruit yield and better fruit quality.

Do I Need Grafted Watermelons?

This is a question you should always ask before making a decision. The following are some of the benefits from using grafted watermelons. If you have the

50 45 40 35 30 25 20 15 10 5 0 FRUIT YIELD (TONS/ACRE)

SECOND HARVEST FIRST HARVEST RS2 SC RS1

Figure 1. A grafted watermelon plant is a recombined physical hybrid from two different plants. The lower part of a grafted plant comes from a rootstock seedling, which was bred for superior root traits, while the upper part is the regular commercial watermelon plant for producing fruit.

THIRD HARVEST FOURTH HARVEST

Figure 2. Cumulative fruit yield for the two grafted watermelon combinations (RS1 and RS2) compared to the non-grafted scion (SC). Note the similar yields in the first harvest.

Figure 3. Canopy coverage for watermelons grafted onto rootstocks Cobalt, Flexifort and RS841 compared to the non-grafted watermelons (NonG). Note: the field was transplanted on May 17, 2022. The first harvest was made on August 9, 2022.

32 Progressive Crop Consultant January / February 2023
JUNE 10 JULY 7 JULY 12 JULY 27 AUGUST 4 JUNE 24 COBALT
FLEXIFORT RS841 NONG CANOPY COVERAGE (%) 100 90 80 70 60 50 40 30 20 10 0

related issues but with limited solutions, you may consider grafting as your “icebreaker”. Again, please be mindful that these benefits may not be observed at each farm. Using grafting must be proceeded in a case-by-case protocol.

• Grafted watermelon can have a stronger resistance to soilborne diseases (e.g., Fusarium wilt, Fusarium crown and root rot, Verticillium wilt, etc.)

• Grafted watermelon can produce a higher fruit yield under soilborne pathogenic pressure than nongrafted plants.

• Grafted watermelon can produce a higher fruit yield under low-disease or disease-free conditions.

• Grafted watermelon can use water and nutrients differently compared to non-grafted plants.

• Grafted watermelon may have better fruit quality than non-grafted plants.

Where to Find Rootstock Information and How to Graft?

A majority of the rootstock varieties can be found at vegetablegrafting.org/re sources/rootstock-tables/cucurbit-root stocks/ Please note that 1.) not all cucurbit rootstocks can be grafted onto watermelons; 2.) information about the disease resistance of each rootstock was collected from the seed company; and

3.) the rootstock table may be updated as new or old rootstocks emerge or disappear. In addition to the table, you can also seek help from rootstock seed suppliers, nurseries that work on grafting watermelons, extension advisors and your trusted growers. For information about grafting nurseries, feel free to give me a call or email me (209-525-6822, zz-

wwang@ucanr.edu) and I will give you a list. If you need to know the grafting methods, check out the grafting manual at vegetablegrafting.org/resources/grafting-manual/.

Possible Challenges and Pitfalls

Using grafted watermelons can be challenging. Such challenges can be serious under some, though rare, circumstances.

Cost

In the past, growers only dealt with scion, but now they must think about rootstocks. Paying extra money for the rootstock seeds and producing grafted transplants will definitely increase the production cost. Currently, the most effective way in balancing the cost is to plant grafted watermelons in a wider spacing while still managing them for a higher fruit yield. Nowadays in California, grafted watermelons should be planted in a 4- to 5-foot in-row spacing,

January / February 2023 www.progressivecrop.com 33
PROTECT BAREROOT AND POTTED TREES agbiochem.com | 2 0 9 - 6 0 6 -27 37 Available from your local agricultural dealer GALLTROL-A AgBioChem, Inc. To prevent crown gall disease, spray roots just before planting with: ContinuedonPage34 Figure 4. Seasonal canopy coverage between grafted watermelons grafted onto Camelforce and Cobalt rootstocks and the nongrafted control. Note the fluctuation of canopy regrowth curves due to continuous irrigation and fertilization after each harvest since mid-July 2022. 4/29/2022 5/19/2022 6/8/2022 6/28/2022 CAMELFORCE DATE COBALT NONG 7/18/2022 8/7/2022 8/27/2022 9/16/2022 10/6/2022 100 95 90 85 80 75 70 65 60 55 50 45 40 35 25 20 15 10 5 0 PERCENT CANOPY COVERAGE

6.

which is equivalent to 1,200 to 1,500 plants per acre compared to 2,200 plants per acre for the non-grafted plants.

Extended vegetative growth and delayed harvest

Due to their stronger rootability and growth vigor, grafted watermelons usually produce more and larger canopies than regular plants, possibly resulting in delayed fruit maturity. Also, the typical exterior changes that indicate fruit maturity (e.g., a dried tendril and leaflet) on non-grafted watermelons may not be true for grafted plants. An early harvest that causes a lower sugar content can occur frequently in grafted fields. From our past observations as well as research from other areas, a possible 7- to 10-day delay from non-grafted plants could be reasonable for harvesting grafted watermelons.

Yield advantage at later harvests

If you don’t see a higher yield at your first harvest or even a lower yield, be patient and the longer harvest window of grafted plants will give you the subsequent melons. Figures 2 and 3 were from my previous trials in 2021 and 2022 and indicated the yield superiority in the subsequent harvests for grafted plants (Figure 2, see page 32) and the duration for grafted plants to maintain canopy compared to non-grafted plants (Figure 3, see page 32).

Different responses to irrigation and fertilization

With the changes of growth character-

250

0 CUM MULATIVE N UPDATE (LBS/ACRE) 20 52 68 84 DAYS AFTER TRANSPLANTING (DAT) 100 RS2 SC RS1 116 132 148 164 36

Figure 5. Cumulative N uptake for the two rootstock-scion combinations (RS1 and RS2) and the non-grafted control (SC). Note the timing of the first (93 DAT), second (104 DAT), third (114 DAT) and fourth harvests (166 DAT, unmarked).

istics, you may need to consider adjusting your irrigation and fertilization to meet the needs of grafted watermelons. Figure 4 was also from a field trial in 2022 and showed the different canopy regrowth after supplying with irrigation after each harvest between grafted and non-grafted watermelons. It is obvious to see that the canopy of non-grafted watermelons was consistently lower than the grafted plants since the start of fruit harvest on mid-July 2022 (Figure 4, see page 33). In the meantime, grafted watermelons may take up nitrogen differently from the non-grafted watermelons as well. Figure 5 was a trial I conducted in 2021 which demonstrated the different patterns of nitrogen uptake between grafted and non-grafted watermelons, especially at the last part of the growth cycle.

Scion-rootstock incompatibility and change of fruit exterior and interior quality

This is a complex question. In many cases, you will not be able to detect the incompatibility until the plants are

transplanted or even when fruits are harvested and cut open. Symptoms of incompatibility early in the season could have 1.) poor early growth compared to other combinations and the non-grafted control; 2.) death after a few days of transplanting; 3.) incomplete removal of rootstock shoot part at grafting (Figure 6); and 4.) deformed plants. Of course, some of the symptoms may look similar to pathogen infestations. Symptoms of grafting incompatibility at a later stage of the growth cycle usually include a much lower final yield compared to others and a significant reduction in fruit quality (e.g., smell, flesh color, sweetness and hollow heart). For fruit quality, most noticeable changes after grafting that you may see or taste include thicker rinds, bigger fruit and firmer flesh. Therefore, preparing accordingly to meet your needs and your customer’s preference is important.

Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com

34 Progressive Crop Consultant January / February 2023
ContinuedfromPage33
Figure Rootstock shoot protruded from the graft union, indicating an incomplete removal of rootstock shoot at grafting.
200 150 100 50
January / February 2023 www.progressivecrop.com 35 Agriculture in this region is unlik else, and successful growers nee plan that meet s the unique goa and challenges we face. Get pre the advanced product s and agr knowledge you need to suppor t crops, your soil and a sustainab Sure -K® and Kalibrate® are registered trademarks of AgroLiquid. © 2023 AgroLiquid All Rights Reser ved Find an AgroLiquid dealer near ApplyLessExpectMore.co Apply less, expect more?
* DATA ON FILE. Important: Always read and follow label use directions. All TM/R © 2023 Verdesian Life Sciences. All rights reserved. VLS 22.0636 800-868-6446 | VLSCI.COM The Nutrient Use Efficiency People.® Advisors’ When it comes to Nutrient Use Efficiency for California crops, there’s only one alpha. Don’t let your growers leave nutrient use efficiency to chance. PrimacyALPHA® works inside the plant to stimulate the efficient assimilation and utilization of nutrients that result in healthier crops and higher yields. Proven on a wide variety of crops, primacyALPHA also delivers key secondary nutrients that helps optimize flowering, fruit size and fruit set. Make the recommendation you can be confident in –make it primacyALPHA. +9 -22% YIELD INCREASE ORCHARDS* +11-39% YIELD INCREASE ANNUALS*

Turn static files into dynamic content formats.

Create a flipbook
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.