Progressive Crop Consultant - July - August 2016

Progressive

Crop Consultant The Leading Magazine For CA Ag Professionals

July - August 2016 Advancing the Next Generation of Groundwater Management in California Organic Blueberry Production Weedy Red Rice Update Potassium Deficiency in Vineyards

PUBLICATION

Volume 1 : Issue 2

Progressive

Crop Consultant The Leading Magazine For CA Ag Professionals

Publisher: Jason Scott Email: jason@jcsmarketinginc.com Editor: Kathy Coatney Email: kathy@jcsmarketinginc.com Production: Logan Willems Email: logan@jcsmarketinginc.com Phone: 559.352.4456 Fax: 559.472.3113 Web: www.progressivecrop.com

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In This Issue 4

Spotted Wilt Virus Management in Tomatoes

10

Advancing the Next Generation of Groundwater Management in California

Contributing Writers & Industry Support Timothy Blank Certified Seed Program Representative, California Crop Improvement Association Mark Gaskell Farm Advisor, University of California Cooperative Extension, San Luis Obispo, CA David Guy President, Northern California Water Association

15

Cecilia Parsons Contributing Writer Thomas A. Turini University of California Agriculture and Natural Resources, Vegetable Crops Advisor in Fresno County

22

Stephen Vasquez Research Agronomist – West of the Rockies Tessenderlo Kerley, Inc. Crop Vitality

Organic Blueberry Production Nutrient Management Requirements in Mild-Winter Areas of California

Weedy Red Rice Update Weedy Red Rice Rivals Watergrass as being the Worst Weed in Rice Production Worldwide

24

Post Harvest Nutrition in Almonds

26

Potassium Deficiency in Vineyards

UC Cooperative Extension Advisory Board Kevin Day

County Director and Pomology Advisor, Tulare/Kings County

David Doll

UC Farm Advisor, Merced County

Dr. Brent Holtz

County Director and Pomology Farm Advisor, San Joaquin County

Steven Koike

Plant Pathology Farm Advisor

Emily Symmes

Integrated Pest Management Advisor, Sacramento Valley

Kris Tollerup

Integrated Pest Management Advisor, Parlier, CA

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.

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Photo Credit: Thomas A. Turini

Tomatoes

TSW symptom fruit. Fruit distortions and irregular color are associated with TSWV.

Spotted Wilt Virus Management in Tomatoes Thomas A. Turini University of California Agriculture and Natural Resources, Vegetable Crops Advisor in Fresno County

T

omato spotted wilt virus (TSWV) is a thrips-transmitted virus that can infect many crops and weeds. In California’s Central Valley, in an important processing tomato production area, this virus disease may cause substantial economic damage. The most recognizable symptoms include fruit with protruding oval deformities or irregular concentric ring color patterns and this virus can kill shoots and plants, so both quality and Page 4

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yield are affected. The host range of this virus includes many common crops and weeds and likely survives the winter on a few weed or crop plants, but quickly amplifies on tomatoes in spring. Therefore, risk increases during the season. The virus is transmitted by thrips; primarily Western Flower Thrips, Frankliniella occidentalis in the Central San Joaquin Valley. The vector must feed on an infected plant as a nymph to be capable of transmitting the virus as an adult. Risk of loss due to TSWV can be reduced but management in high risk situations is going to depend upon several tactics.

Resistance to the virus is available in

July/August 2016

both fresh market and processing tomato varieties; however, in some production areas, resistance-breaking TSWV has been reported and is likely to develop in regions where the gene is heavily relied upon. A few foliar insecticides have been shown to bring down thrips population densities and reduce incidence of TSWV symptomatic plants, but will not keep the virus down to commercially acceptable levels under high disease pressure.

Under situations where there is a history of the virus, identify risk factors, which may include weed or crop sources of the virus in early spring, ensure that transplants are not arriving with in-

fection, consider variety susceptibility, plant date, thrips management programs to calculate your risk of experiencing damage. Once there is an appreciation for your risk factors, you have capacity to mitigate disease risk by modifying any of these components that contribute to a situation in which this disease causes economic damage.

Tomato spotted wilt virus was present at low levels and was largely regarded as a curiosity 15 years ago, but by 2005, this severity and incidence of this virus increased to levels that caused severe economic damage in the Central San Joaquin Valley. In response the California Tomato Research Institute funded a comprehensive research project to better understand and control this viral disease.

Identification is critical to implementation of an effective program because management of TSWV requires different tactics than other diseases. This virus disease is associated with several striking symptoms, but also has symptoms that can be confused with other virus diseases or even diseases caused by very different pathogens. Symptoms of TSWV vary by stage of crop development when infection occurs and by other factors.

The most recognizable symptoms of TSWV in tomato include fruit with protruding oval deformities or irregular concentric ring color patterns. Plants infected shortly after transplant will produce foliage with dead spots or have more superficial patterns on the upper leaf surface giving a bronzing appearance and the entire plant will die before producing fruit. When fruit are forming at the time that infection occurs, fruit will be deformed and discolored, foliage will show bronzing symptoms and dieback. Plants infected at late stages of development will have symptoms limited to shoots. There are quick tests that are easily preformed in the field or office available for purchase from AgDia at www.agdia.com or EnviroLogix at www. envirologix.com.

An awareness of virus and vector characteristics is helpful in considering control program components. The virus has a wide host range that includes sow thistle, prickly lettuce, mustard, London rocket, malva, Russian thistle and many others. Crops that also may be infected Continued on Page 6

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Table 1. Summarized processing tomato variety response to Tomato spotted wilt virus.

includes beans, eggplant, lettuce, pepper, potato, and spinach. The virus does not survive outside of a living host, so it is likely to be surviving in winter weed or crop hosts while there are no tomatoes in the area. In central California the primary vector is Western flower thrips (WFT), Frankliniella occidentalis. The thrips must acquire TSWV by feeding on an infected plant as a nymph, pupate in the soil in the case of WFT, and emerge as an adult capable of transmitting the virus. The thrips may survive for more than 45 days and is capable of transmitting the virus. During most years, thrips movement is very low from November through January, and the levels observed in weeds and crops in January and February are very low, so all indications are that after winter, this virus is present in very low levels in the environment.

In March and early-April, there are low levels of TSWV present in the processing tomato production areas, but the virus quickly amplifies on the large and concentrated areas of tomatoes so that by June, the virus is present at much higher levels and risk of economic damage due to TSWV is much higher than early in the season.

In addition to crop and weed sources, recent research suggests that adult thrips with TSWV emerging from pupae in the soil are another potential source of early season TSWV inoculum. In this case, the immature thrips that fed on an infected plant prior to pupating in the fall harbor the virus through the winter.

As soil temperatures increase in spring, the infectious adults may emerge and serve as a source of the virus early in the season.

Varieties resistant to TSWV are available for both processing and fresh market production. Commercial varieties with resistance are using a single gene resistance, Sw5. With repeated and widespread use of single gene resistance, virus strains with capacity to reproduce within resistant plants will be selected for. In the event that a strain or strains with resistance breaking capacity is present in the population, selection for an increase of that strain or strains will occur in the presence of dense use of this single gene resistance. Therefore, Continued on Page 8 Page 6

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Low BQ 163 paste, peel H 2206 multi use

UG19406 multi use

SUN 6368 peel, solids H 4007 multi use K 2769 -----------

H 3044 multi use N 6397 multi use

UG 15308 Peel

BQ 205 multi use

UG 4305 multi use

Variable or Medium H 2005 multi use

SUN 6366 multi use

H 1015 early multi

High H 8004 multi use

BOS 602 multi use H 8504 paste

NDM 5578 multi use

HM 6898 multi use

H 9780 multi use

NUN 672 Viscosity

CXD 282 multi use AB 2 multi use

K 2770 -----------

CXD 255 multi use

H 2601 pear

AB 3 multi use

APT410 Multiuse

HMX 7885 pear

PX 1723 dice, peel Photo Credit: Thomas A. Turini

Continued from Page 5

Ring spots may be obvious on green fruit and blister-like protrusions may be obvious on red or partially colored fruit.

Fallow fields can serve as sources of both thrips and TSWV.

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while plant resistance is a critical tool in managing TSWV, exclusive reliance on this tactic should be avoided. In addition, careful attention to any evidence of the presence of plant resistant strains is critical. If typical fruit and foliar TSWV symptoms are present on more than 3% of the plants that have Sw5 resistance, there may be resistance breaking strains present.

Some susceptible varieties are more susceptible than others. In the absence of genetic resistance, differences in TSWV expression were documented in susceptible varieties. In studies conducted at the University of California West Side Research and Extension Center (UC WSREC), 10 to 16 varieties were compared in 13 trials conducted from 2007 to 2012. Based on TSWV incidence in susceptible varieties, entries were placed into three categories (Table 1, Page 6).

It is notable that there are factors aside from variety that influence performance of these varieties.

Insecticide use to control thrips can be challenging, but use of some foliar insecticides reduced TSWV incidence in studies conducted at UC WSREC. Thrips concentrate in flowers or other protected location, have tremendous reproductive potential and may develop resistance to insecticides; however, as a component of a management program, they may be useful in reducing economic impact due to TSWV. In foliar insecticide efficacy comparison experiments conducted from 2007-2012 the only insecticides that consistently reduced WFT densities were Radiant, Dimethoate and Lannate (data not shown). Insecticide program evaluations conducted at UC WSREC included drip injected materials as well as transplant drenches and foliar applications as detailed in Figures 1 and 2. Under the conditions of comparisons of program studies over five years, drip injected materials were ineffective, but foliar applications were generally helpful in reducing TSWV disease incidence. No significant differences were documented with drip injected materials (Fig 1 and 2) while foliar programs reduced TSWV incidence in 2009, 2011 and 2012 (Figure 2).

In 2010, no significant differences were observed between any treatments (foliar, drench or control) (Figure 2). In 2010, Page 8

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Figure 1. Drip irrigation applied materials had no significant effect (P=0.05) on Tomato spotted wilt virus symptom incidence 2009-2012 at University of California West Side Research and Extension Center.

Green fruit with blister like protrusions are typical of TSWV.

TSWV infected weeds, like this sow thistle, may show symptoms, or they may be symptomless.

Moderate necrosis and yellowing.

Irregular necrotic spots and yellowing is common on leaves of TSWV infected tomato plants.

July/August 2016

TSW bronzing symptom. A bronze coloration of the foliage is a typical symptom of Tomato Spotted Wilt Virus (TSWV).

Photo Credit: Thomas A. Turini

Continued from Page 6

Photo Credit: Thomas A. Turini

Severe yellow and necrosis.

Figure 2. Effect of transplant drench and foliar insecticide programs on Tomato spotted wilt virus symptom incidence at University of California West Side Research and Extension Center, 2009-2012.

Performance of Verimark as a transplant drench was inconsistent. In comparison to the program lacking the Verimark application, the Verimark transplant drench reduced TSWV symptom incidence in 2011, but not in 2010 and 2012 (Figure 2) ). In 2010, regardless of the treatment, there were no differences between treatments and the untreated control, which was likely due to very high population densities of thrips from an infected tomato field near the experiment. This highlights the limitations of what can be accomplished with insecticide treatments and that without other strategies also implemented, the likely failure to provide commercially acceptable levels of control under high disease pressure. The insecticide treatments are effective largely in that they reduce secondary spread, or spread of the virus within the field, to prevent spread from external sources of infective thrips is unlikely with infield applications.

Rogueing, which is removal of TSWV symptomatic plants, may be effective and even economical under some circumstances. However, if substantial external sources of infective thrips are contributing to the disease increase or there are already substantial levels of TSWV infected plants in the field, this is not likely to be effective. Also, it may be difficult to economically justify this approach depending upon the market for the tomatoes or the value of labor.

Integrated Pest Management can be applied specifically to TSWV for the greatest sustainable levels of success under high pressure situations. Careful inspection of the area for potential sources of inoculum and avoiding planting crops near sources, to prudent selection of varieties to starting with virus-free transplants are important preplant steps. Following planting, continue to monitor not only your field but fields in the vicinity for TSWV symptoms. At the first detection of the virus in the area or in the field, begin treatments with insecticides. Generally, few applications will be needed and under the conditions of the studies in Central California, two applications were as effective as more treatments. After harvest of tomatoes or any crop, quick and complete removal of the crop and weeds are critical and weed control throughout the year in the production area can reduce pressure.

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Water

Advancing the Next Generation of Groundwater Management in California David Guy President, Northern California Water Association

T

he past four dry years in California have brought into sharp focus the importance of groundwater resources for farmers, cities and rural communities throughout the state. The California Department of Water Resources (DWR) has found that “groundwater is a vital resource in California, providing close to 40 percent of the state’s water supply in an average year. In some regions of the state, groundwater accounts for as much as 60 percent of the supply during dry or drought years.” In the past several years, certain parts of the state have received no surface water, instead relying upon groundwater for 100 percent of supplies.

Extended drought conditions typically result in an increase of groundwater well activity and pumping to compensate for surface water supply shortages.

Increased groundwater pumping can lead to adverse conditions including dry wells, land subsidence, water quality impacts, seawater intrusion, and stream depletion.

In the midst of this recent drought, the California Legislature passed and the Governor signed into law on September 16, 2014 the Sustainable Groundwater Management Act, now being referred to as SGMA or pronounced as “Sigma.” The passage of SGMA raises some fundamental questions for California’s farmers and ranchers and the rural areas throughout the state as they plan for the future. The central question is whether farmers and ranchers, as well as the various overlying local agencies (water districts and counties), will step up and take the actions that are truly necessary for sustainable groundwater management.

In some parts of the state, it is generally acknowledged that there is overdraft as shown by the map on page 12, which suggests that groundwater pumping is out of balance and exceeds the available Page 10

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supplies. To bring these basins back into balance will require aggressive water management strategies (both surface and groundwater), an adjudication of the rights to pump groundwater, more stringent land use policies, or some combination of these measures.

In other areas, the groundwater is currently in balance and the available supplies exceed pumping. Here, the strategy will be for local agencies to manage the surface and groundwater resources to keep and maintain the balance.

For all areas, SGMA provides a process and guidance for how local agencies can develop groundwater sustainability plans, but the real question is whether there will be local leadership to drive a cultural change that will be necessary for sustainable groundwater management. For success, the next generation of groundwater management will require a different mindset where farmers and other landowners look beyond the borders of their land and recognize the need to work collectively as the best way to protect and manage the groundwater resources for their benefit and the longterm value of their land and the various functions it supports. In the alternative, there are many adjudicated basins in California and there will continue to be adjudications in areas where SGMA and these cultural shifts do not take form.

What is Sustainable Groundwater Management?

Although sustainability is a difficult term to define with any precision, SGMA has a sustainability goal for groundwater management and planning to avoid “undesirable results” that include: “(1) Chronic lowering of groundwater levels indicating a significant and unreasonable depletion of supply if continued over the planning and implementation horizon. Overdraft during a period of drought is not sufficient to establish a chronic lowering of groundwater levels if extractions and groundwater recharge

July/August 2016

are managed as necessary to ensure that reductions in groundwater levels or storage during a period of drought are offset by increases in groundwater levels or storage during other periods.

(2) Significant and unreasonable reduction of groundwater storage.

(3) Significant and unreasonable seawater intrusion.

(4) Significant and unreasonable degraded water quality, including the migration of contaminant plumes that impair water supplies.

(5) Significant and unreasonable land subsidence that substantially interferes with surface land uses.

(6) Depletions of interconnected surface water that have significant and unreasonable adverse impacts on beneficial uses of the surface water.”

Organizing: Forming Groundwater Sustainability Agencies (GSAs) The first task under SGMA is for local public agencies or a combination of local public agencies overlying a groundwater basin to decide whether to become a Groundwater Sustainability Agency (GSA). This is a big decision as local agencies look at the tremendous responsibility and potential costs that will inevitably come with GSAs. As local agencies consider whether to declare as a GSA it will be important that they fully understand the requirements for developing a Groundwater Sustainability Plan that is the heart of SGMA, as described in more detail below.

The requirements in SGMA apply to basins designated as high and medium priority that have not been adjudicated, as shown on the map on page 13. In some areas there is already a local or regional agency that can serve as the GSA. In areas where multiple agencies overlie a groundwater basin, multiple agencies may come together and act as a single GSA through a memorandum of agreement (MOA), a joint powers agreement (JPA), or other legal agreement. In addition to public agencies, SGMA also

allows a water corporation regulated by the Public Utilities Commission or a mutual water company to participate in a GSA through similar agreements with the local public agencies.

Importantly, in areas that are not covered by local water agencies acting as a GSA (generally referred to as “white spaces”), the county will be presumed to be the GSA for these areas unless it formally notifies DWR that it will not take on this responsibility. County participation in SGMA and coordination with local water agencies may be very difficult: yet, it may be the most important element of forming meaningful GSAs that can effectively work towards sustainable groundwater management.

After a local agency submits a formal GSA notification to DWR, the agency is presumed to be the exclusive GSA in the area covered by the notification if no other local agency submits a notification within 90 days for all or any portion of the same area. For additional details regarding the current GSA formation notifications submitted to DWR, visit the following website: http://www.water. ca.gov/groundwater/sgm/gsa_table.cfm

So what happens if local agencies do not submit the formal process for GSA? The simple answer is that this provides an opportunity for state intervention.

Under SGMA, when local or regional agencies cannot or will not manage their groundwater sustainably in a mediumor high-priority groundwater basin, SGMA provides for state intervention until the local agencies are prepared to assume responsibility. The State Water Resources Control Board (SWRCB) may intervene if a GSA is not formed or if a GSA fails to adopt or implement compliant plans by certain dates. Thus, if no GSA is established by June 30, 2017 for all or a portion of a high- or medium-priority basin, the basin may be designated as a probationary basin by the SWRCB. This is the first date where the state can intervene and may develop an interim plan for managing the basin until the local agencies can reach agreement and identify a GSA or GSAs. If the basin is designated as probationary, there are reporting requirements for groundwater pumpers and the state may also assess fees to provide funding required to develop an interim plan.

There are many resources to assist local agencies in this process. To assist in coordinating GSA formation, DWR has provided facilitation services to support local public agencies. Further information on facilitation services is available at: http://www.water.ca.gov/ irwm/partnership/facilitation_services. cfm. Additionally, there is more information on the DWR website regarding formation: http://www.water.ca.gov/ groundwater/sgm/pdfs/GSA_Notification_Requirements_v2_2016-01-06.pdf.

The Water Education Foundation has a handbook available at: http://www.watereducation.org/publication/2014-sustainable-groundwater-management-act. and the California Water Foundation has a guide: http://waterfoundation.net/ wp-content/uploads/2015/09/CF_GSA_ Guide_09.30.15_web.pdf.

Planning: Developing the Groundwater Sustainability Plan (GSP) Following GSA formation, the next step is for the GSA(s) to develop a Groundwater Sustainability Plan (GSP).

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Continued from Page 11

Critically Overdrafted Basins - Groundwater January 2016 Basins – January 2016 Critically Water Overdrafted

For high- and medium-priority basins that are not critically over-drafted, the GSPs are due by January 1, 2022. For areas with critical overdraft (see map), the GSPs are due on January 31, 2020.

Where multiple agencies agree to form a single GSA through a legal agreement, the agencies may develop a single GSP. However, multiple GSAs may also coordinate to develop a single GSP or multiple GSPs for a single groundwater basin or sub-basin. In groundwater basins where there will be more than one GSP, the responsible GSAs must coordinate management of the basin through a single coordination agreement that covers the entire basin.

On May 18 the California Water Commission (Commission) approved DWR’s GSP regulations.

The regulations specify the components of GSPs, acceptable alternatives to GSPs, and coordination agreements among local agencies. The regulations also describe the methods and criteria used by DWR to evaluate those plans, alternatives, and coordination agreements, and information that DWR requires for evaluation, which is to be based on a substantial compliance standard provided that the objectives of SGMA are satisfied.

In sum, a local agency “shall have the responsibility for adopting a GSP that defines the basin setting and establishes criteria that will maintain or achieve sustainable groundwater management.”

DWR will “have the ongoing responsibility to evaluate the adequacy of the GSP and the success of its implementation.” A GSP will be evaluated, and its implementation assessed with the objective that a basin be sustainably managed within 20 years of GSP implementation without adversely affecting the ability of an adjacent basin to implement its GSP or achieve and maintain its sustainability goal over the planning and implementation horizon.

The full text of the GSP regulations and additional information are available at: http://www.water.ca.gov/groundwater/sgm/gsp.cfm The Importance of Surface Water for Sustainable Groundwater Management Although SGMA focuses upon groundwater, successful implementation Page 12

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Crescent City

Groundwater basin/subbasin Critically Overdrafted Groundwater Basins DWR Region Office boundary

Eureka

County boundary

Redding Susanville Red Bluff 0

Quincy

25

50

100

Miles 200

150

Chico Fort Bragg

Willows

Downieville

Oroville

Ukiah

Northern Region Office

Truckee

Marysville Auburn

North Central Region Office

Placerville Sacramento

South Central Region Office

Napa Antioch San Francisco

Oakland

Southern Region Office

Stockton Modesto Mariposa

San Jose

Merced

Santa Cruz Monterey

Fresno

Visalia

Critically Overdrafted Basins Basin Number

Basin/Subbasin Name

3-01 3-02 3-04.01 3-04.06 3-08 3-13 4-04.02 4-06 5-22.01 5-22.04 5-22.05 5-22.06 5-22.07 5-22.08 5-22.09 5-22.11 5-22.12 5-22.13 5-22.14 6-54 7-24

Soquel Valley Pajaro Valley 180/400 Foot Aquifer Paso Robles Area Los Osos Valley Cuyama Valley Oxnard Pleasant Valley Eastern San Joaquin Merced Chowchilla Madera Delta-Mendota Kings Westside Kaweah Tulare Lake Tule Kern County Indian Wells Valley Borrego Valley

Bakersfield

Needles Lancaster

Cadiz

Santa Barbara San Bernardino

Los Angeles Anaheim

Riverside

Long Beach

Oceanside El Centro San Diego

Total number of Basins/subbasins: 21 January 1, 2016

of SGMA and sustainable groundwater management will rely upon the availability, utilization and integration of surface water.

Under SGMA, DWR was directed to prepare a report on water available for replenishment. DWR has prepared a White Paper to provide an initial response to the “water available for replenishment” requirements under SGMA, including background information and next steps for completing the analysis.

This White Paper is available for public review and comment at: http://water. ca.gov/groundwater/sgm/wafr.cfm. The report will be completed by December 31, 2016.

In addition to the DWR report, there is new thinking and more concerted efforts around groundwater recharge opportunities and the ability to recharge groundwater is receiving increased at-

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tention in California. The Legislature in SGMA found that “sustainable groundwater management in California depends upon creating more opportunities for robust conjunctive management of surface water and groundwater resources. Climate change will intensify the need to recalibrate and reconcile surface water and groundwater management strategies.” Furthermore, the Legislature expressed its intent “to increase groundwater storage and remove impediments to recharge.” (Water Code §10720.1)(g).)

Looking forward, sustainable groundwater management will thus be dependent in large part on the effective management of surface and groundwater supplies in an integrated manner. This includes the recharge of groundwater--either directly or through in-lieu opportunities--by maximizing the availability and use of surface water supplies.

CASGEM Groundwater Basin Prioritization CASGEM Groundwater Basin Prioritization

Crescent City

Groundwater basin/subbasin Basin prioritization ranking High Medium Low Very low

Eureka Redding

DWR Region Office boundary

Susanville

Hydrologic region boundary

Red Bluff

County boundary

Quincy Chico Willows

Fort Bragg

Downieville

Oroville

Ukiah

Truckee

Marysville

Northern Region Office

Auburn Placerville

North Central Region Office

Sacramento

Southern Region Office

Napa Antioch San Francisco

South Central Region Office

Stockton

Oakland

Modesto Mariposa

San Jose

Merced

Santa Cruz Fresno

Monterey

Visalia

Bakersfield

Needles Lancaster

Cadiz

Santa Barbara

Statewide Groundwater Basin Prioritization Summary Basin ranking

Basin count per rank

Percent of total for State GW use Overlying population

High

43

69%

47%

Medium

84

27%

41%

Low

27

3%

1%

Very Low

361

1%

11%

Totals

515

100%

100%

San Bernardino

Los Angeles Anaheim

Riverside

Long Beach

Oceanside El Centro San Diego

Basin Prioritization results — June 2, 2014 0

In other words, sustainable groundwater management will largely depend upon sustainable surface water management.

In November 2015, the Governor issued an Executive Order encouraging new recharge opportunities: “To demonstrate the feasibility of projects that can use available high water flows to recharge local groundwater while minimizing flooding risks, the State Water Resources Control Board and California Regional Water Quality Control Boards shall prioritize temporary water right permits, water quality certifications, waste discharge requirements, and conditional waivers of waste discharge requirements to accelerate approvals for projects that enhance the ability of a local or state agency to capture high precipitation events this winter and spring for local storage or recharge, consistent with water rights priorities and protec-

25

50

100

150

Miles 200

tions for fish and wildlife.” Several areas took advantage of this opportunity, including the Yolo County Flood Control and Water Conservation District.

There are also several other programs underway to explore and encourage groundwater recharge opportunities.

This includes: A recent study conducted by scientists with University of California, Davis and the University of California Cooperative Extension, where they investigated the value deliberate winter flooding of fields during rainy years would have in recharging groundwater in California.

According to the study, “flooding agricultural land during fallow or dormant periods has the potential to increase groundwater recharge substantially.

The study identified 3.6 million acres of agricultural land statewide as having Excellent or Good potential for ground-

water recharge. The index provides preliminary guidance about the locations where groundwater recharge on agricultural land is likely to be feasible.

A variety of institutional, infrastructure and other issues must also be addressed before this practice can be implemented widely.” http://californiaagriculture. ucanr.edu/landingpage.cfm?article=ca. v069n02p75&fulltext=yes.

A recent study by RMC that “evaluates the potential benefits of recharging groundwater through flooding of agricultural lands using excess winter river flows, focuses on a portion of the east side of the San Joaquin Valley in Merced, Madera, and Fresno counties.” http://waterfoundation.net/wp-content/ uploads/2015/09/Creating%20an%20 Opportunity%20On%20Farm%20Recharge%20Summary%20Report%20 (00306326xA1C15).pdf.

The Almond Board of California is working with Sustainable Conservation to work with San Joaquin Valley farmers to accept flood flows from storms to help replenish groundwater, California’s underground “savings account,” for dry seasons. See: http://plantingseedsblog. cdfa.ca.gov/wordpress/?p=9570.

Water resources managers throughout the state have and will continue to explore various ways to recharge groundwater and conjunctively manage water in this manner.

Conclusion Sustainable groundwater management is and will be hard work and require new levels of collaboration. The passage of SGMA now provides an opportunity for local leaders to come together to develop plans and implementation strategies that will help advance sustainable water management in California. In places where sustainable local groundwater management does not emerge, there will be regulatory (i.e., SWRCB action) or judicial (adjudication) actions leading to sustainable groundwater management.

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Blueberries

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Photo Credit: Mark Gaskell

Organic Blueberry Production Nutrient Management Requirements in Mild-Winter Areas of California Mark Gaskell Farm Advisor , University of California Cooperative Extension, San Luis Obispo, CA

T

he expansion of California organic blueberry production area targets growing demand for fresh organic fruit all over the US. Early and out of season blueberry markets tend to maintain higher prices and organic fruit often receives an additional price premium. Organic blueberry production also requires specialized management — and often higher costs — primarily associated with challenges for efficient nutrient management and higher costs for weed control.

Fresh blueberry acreage and production has increased annually in California since the late 1990s. Prior to 2000, California was not known as a fresh blueberry production area and California blueberry volumes were not sufficient for USDA to report prior to 2005. Between 2010 and 2015, California blueberry market volume increased 250% to nearly 9 million trays and California had become the leading fresh blueberry shipping point of all domestic or import sources (US Berry Report, USDA Market News Service). The percentage of US fresh produce consumption that is organic, increased from 5% in 2010 to 8.4% in 2015 (The Packer 5/2/16) and organic blueberries are typical of that trend.

Soil and Climate Conditions Dictate Critical Blueberry Cultural Practices In mild areas of California, there is relatively low chill hour accumulation, but earlier blueberry production. Specific blueberry types predominate in these areas — typically Southern Highbush (SHB) cultivars or rarely, Rabbiteye cultivars (RE). More traditional blueberry produc-

tion areas in the eastern, northern, and Pacific Northwestern US primarily grow Northern Highbush (NHB) types. The NHB cultivars by nature are larger plants that require more chill hours to fruit and lose their leaves during a dormant winter period. Growing seasons are generally shorter in those areas than milder areas of the southern and western US. Organic fertilization of blueberries has been more thoroughly studied with NHB cultivars in Oregon, Michigan, and New York. These studies are helpful in guiding organic management of SHB cultivars, but the mild-winter conditions of California’s coast present special challenges. Studies with conventional nutrient management of SHB blueberry cultivars from the Southeastern US also provide insight into effective organic fertilization programs.

Some SHB cultivars will begin flowering and fruiting in September and October with little or no chilling hour accumulation.

While these cultivars begin flowering in fall of the prior season, they remain green and active during the cool winters. This is described as the evergreen production system. There may be periods of relatively slow growth in the shorter, cooler days of winter, but plants do not lose their leaves.

If regular banded applications or pre-plant broadcast nutrient applications were made the prior season, little or no fertilization may be required during this wetter winter period from November to February—especially in higher organic matter soils (> 3%).

The SHB plants in the evergreen system, are pruned in mid-summer following harvest as opposed to winter pruning of dormant plants with the NHB cultivars.

California blueberry growing areas are predominated by soils with higher pH than traditional blueberry production regions— pH 7-8 as opposed to pH 4.5 to 6.5—and the California blueberries require careful

July/August 2016

Continued on Page 18 www.progressivecrop.com

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Page 27

attention to soil and water acidification to maintain productivity. Organic blueberry cultivation generally in California requires applications of acidification agents to soils and irrigation water. These are typically sulfur, or weak organic acids approved by the National Organic Program (NOP). There are approved granular sulfur materials for soil application and approved organic acids—primarily citric and acetic acid—for maintenance of low pH in irrigation water.

The use of sulfur burners is also approved for acidifying irrigation water and may be the most cost effective and efficient option for organic blueberry production. Occasionally, foliar or fertigated minor elements may be used to correct short-term minor element deficiencies (e.g. iron, zinc, etc.) resulting from higher soil or water pH. Major and Minor Nutrients Organic production systems place an emphasis on turnover of nutrients from soil organic matter (SOM), and the related cultural practices for enhancing SOM combined with nutrient applications can supply most major and minor elements with the exception of nitrogen. These practices in effect raise overall background soil levels to medium to high levels, and with periodic soil tests for these levels, they can be maintained via banded applications. Soil levels of most major and minor elements can be managed with timely soil testing and broadcast or banded incorporation of NOP-compliant nutrient sources such as compost and various other potential nutrient sources.

Nitrogen (N) is an exception however, because of dynamic cycling of N during SOM turnover the importance of matching N availability with plant demand and movement of soluble N out of the root zone. Nitrogen is often the most critical element limiting crop growth and matching plant N demand with N availability is the most difficult challenge with efficient organic blueberry production. Blueberries show some preference for ammonium forms of N and ammonium is relatively plentiful at the lower soil pH preferred by blueberries. Nitrate-N however, is the most common and abundant form of nutrient N in most field soil situations. Studies in Florida with SHB blueberries—comparing Ammonium-N and Nitrate-N sources— confirmed a preference for Ammonium-N, but concluded that overall vegetative Page 18

Progressive Crop Consultant

Fertilizer solutions used for conventional fertigation are soluble and more uniform compared to most liquid organic fertilizers.

growth was not limited by N form. The most important benefit of efficient N management for blueberries is the development of a large, vigorous vegetative plant on which to hang berries.

Nutrient Management Requirements of Organic Blueberries Seasonal needs for N can vary considerably for blueberries. Highest NHB blueberry yields were observed with approximately 100 lb. N per acre per season in recent studies in Oregon, and those studies also showed benefits to low, stable nutrient applications throughout the season. In mild production areas of California, the SHB plants in the evergreen system are growing over a longer season, and the overall nutrient requirements may exceed those of traditional NHB production areas. In established California evergreen plantings, after the first 6-12 months, blueberries will respond to regular N applications from spring into late fall. In these areas, a seasonal N requirement of 180-220 lb. of N per acre, per season, is more typical. Wood waste is often incorporated to improve soils for blueberry plantings, and there may be a need to compensate for additional immobilization of applied N by the decaying wood waste with application of additional periodic or pre-plant N. Synchrony of Plant Uptake and Nutrient Availability Plants have relatively slow nutrient uptake initially as new plants become established, but root systems are small and unable to explore large soil volume. The

July/August 2016

blueberry root system is relatively shallow and fibrous, so needed nutrients should be concentrated in upper part of soil profile (2”-10”), near the developing plant, and in contact with moist soil to speed decomposition and mineralization of N. Pre-plant applications of compost can provide uniform amounts of balanced nutrients for overall soil improvement. Nutrient placement is critical for small plants however, and a balanced source of pelleted or granular organic fertilizer should be added and mixed into the hole at planting.

Pre-plant incorporation of organic nutrient sources such as compost at very high rates may also contribute to net losses of soluble nutrients such as Nitrate-N during periods of slower uptake and higher rainfall typical of California winters. Thus, soil nutrient and organic matter building programs for the first 12-24 months, should rely partly on periodic application of banded and incorporated compost and/or granular NOP-compliant materials. Calculate rates of application based on the percent N in the material—adjusting for moisture content—and do not exceed overall monthly application of 30-50 lb. N per acre to avoid loss of soluble N. As plants become established and new growth flushes emerge, N need increases rapidly and periodic applications N is important to match N demand. Low chill SHB blueberries typically are growing year around in the evergreen system that typifies mild-winter areas. Plants need continual nutrition and water but those needs Continued on Page 20

Photo Credit: Mark Gaskell

Continued from Page 15

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Continued from Page 18 change. In the second year and beyond, blueberries may require 5-8 lb. N per acre per week during the periods of most active vegetative growth from mid-February to early November. Lower N rates can be applied in situations with high organic matter soils or added N in irrigation water.

acre inch of irrigation water applied, so it would not be unusual for a blueberry planting to be receiving 1-4 lb. N per acre week via irrigation water alone. Irrigation water should be analyzed and N credits given for any N present.

Recent continuing drought conditions in California have affected many fruit crops including blueberries when salinity and chloride and/or sodium levels rise because of lower than normal winter rains to wash salts from the root zone. These problems have affected fertilization regimes generally and more attention should be directed toward management of soil salinity in addition to maintaining adequate nutrition in the root zone. Drip irrigation performs better than micro-sprinklers in Florida studies, but salt accumulation can occur at the edge of wetting zones in more arid areas like California. Granular N fertilizer can also increase soil salinity over fertigation and aggravate salinity problems.

Uncertain and diminishing water supplies and marginal irrigation water quality also add to challenges for efficient management.

Additional leaching irrigations are needed to flush the root zone to control salinity and potentially harmful ions such as sodium Photo Credit: Mark Gaskell

Sources of Nutrients for Organic Blueberries Heavier textured and higher organic matter soils have higher reserves of nutrients and more capacity for cycling of nutrients, while sandier soils require more frequent and continuous nutrients supplied from fertilization. Different soil areas on the farm can require different management strategies. Pre-plant application of organic matter and compost can bring overall levels up to optimum and recurrent application can be used to maintain a balance of nutrients from cycling organic matter—particularly in sandy soils. Band or strip incorporation of granular materials can be more reliable and in some cases more efficient then fertigation. These granular fertilizers must be applied near the root zone and

covered with moist soil to accelerate microbial decomposition. Organic wood waste mulches are often used with blueberry plantings to encourage high organic matter levels around superficial blueberry root systems, and this favors efficient cycling of nutrients in this root zone.

If soil N and moisture are sufficient, the SHB blueberries normally respond to post-harvest pruning in June with vigorous vegetative growth and development of large new canes. This new vegetative growth is key to the plant’s productivity during the following harvest cycle. Ideally, large new, thick canes and branches will set the stage for high yields of relatively large fruit.

Higher numbers of larger fruit are set on larger canes emerging from the base and from larger branches from pruned canes.

This development will occur between pruning and November in mild areas of California, and N encourages larger and more canes if moisture is adequate.

Another potential source of N is irrigation water. Nitrogen is common in irrigation water in many California blueberry production areas, and 10-20 ppm of Nitrate-N is not uncommon. These amounts would contribute 2-4 lb. N per

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During this period is occurring a second peak of root growth or root flush.

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Preplant incorporation of compost and other organic nutrient sources can build overall soil organic matter and nutrient availability but periodic additions of organic matter are also important.

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Progressive Crop Consultant

July/August 2016

Photo Credit: Mark Gaskell

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559-564-1236 and chloride among others. This challenges N management related to soluble N forms like Nitrate-N from N cycling and the potential for losses of this N in the leaching process.

Limits of Organic Fertigation Fertigation is widely used by growers of both conventional and organic fruits and vegetables as a means to manage fertilization efficiently. Regular fertigation of blueberries has been shown to be more productive compared to granular fertilization in recent Florida studies with conventional fertilizer sources. Fertigation with NOP-compliant organic fertilizers, however, can be a relatively inefficient process.

Conventional fertigation materials, for the most part, utilize soluble fertilizer sources, but this is not usually the case with organic fertilizers because completely soluble NOP-approved organic materials are very limited. Chilean nitrate (CN) is soluble for example, but CN is limited to no more than 20 percent of total N application for compliance with the NOP. Some studies and grower experience have identified potential problems with NOP-approved fertigation materials related to their uncertainty in

micro irrigation systems.

Irrigation engineers are calling attention to the potential for “bacterial slimes” forming from fertigation with organic nutrient sources and the potential for plugging and loss of nutrients behind irrigation filters or emitters. These problems can contribute also to variable irrigation system distribution uniformity (DU) and undue plant stress due to moisture and/or nutrient deficiency. Growers have noted shortened intervals between filter cleanings and have occasionally responded by eliminating the filtering during fertigation, which can be devastating to irrigation system DUs. It is important that micro irrigation systems be maintained for use with fertigation regardless of the material. And irrigation systems require acidification as maintenance also to avoid build-up of precipitates.

There are NOP-approved materials for acidification—usually weak acids—and chlorine, and other materials may also be used for control of algae and bacteria in the lines. Carefully verify limits on chlorine concentrations for irrigation systems to remain compliant with NOP restrictions.

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systems, it is especially important to use a filter, clean the filter and the lines often, and use NOP-compliant materials with a high percentage of N in soluble form.

NOP-approved fertigation materials from organic byproducts that have undergone varying rates of fermentation and other organic transformation are sometimes stabilized with the addition of acids. These materials may have acid pH reaction that also makes them desirable for blueberry production. These materials may nevertheless, have elevated levels of salt, chloride, sodium, or other ions that may aggravate soil salinity, and ion toxicities, and compromised water quality exacerbated by extended drought conditions in California.

Blueberry growth, development and fruiting have clearly defined patterns in mild-winter areas of California. Efficient fertilization and nutrient management programs for organic blueberry production can be built upon a basic understanding of organic matter cycling in soils, different alterative NOP-compliant cultural practices, and the special nutrient requirements of PCC blueberries.

July/August 2016

www.progressivecrop.com

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Photo Credit: Timothy Blank

Rice

Weedy Red Rice Update Weedy Red Rice Rivals Watergrass as being the Worst Weed in Rice Production Worldwide

Timothy Blank Certified Seed Program Representative, California Crop Improvement Association

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n the southern rice growing states, where weedy rice is widespread, high infestations have resulted in yield reductions of over 60%. A 2008 survey in Arkansas, which has the largest area of rice production in the U.S., found that 62% of rice fields were infested to some degree. Fortunately, California growers have had little opportunity to personally experience this weed on their own land, primarily due to isolation from affected rice growing regions, careful import protocol for new varieties and breeding material, and largescale use of certified seed. Over the past 100 years of rice production in California, there have been periodic infestations. Most of these populations were eradicated or taken out of rice production.

After the discovery of six new weedy rice populations in 2003, an effort was made to eradicate these populations.

While these efforts bore some success, not only has one of these populations not been eradicated, several new populations have since been discovered.

With the known economic harm this pest can have on the industry at large, it is important that growers report infestations to their farm advisor or county Agricultural Commissioner’s office. Early infestations are often confused with watergrass, specialty rice varieties, or bakanae. While there is abundant phe-

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notypic diversity of weedy populations in the United States, three characteristics that are consistent across weedy U.S. rice populations are: 1) red colored bran, 2) shattering, and 3) seed dormancy. It is the long seed dormancy, in some cases remaining viable in the soil for over 10 years, which makes weedy rice control a persistent, long-term effort. Weedy rice can be distinguished from most conventional rice varieties in that it has lighter green leaves, rougher leaves, a wider canopy, and is taller.

Best Management Practices (BMPs) have been updated and can be viewed on the UC-ANR website, http://rice.ucanr. edu/files/240623.pdf. The BMPs outline proper equipment cleanout, roguing, harvest scheduling, burning of straw, avoiding tillage and straw incorporation to prevent incorporation of weedy rice into soil, and fallowing/irrigating/spraying. Other techniques to help reduce weedy populations include planting to a stale seed bed, using high seedling rates to increase competition with weedy rice, water seeding, and maintaining a continuous flood. The ‘stale seed bed method’ is a technique to reduce weeds on the soil surface prior to planting by irrigating, germinating weed seeds, spraying a broad-spectrum herbicide, flooding, and then planting.

The Weedy Red Rice Task Force has been reestablished to determine the most effective path to form a collaborative effort to eradicate weedy rice. This taskforce includes representatives from

July/August 2016

the Butte and Glenn Agricultural Commissioner offices, University of California Cooperative Extension, University of California - Davis, California Rice Commission, Rice Experiment Station, Rice Research Board, and California Crop Improvement Association.

During the 2016 growing season, the Task Force would like growers or PCA’s to notify their county agricultural commissioner office or local UC Farm Advisor if they suspect their fields may have weedy red rice. Plant samples will be taken and compared with samples of other populations. At least two genetically distinct populations are present in California. Plans are in place to publish images of different biotypes to aid growers and PCA’s while they scout fields.

For the vast majority of growers who do not have weedy red rice on their farms, the two best ways to stay uncontaminated is to 1) plant only certified seed, and 2) clean equipment coming from offfarm locations, and especially clean used equipment purchased from the southern rice growing regions.

The California rice industry is still at a stage where this weed can be eradicated. The Weedy Red Rice Task Force believes this effort will best be achieved when growers and PCA’s work voluntarily and cooperatively with their local UC Farm Advisor and county Agricultural PCC Commissioners office.

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Almonds

Post Harvest Nutrition in Almonds Cecilia Parsons Contributing Writer

C

rop yields, leaf tissue analysis and timing are all factors in determining a successful strategy for providing post harvest nutrition to almond trees.

University researchers and crop care managers agree that fall can be an excellent time to apply certain nutrients in almond orchards, but actual benefits to tree health and the bottom line depend on calculating exactly what trees need and timely delivery of nutrients.

“The fundamentals remain the same,” said University of California farm advisor Roger Duncan of post harvest nutrition. Rather than applying a set amount of fertilizer each year, he stresses a July leaf tissue analysis and a hull testing for boron at harvest to determine the nutritional status of an orchard and a plan for delivering the nutrients at a time and place where they will be taken up by the tree. Knowing the levels of nutrients in the trees helps growers avoid over application of nitrogen and delivering sufficient levels of other nutrients. Annual leaf sampling aids in adjusting nutrition programs.

The four materials that are most commonly used in post harvest almond nutrition applications are zinc, boron, nitrogen and potassium.

In Stanislaus County, boron is often deficient in almonds east of the San Joaquin River but can reach toxic levels on the west side, Duncan reports. Boron does not accumulate in almond leaves, so hull samples are the best indicator of boron status. If hulls have less than 80 ppm trees are deficient and yields may suffer, Duncan warned. This nutrient is commonly applied in the fall as a foliar spray as long as trees retain functioning leaves. Two pounds of a 20% product per 100 gallons water is a typical rate.

Fall applied boron will be remobilized in the spring and benefit development of healthy flower parts, particularly pollen tubules. Boron also aids in the translocation of calcium.

Duncan said boron is best applied to the soil in the spring, as fall sprays do Page 24

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not have enough boron to correct an overall boron deficiency. Boron applied to the soil in the fall is subject to winter leaching. The fall foliar application acts to temporarily replenish boron levels in the dormant fruit bud.

Rapidly growing young trees or trees planted in alkaline soils are prone to zinc deficiency, especially on Nemaguard rootstock. Symptoms are most noticeable in the spring with delayed opening of flower buds, smaller leaves with chlorotic areas between the veins and a wavy leaf margin. The most cost effective method for delivering zinc is a fall application of zinc sulfate, Duncan said. Some growers prefer to apply more expensive, less phytotoxic formualtions of zinc in the spring when it can be tank mixed with fungicides or other materials.

Crop advisor Justin Nay said zinc sulfate also helps with disease management and helps prevent tree blow over from fall rains. Nay said that in many orchards gypsum and compost are also applied in the fall before winter rains.

Leaf analysis is also important in tracking potassium levels. A research trial cited by Duncan showed that almond yields decline when potassium levels are less than about 1.4 percent in July-sampled leaves. Yields decline in potassium deficient trees because fruiting spurs die prematurely.

Duncan advises shooting for potassium levels higher than 1.4 percent because dropping below that threshold will put trees in a deficit for next year, setting the stage for lower yields. With an average reading of 1.4 percent, some trees will need more and some less, but wasting some fertilizer will ensure sufficient amounts of this nutrient across the entire orchard.

Potassium applications can be made with sulfate of potash or potassium chloride. It can be banded on the soil in the fall in flood, solid set or microsprinkler irrigated orchards. In orchards that are drip irrigated, this nutrient can be injected.

The amount of nitrogen applied post harvest depends on yield, said University of California researcher and plant science

July/August 2016

professor Patrick Brown. If a tree is still growing and soil moisture is adequate, it will take up nutrients through the roots.

If a tree is stressed for water, it has been more than a month since harvest or the tree is flush with nutrients, it will take up less. Soil or foliar application of nutrients will give trees a small boost in the fall if conditions are right, Brown said.

Crop yield and tissue analysis will show the amount of nitrogen that has been removed at harvest. A tendency to apply the same amount of nitrogen each year post-harvest can lead to over or under application. Brown said with higher yields there is a greater chance of higher uptake of nutrients — and less chance of over — application of nitrogen.

To avoid leaching of nitrogen, Duncan said that only 10-20 percent of annual nitrogen needs should be applied post-harvest. Timing is an important consideration in nitrogen applications. October may be too late for significant uptake, Duncan said. Trees that are losing their canopy will not be efficient in uptake.

Soil type can play a part in uptake of nutrients. In sandier soils, nitrogen may leach below the root zone. Some growers may consider a fall foliar spray of lo-biuret urea instead of a traditional ground application.

Type of irrigation can play a part in efficient use of nutrients. If an orchard is flood irrigated and is not scheduled to receive water for more than a month post harvest, the trees will not be able to take up soil-applied nutrients. Drip or micro sprinkler systems allow for better uptake by keeping the soil profile filled.

The post harvest nutrition picture is fairly similar from northern to southern almond growing regions, Brown said, but in the south, the sooner after harvest is best. Once signs of defoliation appear there will be little uptake of nutrients.

With early harvested varieties like Nonpareil and Independence, growers or managers have about a month after harvest is completed to apply their post harvest nutrients. Trees that are actively growing and healthy will make the best PCC use of applied nutrients.

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Page 23

Vineyards

Potassium Deficiency in Vineyards Stephen Vasquez Research Agronomist – West of the Rockies Tessenderlo Kerley, Inc. Crop Vitality

T

he past four years have been challenging for California grape growers with persistent drought. In 2015, vineyards were displaying a variety of foliar and fruit symptoms as a result of insufficient water, poor water quality, high soil salts, pests and diseases as well as many other abiotic and biotic causes. Although El Nino brought more precipitation to the state in 2016, unusual foliar symptoms continue to be expressed this season, including potassium deficiency symptoms and some that resemble potassium deficiency. It’s important to properly identify foliar symptoms so solutions can be implemented as soon as possible.

Potassium deficiencies, when properly identified using visual and lab analysis can be corrected in-season, allowing fruit to mature properly.

Role of Potassium in Grapevine Health Potassium has many roles in maintaining plant health. Taken up Page 26

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by plants as K+, an important role is its activation of at least 60 enzymatic events within grape plants. Potassium “activates” enzymes by changing their shape, which then initiates one or more metabolic activities important for grapevine health. For example, the uptake of other macro and micro nutrients are dependent on potassium for their movement into the plant and final incorporation into proteins, sugars and cell structure by way of enzymes initially activated by potassium.

Another important potassium role is the translocation of sugars made in the leaves during photosynthesis to maturing berries. Without adequate potassium, the energy needed to transport sugars decreases, resulting in a surplus of sugars in the leaves and a reduction in photosynthesis. Potassium also has a role in water management within the plant by controlling the opening and closing of stomata guard cells found on the underside of leaves; allowing the diffusion of water vapor out of and carbon dioxide into the leaf. Under drought conditions, grapevines with sufficient K+ will close

July/August 2016

stomata, reducing water vapor loss, carbon dioxide passage into the plant and photosynthesis. However, when water and potassium are abundant, the making of sugars becomes an efficient process.

Some Essential Functions of Potassium Include: • Activation of enzymes • Regulation of stomata opening and closing • Regulation of phototropism (tracking of light) • Production and translocation of proteins and sugars • Maintenance of cellular pH and electrical charge • Promotion of root growth • Uptake of other elements • Winter hardiness • Pest and disease resistance Potassium Deficiency Symptoms and Causes Potassium is a mobile element, which allows the plant to move K+ Continued on Page 28

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Continued from Page 26

Additionally, vineyard sites that were leveled to make use of flood or furrow irrigation may show deficiencies in the areas where the top soil was removed to fill-in low lying areas. This is often the case at vineyard sites developed prior to drip irrigation, which now makes fertigation much easier on sites with uneven ground.

Absolute Deficiency When potassium is absent or inadequate amounts exist in the soil profile to support a crop, deficiency symptoms will appear early and persist throughout the season. Such cases arise when potassium is mined season after season without replenishing the soil profile with the minimum amount of potassium removed with the crop.

On average, between 6-13 lbs. K 2O is removed with each ton of grapes that needs to be replaced each season. In general, vineyards planted to sandy soils with low cation exchange capacity will display potassium deficiency much sooner than those planted to a clay soil. However, soil texture is not a definitive indicator as to the amount and availability of potassium. Some soils will “fix” potassium, making it unavailable to the vines, even when soil lab analysis indicates it exists in the root zone. Therefore, potassium fertilization programs should take into account a soil’s ability to fix potassium as well as past cropping history and occurrence of potassium deficiency.

Induced Deficiency When soil has adequate potassium and is not being fixed, other factors may impact uptake. Soil pests, like nematodes and phylloxera (Figure 3) can cause considerable root damage, influencing root growth and nutrient and water uptake. Vineyards planted to their own roots often suffer the most damage since they have little to no tolerance to soil pest feeding.

The selection of a proper rootstock with resistance to nematodes and/or phylloxera can minimize root damage.

However, there isn’t a single rootstock that has all the characteristics for all vineyard sites. Table 1 shows how some rootstocks might perform when planted to different soil conditions. Freedom and 1103P are popular rootstocks used for raisin, table and wine grape production. Freedom has relatively good resistance to nematodes but poor resistance to phylloxera, while pest resistance is reversed for 1103P. Differences can also be found with respect to nutrient uptake amongst rootstocks. Freedom is better at foraging for potassium when compared to 1103P. However, in the presence of nematodes, Freedom will probably be the best choice and can be supplemented with liquid potassium injected into the drip irrigation

Figure 2. “False potassium deficiency” (spring fever) resulting from cool spring weather.

Figure 3. Root damage from nematodes limits water and nutrient uptake.

Photo Credit: Stephen Vasquez

from locations of low demand (older, shaded leaves) to high demand sites, such as maturing grape bunches.

When soil potassium is inadequate, grapevine foliage becomes the potassium source for new leaves and clusters.

Foliar symptoms begin to appear in late spring or early summer on mature leaves by displaying a light yellow (white varieties) or red (red varieties) hue along the leaf blade and fading green color between veins under mild deficiencies. A more pronounced deep yellowing (chlorosis) or reddening between veins as well as leaf curling and leaf blade necrosis signals a more significant potassium deficiency.

In addition to older leaves showing symptoms, a transition between veins from green to yellow in young leaves indicates severe potassium deficiency, which often begins at bloom/berry set and worsens as harvest approaches. By harvest, potassium deficient grapevines will have low yields, reduced fruit quality and low vigor with significant leaf drop, exposing fruit that will raisin (Figure 1).

Identifying potassium deficiency solely by grapevine canopy visual observations can be tricky, given that foliar symptoms can be confused with other maladies. One common disorder known as “spring fever” or “false potassium deficiency” is caused by the vines inability to metabolize nitrogen during cool spring weather; resulting in high levels of ammonium and the amino acid putrescine (Figure 2). Lab tissue analysis is the best method for correlating symptoms with either spring fever or a true potassium defi-

ciency. Grapevines expressing spring fever symptoms will not be deficient in potassium when lab tissue analysis is used for confirmation. Bloom time petiole levels should be greater than 1.5% potassium to properly mature a crop (Table 2).

Additional foliar symptoms often confused with potassium deficiency are water stress, other nutrient deficiencies that may initially resemble potassium deficiency (i.e. Mg), pest, disease (i.e. Pierce’s disease), and herbicide damage, as well as others.

Figure 1. Potassium deficient grapevines displaying significant leaf drop and dried fruit.

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Table 1. Rootstock characteristics under different soil situations. Adapted from Rootstock Selection 2003, L. Peter Christensen, in Wine Grape Varieties in California. *Represents root knot/dagger nematodes.

Resistance Rootstock

Phylloxera

*Nematode

Tolerance Drought

Wet Soil

Influence on Scion Salinity

Vigor

Mineral Nutrition

Soil Adaptation Performs well in moist, clay soils

5C

high

med/low

low

low/med

med

low/med

N:low P,K:med Mg:med/high Zn:low/med

420A

high

med/low

med

low/med

low

low

N,P,K:low Mg:med Zn:low/med

Performs well in fine-textured, fertile soils

1103P

High

med/low

med/high

med/high

med

med/high

N:med/high P,Mg:high K,Zn:low/med

Performs well in drought and saline soils

3309C

High

low/low

low/med

low/med

low/med

low/med

N: low/med P,Ca:low K,Mg,Zn:med

Performs well in deep soils Performs well in sandy loams to loamy sand soils Performs well in sandy to sandy loam soils

Harmony

low/med

med/med-high

low/med

low

Low/med

med/high

N:low P: med K:high Zn:low/med

Freedom

low/med

high/high

med

low

low/med

high

N,P,K:high Mg:med Zn,Mn:low

Table 2. Laboratory potassium analysis values for grape petioles at bloom and veraison. Adapted from L. Peter Christensen, 2005. *80-100 petioles should be collected at bloom (≈60-70% cap fall) opposite a cluster and veraison (≈50% berry softening). Postharvest K levels have not been determined but should increase to > 0.8 once fruit has been harvested. **No values have been set for excessive or toxic levels of potassium.

Tissue*

Deficient

Adequate

Excessive**

Bloom K (Total) %

1.0

1.5

n/a

Veraison K (Total)%

0.5

0.8

n/a

system.

Low soil moisture, elevated levels of other cations (i.e. sodium, magnesium, etc.) and sometimes soil pest root feeding can be overcome by applying water more frequently and employing fertigation (aka fertilizer irrigation injections) management strategies.

Soil and Tissue Analysis Soil analysis is not generally the best tool for determining grapevine potassium need for an established vineyard. Soil texture (sand, silt, clay and organic matter) and its overall characteristics can have varying effects on potassium availability and uptake. As previously mentioned, soils

that test “high” for potassium, may also “fix” potassium; making it unavailable. However, general soil analysis prior to vineyard establishment can be valuable. The best information obtained from a lab soil analysis includes problems related to chemical imbalances or excesses. Problems such as pH (alkalinity and acidity), high salts, cation imbalances (Mg:Ca:K), and high boron levels can be identified through soil analysis prior to vineyard establishment, cautioning a grower as to the need for correction pre- or post-planting. Previous crop history and practices—like deep ripping— will dictate how a particular soil and grapevine cultivar responds to current

farming operations, including fertilizer and soil amendments.

Another useful and free tool is the National Resources Conservation Service (NRCS) Soil Web Survey, which gives general information about a site without digging a hole. The Soil Web Survey contains nationwide soil information for all 50 states and can be found here: http://websoilsurvey. sc.egov.usda.gov/App/HomePage.htm.

Your local NRCS and/or UC Cooperative Extension advisor can help access and interpret the Soil Web Survey results.

Since only general information is

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will help mature the crop

Continued from Page 29 available about a given site, a detailed soil analysis should be completed by a local lab or consultant prior to planting. Some factors to consider when soil sampling a mature vineyard or open ground (or site previously planted) are: age, variety, rootstock(s), soil pests, soil characteristic and other unique factors that will help you make fertilizer decisions. In a mature vineyard, areas that are displaying potassium deficiency should be sampled separately from areas with normal growth so differences and nutritional needs can be identified.

Tissue analysis is a better predictor of plant potassium need. Sampling should be done at phenological stages (i.e. bloom, veraison and harvest) so comparisons can be made between seasons. Pulling tissue samples from a uniform vineyard planted to a single variety and rootstock is easy.

Conversely, a vineyard planted to a single variety grafted onto different rootstocks, on different soils will need multiple collections of petioles representing the differences in order to make good management decisions.

Tissue samples can be pulled by you, a PCA/CCA or lab technician. It’s important to keep in mind that pulling samples from the same location within the vineyard will give the best results over seasons. Doing so will provide historical data that will help better manage the vineyard site.

General Tissue Sample Protocol • Pull bloom (60-70% cap fall) petioles from mature, non-shaded leaves opposite basal clusters • Collect approximately 80-100 petioles • Wash (removing dirt and foliar nutrients) and dry petioles and deliver to a lab • Have analysis completed for macro- and micronutrients and salts of interest • Interpret results, comparing data with past seasons so management decisions can be made • Potassium levels should be at or above 1.5% at bloom.

• Make potassium corrections by injecting liquid potassium into the irrigation system at intervals that Page 30

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Growers who use tissue analysis to monitor for fluctuations in nutrient status in coordination with soil and water analysis will maximize its benefit. Locations within a vineyard that have been characterized for differences should be mapped and evaluated season after season. By understanding the variability in the vineyard, fertilizer applications can be applied as needed, which could be more cost effective than simply applying the same fertilizer regime to the entire vineyard (Table 2, Page 29).

Fertilizer Management Once lab analysis has identified a nutrient need such as potassium, a grower or PCA/CCA must make a choice in the type of fertilizer product that will be used. In the case of potassium, growers can use dry or liquid formulations to supply a vineyard.

A decision on the type of fertilizer product often depends on the style of irrigation system that’s installed.

Vineyards irrigated using flood or furrow irrigation are best suited for dry fertilizers that can be banded in-furrow, close to the root zone and watered in. Although this method of applying fertilizer has been used for decades, it is not very efficient. Depending on the soil type and severity of the deficiency a typical, flood irrigated vineyard will not respond quickly enough to correct a deficiency once fruit begins developing; when demand is at its highest. Additionally, soil issues, perched water tables, high crop loads, pests and diseases and other issues that restrict potassium uptake, will make it difficult for grapevines to recover.

Mature or newly established vineyards irrigated with drip or micro sprinklers have a few more options.

Solubilizing dry fertilizers can be done but have added costs in labor that’s needed to maintain fertilizer in solution so emitters don’t plug. Products like potassium chloride dissolve easily and can be injected through drip irrigation but add chloride to the soil profile, which grapes can be sensitive to. Additional products like potassium sulfate or potassium nitrate add significant costs in handling,

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mixing and the addition of nitrogen during fruit development.

Manufactured liquid products are better suited for vineyards using drip or micro sprinkler irrigation systems.

Products like potassium thiosulfate (KTS ®) are easily injected into irrigation lines as standalone products or blended with other liquid fertilizers.

Liquid fertilizers allow the option of applying small amounts over an entire season, maximizing grapevine uptake because potassium is available in the root zone. As western states continue to deal with drought conditions and water becomes more limited, growers and PCA/CCA’s will find that fertigation with the right liquid fertilizer is a practice that will maximize yields and PCC profits.

References Adams, D.O., Franke, K.E. and Christensen, L.P. 1990. Elevated putrescine levels in grapevine leaves that display symptoms of potassium deficiency. Am. J. Enol. Vitic.

41:121-125. Print.

Bettiga, L. J, et al. In: Bettiga, L. J. (ed), Grape Pest Management, 3rd ed. Oakland: University of California Division of Agriculture and Natural Resources, 2002. Publication 3343, 29-45. Print.

Fidelibus, M. and Vasquez, S. 2012. Spring Fever. http://ucanr.edu/blogs/blogcore/ postdetail.cfm?postnum=7244. San Joaquin Valley Viticulture-California Viticulture Information. Web. Ludwick, A. E. et al. Western Fertilizer Handbook, 9th ed. Danville: Interstate Publishers, Inc. 1995. Print.

Nutri-Facts: Agronomic fact sheets on nutrients-Potassium, No.3. www.ipni.net/ nutrifacts. International Plant Nutrition Institute. Web. Pettygrove, S. et al. Potassium Fixation and Its Significance for California Crop Production. Better Crops Vol. 95:4 (2011). Web. Tindall, T. A. and Musso, G. 2015. Using Fluid Fertilizers In Drip Irrigation. The Fluid Journal. 23:6-8. Web.