Ground Truths Uncovered Managing groundcover for erosion control and productive pastures
Acknowledgements This publication was originally written by Mike Lloyd from Red Frog Environmental Solutions for the Border Rivers-Gwydir Catchment Management Authority, in partnership with the Department of Primary Industries (Bob McGufficke and Jeff Lowein) and GWYMAC Landcare. This revised edition has used the original material produced in 2005 as well as the input from staff of the Border Rivers-Gwydir Catchment Management Authority (Bruce Gardiner, Nicole Gammie, Stephen McLane, Kelly Coleman, Liz Blair, Alan Ede and Annabelle Monie). Cover Photos: A. Sendall, L. McKinley and J. Easey Design and Layout: K. Coleman Printer:
Greenridge Press www.greenridgepress.com.au
Š 2011 Border Rivers-Gwydir Catchment Management Authority ISBN: 978-0-9804706-7-3 Citation: Border Rivers-Gwydir Catchment Management Authority (2011). Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures. Border Rivers-Gwydir Catchment Management Authority, NSW. Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Contents Groundcover • 1 Groundcover and effective rainfall • 4 Good groundcover improves soil health • 8 Assessing groundcover is quick and easy • 11 Dense groundcover increases production • 15 Management for improving groundcover • 19 Groundcover maintenance is vital for drought management • 21 Pasture management & groundcover in a changing climate • 24 Paddock not performing? • 27 Identifying the most limiting factor • 33 References and further reading • 35
Border Rivers-Gwydir Catchment Management Authority
Groundcover What is groundcover?
Border Rivers and Gwydir catchments
‘Groundcover’ is the term used to describe any material occurring on or near the ground surface that provides cover to an otherwise bare soil. It is essentially everything that is not bare ground. On a catchment scale it is most common in the form of pasture and crops, as well as dead plant material and leaf litter.
The Border Rivers and Gwydir catchments cover an area of 50,000 km2 in northern NSW (see map on the following page). The catchments are home to a complex diversity of plants, birds, animals, soils, land use and communities.
Why is groundcover so important? Good groundcover is the most effective way to maximise water infiltration, as it minimises rainfall runoff and erosion. Adequate groundcover provides environmental benefits when combined with good management of our soils, pasture and stock. It also contributes to optimum returns and sustainable agricultural production.
Droughts or extended dry periods have been regular occurrences in the region in recent years. These have led to a significant loss of groundcover on many areas within the catchment. This has not only been detrimental to physical and financial production levels of agriculture but to the condition of the catchment as well. Just 1 mm of soil eroded across one hectare of land (with insufficient groundcover) amounts to between 7.5 and 10 tonnes of valuable topsoil lost from agricultural production.
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Map of the Border Rivers-Gwydir Catchment Management Authority Region Boggabilla ! Boomi
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! North !
Star
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Yetman
Mungindi
Bonshaw ! Garah
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Ashford
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Deepwater
Warialda
! !
Delungra !
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Gum Flat
!Nullamanna !
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Inverell
Glen Innes
Bingara ! !
Bellata
Tingha
Edgeroi !
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!
Bundarra
Cobbadah !
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Guyra
Kingstown Uralla
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!
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Emmaville
Moree Gravesend
Gurley
Tenterfield
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Croppa Creek
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!
Border Rivers-Gwydir Catchment Management Authority
How much groundcover is enough?
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The measurement of groundcover is usually expressed as a percentage value. It is the proportion of a given area that is not bare soil.
improved root development and persistence of pasture and crops;
•
improved productivity of pastures by increasing the quantity of pasture available for livestock consumption;
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quicker response of pasture to rainfall following drought due to adequate leaf area available for regeneration;
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reduced weed potential and weed competition;
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decreased potential for, and frequency and severity of soil erosion;
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increased level of organic matter on the soil surface promoting microbial and biological activity and subsequently healthier soil;
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modified soil temperature and reduced ped breakdown and compaction at the soil surface;
The benefits of good groundcover
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improved capacity of the soil to store water and nutrients, which increases water availability during dry spells;
Maintaining good groundcover has a positive impact on both on-farm environmental and economic sustainability and the overall health of the catchment. Benefits include:
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decreased soil and nutrient losses off-farm and reduced deposits in dams, creeks and rivers; and
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improved water quality and reduced incidence of algal blooms within the catchment.
Research indicates that to sustain production and minimise negative environmental impacts, such as soil degradation, land managers should work toward maintaining at least 70% groundcover on their paddocks year round. This figure increases in steeper sloping country or in areas with erodible soil types.
•
reduced rainfall runoff, allowing more moisture to soak into the soil making it available for plant growth;
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Groundcover and effective rainfall The water balance Water is vital for successful agricultural production, as well as for the health of our catchment’s ecosystems. Results of studies undertaken on the north-west slopes of NSW have shown that maintaining groundcover is extremely TRANSPIRATION important for improving the water balance and sustainability of grazing systems. Sound management of groundcover can reduce runoff and increase the effectiveness of rainfall available for plant growth, resulting in the potential for increased productivity. To maximize the potential of rainfall in a grazing system, it is necessary to understand the balance of the water cycle and how it can be manipulated by pasture management (see diagram on right). The rainfall (inputs) we receive is equivalent to the sum of evaporation, transpiration, deep drainage, and runoff (outputs). While we cannot control the rainfall we receive, many of the management decisions made on-farm can influence how that rainfall is utilised through the four outputs of the water balance equation.
Where the water goes...
EVAPORATION (INEFFICIENCY) i.e. bare earth, transpiration, soil nutrients low 15% high >60%
RUNOFF
DEEP DRAINAGE
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
CROPPING
figures are property specific and can be calculated
LEAF LITTER common 2-4% high >10%
4
GRAZING
low 4% common 10% high >15%
common ½ to 1 handful per 30cm² high 6 handfuls per 30cm²
water table
Border Rivers-Gwydir Catchment Management Authority
Evapotranspiration The term ‘evapotranspiration’ refers to the process of water returning to the atmosphere through evaporation (vaporisation of water from soil surfaces) and transpiration (water use by plants that drives plant growth). Evapotranspiration represents about 93% of annual rainfall in the water balance on grazed pastures on the North West Slopes. In a 700 mm rainfall zone with low groundcover pastures, nearly 520 mm can be lost through evaporation from the bare soil surface. This means the pasture may be using only 130 mm of the total rainfall through transpiration for plant growth. This is clearly inefficient use of a valuable commodity that has been in short supply on many properties during the dry spells of recent years. To improve the water use efficiency of their pasture regimes graziers need to convert evaporation into transpiration. Research has shown that by achieving 70% or greater groundcover plus 1,500 to 3,000 kg/ha of plant litter (this equates to 3 to 6 handfuls of groundcover per 30 x 30 cm square) soil evaporation can be reduced by half or up to 1 mm/ day (Murphy and Lodge, 2001). This provides the opportunity for pasture plants to utilise additional stored soil water through transpiration, resulting in higher pasture production as well as improved sustainability.
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Deep drainage
Runoff decreasing rainfall effectiveness
Deep drainage occurs when water in the soil moves through the profile and beyond the reach of plant roots. At this point moisture is lost to the pasture and enters the local or regional groundwater system.
Runoff occurs when the intensity of rainfall is greater than the capacity of the soil to absorb it and water is forced to flow across the ground surface. Surface runoff can represent a significant part of the water balance of grazed pastures and is influenced by a range of rainfall, slope, soil and pasture characteristics.
It is believed that today’s agricultural practices utilise less rainfall than the native vegetation they replaced. This has generally increased deep drainage, led to rising water tables and, in some areas, caused dryland salinity. Excessive levels of salt can either impede plant growth or cause plant to die. Without significant groundcover and root mass in the soil, serious erosion issues can occur. Reducing the current unnaturally high levels of deep drainage would reduce the impact of salinity on our ecosystems and improve catchment health. From a production perspective, there are also benefits to be gained by utilising some of the rainfall that is lost to the pasture system. In both instances an increase in the amount of deep-rooted perennial pasture species will utilise more deep soil moisture for longer periods of growth than annual species. Further, by increasing groundcover, and thus active pasture production, it is possible to use more rainfall, losing less to deep drainage.
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Rainfall across the Border Rivers and Gwydir catchments is summer dominant with high intensity storms often occurring during summer and early autumn. The impact of such rainfall can be exacerbated by low groundcover. In some circumstances, without adequate groundcover, up to a third of the year’s average rainfall and up to 85% of individual storm events can run off our grasslands and into our water courses (Land and McDonald, 2005). Research has indicated that the average groundcover in the pastures of the north-west slopes is typically 40%. In Graph 1 we can see that an increase of groundcover from 40% to the recommended 70% will lead to a 70 mm/year reduction in runoff. Thus, groundcover is very effective at limiting runoff and allowing rainfall to soak into the soil, making it available for further plant growth. Less runoff also results in reduced soil erosion, suspended sediments and less nutrients entering our waterways. This provides higher quality water in those waterways.
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
For instance, in a typical 700 mm/year rainfall area, by increasing groundcover from 40% to 70%, runoff can be reduced by 70 mm/year. If we assume that half of this becomes available for plant growth and evaporation is halved (from 520 to 260 mm/year) by increasing plant litter to sufficient levels, then the output values in our water balance will change significantly. The associated increases in pasture production with this scenario, along with the introduction of deep-rooted perennial species, could also net a further 5 mm/year.
Graph 1: The effect of groundcover on runoff
200
Average annual runoff (mm)
Adapted from Lang & McDonald, 2005
150
100
When we combine these figures the result is a possible extra 300 mm of effective rainfall available for plant growth each year. This represents a huge increase from 18% to 60% of total annual rainfall and a much more efficient use of such a valuable resource.
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0 10
20
30
40
50
60
70
80
90
100
Groundcover (%)
While it is important for some runoff to fill farm dams, runoff also provides stream flows for downstream users and to maintain healthy rivers and aquatic ecosystems. Rainfall effectiveness is the availability of rainfall for plant development and the ability of a plant to utilise it. Based on research undertaken on the north-west slopes, it is possible for graziers to significantly increase the effectiveness of their rainfall.
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Good groundcover improves soil health Soil health
Reducing soil loss
The health of a soil is a reflection of the condition of its physical structure, chemical components, biological life and susceptibility to degradation. The relationship between groundcover and soil health is mutually beneficial. With careful management, good groundcover will improve several aspects of soil health such as the stability, structure, nutrients and biology of the soil. In return, a healthy soil will not only provide the plant with physical support but will absorb and store more moisture, oxygen and nutrients to stimulate further plant growth.
It is estimated that the natural rate of soil formation on the north-west slopes is as low as 0.2-1.5 tonnes/ha annually. However, just 1 mm of soil eroded across one hectare of land with insufficient groundcover amounts to between 7.5 and 10 tonnes of valuable topsoil lost from agricultural production (Lang and MacDonald, 2005).
The result is a healthy soil/ plant ecosystem that drives productive pastures. In addition, it will provide benefits to the environment through greater utilisation of rainfall and nutrients in the paddock, with reduced risk of erosion and excessive nutrient transfer into streams and waterways.
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The average groundcover of pastures on the north-west slopes is estimated to be 40%. It is also noted that a significant amount of rainfall runoff could be reduced by increasing this level to 70%. The same research indicates that there is a direct relationship between runoff and soil erosion. In other words, by increasing groundcover both runoff and soil erosion can be reduced. In the case of erosion, by increasing groundcover from 40% to 70%, average annual soil loss can be reduced from 30 tonnes per hectare to only 2 tonnes/ha. This is illustrated in Graph 2 on page 9. While the latter figure is obviously far more acceptable, because it is much closer to the natural rate of soil formation, any loss of such valuable topsoil reduces soil health, therefore the productive capacity of the pasture.
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
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Graph 2: The effect of groundcover on soil loss Average annual soil loss (t/ha)
100
Adapted from Lang & McDonald, 2005
50
0 10
20
30
40
50
60
70
80
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Groundcover (%)
It is clear that groundcover is an important component of pasture management that benefits soil health. By providing protection to the soil surface against raindrop impact, it prevents particle detachment and damage to soil structure. If soil structure is maintained the infiltration rate that allows rainwater to soak readily into the soil is also maintained. Groundcover reduces run-off by slowing water movement and allowing more time for it to infiltrate. Thus it controls soil erosion by impeding overland flow, while plant roots also help by binding the soil aggregates together. This is vital considering that the top 10 cm of soil generally contains 40% of the plant roots, 60% of the nutrients, 70% of the organic matter and 75% of the microbial activity.
When soil is lost by erosion the organic matter, micro organisms and nutrients are also lost. The loss of even a thin layer of soil results in a disproportionately larger reduction of organic matter and micro-organisms. Soil lost to erosion cannot be readily replaced. The loss of such a valuable natural resource will have a major impact on the sustainability and profitability of our grasslands. Also, the sediment produced by soil erosion is ultimately deposited in the dams and streams of the catchment, along with large amounts of valuable plant nutrients that negatively affect water quality and encourage algal blooms.
Soil organic matter Organic matter is the lifeblood of a healthy and productive soil. It is essential in maintaining the physical, chemical and biological functions of the soil. Without soil organic matter, pasture production is not sustainable. Organic matter is the fraction of the soil made up of anything that once lived, including plant and animal remains, cells and tissue, plant roots and soil microbes.
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In pastures the main supply of organic matter to soils is from plant litter and animal manures. Plant litter is a component of groundcover and includes any unattached plant material that is in contact with the soil surface. Apart from intercepting rainfall and reducing raindrop impact on the soil, litter is important for providing a living space and the major food supply for soil organisms. Litter also acts as mulch, protecting the biologically active topsoil against extremes of soil temperature and evaporation. Soil organisms include earthworms, dung beetles, ants, nematodes, protozoa, mites, fungi and bacteria. These organisms play an important role in converting litter into soil organic matter and then degrading organic matter further to release nutrients essential for plant growth. Living soil organisms will also retain nutrients, suppress soil diseases and pests, enhance soil structure, improve soil infiltration and water holding capacity, degrade harmful chemicals and generally promote plant growth and productive pastures.
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Any appraisal of the health of a soil must take into account the wellbeing and interactions of the living communities that exist within it. The interactions between pasture, groundcover, litter and soil organisms play a vital role in maintaining soil health and determining many soil characteristics. Grazing management impacts on soil organisms at ground level and below. With so many benefits to soil health it is essential that sufficient food is made available to soil organisms. Researchers have established a relationship between the level of groundcover and the quantities of pasture and litter produced. Graziers need to be mindful of this and endeavour to manage pastures to maintain optimum levels of groundcover and litter for sustainable and productive pasture production.
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Assessing groundcover is quick and easy How do I measure groundcover?
Assessing groundcover
There are numerous ways of assessing groundcover in pastures. Two of these are the Step Point and the Visual Estimation Methods. The following pages describe how to undertake both methods.
Groundcover is an estimate of the proportion of the ground that is not bare soil. It includes the area covered by the plant base, stem and leaf material that is spreading from the base, litter, manure and rocks that are lying on the soil surface. When assessing groundcover it is important that a representative section of the paddock is selected, as groundcover is typically variable across individual paddocks, between paddocks and over time. There are several methods of assessing groundcover in pastures. The following pages describe two of the most popular methods - the step point and visual estimation methods.
Taking stock Our native grasslands and pastures are important for catchment health, but they are also an essential resource for graziers who rely on livestock for their livelihood. Regular monitoring of the health and condition of pastures is vital for making management decisions that determine the productivity and sustainability of any livestock producing enterprise. It is important for graziers to keep a watchful eye on pastures as many changes in the paddock occur slowly, sometimes so slowly that they are barely noticeable at all. Changes occur constantly, for example, to pasture species composition, available feed, pasture digestibility, soil fertility, soil moisture and groundcover.
Monitoring for management Assessments, if undertaken on a regular basis, will identify any changes that may occur over time in response to different management practices. Groundcover is an extremely useful, quick and effective measure for graziers to use and understand. In general, low groundcover is associated with low plant and animal production and low sustainability. If groundcover is low, it is a warning signal that some sort of management is required to bring the level back up to 70% or greater.
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Step point method The ‘step point’ method is an easy and simple way of assessing groundcover and monitoring changes in its composition. However, it can be less accurate than the visual estimation method described on page 14. This method involves making observations along a straight path at specified intervals and recording the type of groundcover. Firstly, make a mark on the toe of each of your boots. Secondly, select a prominent feature, such as a rocky ridge or water tank, that can be used as the bearing point. Then simply walk in a straight line towards the bearing point, for 100 or 200 equally spaced steps, through the pasture. At each step, look at what the mark on your boot has hit, be it bare soil, a pasture plant, leaf litter, manure or rock. Record the hit in the appropriate column of the following table. Additional types of cover can also be added to the table and recorded, such as grass/legume or pasture species, if desired. In larger paddocks, it may be necessary to increase the length of the transect by increasing the distance between hits from 1 step up to a maximum of 5 steps. Groundcover percentage is determined by dividing the total number of hits for all types except bare soil (B) by the total number of hits including bare soil (A+B).
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Paddock Name: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Groundcover TYPE
TALLY OF ‘HITS’
% OF TOTAL
Pasture Plant Litter Weed Manure Rock Groundcover Total
(A)
Bare Soil
(B)
Total
(A+B)
100%
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Visual estimation method The ‘visual estimation’ method is the quickest, easiest and most accurate way to get an approximate estimate of groundcover. To use this method, visualise a square 0.5 Ă— 0.5 metre in front of your feet and look vertically into the pasture to estimate the percentage of the area that is covered by plants and other materials. This estimation is carried out a number of times (ten or more) at random locations across the paddock and the results are then averaged out to provide the overall figure for the percentage of groundcover in that particular paddock. It should be noted this method, although quick and simple, can be less accurate than other methods. It has been shown that observers tend to underestimate groundcover using this method, particularly in the mid-range, in comparison to other more scientific methods.
Groundcover Photos: G. Lodge (Principal Research Scientist, Dept. Primary Industries)
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Dense groundcover increases production Production influences
Groundcover and production
The process of achieving a productive and sustainable grazing enterprise with high livestock production is dependant upon many influencing factors.
The effective use of rainfall and the maintenance of healthy, fertile soils are the driving forces behind pasture growth. Of course, other factors relating to the characteristics of individual plant species also determine pasture productivity. However, it is by improving the groundcover aspect of pasture that a cycle of water use efficiency and soil health improvement can enhance pasture production, potential stocking rates and ultimately farm profitability.
On the north-west slopes of NSW, low producing native grasslands are the most common type of pastures, occupying over 60% of the agricultural area. Much of this land has become less productive due to soils with low fertility, little organic matter and poor soil structure or due to grazing practices that remove highly productive native species. But perhaps the most limiting factor to pasture production in the catchment, and indeed across Australia, is water. Of these influencing factors, all except grazing management can be improved over time by achieving and maintaining a dense groundcover of 70% or more. Grazing management, meanwhile, directly influences the proportion of this groundcover in pastures.
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A dense groundcover has the following beneficial impacts on pasture productivity: •
•
•
•
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It increases the amount of rainfall that infiltrates into the soil by slowing and reducing overland runoff. This could, in many instances, provide grasslands with an extra 70 mm or more of annual soil moisture available for pasture growth. It can improve root development, pasture persistence and increase the herbage mass produced by the pasture to be available either for livestock consumption or as plant litter. Additional plant litter provides the pasture with a protective mulch that can reduce bare soil evaporation by up to 50%. This could provide an additional 260 mm per year of stored soil water for pasture plants to utilise through transpiration - a dramatic improvement in water use efficiency. Extra plant litter increases the amount of organic matter throughout the soil profile, promoting microbial and biological activity in the soil. This increases the availability of plant nutrients as well as improving soil structure and soil stability.
•
It improves the capacity of the soil to store water and nutrients, increasing water availability during dry spells. This factor is crucial to providing consistent productivity and income, especially through drier seasons.
•
An actively growing pasture with good groundcover generally has sufficient leaf area to respond quickly to rainfall following a drought, to provide feed for livestock sooner than sparse or overgrazed pastures.
•
Vigorous pastures with a dense groundcover of productive species compete with undesirable plants to reduce the potential and density of weed problems and associated control costs.
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It protects the soil from the impact of raindrops that can cause the breakdown of soil aggregates and compaction of the soil surface, which prevent water infiltration.
•
By reducing rainfall runoff, groundcover decreases the potential, frequency and severity of soil erosion. It typically reduces the loss of valuable topsoil, high in nutrients and organic matter, from 30 tonnes/ha to only 2 tonnes per hectare per year on average. This decreases soil and nutrient losses off-farm and prevents sedimentation from occurring in dams, creeks and rivers.
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Production and sustainability Research shows that in grazed native pastures on the northern slopes there is a strong relationship between levels of groundcover and the amount of pasture and litter produced. It is for this reason that groundcover is a key indicator of pasture productivity and sustainability. Other important indicators include litter mass, soil surface condition, the proportions of green productive perennial grass and legume species, and their suitability for animal production. These indicators are listed in Table 1, which can be used as a simple guide for monitoring pasture production and assessing its sustainability. By going through the check list on a paddock by paddock basis and recording results over time, it is possible to monitor your pasture resource and quickly assess whether it is producing at its potential, or if it is degrading.
When assessing a paddock consider whether your pasture scores low, medium or high for each of the indicators according to the guide. If you score 3 or more indicators in the LOW column, then your current grazing management techniques may need changing so that the soil and pasture can improve in condition and productivity. If you scored mostly in the MEDIUM column, your pasture may be slowly degrading, even if there is not yet any noticeable decline in production. In this case, concentrate on improving the indicators with low or medium scores. If you scored mostly HIGH, then your pasture is generally performing well, but you may still need to improve some aspects with lesser scores. Regular monitoring of pastures is necessary to avoid future production losses and paddock degradation due to their dynamic nature and constantly changing influences.
Watch when you measure! Seasonal monitoring is important. If groundcover is measured in spring and legume or medic content is 40%, this is scored HIGH. Four months later it may score LOW. Regular monitoring will allow you to take into account seasonal conditions and allow management to adapt to ensure yearround cover.
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Table 1: Indicators of pasture production and sustainability (Source: McCormick and Lodge 2001)
INDICATORS Perennial groundcover
LOW
MEDIUM
HIGH
Less than 40%
40-70%
More than 70%
Less that 1 handful/ 0.1 m2
1-2 handfuls/0.1 m2
3 or more handfuls/ 0.1 m2
Soil surface
Hard or capped no indent
Firm small indent
Soft and friable easily marked
Proportion of green
Less than 20%
20-60%
More than 60%
Proportion of productive pasture species
Less than 45%
45-60%
More than 60%
Less than 1% Less than 5% Less than 10%
1-5% 5-10% 10-30%
More than 5% More than 10% 30-40%
Lose weight
Maintain weight - dry stock
Gain weight or reproduction
Litter
Legume proportion • • •
Native pastures Fertilised native pastures Improved pastures
Suitability for animal production
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Management for improving groundcover Improving native grasslands The native grasslands in northern NSW are well adapted to the local climate and low fertility soils, but often have poor groundcover and provide poor production and feed quality during the winter and late summer/autumn months. By applying suitable fertiliser, introducing a winter green legume and with a suitable grazing plan, feed gaps can be reduced while groundcover and livestock production can be dramatically improved in our native grasslands.
and soil acidity can greatly affect pasture groundcover and production. •
Develop a pasture/grazing management plan to achieve the desired goals for groundcover and production
•
Fence different land units into separate paddocks to facilitate best management according to characteristics such as soil type, aspect, slope and pasture species composition.
Managing for groundcover There is no one recipe that provides the best management practice for all pastures in need of improved groundcover. The methods that graziers use to achieve productive and sustainable pastures will depend on the specific situation of the pasture environment and the land manager’s resources. However, the following process can assist graziers to improve their pasture groundcover to levels of 70% or greater: •
Assess groundcover and pasture condition regularly.
•
Test soils to determine the level of soil nutrients, correct deficiencies and monitor regularly. Nutrient deficiencies
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•
Spread appropriate fertilisers over nutrient deficient paddocks to stimulate dense pasture growth.
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Introduce and encourage winter green legumes such as subterranean clover to improve soil nitrogen levels and pasture vigour.
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Use flexible stocking rates and rotations that reflect seasonal conditions and plant growth.
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Practice rotational grazing so that rest periods allow plants to recover from grazing. This can also reduce localised stock camping activity, increase accumulation of litter and humus, and encourage micro-organism activity and nutrient cycling.
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
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Groundcover maintenance is vital for drought management Dry country Dry seasons and drought are regular occurrences in Australia that result in shortages of forage and subsequent stress on both pastures and livestock. Pastures are often faced with water stress and overgrazing, causing loss of groundcover, perennial grasses and other desirable pasture species. By improving pastures and with careful grazing management before, during and after drought, it is possible to ensure pastures will survive, recover well, and remain productive.
Insufficient groundcover and drought conditions can lead to severe erosion.
Managing groundcover for drought The native pastures on the north-west slopes have developed according to the conditions of their environment. As a result they are generally more tolerant of drought than introduced pasture species. However, as previously discussed, many pastures in this region grow on infertile soils, are inappropriately grazed and are typically inefficient in terms of their water use.
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Recent research in the area has shown that with certain management strategies, pastures can be improved to be more productive, sustainable and drought tolerant. The key strategies to manage drought in our grasslands are: •
•
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Improve pastures before drought to a point where water use efficiency is maximised to reduce the severity of dry weather conditions. This can be achieved by maintaining groundcover above 70%, including a good coverage of pasture litter. Ensure that pastures are predominantly deep-rooted perennial species that are more persistent through drier times and recover quickly after rain. Rest perennial grasses from grazing during subsequent seed-set opportunities.
•
Graze paddocks on a rotational basis where possible, to spell pastures and allow them to recover before the next grazing. This method also allows easier forage budgeting.
•
Feed livestock, if necessary, in specific containment areas or ‘sacrifice’ paddocks to allow pastures to recover elsewhere, or destock early.
•
Plan grazing strategies, continually monitor pasture and destock to planned pasture benchmarks to reduce the risk of pasture and soil degradation.
Case study - Planned grazing for drought Trevor and Colleen Jorgensen are cattle producers on their property ‘Magnet’ and a number of adjacent blocks totaling 1,800 ha, south of Delungra on the slopes of the Gwydir Catchment. The property consists of undulating to hilly country with fertile creek flats and a mixture of basalt and lighter trap rock soils. Since purchasing ‘Magnet’ in 1991, and despite two lengthy droughts, they have transformed it from being a cropping and sheep property into a high performance Brangus beef and stud cattle enterprise, running about 1000 head. Trevor and Colleen have sown 180 ha of old cultivation to perennial tropical grasses and clover. In their native grasslands, dominated by Wallaby, Red and Queensland blue grasses, they spread clover and Single super (at a rate of 110 kg/ha) over about 500 ha each year. Fodder crops such as oats and lucerne are sown on the more suitable cultivation soils, for strategic The Jorgensen’s maintain good use in the grazing plan. groundcover for their stock
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Border Rivers-Gwydir Catchment Management Authority
With subdivision into 20-40 ha paddocks and a flexible rotational grazing system, Trevor and Colleen have greatly enhanced the performance of their pastures and livestock. They use tactical grazing to manage the various types of stock at different times of the year. Young cattle are grazed on oats, lucerne and improved pasture rotations initially, while cows are run on improved pasture in smaller mobs at joining for single sire mating. After joining they are all run as a single herd that is grazed on a rotational basis through all the paddocks on the property. In drier times, the Jorgensens continue with the rotation and find that the perennial pastures persist much longer than the annuals. Grain supplement is fed to steers so they can be off-loaded sooner, to free more country for the weaners. Dry cattle and weaners are supplemented reserve fodder in the form of lucerne hay, oats and wheat or purchased protein meal and urea. Sacrifice paddocks are used for feeding if necessary to save priority paddocks from overgrazing by livestock. These tend to be flatter or more stable areas that are less likely to erode and can easily be re-sown if necessary. Their grazing plan is to always have about three quarters of the property ungrazed. This allows pastures to regenerate before the next grazing, while
matching the herd’s feed demands with available pasture. Trevor believes that resting pastures in a rotation is especially important during drought to maintain good groundcover and minimise soil erosion. Spelling country, particularly if it is fertilised, also readies the pasture for a quick response when rain finally falls. Under this management, the perennial tropical grasses and clovers in the old cultivation have greatly increased groundcover, which has reduced erosion, improved soil structure and created a highly productive pasture. Some of the native pastures in heavy soil areas were slow to respond to fertiliser initially, however these paddocks have since seen an increase in groundcover to levels generally in excess of the 70% benchmark, along with an excellent mix of introduced and naturalised legumes. By improving the pastures on the property they are now running 30% more livestock in better condition overall, and managing to do so even through drought. Trevor and Colleen have been awarded the coveted Black Woods Shield, which recognises the district’s leading landholders for their achievements in managing their natural resources.
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Pasture management & groundcover in a changing climate For many areas across the Border Rivers and Gwydir catchments, the richness and biological diversity of native pastures is a valuable component of grazing systems. Knowledge of possible impacts and management for the effects of climate change on plants is important when considering grazing management for groundcover. Australia’s agriculture and unique biodiversity have been under threat from a wide range of stressors for many years, like salinity, erosion and vegetation clearing. They are now facing a rapidly changing climate.
Predicted Outcomes for Plants Many of Australia’s most valued and iconic natural areas, and the rich biodiversity they support, are among the most vulnerable to climate change. Agriculture is also vulnerable to climate change because there is very little scope to use either coping or adapting strategies to overcome this change. Australian agriculture already operates at the margin of temperature and rainfall. Small changes may be catastrophic. Agriculture and forestry would become vulnerable with a temperature rise of 3°C (Steffen et al. 2009). Beyond the great richness it lends to our most iconic natural areas, biodiversity underpins our quality of life, our economy and much of our national identity. Management objectives for the future, aimed at maintaining all species in their present locations and ecosystems in their present composition, will no longer be appropriate. Perhaps in future years, different pasture composition will be required to maintain groundcover and build systems that are resilient to a changing climate.
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Plant Performance Increasing temperature and lower winter/spring rainfall could lead to a change in species dominance across the Border Rivers and Gwydir catchments. This means we could see an easterly and southerly expansion in the area dominated by arid/subtropical zone plants, including woody weeds. These conditions may also favour drought tolerant grass weeds such as African lovegrass, Coolatai grass (top left), Serrated tussock (bottom right) and an increase in low productivity native species such as Spear grass (top right). Hotter, drier conditions will increase the threat and intensity of bushfires, providing the potential for the loss of fire susceptible species and increasing the proportion of species that respond to regular burning. This will be exacerbated by the increase in exotic grass species such as Coolatai grass which are not only fire tolerant but create hotter fires than native groundcover. The increased probability of drought combined with higher evaporation (each 1째C rise in temperature increases evaporation by 3-6%, Steffen et al. 2009) will mean that most agricultural and natural systems will be under stress more often. Likely impacts are shown in Table 2 on page 26.
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Table 2: Likely changes in performance of economically significant plants by 2030 (Source: Steffen et al. 2009)
Change in growing season rainfall
Change in evaporation (mm)
Winter cereals
Decline of 30 mm (west) to 70 mm (east)
Winter pulses
Cool season grasses
Plant type
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Vegetative yield
Grain yield
Grain protein
Vegetative protein
Increase of 12 to 20 mm
Decline by 500 to 1200 kg/ha green dry matter
Decline by 450 to 1000 kg/ha
Decline but no reliable estimates of how much
Decline but no reliable estimates of how much
Decline of 30 mm (west) to 70 mm (east)
Increase of 12 to 20 mm
Decline by 500 to 1200 kg/ha green dry matter
Decline by 240 to 560 kg/ha
Decline but no reliable estimates of how much
Decline but no reliable estimates of how much
Decline of 30 mm (west) to 70 mm (east)
Increase of 12 to 20 mm
Decline by 500 to 1200 kg/ha green dry matter
N/A
N/A
Decline from 15% to 12% crude protein
Warm season crops
Increase by 10 to 15 mm
Increase of 20 to 30 mm
Decline by 300 to 450 kg/ha green dry matter
Decline by 100 to 200 kg/ha
Decline but no reliable estimates of how much
Decline but no reliable estimates of how much
Warm season grasses
Increase by 10 to 15 mm
Increase of 20 to 30 mm
Decline by 300 to 450 kg/ha green dry matter
N/A
N/A
Decline from 11% to 9% crude protein
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Paddock not performing? The 6 key factors of sustainable landscape management Maximising the profitability and sustainability of the farm business is achieved by maximising the effectiveness with which rainfall is utilised (Rainfall Use Efficiency). The following six factors are the key to maximising Rainfall Use Efficiency:
If crops or pastures are not achieving these outcomes there are some simple soil tests that may help diagnose the problem. The following tests and observations can help. If more information is needed then a soil sample should be sent away for complete analysis.
Assessing your paddock’s performance
1.
More than 70% groundcover to minimise soil erosion.
Equipment
2.
More than 2 tonnes/ha of litter to minimise water loss by evaporation.
You will need:
3.
More than 1,500 kg/ha of green, dry plant mass to maximise energy utilisation by plants.
4.
A diversity of plant species that can utilise rain whenever it falls.
5.
Sufficient shelter to minimise the impact of wind run1 and temperature on plants and animals.
6.
Soil with a balance of physical and chemical properties that optimise water retention and nutrient availability.
1
Wind run is a measurement of the amount of wind passing a point in the landscape over a given period of time.
•
mattock
•
2 litres of rainwater
•
the lids from 2 jars
•
pH kit
•
plastic bags
While the soil surface can show some problems, it is often just below the surface at 10-20 cm, that things can change dramatically and affect plant growth. So tests should be done on both surface and sub-surface soils as parameters can change over small distances.
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Sampling Select a representative area and dig a hole 20-30 cm deep. For some of the tests, the soil needs to be in a lump and the plant roots need to be intact so don’t destroy them. If it is a pasture paddock then try and find a legume (e.g. clover) and/or tap rooted plant to look at.
Plant checks Try and extract the tap rooted plant intact if possible, remove the soil and check where the roots are going. If they are not growing straight down or are dramatically thin at shallow depths, then there is a barrier within the soil that prevents the plants from accessing nutrients.
Check the legume for nodules - if there are no nodules then it is not producing nitrogen to feed surrounding grass plants. Nodules appear like a lump of grapes just below the soil surface and singularly on the roots. If they appear white or hard then they are not working. If, when crushed, the nodule produces a pink stain on your thumb nail then they are working.
Plants themselves can also provide information on nutrient imbalances. Table 3 outlines some of the symptoms of deficiencies that plants exhibit.
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Table 3: Symptoms of nutrient deficiencies in plants
ELEMENT Nitrogen (N)
DEFICIENCY SYMPTOMS
PROBABLE CAUSE OF DEFICIENCY
Yellow leaves
Low soil nitrogen due to legumes not working or not present. The break down of high Carbon:Nitrogen (C:N) ratio in organic material.
Stunted growth Phosphorous (P)
Small plants Reddish-purple leaves
Low soil phosphorous due to low soil temperatures or soil pH (acid soils tie up phosphorous).
Slow growth Potassium (K) Calcium (Ca)
Brown margins on lower leaves
Low soil potassium
Deformed buds
Low soil calcium due to parent material. Calcium can be leached beyond the root zone to form a band at depth in heavy soils.
Distorted leaves Failure to grow Magnesium (Mg)
Leaves turn yellow with green interveinal areas
Low soil magnesium.
Sulphur (S)
Yellow plants
Low soil sulphur which may be due to tie up in pasture stubble.
Slow growth Low crop yield and quality
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Soil checks
Sodicity
There are a series of basic soil tests that can help identify the presence of soil issues creating poor crop and/or pasture growth.
A sodicity test checks for the presence of sodium in the soil. The soil surface may crust or waterlog with wet weather. If the water does not infiltrate deep into the soil then this may be the problem.
POSSIBLE SIGNS
COULD BE DUE TO
• Stunted growth • Poor germination
• • • • •
TESTS FOR DIAGNOSIS
Waterlogging Soil structure Sodicity Slaking Nutrient deficiencies/ toxicities
• Slaking • Dispersion • Observation for nodules/ arrangement of soil particles
Soil structure Sodicity Slaking Nutrient deficiencies/ toxicities
• Slaking • Dispersion • Observation for nodules/ arrangement of soil particles
• Wilting despite adequate water • Hard setting soil
• • • •
• Leaf colour • Lack of nodules
• Nutrient deficiencies/ toxicities
This test is done by: 1.
Taking a small lump of soil.
2.
Placing it carefully into a saucer of rainwater.
3.
If a milky cloud appears around the clod of soil within 2 hours then the soil has some sodium in it.
If the soil goes milky in the lid quickly e.g. 5-10 minutes after being submersed then it is likely that the soil is sodic. The longer it takes to create a milky cloud the less sodic it is.
• pH • See Table 3
Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Slaking The slaking test checks for the amount of organic matter or ‘glue’ present in the soil. This test is done by: 1.
Taking a small lump of soil.
2.
Placing it carefully into a saucer of rainwater.
3.
If the clod collapses then there is little glue to hold the soil particles together.
Soil pH A soil pH test measures the acidity or alkalinity of the soil. This can influence the plant’s ability to take up nutrients. The pH kit contains 2 bottles and a colour match chart. One is a liquid and the other is a powder. 1.
Place soil for the test on cleaned saucer.
2.
Shake a few drops of liquid indicator on to soil.
3.
Sprinkle soil with a thin cover of white powder.
4.
Leave 2-3 minutes to allow colour to develop.
5.
Match colour with the colour chart.
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Precipitates (nodules)
Texture
Look for mineral precipitates present in the soil. These will often be identified as small lumps in the soil or as a band. This level is the point where intermittent waterlogging has occurred in the soil leaving the precipitates behind as the soil dries.
This is important to determine how readily water can move through the soil. Confer with the “Practical Guide to Soil Erosion� (Miller, 2008) for details on conducting a soil texture test.
White precipitates are usually Calcium Carbonate (CaCO3), and will fizz on the application of vinegar, but they may be gypsum, which wont fizz. CaCO3 precipitates form when the pH is above 8 at depth. Dark purple precipitates are manganese, and red/brown precipitates are ironstone. Both of these are an indication of periodic waterlogging. Pale coloured soil also means there is little oxygen present which may affect plant roots trying to access nutrients. Where there is little soil structure plant roots may have problems moving down through the soil which may lead them to grow sideways (see images on page 28).
Other issues If you have Couch grass and bare areas with white crusting where the top soil has been lost then it is possibly salinity (see image left). Further tests can confirm this.
Unsure? If the above tests have not answered your questions, or more information is needed, then send a sample away to an accredited soils laboratory for further testing. To get the most benefit from testing make sure that the sample only contains the 1 type of soil from 1 landscape. Further details and support can also be sought from staff at the Border Rivers-Gwydir CMA.
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Border Rivers-Gwydir Catchment Management Authority
Identifying the most limiting factor Use this guide, or create one based on this, to monitor your paddocks. Measure on a seasonal basis e.g. spring and autumn or after a mob of stock have left a paddock.
Species
Date:
Legumes
Paddock Name:
Factor
Result
A. % Groundcover
Number
% Cover
Grasses Trees/shrubs (shelter) Obvious plant deficiency symptoms
B. % Green plant material C. Average grass height (mm) seed heads removed D. Green dry matter (kg/ha) = A x B x C x 3 รท 1000 E. Litter (handfuls) F. % Desirable pasture species G. Available feed for grazing H. Surface soil structure no indentation small indentation soil easily indented
hard okay good
Soils
Surface
Sub-surface
Slaking Dispersion pH Texture Depth Soil biology (present/absent) Other comments
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Inefficiencies Does the paddock have...
From the information gathered, identify what the most limiting factor is for this paddock and list management options to address these issues.
...physical, chemical or biological constraints?
Management Options Short Term
...limited variety of plant types (e.g. C3, C4, perennial, annual, grasses, legumes, forbs, herbs, trees, shrubs)?
...wind breaks and shelter belts?
...below the minimum groundcover (70%)?
...below the minimum dry green matter (1500 kg/ha)?
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Ground Truths Uncovered: Managing groundcover for erosion control and productive pastures
Long Term
Border Rivers-Gwydir Catchment Management Authority
References and further reading Charman, P. and Murphy, B. (Editors) (2007) Soils: their properties and management (3rd edition). Oxford University Press, Victoria. Jenkins, A. and Lines-Kelly, R. (2004) NSW Agriculture and soil health. Agnote DPI-464, NSW DPI. Lang, D and Holmes, M. (1995) The Cover Equation: How much is enough? Department of Land and Water Conservation. Lang, D and McDonald, W. (2005) Maintaining groundcover to reduce erosion and sustain production. Agfact P2.1.14, NSW Department of Primary Industries. Lloyd, M. (2005) Ground Truths Uncovered: Ground cover fact sheets for on-farm environmental and economic sustainability. Border RiversGwydir Catchment Management Authority, NSW.
Mason, W., Warn, L. and Cahill, G. (Editors) (2004) Towards sustainable grazing: The professional producers guide. Meat & Livestock Australia, Melbourne. Miller, W. (2008) Practical Guide to Soil Erosion: a guide to preventing, assessing, and treating soil erosion on your farm. Border Rivers-Gwydir Catchment Management Authority, NSW. Murphy, S.R. and Lodge, G.M. (2001) Plant density, litter and bare soil effects on actual evaporation and transpiration in autumn. Proceedings of 10th Agronomy Conference 2001, Hobart Tasmania. Murphy, S.R., Lodge, G.M. and Harden, S. (2004) Surface soil water dynamics in pastures in northern NSW - 3. Evaporation. Aust. Jour. Exp. Agr. 44, 571-583.
Lodge, G. (1999) The Great Grazing Debate. NSW Agriculture.
Sheahan, M. (Editor) (1998) Monitoring native vegetation. Vegnote 1.6. Murray CMC & DLWC.
Lodge, G.M. (Editor) (1998) Themes and experimental protocols for sustainable grazing systems. Land and Water Resources Research and Development Corporation, Canberra.
Steffen, W., Burbidge, A., Hughes, L., Kitching, R., Lindenmayer, D., Musgrave, W., Stafford Smith, W. & Werner P. (2009) Australia’s Biodiversity and Climate Change. CSIRO Publishing.
Lodge G.M. and Murphy S.R. (2002) Ground cover in temperate native perennial grass pastures. II. Relationship with herbage and litter mass. The Rangeland Journal 24 , 301–312.
Watson, R., McDonald, W. and Freebairn, B. (1994) Saleable stock from stable pastures. NSW Agriculture.
McCormick, L.H. and Lodge, G.M. (2001) Pasture Health Kit. NSW Agriculture & North West Sustainable Grazing Systems.
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15 Vivian Street | PO Box 411, Inverell NSW 2360. t: 02 6728 8020 f: 02 6728 8098 66 - 68 Frome Street | PO Box 569, Moree NSW 2400. t: 02 6757 2550 f: 02 6757 2568
www.brg.cma.nsw.gov.au