The drivers of Water use efficiency and productivity real farm results
| Date: 11 Aug 2010
The drivers of Water use efficiency and productivity – real farm results
|
Matt McRae
AGnVET Services
AGnVET Services
Forbes
The drivers of Water use efficiency and productivity – real farm results
AGnVET Services is an independent agribusiness, providing rural supplies and services to over 27 regional centres of NSW. BettaCrop is a regular and comprehensive paddock monitoring program, designed to optimise crop potential and pasture productivity. BettaCrop forms a pro-active and consultative approach to crop and pasture management. Paddock plans are formulated, potential problems identified and mutual aims developed prior to commencement of the fallow. Crops, pasture and fallow are then monitored through the season for plant establishment, weed, disease and insect management. This allows prompt identification of issues and timely responses.
The BettaCrop database currently has information for over 10,000 paddocks and includes over 120 current growers across northern, central and southern areas of NSW. Analysis of the database is conducted each year and is able to provide comparisons of various agronomic and management factors that contribute to achieving high water use efficiency (WUE).
The database is able to be interrogated to examine the key drivers of paddock productivity on many levels. Measurement of paddock inputs, soil conditions and crop physiology are maintained to provide insight into the practices that have the most efficient water use across the regional area.
Central West Farming Systems (CWFS), CSIRO, Department of Industry & Investment NSW (DII) and AGnVET services are engaged in a GRDC project examining WUE in the central west. The project - Increasing Farm Water Use Efficiency in the Central West NSW is utilising the BettaCrop database to benchmark the WUE across the central grains region. The project commenced in July 2008, and will examine the effects of management practices on WUE. Soil water characteristics will be determined and WUE will be calculated and modelled for the growing season. The farms, located at Gunningbland, Ungarie & Condobolin, will provide a range of stages within the rotation and cropping system to examine the impact of crop management on soil water storage and availability.
What are the key drivers to water use efficiency and productivity?
Financial outcomes of BettaCrop analysis show the productivity gross margins are driven by yield (62%), grain price (14%), all variable input costs (4%) and other factors not measured equate to 20%. The most efficient WUE paddocks in 2008 delivered higher gross income than poor WUE with high grain prices in 2007. Better WUE in 2008 overcame high input costs in that year despite having 250mm less moisture available to produce yield.
Table 1 displays analysis of crops from central NSW in 2008 where high WUE can off-set high crop input costs. Poor WUE efficient paddocks (11kg/mm) in 2008 returned a negative gross margin per mm of moisture (-$0.82/mm), while paddocks that received the same in-crop rainfall (ICR), but conserved more plant available water (PAW) in the fallow period returned a positive gross margin per mm moisture ($1.52/mm) and WUE of 26kg/mm. High WUE paddocks from 2005 to 2008 showed a consistently positive gross margin per hectare.
Table 1. Wheat Top 20% vs. Bottom 20% for all Regions & Central NSW (AGnVET 2009).
Year
|
Benchmark
|
Est PAW
|
ICR
|
Yield
|
WUE
|
Cost/ha
|
GM/ha
|
GM/mm
|
2005 to 2008
|
Top 20% $/mm
|
80
|
140
|
2.64
|
26
|
$215
|
$393
|
$2.02
|
2005 to 2008
|
Bottom 20% $/mm
|
55
|
81
|
0.39
|
8.3
|
$192
|
-$96
|
-$0.84
|
2008 Central
|
Top 20% $/mm
|
81
|
99
|
1.74
|
26
|
$203
|
$250
|
$1.52
|
2008 Central
|
Bottom 20% $/mm
|
54
|
99
|
0.56
|
11
|
$259
|
-$108
|
-$0.82
|
If yield is driving profit what is driving yield?
WUE is a valuable tool to assess the performance of paddocks across a wide range of parameters. WUE is a measure of the ability of a crop to convert plant available water to grain. There are many drivers of WUE, which have been interpreted using the BettaCrop database. Biological and crop physiology factors combine with management factors to affect yield and WUE.
Crop WUE is maximised when physiological and management interactions match moisture available to the plant. Yield is a factor of heads at harvest and grains per spikelet; however the crop must be ‘set up’ to match available moisture. Analysis shows that in-crop rainfall and soil moisture at sowing are the key components that set up the WUE of paddocks within the database. It is crucial that available water be stored and used efficiently. Table 2 illustrates the range of WUE for paddocks monitored within the BettaCrop service program.
Table 2. Analysis of WUE from BettaCrop Database 2005 to 2008 (AGnVET 2009)
WUE
|
North
|
Centre
|
South
|
Good
|
18.5
|
19.1
|
18.2
|
OK
|
13.3
|
13.5
|
13.2
|
Low
|
8.6
|
9.6
|
8.8
|
Management focusing on minimising nutritional, disease and weed stress will enable the crop to become adaptive to seasonal conditions. Soil health is a very popular topic at present. While soil carbon is difficult to build, it is very easy to destroy through cultivation, grazing effects and erosion. High organic carbon leads to higher cation exchange capacity (CEC), which in turn leads to higher soil moisture retention. While heavy clay soils generally have higher moisture holding ability than sandy or loamy soils, not all clay soils have the ability to repair structure. Clay soils are not all the same which is indicated by differing CEC’s. Fragile clay soils need specific cropping and grazing management which focus on at least maintaining soil carbon levels, if not building them over time.
Anderson & Badgery (2010) discuss that soil organic carbon (SOC) is important because it positively influences many chemical and physical soil attributes. High SOC levels improve soil structure, water holding capacity, nutrient availability and enhance microbial activity. Yield benefit from increasing organic carbon levels by 0.1% can be as high as by 150kg/ha (AGnVET 2009).
Soil carbon is receiving a lot of attention, but there are many other soil factors that contribute to achieving high yields and high WUE. Analysis shows that addressing soil pH has a consistent effect on yield. For every 0.1 increase in soil pH, potential yield can increase by 100kg/ha. Moving a soil pH from 5.0 to 5.2 on a CEC of 10 will require approximately 1t/ha of lime. This $60 investment in lime could potentially return an extra 200kg/ha/yr over five years. At $250 per tonne of wheat this equates to a $4.10 return for each $1 invested.
Growers that have invested in effective seeding equipment, or are highly skilled at managing their available infrastructure are able to capitalise on the small sowing opportunities. Graph 1 illustrates the effect of soil opening device on wheat yield. Minimal disturbance seeding systems, especially disc planters can contribute 390kg/ha to final yield. Research conducted by Birchip Cropping Group members (Walsh et al 2009) stated that low disturbance single disc systems are particularly effective at minimising seedbed moisture loss and weed seed germination.
Graph 1. Effect of Opening Device on wheat yield – AGnVET 2009
AGnVET analysis shows that 310kg/ha additional yield can be achieved through the selection and efficient management of press wheels and soil packing systems over finger harrows. Walsh et al (2009) mentions that knife point press wheel seeding systems operated at low speeds consistently established high wheat seedling numbers. Graph 2 illustrates the additional benefit to yield through closing device.
Incorporation of pre-emergent herbicides is often an argument for greater disturbance at the soil surface; however the implications for soil moisture management and effective crop establishment can be measured. Walsh et al (2009) points out that it is not just a case of swapping knife points and press wheels for discs. A complete and integrated agronomic package – incorporating weed control, pest management, fertiliser inputs, row spacing, residue management etc is required for yield and WUE benefits.
Graph 2. Effect of closing device on wheat yield (AGnVET 2009)
Integrating livestock and cropping in the central west to enhance both systems may have some trade offs. Grazing stubble may reduce the following crop yields by 260kg/ha (see Graph 3). This may be through the effects of reduced ground cover, or the disturbance of surface soil structure that reduces moisture infiltration. Soil compaction which results when paddocks are grazed whilst the soil is wet may also have implications for following crop sequences.
Graph 3. Effect of grazing stubble on subsequent wheat yield (AGnVET 2007)
Passioura & Angus (2010) describe new management practices leading to yield increases as strategic or tactical management. Strategic advances in WUE through effective management come before or at planting, but involve some prior planning. In dryland environments early sowing is usually one of the most reliable strategies to maximise WUE. Tactical management can be as simple as fertiliser rate changes or varietal or crop type adjustments to cropping systems. Passioura & Angus also state that tactical management has the potential to increase yields in favourable seasons with little effect on yields in poor seasons.
The AGnVET BettaCrop agronomy service is well into the 10th cycle, with significant resources and information contained in the database. Over the years AGnVET have refined the analysis of the database to explore the most significant influences to WUE through management decisions. The idea of ‘if you measure it you can manage it’ is paying dividends through increased WUE and productivity in a commercial farming business environment.
Figure 1. AGnVET Services Pathway to Wheat Yield
Farrell 2008 writes that the benefits from the adoption of conservation farming need to be assessed over a period of at least eight years, and preferably ten to twelve years, to account for the improvement in soil quality and the corresponding capacity to increase crop yields through an increase in water holding capacity and soil nitrogen.
Figure 1 proposes a yield pathway that can be implemented through the refinement of management factors that will enhance WUE. Within each farming business there will be certain trade-offs for WUE depending on individual enterprise mix. Understanding the limitations of management decisions may be just as useful as the striving to reduce them.
Summary
Key drivers of WUE and productivity have been found using the AGnVET BettaCrop database over a series of years. Yield is king, with grain price a close second. Management which aims to improve soil health to store soil water will enhance WUE. Strategic and tactical crop management systems that minimise risks associated with crop disease, grazing impact, nutrition and weed issues will achieve maximum WUE.
Matt McRae
Field Service Manager
AGnVET Services
mattmcrae@agnvet.com.au
0429 839 271
AGnVET Services
mattmcrae@agnvet.com.au
0429 839 271
References
Anderson, K.O. & Badgery W.B. 2010 Soil Carbon levels in Southern NSW. Proceedings of the 25th Annual Conference of The Grasslands Society of NSW.
AGnVET Services – BettaBiz Productivity Analysis, 2008. Ian Elliot AGnVET Services & David Duncan Sustainable Soil Management.
AGnVET Services – BettaBiz Productivity Analysis, 2007. Ian Elliot AGnVET Services & David Duncan Sustainable Soil Management.
CWFS - Increasing farm water use efficiency in Central West NSW. GRDC Project No. CWF00013. www.cwfs.org.au
Walsh, M; Browne, C & Desbiolles J; 2009 Establishment of wheat as influenced by seeding systems. Birchip Cropping Group 2009 Season Results. www.bcg.org.au
Farrell, T; 2008 An Economic Evaluation of Conservation Farming Practices for the Central West of NSW. Australasian Agribusiness Review Vol 16, Paper 5 2008.
Passioura, J.B. & Angus J.F. 2010. Improving Productivity of Crops in Water-Limited Environments. Advances in Agronomy Vol 106 pp 37-55.
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