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Beyond the Bale : December 2017
Table 1. Descriptive statistics of key soil attributes for the improved and native pastures fields Field Soil characteristic Minimum Maximum Mean Standard deviation CV log10 CV Improved pH 5.0 6.6 5.9 0.30 5.0% – Phosphorus (mg kg–1) 19.3 110.6 49.9 18.2 36.6% 9.0% Potassium (cmol(+) kg–1) 0.11 1.61 0.52 0.34 66.2% 50.6% Sulfur (mg kg–1) 3.7 17.0 8.3 2.9 35.0% 16.7% Native pH 5.7 6.4 6.1 0.17 2.8% – Phosphorus (mg kg–1) 13.0 121.1 30.5 17.8 58.5% 12.9% Potassium (cmol(+) kg–1) 0.19 1.89 0.50 0.33 66.0% 48.5% Sulfur (mg kg–1) 7.1 41.8 11.0 6.6 59.9% 17.9% Improved field pH Phosphorus (mg kg–1) Phosphorus (mg kg–1) pH 6.6 – 6.6 6.45 – 6.44 6.29 – 6.44 6.14 – 6.28 5.84 – 5.98 5.68 – 5.83 5.58 – 5.67 5.99 – 6.13 6.4 – 6.5 6.1 – 6.3 73.0 – 110.9 75.3 – 129.3 57.8 – 75.2 40.3 – 57.7 22.9 – 40.2 9.8 – 22.8 57.5 – 72.9 42.1 – 57.4 26.6 – 42.0 14.3 – 26.5 5.9 – 6.0 5.6 – 5.8 5.3 – 5.5 5.0 – 5.2 Native field 0 125 250 500 Metres (a)( b) (c)( d) Fig. 3. Spatial variability in (a, b) pH and (c, d) phosphorus across an improved and a native pasture paddock. Spatial variability in soil characteristics Crop & Pasture Science 821 AWI-funded Nuffield Scholar Jack England has identified clear opportunities for woolgrowers to integrate precision agriculture (PA) and variable rate technology (VRT) in their businesses, to improve pasture efficiency and environmental outcomes. TIME TO EMBRACE KEY POINTS FROM JACK’S RESEARCH • Variable rate technology has demonstrated significant productivity gains for the livestock sector through strategic placement of fertiliser. • Mature animals absorb minimal phosphorus (P) obtained from grass, but redistribute nutrients and excrement to frequently used small parts of a paddock. Don’t spread P here. • Young, growing stock absorb the lion’s share of P and are commonly weaned and grown out in the same paddocks annually. Replace what is removed using grazing data. Feeding to the farm average is potentially penalising pasture growth in these paddocks. • Easy to use software programs capture individual paddock carrying capacities amongst other benefits. Fertilise appropriately, based on each paddock’s stocking rate. • Sensors fitted to an animal turns them into yield monitors and identifies where nutrients are being removed and redistributed. • ʻSoil tests from the sky’, pasture quality and quantity measurements using optical sensors will aid targeted grid/ zone-based soil testing programs. • Start somewhere. Start small and assess costs vs benefits. Paddocks with known pasture growth variability or soil constraints are a good place to start. 2016 Nuffield Scholar Jack England manages his family’s 3,200 ha mixed sheep, beef and cropping property near Kingston South East in South Australia. With a background in agronomy, he brought a scientific approach to his Nuffield farming scholarship, supported by AWI. Variable-rate technology (VRT) is a technology that enables producers to vary the rate of inputs to their pastures or crops. It allows inputs such as fertiliser or irrigation water to be applied at different rates across a field, without manually changing rate settings on equipment or having to make multiple passes over an area. “One of the largest overheads for a livestock business is the fertiliser bill. Yet despite limited global resources of fertiliser and associated future price increases, it is generally applied in a grossly inefficient manner where agronomic potential is left unrealised,” Jack said. “It makes economic sense for farmers, and society, to create more efficient livestock farming systems and make better use of the finite reserves of macro fertiliser nutrients, water and arable land. This also fits in well with society quite rightly demanding stronger agricultural nutrient run-off restrictions.” Jack’s research took him to the UK, Israel and New Zealand, as well as Australia, to discuss the use of VRT with cropping and horticultural specialists, researchers and livestock producers. His goal was to establish an understanding of how PA and VRT could be extrapolated across the livestock industries. Jack said his research was driven by his perplexity at livestock producers’ willingness to acknowledge the cropping sector has enjoyed enormous efficiency and productivity gains using PA and VRT, while simultaneously having a resistance to applying the same technology to pasture. “PA and VRT have been applied in cropping and horticultural industries to maximise plant biomass and quality parameters for many years, but are not yet widespread across pasture and livestock systems,” Jack said. “I believe livestock farmers must, like the cropping fraternity, make better use of our finite resources by applying VRT to suit various agronomic growing conditions found within a field.” COST OF PRODUCTION Reducing cost of production was a key driver of Jack’s research. Discussions with livestock producers across the globe pertaining to their willingness to implement PA and VRT led to Jack developing a suite of recommendations based on soil science, plant monitoring and better understanding the relationship between animal behavior and nutrient removal. These include the adoption of farm management software, use of spatial tools such as yield and topographical maps to identify variations in paddocks and biomass, fertiliser application based on zoning, objective measurement of treatment responses and continued monitoring of application sites. Jack also recommended external assistance be sought by producers whose knowledge of PA or VRT is limited and a ‘nursery’ or staged approach to integrating this management framework by starting with a small number of targeted paddocks. “Development of zone-based variable rate fertiliser applications, driven by an understanding of how all soil, animal and plant spatial datasets interrelate, could soon unleash substantial improvements in the livestock sector’s productivity,” he said. “These systems will also enhance growers’ ability to analyse enterprise and management differences. “While presently a daunting task, development of spatial tools incorporated into easy-to-use commercial decision support applications will most certainly allow farmers to make better fertiliser investment decisions and grow more pasture more efficiently in the future.” MORE INFORMATION Access Jack’s Nuffield report and view a recording of his Nuffield presentation at www.wool.com/nuffield Phosphorus in-field variation in Australian livestock grazing system as measured using Colwell P. Five zones of Colwell P (mg/kg) are shown, depicting the effect of slope and vegetation, and showing the high concentration of P in stock camps. (Source: Trotter et al, 2014, Crop and Pasture Science). ON FARM 53