Ground Cover Supplement : GC Supplement - Precision Agriculture
GROUND COVER PRECISION AGRICULTURE ADOPTION 4 OF COURSE VARIABLE RATE (VR) fertiliser pays -- we just need to be able to work out where and when it pays, because it does not pay in all circumstances. This uncertainty around the relative advantage of VR in specific paddock and seasonal situations continues to undermine confidence in the adoption of VR fertiliser. As part of the Demystifying Precision Agriculture (PA) workshops, a simple economic model was developed to help advisers and growers run the figures on the potential for VR fertiliser in their own paddocks. The spreadsheet-based model has been developed and tested by a team from CSIRO, Curtin University of Technology and the Department of Agriculture and Food, Western Australia (DAFWA), which includes Roger Mandel, Bill Bowden, Roger Lawes and Michael Robertson. It is being used as a tool with advisers developing businesses in PA services and the PA grower groups in WA (see page 18). Experience with grower and grower group trials in WA has shown that generally VR fertiliser (phosphorus or nitrogen) can pay when the difference in yield potential between two zones is likely to be one tonne a hectare or greater for cereals. However, physical and biological factors and input and output prices all influence the bottom line in individual paddocks and seasons. Historically, profit curves for changing fertiliser rates were so flat that it was difficult to prove that under- or over-application would reduce returns. This has changed with the large fluctuations in grain and fertiliser prices experienced in recent years. Consequently, there has been greater interest in understanding where THE DOLLAR RETURN FROM VARIABLE RATE A simple economic spreadsheet is helping to put variable rate on the ground in Western Australia By Michael Robertson and when VR fertiliser makes economic sense. A range of questions can be explored using the 'economic analysis of zone management' spreadsheet. Such questions include: nShould a paddock be managed uniformly or differentially using input management zones? nHow are the economics influenced by the number of zones, the relative size of zones, the cost of inputs and price of outputs or variation in yield? Using the spreadsheet requires details of input costs and output prices to be entered, as well as the total paddock area plus the percentage of the paddock in each of up to three zones. In addition, an average yield for each zone is required. Finally, details of soil-available phosphorus and nitrogen for each zone must be added, so zone- based soil tests or estimates are required. The model will then produce recommended rates of phosphorus and nitrogen for each zone under VR and for whole paddocks, if the paddock was treated uniformly. It is then able to calculate the change in gross margin that occurs by using VR fertiliser compared with applying a uniform rate across the paddock. The spreadsheet is designed for growers and agronomists who are already gathering and analysing yield data, to help them make informed decisions about adopting variable rate fertiliser at seeding or in-crop. Copies of the spreadsheet are available from Dr Michael Robertson. □ GRDC Research Code CSA00016 More information: Dr Michael Robertson, group leader, CSIRO Sustainable Ecosystems, 08 9333 6461, email@example.com www.grdc.com.au/CSA00016 A simple economic spreadsheet can help establish where and when variable rate fertiliser application will pay.
GC Supplement - Biosecurity
GC Supplement - Climate