• Why is it important to me as a farmer?
• What is variable rate application?
• What is the best practice in potentially adopting this technology?

• Precision agriculture (PA) enables land and crop variability to be identified and managed
• This may include more accurate management of sowing density, crop nutrition, crop protection, soil amelioration
• Do the sums before investing in PA to ensure any investment in new technology will increase returns and/or improve efficiency

• When first shifting to variable rate inputs, start with those that are not time-critical such as applying lime, gypsum or top-dressed nitrogen or potassium

• Variable rate technologies can allow for the matching nutrient or lime application onto the land where it is required, rather than blanket applications at one rate across a paddock or farm
• This approach may overcome inefficiencies in fertiliser/lime use and off-farm loss of nutrient in the form of runoff

• At seeding, PA tools such as guidance, autosteer and variable rate allow seed and fertiliser inputs to be changed on-the-go and placed where they are most needed; in many situations this results in improved productivity

• Precision Agricultural (PA) technologies are management tools that can assist growers to manage their farms on a site-specific basis
• Precision Agriculture technologies are a suite of tools which include Global Positioning Systems (GPS), yield maps, auto steer tractors, Controlled Traffic systems and Variable Rate (VR) and Site Specific Technologies. PA tools are discrete products that can be adopted individually or as an entire package
• Variable Rate is a subset of the PA suite of tools that allow growers to specifically treat areas within their cropping field
• Grain growers usually treat individual paddocks on a uniform basis regardless of variation due to soil type, topography and historic variation in yields

• VR allows growers to manage different areas within a paddock at a micro level, thereby applying inputs according to the potential of specific sites within a paddock
• In doing so, inputs, such as nitrogen, can be applied more efficiently and effectively. The applied rate is changed according to pre-set maps or through real time sensors. Real time crop sensors are able to deduce the crop�s physiology and detect early stress signals
• Sensing technologies can be used to assess nitrogen status in real time. Inputs are applied to alleviate crop stress. In this way inputs such as nitrogen fertiliser are applied at the right amount, at the right time, in the right place
• The greatest benefits from the application of VR are to be seen in areas of high variability

• Benefits of VR application will vary between regions and also between farmers within a region
• There is no clear answer what the benefits will be � therefore VR must be tailored to each farmer separately
• The first step is to start collecting spatial data about the farm such as yield, biomass, elevation etc. This information will empower farmers to make a sound investment decision about potential adoption of VR application technologies
• This step will identify in-paddock variation and will allow the farmer to decide whether the location warrants variable management. In-paddock variation can be measured and mapped at harvest and during the growing season while crops are growing. Soil variation is best measured between seasons. This data can be combined to produce management zones
• If in-paddock variation is present, then consider investing in low-cost technology first and then moving to increasing levels of sophistication as experience grows

• For example, many growers start with a yield monitor with GPS guidance that provides �10cm accuracy, and combine this with some soil sampling to produce blocked management zones; rates are then changed manually
• More experienced growers may install or share a base station and use Real Time Kinematic (RTK) guidance that gives �2cm accuracy, using auto-steer and equipment that can vary rates on the go in response to more complex management zones
• As a first step, the lime, gypsum or top-dressed nitrogen and potassium rate may be varied within or between paddocks based on a comprehensive nutrient analysis involving soil and/ or plant tests
• Starting VR with these activities allow operators to gain experience with equipment setup and coverage maps at periods when breakdowns or delays will not impact on harvest returns
• As experience and confidence grows, inputs can be varied at seeding when every second counts

• How do I manage the impact of compaction?
• How do I manage waterlogging?

• Precision Agriculture Factsheet - Grains Research and Development Corporation

• Tim Johnston - formerly DPI Geelong (pers. comm.).
• Andrew Whitlock - formerly DPI Geelong (pers. comm.).
• Insight into the Relevance of Precision Agriculture Technologies in Victoria�s Grain, Dairy and Horticulture Industries (2007). See Discussion Section � Department of Primary Industries, Victoria.

Page Updated: September 2013
Produced by AS Miner Geotechnical