Is it worth mapping your paddocks?

PA"s tools produce a considerable amount of visual data like these yield/biomass paddock maps

Full PA could mean a big commitment in equipment, training and time. But it need not be a leap of faith: initial steps can help determine whether it will be worth doing, writes Phil Price.

The term Precision Agriculture (PA) means different things to different people. The definition used by the GRDC for its national PA research initiative is: "information-rich agriculture. The use of yield maps, other spatial information and input-control technologies to better match agronomy to paddock variability. The aims are to increase profit and improve environmental management."

The underlying concept of PA is that by better matching crop inputs and agronomy to the specific characteristics of particular parts of a paddock or farm, graingrowers can improve profit and protect the natural resource base by reducing over- or underapplication of expensive inputs.

The basic tools needed for PA - GPS positioning and guidance, biomass maps and yield monitors, and variable rate applicators - have been available in Australia for more than a decade. Early research into PA showed potential for significant cost savings and/or improved crop returns of around $10 to $50 per hectare. More and more growers are starting to use some components of PA, for example guidance (maybe with autosteer), to improve the efficiency of spraying and spreading or to sow accurately between last year"s crop rows. But the full adoption of PA as defined previously remains very low.

Why? There are several reasons. Getting the different parts of a PA system to work together can be difficult, especially if they come from different manufacturers. The investment needed to buy and set up for full PA is quite high (although decreasing), and growers are not yet confident of getting a return on their money. For many growers, variability in crop yield across the farm or within individual paddocks is not their first priority, either because this variability is naturally low, or because better management of weeds, diseases, nutrients, or matching crop inputs to season, remain more important in driving yield and profit. In some paddocks the potential management zones (those of high or low yield and profit) seem to change position from year to year according to the season or crop type; this makes it difficult to predict with confidence what zones should be used in the coming season for differential management.

A final and very important reason is that to turn PA data into useful knowledge, and to interpret it in a way that enables growers to make better decisions, requires a high degree of skill and experience, and so far there are not enough people trained in PA to support graingrowers in this way.

Against this background, the GRDC PA Initiative was established in 2002-03, with the aims of further developing PA methods for use by Australian growers, evaluating and demonstrating those methods in different cropping regions and systems, and providing education and training information about the practical use of PA. It comprises 10 projects where growers and researchers are working closely together to make the promise of PA a reality. Within the PA Initiative we consider there are four broad stages in growers using PA. They involve:

Recognising that significant variability in yield and profit is occurring within a paddock or across the farm, and determining whether the yield zones are stable or unstable between years (seasons) and different crops. This stage is generally achieved from growers" own knowledge of paddocks, and from biomass (NDVI), yield, quality (for example, protein) or gross margin maps based on processed data from satellites or the header.

Identifying the underlying causes of yield variability. These could include soil depth, soil type (water holding capacity, nutrients), elevation, acidity, sub-surface salinity or compaction, presence of soil pests and diseases, or the influence of past management (old fencelines, windrows, previous crop type). This stage requires the comparison of biomass or yield/quality zone maps with other mapped data for the paddock, for example from soil tests, EM or gammaradiometric surveys, disease testing, aerial photographs or contour data, followed by field inspection and tests to ensure the correct causal factors have been determined.

Where there are several likely causes, it is important to get a sense of their relative impact on yield and profit. By the end of this stage, growers should know what the main underlying causes of yield variability are, and whether it is practical to do anything about them, either by direct amelioration (for example, ripping, correcting nutrient deficiency, liming) or by changing management (for example, use of a tolerant crop, reducing fertiliser inputs on non-responsive areas and increasing them where there is a good yield response).

Asking "is it worth managing the spatial variability?" in other words, knowing the scale of variation in profit (stage 1) and the underlying causes and possible solutions (stage 2), is it worth doing anything about it? in this stage we can use grower/adviser experience and crop models to help assess the likely impact on yield under different seasonal conditions and between different crops. By combining the results with financial analysis, growers can work out whether it is economically sensible to tackle spatial variability using PA, and if so what its relative priority should be in the farm or cropping budget.

This is where we can "roll out" PA within a cropping district. Having gained experience from the first three stages on several paddocks or farms in the district, growers, advisers, farm consultants or extension officers should be able to go to a new paddock or farm and identify, with some confidence, the likely underlying causes of yield variation and advise whether and how that variation can be managed to improve overall yield and return.

The SIP09 projects are tackling the different stages in PA in different ways, as described in this supplement. By the end of the initiative, in 2007-08, a significant number of growers and grower groups will have used and tested PA methods through all four stages, with the results reported widely throughout the grains industry.

It is unlikely PA will be a panacea or "silver bullet" for all graingrowers, and the best PA techniques to use and how best to apply them are likely to vary across districts, farms, and perhaps even paddocks.

In some situations, PA may have little to offer, for the reasons listed earlier. But for many growers, once the basics of the cropping program are working well and management is being varied according to season and available soil water, then PA may well be the "next big thing" to lift profit and sustainability. The experiences gained across the different PA projects, and the tools being developed to help growers decide whether (and when) PA may be valuable for them, will assist growers in making decisions about, and applying, the different components of PA.

The project teams within SIP09 are also developing a national framework for education and training in PA, as well as education and training materials. This will, in time, help to overcome a major impediment to adoption of PA in the Australian grains industry: the lack of people with technical training in PA. GRDC Precision Agriculture Initiative (SIP09)

Below: PA"s tools produce a considerable amount of visual data like these yield/biomass paddock maps. Such maps give growers and advisers a ready appreciation of the situation, which can then be analysed in detail.

For more information: Phil Price, consultant to GRDC Agronomy, Soils and Environment Program, 02 6251 4669,