From sowing to selling - PA techniques' whole-of-farm promise

Figure 1: a nitrogen fertiliser experiment laid out within paddock management classes, the resulting yield map and the responses from each class to the different nitrogen rates.

Precision agriculture is about more than knowing where to put extra fertiliser. For example, the highest-protein grain could be segregated for special orders, by Brett Whelan and James Taylor.

The Australian Centre for Precision Agriculture (ACPA) at the university of Sydney is looking at a practical approach to utilising PA tools. The team"s goal is the exploration and delivery of a generic strategy for the efficient integration of information from crop, soil and environmental sensing systems into farm management.

Working as part of the GRDC PA Initiative, with a number of grower groups and their consultants from around Australia, means that various differences in crop production systems can be considered and options tailored to suit. The table (below) provides a summary of the generic pathway that has been developed and considered by project participants. The steps are to be considered in numerical order so that the most benefit is gained with the least additional cost.

Generalised steps to making progress with precision agriculture

This does not mean they cannot be applied in conjunction, but each additional step in this process does require some new tools or techniques to be acquired and applied.

When we concentrate on the use of PA at the within-paddock scale, it is at steps two and three that most progress is being made. The team has been researching the most efficient approach (in terms of cost and descriptive ability) to completing these steps. The approach being examined involves:

Figure 1 shows the results of this process in a 50-hectare paddock in crystal Brook, South Australia. The uniform application rate for nitrogen was 15 kilograms per hectare. The in-season rainfall was slightly above average (decile 6); however, 77 per cent fell during the first three months and only four millimetres was received during grain filling in October.

Figure 1: Anitrogen fertiliser experiment laid out within paddock management classes, the resulting yield map and the responses from each class to the different nitrogen rates.

For this type of season, the results suggest that zones one and three were under-fertilised by the uniform rate and zone two was over-fertilised in terms of achieving the economically optimum barley yield. Results of this type are being shown across crop types and agro-ecological regions.

What is not considered in a basic yield optimisation experiment is the impact of nitrogen and soil moisture supply on the protein content of the grain. Having a grain protein sensor mounted on-harvester would provide valuable data to be used in conjunction with yield data.

The ACPA team and local farmers have been working with two international collaborators to modify and calibrate such an instrument for Australian conditions.

With the ability to monitor within paddock variation in grain protein, yield and moisture content, farmers will have a chance to more closely monitor the actual use of nitrogen.

A more complete economic analysis will be possible as quality (protein or oil content) can be incorporated into the calculations for each area in the paddock.

Gross margin, nitrogen uptake, nitrogen- use efficiency and nitrogen export can be estimated and mapped using this data. Figure 2 shows the type of information obtained from a 70ha paddock in Gilgandra, NSW.

Figure 2: Yield, protein and gross margin maps for a single paddock. potential revenue calculated at each point using grain yield, protein and moisture.

Figure 2: Yield, protein and gross margin maps for a single paddock. potential revenue calculated at each point using grain yield, protein and moisture.

The use of a protein monitor also offers the possibility for differentially harvesting or post-harvest grading of grain to fit particular receival standards or contract requirements. This is probably most suited to malting barley and specialised wheats such as durum and noodle varieties.

Using quality monitors in this way would allow growers to move towards quality control and marketing on the whole farm (step four in the table above).

The use of PA in the farming system requires benefits to at least match the costs of gathering and using the information. In simple terms, the potential benefits of PA are an increase in quantity and/or quality of production and/or environmental management along with a similar or decreased use of inputs.

We could also benefit from long-term improvements in operability, product auditing, tracking and marketing, storage of knowledge relevant to enterprise management and improvements in our overall contribution to rural communities.

Many of the potential benefits are overlooked because they are difficult to quantify on the "money-metric". collaboration between the ACPA, participating farmers and other PA teams is attempting to overcome this inadequacy.

GRDC Precision Agriculture Initiative (SIP09)
GRDC Research Code: US00017

For more information: Brett Whelan, b.whelan@acss.usyd.edu.au