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Precision measurement for more effective management

Precision farming is a concept that is seen in every magazine or publication nowadays and is defined and approached from every angle. According to the McGraw-Hill Dictionary of Scientific & Technical Terms, precision farming is “the application/use of technology and agronomic principles to manage the spatial and temporal differences associated with all aspects of agricultural production, with the aim of improving crop performance and environmental quality”.

Precision farming is currently regarded as the most promising agronomic approach to ensuring sustainability. This approach focuses on making the right choices to optimise yield and quality, while reducing the impact on the environment and lowering risk.

There are, of course, several aspects to precision farming such as soil classification, grid-based soil sampling, variable rate fertilization, variable rate seeding, yield monitor data, remote sensing, etc. These different aspects all represent ways of measuring soil, crop and management aspects in order to continuously improve economic sustainability, as well as the impact on the environment.

If measurements are not taken, how will the producer decide which matters should receive attention to ensure that he achieves optimal production from all his assets and that inputs are correctly applied? And furthermore, on what basis will he determine and manage his risks?

Over the last seven years, OmniPrecise™ has taken and measured 843 410 topsoil samples, 91 000 subsoil samples and 80 000 soil profile observations across South Africa on behalf of farmers. This information was converted into maps whereby the farmer and his Omnia agronomist could make informed decisions. Hundreds of farmers trust Omnia every year with their soil and yield data to supply tailor-made recommendations, as well as the eventual prescription maps used by unique application computers of the various tractors and applicators. OmniPrecise™ is continuously challenged by agronomists and clients to stay well-informed of the latest technological developments in terms of measurements and sensors.

Although there are various methods and sensors for measuring, this article deals with the value of long-term yield monitor data and its use to identify, quantify and manage risk and fertilization strategies.

Yield monitors measure several parameters and link them to their spatial position in a given field by means of various sensors as well as GPS technology. The most important parameter is, of course, the amount of grain harvested. Yield is the integration of all the facets that had an impact on a specific season. Most producers only look at the yield monitor as the harvester moves across the field, just to obtain the maximum yield harvested on the day. There is, however, so much more that a producer can get out of this information that will simplify his future decision making and increase his productivity and efficiency as a result.

An employee of a well-known American company once said: "The information that this equipment gathers these days, is worth much more than the equipment itself". We should therefore ensure that the data gathered by the yield monitors is processed properly so that key parameters can be calculated to support management decisions. One of these parameters or derivatives is the management zones obtained by comparing the information over a number of seasons. Even though this information is historical in nature, it can serve as a foundation on which future decisions can be based.

Figure 1 shows yield maps for four different years. There are obvious similarities between the various seasons, even though the rainfall differed drastically between them.

Figure 1: Yield maps of different years
Figure 1

Data from these four seasons were added to identify spatial management zones over time (Figure 2). In this case, three management zones were identified: Low, average and high. "Low" represented the zone where the yields realised were less than 75% and "high" were where more than 125% of the average yield over the four seasons were realised.

Figure 2: Spatial management zones
Figure 2 management zones

This management zone map (OmniZone) can be used to set yield targets for every zone in order to make effective fertilizer recommendations.

We have the different zones, but the question now is: What should my planned yield per zone be for the coming season? This is where decisions regarding risk have to be made.

"RiskIQ" (Graph 1) is a unique model of Omnia Fertilizer which plots the cumulative probability for a certain yield per zone on a graph by looking at what happened in the previous seasons. It is also applicable in crop rotation systems.

Graph 1: Risk analysis based on yield data from previous years
Risk analysis based on yield data from previous years

If the producer decides to aim for a yield that, according to historical data, has a 50% probability of being realised, then the yield target for the "low" yield zone (red) will be 4.37 t/ha, the "average" zone (green) will be 6.96 t/ha and the "high" (blue) yield zone will be 8.29 t/ha. If the producer wishes to approach the coming season more conservatively and fertilize according to a yield that, according to historical data, has a 70% probability of realising, the yield targets will be 3.09 t/ha, 4.93 t/ha and 6.89 t/ha, respectively. The more information (seasons) used in this analysis, the more seasonal variation is taken into consideration to better quantify the risk.

This information will assist farmers in preventing under-fertilizing on high-potential areas and over-fertilizing on low-potential areas – in other words the right product, at the right time, in the right place, at the right rate.

Several facets of the Omnia RiskIQ model, such as the gradient of the cumulative probability curves, are quantified and then deliberately monitored year after year to measure whether the applied management zones caused a real improvement and whether it was profitable.

Speak to your Omnia agronomist. Maybe your unused historical yield data can add real value to your precision farming through the use of the Omnia RiskIQ model.

Measure your yields to manage your fields!

By Tiaan Terblanche: Manager - OmniPrecise™