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Trying an integrated optical sensor

Farmers have a lot invested in sprayers. Now they can get even more out of this investment by installing an integrated optical sensor. Sprayer-mounted optical sensors measure crop growth and provide instant information in real time. Sprayers are already making multiple passes over the field each season. Now farmers can easily collect extra layers of data to monitor crop progress and the crop’s response to growing conditions.

The ability to map and monitor a crop throughout the growing season provides a tremendous opportunity to remedy nutrient- deficiency situations by targeting applications specifically to needy areas of the field, or by varying rates. Sensors can identify nutrient-deficient areas and immediately top them up with nitrogen fertilizer, or suggest zones within the field for ground truthing.

Using the GreenSeeker

GreenSeeker is an optical sensor made by Trimble. Ilene Gellings, with Toerper Tech and Precision Ltd. at Wembley, Alta., provides sales and service support for the GreenSeeker optical sensor in the Peace region. Gellings says farmers are using the GreenSeeker as a tool to generate maps showing crop variation.

The core application is using it to read the crop, calculate a target product rate and control application through the sprayer. But Gellings also sees innovative farmers coming up with new applications for the technology.

Farmers using the GreenSeeker are not limited to collecting imagery from satellites and, when they’re using the optical sensors, are not limited by clouds or darkness. Farmers can collect images instantly as they drive across the field with the sensors mounted on the sprayer.

The GreenSeeker uses Norma-lized Difference Vegetation Index (NDVI) or what can be called a crop-growth map. According to Gellings, NDVI imagery is highly correlated to biomass — which is correlated to grain yield. Gellings recommends that growers work with an agronomist who is familiar with the technology to determine nitrogen application rates.

For a top-dressing application, farmers have to plan ahead. At seeding time, farmers should insert a nitrogen-rich strip somewhere in the field to ensure that nitrogen is not the factor limiting crop growth. Later in the season, the nitrogen-rich strip is used to set the upper limits for the GreenSeeker. Areas of the field with NDVI values equal to or higher than that nitrogen-rich strip don’t need additional nitrogen fertilizer.

The GreenSeeker needs access to a crop-specific algorithm and a measure of growing degree days from seeding to sensing. Crop- specific algorithms for wheat and canola in Western Canada have been developed by Agriculture and Agri-Food Canada (AAFC) and are available with the commercial unit.

Guy Lafond, the production systems agronomist with AAFC at the Indian Head Research Farm, has been doing research in this area since 2004. Lafond continues to work with the GreenSeeker technology, collecting information to develop crop- specific algorithms for spring wheat, winter wheat, durum, malting barley, oat and canola. From his field trials, Lafond sees the benefits of measuring not only the growth in the field but also the temporal or seasonal variability in a field. Nitrogen can be adjusted in real time to account for this variability.

Lafond believes that as more farmers use this technology, more applications will be identified for its use. Some of these additional applications may include in-crop fungicide applications, pre-harvest burn-down based on crop density and topography and simple field- mapping replacing the use of satellite imagery.

GreenSeeker at Elkridge Farms

A farmer may not want to commit all his fertilizer at time of seeding until he can observe some indicator of yield potential. The optical sensor can offer this extra information.

Gary Sanocki and Fiona Love from Elkridge Farms in Eaglesham, Alta., used a GreenSeeker system on their sprayer this past season. They were looking for increased yields and more efficient use of products. The plan was to apply a little less nitrogen with the drill and more in crop using, either liquid urea-ammonium nitrate (UAN), (28 per cent), or dissolving urea in water as a strategy to increase grain protein in wheat.

Sprayer operators at Elkridge Farms quickly learned to watch out for strips of green where the seeder missed. These missed strips will throw off the optical sensor. Sanocki says it took some time working with the machine to understand the sensor’s operation and capabilities. For example, it took a few hours in the sprayer to learn how the sensor reads straw and ground cover, and how big a plant has to be before the optical sensor recognizes and picks it up.

Sanocki is looking at doing more trials with the GreenSeeker to understand how plants respond to root-based uptake of nutrients compared to foliar-based uptake. He suspects that, after a wet growing season combined with higher crop yields, there should be less nutrient carryover into this spring.

Mineralization of nitrogen is not a constant process, but will vary throughout the year and between years, the main driver being weather. Sanocki said that the GreenSeeker “gives us a tool to quantify whether putting on more fertilizer makes sense.” Sanocki applies some fertilizer at seeding and plans to continue doing that, actually using some of the information from the imagery to help establish dry fertilizer rate-application maps.

Sanocki says they can top dress without the optical sensor, but GreenSeeker provides an additional layer of precision. They got into the field a little later than they wanted to this year, top dressing some of the canola when it was starting to flower. With the flowering canola, they had to make some adjustments to the basic algorithm.

Sanocki sees the GreenSeeker as a real diagnostic tool that logs information with every sprayer pass. It did show wild oat and thistle patches, but the sprayer valves probably do not have a fast enough reaction time to spray them. Last season, Elkridge Farms was able to apply 800 acres worth of canola fungicide over 1,000 acres — product was spared where the crop was poor from water logging or drowning, saving money and making their operation more efficient.

An integrated crop optical sensor is a tool farmers can use to assess the growth of their crop for nutrient sufficiency. The ability to map and monitor the crop throughout the growing season provides a tremendous opportunity to get the most from a crop using targeted application rates of nitrogen fertilizer and maybe for other crop protection products. †

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