In-Season Use Of VR

On the fields where we used this program last year, we saved between $3 and $4 per acre after the cost of the imagery and variable-rate prescription generation. This is compared to applying the full rate over the whole field.

Say an economical level of disease damage is expected in only the thickest parts of a field. Wouldn’t it make sense, therefore, to target fungicide sprays to those areas and skip over the rest? Variable-rate application of pesticides has been very successful in certain areas. In the U. S., high resolution aerial imagery is being used for variable-rate application of defoliants in cotton fields with very positive results.

Data needed to determine where to spray can come from remote sensing, say from a plane or satellite. You can use images from cameras or from sensors that record different bands of light that are reflected from the crop or soil. This can highlight foliage density, highlighting areas that are thickest — and therefore most like to have canopy conditions most hospitable for disease. In most cases, we are working with NDVI images or maps of the field. NDVI stands for normalized difference vegetative index, which is a combination of red and near infrared reflected light.

NDVI images show variations in vegetative growth, density, plant health and vigour. In the past, the only easily accessible remote-sensing product that was affordable for agricultural use was satellite imagery at 30-metre (100-foot) resolution. This gives a reflective value for every 30 m by 30 m square across the field — which is not very useful for variable-rate application of pesticides. But now one metre resolution is affordable, which is 900 times higher resolution. This more clearly shows what is going on in the field. And we can get these images when we need them, which is equally important.

Unlike variable-rate fertilizer application, which can use data collected over a period of years to write a prescription, variable-rate pesticide application requires immediate and detailed data. Because growing crops are affected by so many factors, you cannot predict crop growth, density, weed, insect and disease pressure ahead of time. We are not able to use dated satellite imagery or previous yield maps to guide these type of variablerate applications.


Green Seeker is a remote-sensing product that can be mounted on a sprayer. It records variations in the field as you drive. This product is mainly being focused on in season variablerate applications of nitrogen.

The technology we are most excited about is higher-resolution images that we can acquire in a timely fashion. Real Shot’s one-metre aerial imagery is one example. This technology combines highly advanced camera systems mounted on planes that can be dispatched over your fields. We get a very accurate one-metre resolution image that can be collected when you need them. Turnaround time is usually under a week and in some cases within a few days. We can then scout the field to verify — or ground truth — the information.

Another exciting remote-sensing product just hitting the market is a new satellite imaging service offered by Rapid Eye. The Rapid Eye system can take high-resolution satellite imagery when you request it, and deliver the product very quickly. So let’s get down to what we can do this stuff.


One of the biggest opportunities for these imaging products on Prairies is variable-rate fungicide applications on canola for control of sclerotinia. This makes sense for numerous reasons. First, we know that heavier or denser canopies of canola will be at higher risk for disease. Heavier canopies will hold moisture longer during the day and have a lot higher risk of catching infected petals in the branches, which will in turn infect the plant. Lighter areas of the field will not hold as much moisture in the canopy and will have less chance of catching petals in the branches. Therefore having a lower risk of infection. Second, applying fungicide is like applying paint. The more surface area (plants or biomass), the more “paint” you need to provide coverage and protection.

The example shows a picture of a canola field taken using high-resolution one-metre Real Shot imagery on July 10, 2008. By Monday morning, July 14, we had an image in our hands and created a variable-rate prescription. We were in the field spraying by noon.

We split the field into three zones. In the lighter or poorer areas of the field, we shut off application of fungicide. In medium areas of the field, we applied the lower rate. And in the heaviest areas, we apply the full rate.

On the fields where we used this program last year, we saved between $3 and $4 per acre after the cost of the imagery and variable-rate prescription generation. This is compared to applying the full rate over the whole field.

This does not factor in the value of increased efficiency or the environmental benefit of applying products only where most needed. At a recent meeting I attended, it was mentioned that Europe is concerned about the amount of fungicides being used and their impact on the environment.


Variable-rate pesticide application could also work to control wild oat patches in wheat and other crops. Imagery can show higher pressures of wild oat infestations. In one particular field, we had a Real Shot one-metre NDVI image taken a couple weeks after application of herbicide. We were able to identify different patterns in this field. After some investigation out in the field, we found that heavier areas of vegetation as shown on the image were caused by heavy wild oat infestations and poor control.

With a quick trip to the field and a little bit of scouting, we could have easily created an application map so you would only have to apply a second pass of wild oat control in the areas needed. We were not able to execute this plan at the time, but there would have been some good savings in using a variable rate application compared to spraying the entire field.

These examples show how new advancements in remote-sensing can help reduce pesticide costs. We will continue exploring the different uses for this technology with my clients and other clients and agronomists within the Agri-Trend network. Farms will need good GIS mapping, GPS and technical support. They will also need very strong agronomic support to help build the proper processes to best utilize these new technologies to create precision profits.

Terry Aberhart farms at Langenburg, Sask. He is also an Agri-Coach with Agri-Trend Agrology. You can reach him at [email protected]or 1-306-743-7657.

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