Saskatchewan farmers Grant Fulton and Lee Moats like the idea of applying nitrogen fertilizer when and where it is needed. For years they’ve had little option other than applying all their nitrogen at the time of seeding or before with hopes the growing season co-operated. This year, using GreenSeeker technology on field sprayer, s they’ll have the choice of top dressing wheat and canola crops with liquid nitrogen based on current weather and moisture conditions.
The two producers will be using GreenSeeker technology for the first time in 2009. Fulton crops about 2,800 acres of grains and oilseeds and pulses at Shelbrook, just west of Prince Albert. Moats produces about 2,600 acres of winter wheat, canola, lentils or durum, canary seed and flax at Riceton, just southeast of Regina.
GreenSeeker is variable rate fertilizer application technology developed at Oklahoma State University and licensed to NTech Industries in the United States. Pattison Liquid Systems of Lemberg, Sask., markets GreenSeeker in Western Canada. In simplest terms, GreenSeeker sensors mounted on the sprayer read the growth — or “biomass” — of the existing crop. It determines if more nitrogen fertilizer is needed to optimize yield by comparing sensor readings to those from an area that is not limiting in nitrogen. The system doesn’t flog a dead horse. It stops applying nitrogen when it comes to poor producing sites in a field and increases the rate of N when it comes to the better producing sites.
“I like the idea that when I pass over those sandy knolls or poorer producing sites, it’s not going to apply more nitrogen,” says Fulton. “Instead when I come to the better producing areas of the field, that’s where it will increase the nitrogen rate to increase yield where it has most potential.”
Moats says he hopes GreenSeeker technology will help him avoid situations like he ran into last year. “In 2008 on our farm we started out the year applying a full rate of nitrogen as recommended by the soil test, with a bullish outlook for wheat for the year,” says Moats. “Then we were struck with a very dry spring. The result was that we didn’t recoup a very good return for the amount of nitrogen we applied.”
If he had been using the GreenSeeker system last year, Moats figures he would have saved enough on nitrogen to recover the cost of the technology in one year.
A lot of science and leg work over the past four years that has gone into developing GreenSeeker technology, making it applicable to grain and oilseed crops in Western Canada. That said, the system is simple and can be adapted to most field sprayers.
FULTON LIKES THE CONCEPT
“The beauty of this system is that you can apply part of your nitrogen at time of seeding and then if growing conditions are poor, you don’t need to apply more nitrogen,” says Fulton. “On the other hand, if we have good growing conditions we can top up the amount of nitrogen in crop and maximize yields.
“I haven’t used it yet, but it is a much better concept than putting everything on at seeding and then hoping for good weather. You can decide mid-season if conditions warrant more fertilizer.”
Rick Pattison of Pattison Liquid System became the Canadian marketer of NTech’s GreenSeeker technology five years ago. The proven technology was developed for crops produced under U. S. growing conditions, so he immediately brought the technology to researcher Guy Lafond at Agriculture and Agri-Food Canada in Indian Head, Sask., and asked if he could calibrate GreenSeeker to work with the main Western Canadian grain and oilseed crops.
Over the past four years, Lafond has worked with Chris Holzapfel, research associate with at the Indian Head Agriculture Research Foundation, to collect data from thousands of crop plots to develop the algorithms or equations that make GreenSeeker compatible with Prairie crops.
“We now have the final algorithms for spring wheat and canola, so 2009 is really the first year that we will be marketing GreenSeeker,” says Pattison. “The data for other crops such as winter wheat, barley and oats is partially complete. It is part of the system, too, but more data is needed before we have the final algorithms for those crops.”
Researcher Guy Lafond says in an era of precision farming, he likes the fact that GreenSeeker responds to both spatial and temporal variations based on current conditions. That means GreenSeeker adjusts fertilizer application over the varying production capability of a rolling landscape (spatial variations), for example, and because it allows for a split application of fertilizer, the producer can decide if more fertilizer is required based on current growing conditions (the temporal variation).
“Some other variable rate fertilizer application systems rely on cropping history,” says Lafond. “Their rates are based on what grew on the field last year and what yields have been over the past several years. GreenSeeker works on a real time basis. Its sensors read the plant growth in the field this year and, based on the algorithms or equations developed after analyzing thousands of plots under various growing conditions, it can determine whether more fertilizer is needed for the crop to reach it’s optimum yield potential.”
HERE’S HOW IT WORKS
A key element that allows GreenSeeker to work is NDVI. That stands for Normalized Difference Vegetative Index. The NDVI, which can be obtained from satellite imagery, is a measure of crop biomass (what is growing out there). There is a strong correlation between the total above ground biomass and the final grain yield.
You can buy NDVI images. Or you can take your own using a field sprayer is equipped with GreenSeeker sensors.
Grant Fulton expects to be able to go out and spray a herbicide on the crop, perhaps in early June, for example, and GreenSeeker will create a new NDVI map for that field while he applies herbicide. If he has a decent growing season, he can then come back with the field sprayer a week or two later and top dress the crop with liquid nitrogen based on those NDVI images. And if it’s a dry year, he can leave the sprayer parked.
Both Fulton and Moats say the basic approach is to apply between 50 and 60 per cent of the recommended nitrogen the crop needs at time of seeding. And then come back to top-up nitrogen mid-season as needed.
One other key element that allows GreenSeeker to work is to create what is known as N-rich strips in the field. This is the yield or biomass benchmark. Lafond says they don’t need to be large strips, but over a good producing area of the field the producer would create a strip of crop (300 or 400 feet long perhaps) at the time of seeding that receives about 150 per cent of the recommended nitrogen rate. That strip serves as benchmark for the GreenSeeker sensors as the upper end of crop growth.
So when it comes time for the in-crop top dressing, the idea is to pass one half of the sprayer boom with GreenSeeker sensors over the N-rich strip, while the other half of the boom with sensors passes over crop that has received only 60 per cent of recommended nitrogen at time of seeding. By comparing the NDVI of the crop being evaluated to that of the N-rich strip in the field, the farmer can make the decision whether a pass with the GreenSeeker sensor is warranted over the field.
“The principle behind this technology is that the plant can provide you with an estimate of its yield potential nitrogen status,” says Lafond. “It reflects the nitrogen applied at time of seeding and the amount of nitrogen mineralized in the soil from seeding to the time of NDVI measurements. The technology provides application only where there is a need for additional nitrogen to avoid over-application. An important aspect of the technology is that it can account for a greater proportion of the spatial (landscape) variability in the field. This allows for more efficient nitrogen use and potentially better economic returns.”
WHEN TO TOP-DRESS
In spring wheat, the top dressing should be made between the fifth leaf and start of flag leaf emergence. In canola the top dressing should be made sometime between the start of bolting and the first flowering.
For the equipment itself, Pattison says the GreenSeeker technology costs about $22,000. Two people can install the system in an afternoon. Components include six sensors that can be attached to any boom width, whether you are using a 60 foot or 100 foot wide sprayer. As the sensors “read” the crop, a built-in microprocessor analyzes the NDVI readings (the crop biomass) and determines the nitrogen requirement to meet full yield potential. That information is relayed to the rate controller to provide variable rate nitrogen application in real time as the sprayer moves across the field.
For more information on the GreenSeeker system contact: Pattison Liquid Systems at Lemberg Sask., at 306-335-2215 or visit the NTech website at www.ntechindustries.comand click on the GreenSeeker link.
Lee Hart is a field editor for Grainews in Calgary, Contact him at 403-592-1964 or by email at [email protected]