INDIAN HEAD, Sask. – Prairie farmers have known about GreenSeeker technology for six years, but the in-crop nitrogen sensor was calibrated for Kentucky growing conditions. This has prevented Canadians from showing much interest until recently.
The installation of GreenSeeker variable rate controllers on a handful of high clearance sprayers in 2005 has put genuine calibration data for Canadian conditions within reach. Field-scale GreenSeekers join the dozens of hand-held sensors used by researchers and a few farmers.
When mounted on a spray boom for in-crop nitrogen application, GreenSeeker tells the variable rate controller how much N is right for each spot in the field.
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When calibrated correctly, the device reads the biomass of the crop at the precise moment the sprayer is passing over that spot. It runs this data through a computer that compares the biomass to the potential top yield of that crop. It then determines the appropriate rate of N for that spot and sends the message to the variable rate controller.
The key words are “when calibrated correctly.” With a decade of financially positive on-farm results in the southern midwestern states, there is no doubt that the machine works.
Although formulas designed for spring wheat in Kentucky can be used with some success for spring wheat in Western Canada, they are not as accurate as if developed for the Prairies.
In 2005, the Indian Head Agricultural Research Foundation launched a three-year project to calibrate Green-Seeker software for Canadian prairie conditions.
By using the GreenSeeker in full-size field trials on an 80-foot boom, and also in small test plots, the foundation is working to develop algorithms that are specific to prairie latitude, soil and other unique enviro-nmental factors.
The foundation is one of the first organizations to do so. But, before it can build usable software, the field tests will need to be run in a variety of prairie conditions, ranging from drought to extreme rainfall, and everything in between.
Does GreenSeeker really do what it’s supposed to do? Chris Holzapfel is the research associate in charge of the first year of the foundation’s project. He operated the high clearance sprayer equipped with GreenSeeker in 10 different 50-acre fields. He also did the small plot work.
“In actual field conditions, the variable rate controller was changing all the time,” said Holzapfel. “On the monitor, we saw a lot of variation in the amount of N required by the crop. It changes quickly, even at five miles per hour ground speed.
“One spot might only require four lb. per acre. Another spot not far ahead might require more than the full amount we had put down in the test strip. In a canola field, the extremes might range from zero lb. of actual N all the way to 60 lb. In wheat, it might range from zero to 45 lb. of actual N.”
Holzapfel explained that the job of the GreenSeeker is to take an instantaneous reading of the health and yield potential of a specific spot in the field. The computer compares this data to the theoretical maximum yield and the environmental conditions up to that day.
Armed with this information, the GreenSeeker tells the variable rate controller how much liquid N to apply, foot by foot, as the applicator travels down the field.
The 80-foot boom on the foundation’s sprayer was equipped with six RT200 sensors. Each sensor takes a reading and sends it to the central computer that averages them. The entire boom then puts out the N dosage recommended by the GreenSeeker computer.
“The GreenSeeker people are testing a more sophisticated set of equipment down in the States. Each nozzle on the boom has its own sensor, so they get one metre square accuracy and a full variable rate from one end of the boom to the other,” said Holzapfel.
The equipment being tested at Indian Head blends the input from all six sensors, so there is just one rate for the whole boom. It’s a lot more expensive to control each nozzle individually.
The RoGator 554 sprayer is owned by the foundation. The RT200 Green-Seeker equipment, valued at $18,000, is donated to the project by Pattison Liquid Systems at Lemberg, Sask.
Holzapfel said the controller prevents high speed N application.
“The GreenSeeker is fast at analyzing the input data and giving us the correct N rate. I’d say the RT200 part of this whole operation could probably handle 15 miles per hour or faster.
“We’ve got a Raven variable rate controller, and it just cannot react quickly enough to let us run at those higher speeds. I think we’d have the same problem with any controller on the market today. They cannot adjust their pressure quickly enough to handle so many rate changes every minute.
“For us, it’s not hard to work around the slow response time this year. We just slow down to five miles per hour ground speed. We knew going into this project that we wouldn’t be spraying at the speeds a farmer or a commercial applicator runs at. But, for research purposes, this is working out just fine.”
The 10 test fields are located near Raymore, Lemberg, Kendal and Indian Head, Sask. There are five canola fields, two durum, two spring wheat and one winter wheat field.
Establishing an algorithm for a certain crop in a specific geographic area requires a large amount of field work and number crunching. To begin with, the scientists need to establish a typical growth rate for each crop in each type of growing environment.
In the test plots, they try to establish the widest possible range of yield potential. They go in with a hand-held GreenSeeker every week from emergence up to maturity, or flowering for canola crops.
“This documents the crops’ above ground biomass,” said Holzapfel.
“The measurement unit is known as NDVI, or normalized difference vegetative index. We can divide this NDVI by the number of growing degree days from the seeding date. That gives us a growth rate.
“We correlate the growth rate through the season until we reach the final yield for each plot. This gives us the algorithm progression we need so that next year, we can move into a similar crop and start to make predictions of what the potential yield might be and how much N is appropriate at the moment a GreenSeeker takes a reading.
“And that is the key to determining how much additional N, if any, should be applied for an economic benefit.”
He said the team of Canadian scientists working on the GreenSeeker project thinks the algorithms will be universal across the Prairies, but they can’t be sure until they have enough years of data under varying conditions.
“It’s too early to say for sure how large each zone will be,” said Holzapfel. “We may have to break things up into smaller climatic regions and soil zones.”
With a price tag of $18,000, commercial applicators and some producers with large farms can justify buying into the GreenSeeker technology, especially with N in the neighbourhood of 50 cents a lb.
But Holzapfel said two things may cause producers to hesitate. The first is ground speed. Five miles per hour is too slow. However, the GreenSeeker is compatible with every variable rate controller on the market, so it’s only a matter of time before competition between those suppliers creates quicker controllers.
The other negative factor is more a matter of perception than reality, said Holzapfel.
“A lot of guys don’t want to top dress N because they think it interferes with their herbicide application. They’re not set up for that one additional N pass over the field.
“But think about this. You can’t spray herbicides if it’s raining or if it’s too windy, and most guys won’t spray herbicides at night. So there’s plenty of opportunity to get out there with your sprayer and put down some liquid N.”
The GreenSeeker has its own light source on each sensor, independent of sunlight, so it can be used on a cloudy day or in pitch dark in the middle of a rainstorm.
Similar three-year calibration projects also started this year at Brandon, Swift Current and Scott, Sask.
Unless there is an unforeseen problem, the four research sites should provide a basic set of Canadian prairie algorithms for using a GreenSeeker technology to top-dress N in canola and wheat.
