Determining optimal nitrogen application rates based on local soil conditions for specific crops can be done quickly and cheaply, said John Heard, a Manitoba agriculture soil fertility specialist based in Carman.
The method was developed at Oklahoma State University for use in calibrating Greenseeker technology. The nitrogen rate “ramps” consist of three metre by three metre test plots in a field placed side by side with application rates that step up incrementally from zero to 200 pounds per acre.
Armed with common sense and a good eye for the deep green colour plants develop when they are getting enough nitrogen to keep them happy, healthy and productive, a producer can find out if an extra 10 lb. of nitrogen is worth the expense.
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“Then they found out, you know, my God, I don’t need that $4,700 piece of equipment. I can just walk along there and see green myself,” said Heard. “It’s that simple.”
Building a ramp during spring seeding needn’t take much time, he added.
First, an unfertilized strip is set aside after seeding. Then, weighed amounts of granular urea fertilizer are added to each plot with a hand spreader at incrementally rising rates.
Later, the farmer can simply look at the side-by-side plots to determine which rate provided the best cost-benefit result.
“You just walk along and look for the darkest green with lowest rate of nitrogen,” said Heard. “It’s very interesting to do.”
Farmers who don’t trust their own eyes could have their crop consultants set up the ramps.
Heard also showed how a simple green colour match chart was developed for rice fields. Much like paint match strips used by homeowners, it enables producers to determine at minimal cost whether a field is receiving an optimum rate of nitrogen using a single leaf taken from a plant or the whole field.
“You can just hold it at arm’s length. It’s made for farmers because you can do it out the window of the pickup truck,” he said.
“It’s just doing what you already know. You know that if you have a pale coloured field you’re lacking some nitrogen but you don’t know how much.”
Test strips for other crops haven’t yet been developed, he said.
Technophiles can also use the Greenseeker chlorophyll meters and tissue testing with their ramps for more precise results, he said. Even the latest high-tech gadgetry is cheap compared to the cost of an unneeded tonne of fertilizer, he said.
Nitrogen rate ramps could be a boon to farmers using manure, whether livestock or plowed-under legumes such as alfalfa or red clover, because it allows them to determine optimal rates for adding supplemental fertility.
Also, traditional soil testing may not indicate how much or how quickly natural manures may be mineralizing in the soil and becoming available to the crop.
“If we’re going to pare manure and (nitrogen) rates right to the bone, you people need to be able to scout those fields so that when you do run short, you can come in and make a correction,” said Heard.
