CALGARY — In the “Case of Disappearing Pesticides” the farmer applied a herbicide with a 45 day active life. Three days later it was gone, nowhere to be found. This happened repeatedly.
The disappearing chemical caper took place not long ago, says Colorado State University re-searcher Raj Khosla, speaking in Calgary earlier this year.
“We were working with a local farmer who told us he had reached the point he needed to apply three or four times the recommended rate to achieve the same efficacy he should achieve with a single application,” recalls Khosla. He says the mystery was the same for herbicides and some insecticides, but not fungicides.
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“In herbicides especially, we found that products which were supposed to remain active 45 days were dissipating in three days. We logically thought his herbicides were leeching into the soil or maybe there was a severe resistance problem. We tested those two theories and they were both wrong.”
Khosla says one of his graduate students suspected carbon. Carbon is one of the components found in crop protection chemicals. And carbon is the basis for all life on Earth, including soil microbes.
Every living species goes after the source of carbon most readily available, even if that source is intended to be a poison.
“We analyzed the microbes and determined they had received so many heavy applications of these products that they adapted. The soil microbes were looking at these pesticides as a carbon source. The farmer applied the pesticide and the microbes would eat it up, chew it up in just three days. One of my graduate students did a literature review and found this same thing happening all around the world.”
Khosla says in situations such as rapidly evolving soil microbes, lab work and open-minded thinking are the best tools for finding the solution. And, he says, there’s no replacement for feet-in-the-field scouting.
But for getting a handle on the overall health of large fields, crop sensors are becoming more useful.
Crop sensors have come a long way in past 10 years since we only had satellite imagery, says Khosla.
“With the satellites, we had problems due to clouds. The timing was often bad, and we didn’t get the information we needed until two weeks after we needed it, by which time it was worthless. We couldn’t always get the kind of high resolution images we needed to analyze what was happening in the field.”
He says there have been major advances in past 10 years. The sensor is now closer to the crop. You can hold it in your hand, mount it on a tractor, mount it on a sprayer, or put it on a drone helicopter or fixed wing UAV.
“However, we’re still working primarily on the principle of reflected data. Light that is reflected off the surface of the plant. It may pick up different wave lengths, but it’s still reflective data.
“Most sensors currently on the market give NDVI. But they don’t tell us if the lower NDVI numbers are coming from lack of nitrogen or lack of iron. We’re harnessing a very narrow portion of the entire world of remote sensing. There’s florescence, absorption, transmission, reflectance.”
Normalized Difference Vegetation Index or NDVI, uses remote sensing to assess whether the target contains live green vegetation.
Given the shortcomings of crop sensors, Khosla says many producers still end up making management decisions based on yield maps, probably the best available tool if dealing with large acres.
He emphasizes that having confidence in your yield monitors requires plenty of information.
“Yes, you really do need seven years of data if you’re trying to make good decisions based on your grain yield monitor. Here’s why. You need to run a stability analysis. It’s not just to pinpoint high and low yielding areas of a field. You need to know how consistently they’re high or low or in the middle. Consistency or stability is the key here.”
He says that once you have the stability analysis, you can make intelligent, informed decisions about how to treat each area. A common reaction to the seven year recommendation is that nobody has the mammoth computing power to handle so much data.
“Not true. The cell phone you’re using today has more computing power than the computer we used to put a man on the moon. We have more computing power than we know what to do with. In most cases, the grower hires a professional agronomist anyway. He’s equipped and trained to work with large volumes of data.”
