Those healthy looking soybeans may be hiding a hunger for nitrogen that could deliver higher yields.
The oilseed’s nitrogen needs have been much studied over the years with researchers generally agreeing higher rates of nitrogen don’t pay, but that may not be the case when growers push for higher yields.
On this episode of the RealAgriculture Soybean School, Horst Bohner, Ontario Ministry of Agriculture, Food and Agribusiness soybean specialist, shares what he’s learning about soybean’s appetite for N in trials across the province.
Bohner notes that researchers concur that there is a nitrogen starter fertilizer affect that will reliably deliver two to four bushels per acre. He also adds that when it comes to nodulation, growers have to be careful with higher rates that could compromise nodulation and also increase lodging, especially in more lodging prone varieties.
In the video, Bohner shares data from 1oo U.S. trials that show soil nitrogen and nitrogen fixation can deliver the needs for up to a 60-bushel crop. According to the data, when a crop gets to 80 bushels its missing at least 30 lbs of N.
“But you can’t visually see that,” says Bohner. He notes, however, that “we now have some good experimental data that shows there is a hidden hunger. There is a yield lag once you start to get into higher yield situations, and it’s a surprisingly big number.”
How big is that number? Bohner points to recent intensive management soybean trials in Ontario. At these high yield locations — good fields with sufficient P and K — yields were reduced by 6 bu/ac when nitrogen fertilizer was removed from the management package.
With those insights, Bohner is now focusing on how growers can best fill this nitrogen need. He’s just harvested a series of trials that looked at a range of nitrogen sources, including slow release products as well as biologicals. He says plot yields will tell the full story, and more replications are needed, but he notes that he has seen encouraging results from tissue tests that have indicated increased nitrogen uptake for some products.
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