Thinking strategically about nitrogen fertilizer, especially anhydrous ammonia, helps hold down costs while maximizing profits, says Sam Ferguson, an agronomist for Dow AgroSciences.
“With the rising price of nitrogen, we don’t want to use excessive amounts. We cannot afford to do that,” Ferguson says. Drawing on more than two decades of experience with Dow and several years as a crop consultant prior to that, he offers the following guidelines to developing a
No-tillers shooting for an above-average year could reasonably target a yield of 105 percent of their 5-year yield average, he says. But, he adds, growers should be realistic. “You might feel no need to go up to the 105 percent; you can fertilize for your 5-year average.”
Having set a bushel-per-acre target, multiply the number of bushels by 1.2 units of nitrogen to determine the amount of fertilizer needed per acre.
The 1.2 is a widely accepted measure, but Ferguson cautions, “That is a highly debatable number that can run anywhere between .9 units of nitrogen per bushel all the way up to 1.2. You typically do not hear people talking about any more than 1.2, and I think 1.2 is plenty high.”
He notes that some experts advocate dropping as low as .8 units of nitrogen per bushel. At that level, he acknowledges, “You might be able to elicit good responses on some of the really high CSR soils that have been farmed for years…