The nitrogen (N) fertilizer that John (Jack) Fuchtman doesn't apply is as important as the N he does put on his corn crop, especially with today's prices
Working with crop consultant John Pavlik, Royal, NE, Fuchtman doesn't apply what's already available to his corn from the following four possible N sources: Nitrate-nitrogen in the groundwater he pumps for irrigation, N mineralized from soil organic matter by soil microbes in the top 8 in. of soil, carryover nitrate-nitrogen in the deep root zone (8-36 in.) and N credit from a preceding soybean crop.
At 35¢/lb. for N, those four N sources amount to about a $30/acre savings, on average, among Fuchtman's four center-pivot irrigated quarters. For his 2005 crop, N application rates ranged from 111 to 155 lbs./acre on his four quarters, where he set yield goals in the 200-bu.-plus area.
Incidentally, he doesn't apply fertilizer to his soybeans. “Every time I fertilize beans, the fertilized beans make less than the others,” says Fuchtman, who farms southeast of Creighton, in northeastern Nebraska.
He applies nitrogen as 32% N solution in three applications — two of them as bookend applications of 30 lbs. each at planting and 30 lbs. through the pivot at tasseling time. The in-between application through the pivot is when he puts on the difference between the 60 lbs. and the recommended total N rate. That way, the bulk of the applied N goes on in late June to mid-July, during the crop's greatest period of N uptake.
Fuchtman is after not only the most profitable N rate, but also the rate that reduces risk of excess nitrates leaching to the groundwater.
Pavlik's N recommendations for his clients follow University of Nebraska N recommendations closely, which include the N credits, as well as credits for manure applications and special conditions, such as shallow root zones and sandy soils. It's a system that works for both irrigated and dryland production — the latter without a groundwater nitrate credit, of course.
In some cases, depending on the relationship between corn and N prices, the most profitable level of applied N may actually be 50 lbs. under University of Nebraska recommended rates. “But we're not saying to go below recommendations,” says Charles Shapiro, agronomist at the University's Haskell Agricultural Laboratory in Concord, NE.
“We are pretty confident” that these credits work and that the recommendations based on them are reliable for both irrigators and non-irrigators, Shapiro says. “We have a lot of demonstration data (more than 200 field demonstrations) that have gone into our thinking on this.”
Anyone with an Internet connection and soil test data can go to a University of Nebraska Web site where they will find “The Corn Nitrogen Needs Calculation Worksheet,” an Excel spreadsheet that can be downloaded. Put in your soil test results and yield goal, and the program automatically calculates the recommended N rate. To use it, go to http://cropwatch.unl.edu/focusnitrogen.htm, and click on “Worksheets.”
However, Shapiro says, “the spreadsheet is geared to Nebraska and we don't claim that it can be used in other states.”
One way of determining a realistic yield goal is to use 105% of your five-year yield average, say University of Nebraska agronomists. Eliminate any years in which events caused unusually low or high yields.
Not spending any more than necessary on fertilizer for maximizing profits from his corn/soybean rotation (two years in corn and one in soybeans) is certainly Fuchtman's overriding goal.
But addressing high nitrate-nitrogen levels in this northeastern Nebraska area's groundwater is equally important to him. Groundwater nitrates range from 20 to 30 ppm in an 830-acre area within what is called the “Bazile Triangle,” where Fuchtman farms.
As a board member of the Lewis & Clark Natural Resources District (NRD), which overseas a special N management program named after Bazile, a site in the area, Fuchtman is especially conscious of N management. Under that program, which has been in effect for about a dozen years, the NRD pays the cost of soil and water sampling and analyses, along with manure analyses for those who include this source of nutrients for their crops.
Even if sampling and analysis isn't paid for, as little as an 8-lb. N credit for residual nitrates in the root zone replaces enough applied N to pay the approximate cost of $2.60/acre for sampling and analysis, says Pavlik.
Fuchtman says he tries to follow crop consultant Pavlik's recommendations “right to the letter.”
On one pivot-irrigated quarter, Pavlik calculated as much as a 43-lb. N credit per acre for nitrates in the 11-12 in. of irrigation water applied. Among the four pivot quarters, credits for mineralization of N from organic matter in the top 8 in. of soil ranged from 15 to 46 lbs./acre, while credit for carryover nitrates in the 8- to 36-in. soil depth ranged from 13 to 45 lbs./acre among Fuchtman's four quarters.
His 2005 corn yields ranged from 175 to 226 bu./acre, with the highest-yielding quarter receiving 115.7 lbs. of applied N per acre after taking a 31 lb. N credit for nitrates in the groundwater, a 30-lb. legume credit and a 28-lb. credit for carryover nitrates in the 8- to 36-in. soil depth.
“I go for top yields,” he says. But he'll tell you it doesn't always work out that way. His lowest 2005 yield was 175 bu./acre where he applied 111 lbs. of N.
Fuchtman says his corn yields in 2005 were down from the previous year. “My yields were just fantastic last year (2004). I know the (high) heat hurt our yields this year.” Nine inches of rain over a short period in the growing season probably didn't help either, he adds.
This past fall, Pavlik took stalk nitrate tests on Fuchtman's fields soon after black layer formation in the kernels (maturity). Those tests involve cutting 8-in. lengths of stalk — beginning 6 in. from the bottom of the stalk — for nitrate analysis. Nitrate levels in the samples were in the normal range where corn followed soybeans, but excessive in stalk samples from corn that followed corn, according to Pavlik.
This was the first year that Fuchtman ran stalk nitrate tests. He and Pavlik believe it will take more testing to determine what implications these results have for N management practices on these fields.
N credits “probably affect my N (use) more than anything,” Fuchtman says. Now he would like to know how nitrates indicated by stalk tests might figure into his N management.