Nitrogen Loss in 2000

May 5, 2000
Producers in most areas of Illinois are more concerned with too little, not too much, soil moisture. However, there are a few areas that have had enough rain that there is a potential for nitrogen loss should we get heavy rains in late May or early June. If you are among the fortunate ones that have had enough water that you could have a problem and you fall-applied nitrogen, particularly if you applied it early and did not use a nitrification inhibitor, you may want to consider applying 50 to 60 pounds of nitrogen in two or three strips through fields that have had nitrogen-loss problems in the past. The strips need only be one pass of an applicator in width, and you might spread them out across the field if there are substantial soil differences to include.

The corn growing in strips that received the added nitrogen can help indicate whether or not to apply more nitrogen to the rest of the field. Starting in early June, periodically compare the color of the corn in the treated strips to adjacent nontreated areas. If the nontreated areas start to show yellowing on the third or fourth leaf from the bottom, add 50 to 60 pounds of nitrogen to the rest of the field. If you have access to a SPAD meter, starting in mid-June, compare the readings on the leaf immediately below the one with collar showing or the leaf opposite and below the ear on treated versus nontreated corn. When the SPAD meter reading of the nontreated is less than 90% of the treated, apply additional nitrogen. Experimental results have shown that application of supplemental nitrogen, as late as tasseling, to corn that is deficient in nitrogen will result in yields as good as from areas that did not show deficiency.

Success from late nitrogen applications requires that you correctly identify the deficiency early and that you receive adequate rain to move the nitrogen into the rooting zone for uptake. The first of these requirements can be met by using the above-suggested program, but the latter requires cooperation from Mother Nature.--Robert Hoeft

Author: Robert Hoeft