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Friday, October 1, 2010

Nitrogen Management Part 3

Last night I tweeted that a colleague has done a lot of stalk testing late this summer to determine the fate of nitrogen. He found out that every field he tested had run out of nitrogen. I was also visiting with a friend along the road in the evening. He said his sloping fields were his best yielding. In fact they were extraordinary. He said he had a flat field that looked excellent all summer, but when he harvested it the yields were below average. In fact he said he had never harvested corn that looked so good and yielded so poorly. How does all this fit together? I told him about the stalk tests and he said that he thought he had run out of Nitrogen too.

Where did the nitrogen go? My hypothesis is that it was dentrified because the soil was so wet most of the summer. The sloping ground was at least not saturated as much so it yielded better. Dentrification is a biological process where bacteria use the oxygen in the nitrate form of nitrogen as an oxygen source when the soils go anaerobic. This renders the nitrogen unavailable to plants. It either leaches or evaporates into the air as N2, NO2 or N2O.

One of my tweeps asked how can the nitrogen loss be prevented. First - it is difficult given the extreme conditions. What might have helped. Nitrification inhibitors even in the spring. This keeps the nitrogen in the ammonium (NH4+) form for a bit longer and keeps it attached to the clays. Another thing that would have helped tremendously this year is tile drainage. Tile drainage would have at least minimized the saturated conditions. Another thing that might have helped some, is sidedressing nitrogen after the corn is up. A nitrate test before sidedressing would have been good information to have as well.

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