Crop Scene Investigation - 51 Solved: Why did Ralph's corn look nitrogen-deficient?

Friday, April 4, 2014

by BERNARD TOBIN

Despite having applied 200 pounds of nitrogen, Ralph's cornfield was indeed suffering from nitrogen deficiency.

Ralph had applied enough nitrogen to the crop, but he ended up suffering a "triple whammy" thanks mostly to Mother Nature, explains Pioneer agronomist Aric Bos.

Ralph followed the same management practices he has used for years, but this year several things conspired against him. The first thing was the wet conditions. "At planting, he surely lost some of the 50 pounds of nitrogen he put down because the clay soil contained a high level of gravel. That likely meant it had an open bottom, and with all the moisture we had in the weeks shortly after planting, there was bound to be some leaching," says Bos.

"The conditions weren't much better when he side-dressed 28 per cent UAN.

"Because the field was so wet, he set a shallow depth on the coulters and that likely left some of the trenches open. When the field got hit by four inches of rain the next day, there was certainly nitrogen loss both by surface runoff and through denitrification," adds Bos. It was evident that runoff was carrying nitrogen to the low-lying areas, making the plants a much deeper green in these places.

The fact that the field was no-till would also have played a role. "No-till just magnifies the coolness and dampness of everything, especially in a year like 2013," explains Bos. "Crop development and root development would have been slower and all that rain could have moved the nitrogen down below the root zone, beyond the reach of the developing seedlings. The saturated soils also let soil bugs be more active. In cool no-till fields, and given the saturated conditions we had, bugs can break down nitrogen pretty quickly."

Ralph was puzzled why the nitrogen-deficient plants were neither short nor stunted. "Corn plants have a tremendous ability to even out in height over the season, even when they lack nitrogen. But stressed plants typically have thinner stalks and less biomass, and that means less yield potential," says Bos. "If we had been able to see the field earlier in the season, it likely would have looked quite different."

Does Bos have any advice for Ralph? "It's tough to beat Mother Nature when she throws everything at you. The one thing he could do is try to avoid mudding in side-dress nitrogen. When it comes to side-dress, the soil conditions are very important for successful nitrogen utilization. I understand that it's something farmers have to get done, but if time is on your side, look at the forecast a little bit, and hold off if you see a big rain coming."

Congratulations to Larry Davis, Burford, for his correct answer. Larry who was a winner for his correct answer to CSI #15 back in January 2009, notes: "you have had some tough ones in the past and I love them all."

CSI will return in the fall. BF