This study, funded by the United Soybean Board (USB), was conducted to understand the potential for cover crops to perform in a corn and soybean rotation, and to collect data on the performance of cover crops in those rotations in relation to the timing of termination.
Continued wet soils in some parts of Iowa are raising nitrogen loss questions that are answered with an understanding of biological processes important to potential N loss.
By John Sawyer, Department of Agronomy
One method to judge nitrogen (N) loss is to calculate an estimate. Predicting the exact amount is quite difficult as many factors affect losses. However, estimates can provide guidance for supplemental N applications.
For the period April 1 through May 6, 2007, much of Iowa received more than 5 inches of rainfall (May 6, 2007 AWIS Inc. report). The Northwest, North-Central, and East-Central districts averaged slightly less than 5 inches, and the West-Central and Southwest districts more than 9 inches. With the large rainfall and flooding conditions, many producers are wondering about nitrogen (N) losses. While this period certainly has an influence on N in the soil, excessively wet conditions later in the spring are especially important for N losses.
The recent heavy rains have raised questions about nitrogen (N) losses. In wet field areas it is common to find off-color corn, but that does not necessarily equate to N shortage. So be careful as you initially are seeing plant response to wet conditions (slowed root activity and growth). The amount of N taken up by corn to the V6 stage is small (about 20 pounds N per acre, so pale-yellow color is now due to wet conditions). Before a decision is made to apply supplemental N, you should consider the potential productivity remaining after soils have dried.
It has been a dry spring in Iowa--too dry in places. Therefore, nitrogen (N) losses are generally not an issue this year. However, some areas have been wet, especially in eastern and northeastern Iowa, in addition to locations that have recently received heavy rainfall. With another warm fall and open winter, producers in these areas may be wondering whether this is a scenario for repeating the last several years' N losses. Some have recently noted N-deficiency symptoms in cornfields.
