High rainfall in some areas the past couple of weeks has produced another wet spring in Iowa. This leads to questions about nitrogen (N) loss and need for supplemental N application to corn. Unfortunately, this question has become almost the norm - I have written approximately 20 articles on the subject since 2007.
Lately it seems to be an annual question with no exception this spring – has there been nitrogen (N) loss from my applied N? That question should also include what has been the N loss from the soil N supply or residual nitrate-N. There is usually tile drainage every spring and sometimes but not usually in the late fall (remember a couple of years ago). Also, losses if soils become saturated (free water filling the soil pores, standing water, anaerobic conditions) and soils are warm then denitrification happens (biological conversion of nitrate to N gas).
Most of Iowa has not received high precipitation amounts this spring, however, some regions have–most notably western Iowa (see maps). Wet springtime conditions typically raise the question about the status of applied nitrogen (N).
Really, it just had to rain large amounts in December. Seems we can’t get any relief from worrying about excess rain and impacts on nitrogen (N). The questions have already begun – what about fall 2015 fertilizer and manure N applications?
A few things to consider.
It is quite hard to make an estimate of losses for such an extreme event and time of the year. Following are factors to consider that will affect loss potential, including if N was applied and if so what fertilizer product or manure source.
This spring's wet conditions are similar to those in 2011. That year's example could help producers this year avoid nitrate loss in fields that are saturated or have standing water.
One way to determine 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.
Continued wet soil conditions into June with warm soils, prolonged saturation and tile drainage enhance nitrate loss. One way to determine nitrogen (N) loss is to calculate an estimate.
Discussion of wet soils in areas of Iowa this spring, questions about nitrogen loss and processes important for potential N loss.
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. While the rainfall this spring has been substantial, it arrived early. This should help moderate loss compared to the same situation occurring in late spring or early summer. In the early spring, soils are colder, so conversion to nitrate and denitrification is slowed. However, having two large rainfall events means that some soils were saturated over a prolonged period.
