Nebraska has received 6 to more than 10 inches of rain in East Central Nebraska since April and concerns of nitrogen loss in saturated soils is becoming a reality. At the West Point Weather Station, the root zone soil moisture profile is the highest recorded for this time of year since the sensors were installed 15 years ago.
There are several ways we loss nitrogen in the nitrogen cycle under wet conditions.
- Runoff and soil erosion
- Leaching of nitrate
- Denitrification in saturated soils
Runoff has not been very high so far in the area. However, future risk of erosion on our wet soils with additional rain is a concern as it can carry away with it nitrogen and soil high in organic matter that contributes nitrogen to our crop during the growing season.
Leaching and denitrification are going to be our two main nitrogen loss mechanisms this year which was the same problem we ran into during June 2014 with all the excessive rain. Leaching occurs when there is a water soluble and mobile form of nitrogen called nitrate that dissolves in the soil water and moves down through the soil profile. When, the nitrate moves below the rooting depth, we have loss some of our nitrogen supply we were relying on to raise a good crop.
The other nitrogen loss mechanism, denitrification, occurs when soil becomes saturated with water and devoid of oxygen. As a result, microorganisms steal oxygen from our nitrate molecule and we lose the nitrogen portion as a gas leaving the soil to the air. This kind of loss varies with the temperature and length of saturated conditions.
Field assessment and visual observations of your corn crop between now and pollination for signs of nitrogen stress will be important to help decide if additional nitrogen fertilization is needed.