When growers face suboptimal crop yields due to drought, a common question is how much fertilizer will be required for the next growing season.
Consider crop removal:
Less grain and stover removal means less nutrient removal.
Nutrients removed at various corn yields:
Nutrients removed at various soybean yields:
Soil Sampling in a Very Dry Fall
- Concern: Clay minerals shrink - hold potassium (K) ions
- Result: Inaccurately low K soil test results
- Action: Wait for adequate soil moisture before sampling
Nitrogen (N) Remaining in Corn Fields
- Poor plant uptake of N due to dry weather
- Nitrogen in nitrate form in the soil
- Lack of moisture has prevented leaching or denitrification
- Environmental loss of N has been minimal
Trap Crops
- Wheat and cereal rye are best crops to prevent nitrogen loss
- Nitrogen will not be available to the subsequent crop due to immobilization of N in the residue
- When growing wheat for harvest, fall N can be eliminated while spring N may be reduced
- Using trap crops improves organic matter and soil tilth, while improving water quality
Conclusions
- Applying maintenance rates or no fertilizer may be acceptable depending on yield and previous soil test results
- Avoid soil sampling until moisture levels return to normal
- Wheat may be a good crop to take advantage of leftover nitrogen. Watch for head scab when planting wheat after corn.