AMES, Iowa ― As June approaches, some northern areas of the state have experienced delays in corn planting due to a cold spring that turned wet. Producers considering changes to crop rotation should pay attention to the impact it has on manure management plans.
The Iowa Administrative Code only allows a maximum of 100 pounds N per acre manure application on ground to be planted to soybean. However, it does allow fields that had liquid manure applied at rates intended for growing corn to be switched to soybean on or after June 1 with no penalty of over-application of manure nitrogen. Thus if a field planned for corn has not been planted and will be switched to soybean, this can be done. Producers should document the changes in crop rotation, application methods and other changes in their annual manure management plans.
Given it has been a wet spring in some areas, nutrient management and specifically, nitrogen loss may be top of mind. Livestock producers with Iowa DNR manure management plans are reminded if they have already applied the maximum nitrogen rate to the field, they can’t apply additional sources of nitrogen unless the need is confirmed by the use of a Late Spring Nitrate Test. This test measures nitrate-N concentration at the 0-12 inch depth.
Results can be interpreted by the ISU Extension and Outreach publication “Use of the Late-Spring Soil Nitrate Test in Iowa Corn Production” (CROP 3140), which considers both the original fertilizer source and the amount of rain that occurred in May (excessive is more than five inches in May). When adding extra nitrogen, be sure to document soil sample results and reference the publication to interpret the test results in management plans.
While fall provided favorable application conditions, and periods in March were favorable, producers should plan ahead if not as much manure as normal is applied in the spring. Having a plan in place will help prevent potential issues from turning into problems. Keep an eye on storage, and have a plan for needed action.
Image caption: Wet weather conditions may force crop rotation changes.