The optimum rate of Nitrogen fertilizer application on corn varies from year to year and from field to field. Here we provide simulation data to aid decision making.
We simulated 25,000 fields across the U.S. Corn Belt from 1984 to 2021 using the Agricultural Production Systems sIMulator (APSIM). In this report, we benchmark Iowa soil N mineralization and N loss by crop reporting district.
Trends in mineralization and N loss rates are important to know while deciding fertilizer rates. Simulation data suggest that the soil N mineralization rates from January 1 to April 19, 2021 are at or above normal levels for all Iowa crop reporting districts (Fig 1). Compared to last year, the soil N mineralization rates are higher this year (Fig 1). Current mineralization rates are low but will increase as the soil temperature will increase in the coming months. Similar results were obtained for other U.S. Corn Belt states (data not shown), except North Dakota, which had mineralization rates below normal.
In terms of N loss (denitrification and leaching), simulation data for Iowa suggest normal to below normal N loss from January 1 to April 19, 2021 (data not shown). Overall, results so far indicate more N supply and less N loss than normal, however, trends may change in the coming weeks depending on soil moisture and temperature conditions. We will follow up with more updates in the coming weeks.