Dexter, Mo., and Ames, Iowa-University of Missouri researchers are putting Future Farmers of America students in the field to help farmers test corn stalks for nitrogen. The results could help farmers cut down on excess fertilizer and keep nitrates out of waterways, where they get into drinking water supplies and even make their way to the Gulf of Mexico. David Dunn, manager of the soil testing lab at The University of Missouri Delta Center, said Missouri traditionally ranks as one of the top states contributing nitrate-rich pollutants that have caused the dead zone in the Gulf. The program will help farmers fine tune their fertilization rate, Dunn added. The stalk nitrate test is based on the concentration of nitrate-N in the lower cornstalk, which is the 8-inch segment from 6 to 14 inches above the ground when the plant reaches maturity. In general, as the amount of plant-available N in the soil during the time period before plant maturity increases, nitrate in the lower stalk also increases. However, the stalk nitrate-N concentration can be greatly influenced by other external and internal plant factors such as precipitation/soil moisture, stated Iowa State University agronomy professor John Sawyer. These external and internal factors complicate interpretation of stalk nitrate test results and make specific interpretation from low to optimal concentrations difficult. Sawyer cautioned that the process has limitations and that more than one year’s results are needed before changes are made in N management. “If high levels are found for several seasons, and with no drought-reduced production, then the interpretation becomes clear that the N applications are too high and there should be adjustment to more moderate rates,” the agronomist advised.
Transparency Across the Fertilizer Value-Chain