Corn Management Systems for Improved Synchrony of Soil N Supply.

Nitrogen supply to the corn producing farmland all along the Mississippi watershed has a significant potential for contributing to the hypoxia in the Gulf of Mexico.  Recent advances in conservation tillage systems, that incorporate manure or slow release fertilizers, have been promoted as a way to synchronize soil N supply with corn demand and thereby limit losses.  The challenge with these cropping systems is to understand and monitor this dynamic release of soil nutrients. Plant Root Simulators (PRS™-probes) are a proven tool for accessing the soil nutrient supply, as they are sensitive to both soil moisture and temperature.  Nitrogen supply rates, measured in Alabama, were highest in the spring as temperature improved to optimal values for N release and the newly planted corn had few roots competing for soil N supply.  The No-till system in this study was found to release substantially more N than conventional-till systems, particularly when poultry litter was applied.  This improved slow release of N from poultry litter on No-till was evident from May until mid-July.  Final N content in corn grain, supported the conclusion that poultry litter improved the N supply as compared to chemical fertilizer.  Coatings and treatments that caused fertilizer to release N at a controlled rate, also impacted overall N supply to corn in Illinois.  Environmentally Smart N (ESN) showed lower soil N supply rates than the Stabl-U/ESN blends. The trend in soil supply was confirmed in the corn N content and ear weights.  This preliminary study suggested utilizing ESN as the sole source of N may be too slow for optimal corn growth.  These two studies highlight the need for a detailed understanding of soil N bioavailability when attempting to synchronize plant demand with soil supply.