Nitrogen Fractionation

This trial is one of the sites of a statewide project aimed at identifying soil nitrogen fractions that can better predict the economic optimum nitrogen rate. Nitrogen is abundant in our soils, often totaling thousands of pounds per acre. However, most of this nitrogen is not in a plant-available form, as it is bound up in organic molecules of widely ranging complexity.

Microbial decomposition of these organic substances eventually releases the nitrogen into inorganic, plant-available forms through a process called mineralization. Each growing season, the soil naturally releases a portion of this stored nitrogen to plants. The exact amount depends on unpredictable seasonal factors, such as temperature and moisture availability. For this reason, precisely predicting both the economic optimum nitrogen rate and the yield-maximizing nitrogen rate remains a challenge.

While we cannot predict the weather, we can measure other soil characteristics, including total nitrogen, organic matter content, carbon content, and labile organic nitrogen fractions. Our current nitrogen recommendation model already accounts for regionality, organic matter, soil nitrate content, and tillage type; however, there is still room to hone its accuracy. In our quest to improve this model, we are focusing on what we can measure, specifically, these more labile fractions of nitrogen.