Lab Investigation of Nitrogen Application Timing, Nitrogen Source, and NZoneMax Addition on Nitrate Leaching

Proper manure and nutrient management is essential to ensure maximum crop production while reducing the risk of N losses. There is concern, that fall application of liquid swine manure can lead to economic and environmental concerns due to potential for losses of nitrate. Thus, the objective of this study was to evaluate the impact of application timing (fall vs. spring) and use of NZoneMax applied with liquid swine manure (LSM) or urea had on nitrogen loss. The study was conducted as a laboratory soil incubation over 35-days with leaching performed on days 3, 7, 10, 14, 21, 28, and 35. Treatments included a control soil receiving no nitrogen application and treatments of LSM or urea fertilizer applied at a rate of 168 kg N/ha (150 lb N/acre) applied with and without NZoneMax, tested on two different Iowa soils, and simulating a spring and fall application. In the spring application soil incubations began immediately after fertilizer application occurred, for the fall applications fertilizer sources were added soils were placed in a freezer for 3 months and then brought to room temperature where they were incubated for 35 days. Results indicated that application timing, nitrogen source, additive, and the application timing x nitrogen source factors were all significant with less nitrogen leaching occurring from the spring application, the manure as compared to the urea, and fertilizers receiving the NZoneMax treatment. In general, NZoneMax reduced nitrate leaching by 13% over the incubation while spring versus fall application reduced leaching by about 35%. Manure initially leached nitrogen more slowly than urea; however, by day 28 of the incubation the difference was no longer statistically significant. These results provide insight into how different fertilization choices may impact nitrogen loss