Nitrogen Dynamics in Corn and Switchgrass Production Influenced By Soils of Varying Depths in Central Missouri.

Optimizing the use of fertilizer inputs is important to achieve sustainable biomass feedstock production from non-agricultural or marginal lands. Excess inputs in such lands can increase non-point source pollution drastically. In many areas in the midwest United States, shallow soils above the argillic horizon (claypan soil or often called depth to claypan (DTC)) are susceptible to loss of nutrients through leaching and runoff caused by unpredictable moisture conditions. Switchgrass based biomass cropping systems have been suggested as an alternative to low corn yields in such areas. The main purpose of this research was to assess differences between corn and switchgrass nitrogen uptake and utilization as influenced by the DTC. Ammonium (¹⁵N) sulphate (5% atom enrichment) was applied in microplots (46 x 46 cm²) at rates corresponding to the normal fertilization rate in the switchgrass and corn plots. Plant materials was harvested after the growing season along with soil cores up to a depth of 60 cm. Soil cores were differentiated into three layers of 20 cm each. Based on the initial results we observed that while there was no trend in the recovery of fertilizer nitrogen in soil (RFN%) among the shallow and deeper soils, the plant uptake and utilization of the applied fertilizer was more efficient in the deeper soils as evident from the nitrogen derived from fertilizer (NDF%) and utilization of fertilizer nitrogen (UFN%). These results suggest that proper management of fertilizer application in marginal soils would be important for economic yields as well as reducing environmental pollution.