Wednesday, November 15, 2006

Slow Release Nitrogen Fertilizers and its Effects on Micobial Biomass Dynamics.

Jorge Hernandez and Rosalia Garcia-Tejeiro. S. Illinois Univ. Mail Code 4415, Dept of Plant & Soil Science, Dept of Plant & Soil Science, Carbondale, IL 62901-4415, United States of America

Slow-release nitrogen fertilizers are used to increase nitrogen use efficiency (NUE) and extend N availability over a growing plant season. After applied to the soil N release is subject to biodegradation (mainly bacteria). Bacterial degradation permits N release from MU as ammonia and urea (using the enzyme MUase); Recently a plant pathogenic strain of Rhizobium radiobacter was isolated and related to MU bacteria presence. These results might have a practical significance, demonstrating the potential to select for this plant pathogen in soils fertilized with MU. It is still don’t know the long term effects of the application of MU’s in the soil microbial population and its effects on soil quality. Preliminary data in tomato plants have suggested that MU caused additional effects than those attributed to an NUE increase. Tomato plants treated with a single application of MU outperformed those treated with weekly N applications in a Georgia soil. The objective of this study is to asses the soil community shifting after the application of nitrogen slow release fertilizer. A field and greenhouse experiment with two different soil management histories (manure and no manure) will be performed. Tomato (Lycopersicon esculentum) and Maize (Zea mays) will be selected as indicator crop. In both soils the effect of urea and MU on the microbial population was tested.