Nitrogen mineralization from ‘AU Golden' sunn hemp residue

ABSTRACT

The tropical legume sunn hemp (Crotalaria juncea L.) cultivar ‘AU Golden’ has the potential to provide substantial nitrogen (N) to subsequent crops to reduce recommended application rates of synthetic N fertilizers. A mineralization field trial was conducted to measure mass decomposition and N and carbon (C) amounts remaining from sunn hemp residue following three planting dates (May, June, and July) during the 2013 growing season at the Tennessee Valley (TVS) and Coastal Plain (WGS) locations of AL. Residue from June and July plantings contained 50.0% and 61.1% N at WGS and 41.5% and 66.5% N at TVS by the end of their respective incubation periods compared to residue from the May planting, which contained 21.1% N at WGS and 47.8% at TVS. In order to create a more synchronous relationship between ‘AU Golden’ residue N mineralization and crop demand, termination must be delayed until approximate planting of the following crop.

KEYWORDS:

• Nitrogen
• sunn hemp
• tropical legumes

Acknowledgements

Special thanks are due to the staff and student workers at the USDA-ARS National Soil Dynamics Laboratory for aiding in field and laboratory work during the course of this study. Deep appreciation is also due to the staff at the Wiregrass Research and Extension Center, and the Tennessee Valley Research and Extension Center for their assistance in carrying out this research. Mention of a trade name, proprietary product, or specific equipment in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.