Improving the synchrony of hairy vetch (Vicia villosa) nitrogen release for corn (Zea mays) growth

Open Access
Author:
Cook, Justine Cecilia
Graduate Program:
Agronomy
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 14, 2008
Committee Members:
  • Robert Paul Gallagher Iii, Thesis Advisor
Keywords:
  • fertility management
  • nitrogen loss
  • cover crop
  • green manure
  • sustainable agriculture
  • no till
Abstract:
Leguminous green manure legume crops can often meet much of the nitrogen (N) demand of a succeeding crop. There may be, however, an asynchrony between N mineralization from green manures and crop N uptake, resulting in substantial nitrogen loss through leaching or denitrification. In our research, we hypothesize that this synchrony can be improved by manipulating the termination date of a hairy vetch (Vicia villosa) cover crop and the sowing date of the succeeding corn (Zea mays) crop. This will regulate the quality and quantity of the N in the vetch, the rate of N mineralization from the vetch residues, and the relative rate of N uptake in the corn. The study was located at the Russell E. Larson Agricultural Research Center in Rocks Springs, PA on Hagerstown soil. The vetch termination/corn planting dates chosen were May 4th, May 15th, and May 31st. A 92 RM variety corn was planted into live vetch, which was then chemically terminated. Corn fertilized with ammonium nitrate was used in order to compare yields of legume derived N with a mineral N control. The vetch biomass at termination was approximately 1500, 5000, and 7000 kg ha-1 for the May 4th, May 15th, and May 31st planting dates, respectively. The N content of the vetch was 4% and did not vary among treatments. The May 31st vetch treatment had higher peak soil inorganic N content in the top fifteen centimeters and greater peak N flux rates, but did not have greater corn biomass or grain yields. The grain yields in the vetch treatments were comparable to the ammonium nitrate-fertilized grain yields, but slightly below the yield capability for the field site’s soil type. A comparison of N inputs and outputs suggests that the vetch terminated on May 31st provided excess N, the May 4th-terminated vetch was not a sufficient N source, and the May 15th vetch treatment probably achieved the best synchrony. We anticipate that these experiments will provide help provide management guidelines to improve the N-use efficiency of green manure systems and reduce nitrogen pollution.