Thesis
Cover crops to enhance soil productivity in organic vegetable cropping systems
Washington State University
Master of Science (MS), Washington State University
2010
Handle:
https://hdl.handle.net/2376/102099
Abstract
The supply of plant available nitrogen (N) is often limiting in organic vegetable cropping systems. Cereal and legume cover crop mixtures may enhance plant available N to subsequent crops. But cover crops often require adjustments to the timing of field operations. The rate of N release from cover crops is also uncertain due to variations in climate, residue quality, and N content. We conducted two field studies and one laboratory incubation study to optimize cover crop growth and N availability to a subsequent crop. A field trial was conducted to assess the effect of planting date, harvest date, and rye (Secale cereal)-hairy vetch (Vicia villosa) seeding ratio on cover crop establishment, N accumulation, and residue quality. While late harvest favored larger biomass, there was an increase in C:N ratio and fiber content. Seeding ratio did not have a large effect on cover crop biomass yield or composition. In a related N mineralization laboratory incubation study, hairy vetch and a 75:25 rye-hairy vetch blend released similar amounts of N over 70 d. But the initial rate of N release was nearly 3-fold greater for hairy vetch. The slower rate of N release from the 75:25 rye-hairy vetch blend may result in N release that is better timed with crop N uptake. Nitrogen release was well correlated with residue C:N ratio, and therefore may be used to predict N release from rye-hairy vetch residues. The effect of a fall planted 50:50 rye-hairy vetch cover crop on organic sweet corn nitrogen use efficiency was determined in a second field trial. Feather meal was applied over top of cover crops at four rates. A trend of increased sweet corn dry matter and ear yield was noticeable in cover crops treatments when no feather meal was applied. But a large contribution from the soil N pool made it difficult to separate the N contributions from cover crops and soil. Early and late planted cover crops had fertilizer replacement values of 57 and 27 kg N ha-1. Our results demonstrate that a 50:50 rye-hairy vetch blend may supply significant amounts of N to a subsequent crop.
Metrics
36 File views/ downloads
11 Record Views
Details
- Title
- Cover crops to enhance soil productivity in organic vegetable cropping systems
- Creators
- Andrew James Lawson
- Contributors
- Craig George Cogger (Degree Supervisor)Ann Marie Fortuna (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525152501842
- Language
- English
- Resource Type
- Thesis