Role of Cover Crops in Regulating Nitrogen Dynamics, Productivity and Phytochemical Quality in Vegetable Production Systems
Date
2022-12-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Cover crops (CCs) can immobilize nitrogen (N) that would otherwise be lost before or after the main crop production, leading to improved N management. However, how CCs influence N management in vegetable cropping systems, where crop N demand and input requirements are inherently high, is poorly understood. Hence, N dynamics and vegetable yield quantity and quality were evaluated via field and greenhouse studies under N fertility gradients with vs. without rye CCs. In the field, a three-year crop rotation trial consisting of broccoli sweet corn root crop sequence under N gradients grown with vs. without a rye CC was set up to determine CC influence on yield, soil inorganic N, and N use efficiency (NUE). In the greenhouse trial, first the fate of above-ground and below-ground rye N into subsequent broccoli under a N fertility gradient, and then the accumulation of glucosinolates in broccoli heads under that N gradient with vs. without a rye CC was studied. In the field trial, CCs had the potential to improve yield, N content and crop NUE indices, reduce post-season N losses through N uptake and subsequent N release through mineralization. Increasing N rate did not continually increase yield, but increased soil N availability at vegetable planting and harvest, and often lowered crop NUE indices. In the greenhouse trial, the percent recovery of rye N into broccoli was about two to three times greater under sufficient N than the limited N or control conditions, with more pronounced recovery from above-ground than the below-ground rye N. Moreover, concentrations of selected glucosinolates frequently decreased by N fertilization more than 5 kg ha-1, but increased by rye CC in some cases. Overall, results indicate the importance of adjusting soil N levels to better align with crop needs and phytochemical quality — and that including a rye CC in the vegetable rotation is one method of doing so. Furthermore, although the above-ground plus below-ground rye derived N can provide a significant N source in agroecosystems, the background soil N level controls how much rye CC derived N is transferred into subsequent crops.
Description
Keywords
Vegetable crops, Nitrogen dynamics, Cover crop, Cover crop derived nitrogen, Glucosinolates
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Plant Sciences
Program
Plant Sciences