Results of Two-year Study into the Effect of Winter Cover Crops on Production of High-tunnel Vegetable Crops

This two-year study investigated short-season winter cover crops to improve soil quality and reduce nitrogen fertilizer inputs in organic high tunnel production systems. Five winter cover crop treatments were investigated including a nontreated control, Austrian winter peas (Pisum arvense), bell beans (Vicia faba), mustard (Brassica juncea cv. Kodiak), and Daikon radish (Raphanus sativus var. longipinnatus). Cover crops were grown in a high tunnel from mid-Nov to mid-April in a randomized complete block design with three replications. After incorporation, the cover crops were followed by a succession of vegetable crops, including tomato (Lycopersicon lycopersicum, cv. ‘Plum Dandy’) and broccoli (Brassica oleracea var. italica, cv. ‘Bay Meadows’). Crops were fertilized at a 0.5x rate (56 kg N ha^-1) with the objective to determine the ability of the cover crop treatments to supplement fertilizer inputs. Yield and performance of the vegetable crops were measured to determine the effects of the cover crop treatments compared to a nontreated control. In both years of the study Austrian winter peas yielded significantly greater cover crop biomass and contributed a greater amount of biomass nitrogen than all other treatments. This led to a significantly lower soil C:N ratio 30 days after incorporation. Tomato leaf chlorophyll measurements were highest following winter pea with significant differences detected in 2015. Though statistical differences were not detected due to plot variation caused by environmental factors, the winter pea cover crop resulted in a 48% increase in mean tomato yield compared to the control. Broccoli early-season leaf chlorophyll was also increased by the winter pea treatment and plant biomass was significantly greater, but harvest data were not significantly different.