Buckwheat Species as Summer Cover Crops for Weed Suppression in No-Tillage Vegetable Cropping Systems

Abstract

Buckwheat is a broadleaved annual species that is often used as a summer cover crop for its quick growth, weed suppressive ability, and ease of management. Tartary buckwheat is a species related to buckwheat, with many of the same traits valued in buckwheat as a cover crop. However, Tartary buckwheat has been reported to grow more vigorously than buckwheat, especially in cool conditions, which might fill a unique niche for vegetable farmers in Wisconsin and other northcentral states. Our research objectives were to determine the effectiveness of Tartary buckwheat relative to buckwheat for weed suppression, both during the cover-cropping phase and after cover-crop termination during cabbage production, and quantify weed suppression, soil compaction, soil nitrogen availability, and cabbage yield in no-tillage (roller-crimped or sickle-bar mowed) and conventional-tillage (rototilled) systems. Across three site-years, we found that buckwheat emerged earlier and produced 64% more shoot dry biomass than Tartary buckwheat. Pretermination weed shoot biomass (predominantlyAmaranthusandSetariaspp.) in Tartary buckwheat treatments was approximately twice that of buckwheat, and did not differ from weed shoot biomass in a control fallow treatment. Cabbage yield did not differ between cover crop species nor did yield differ between conventional-tillage cover cropped and control fallow treatments. However, weed biomass was greater, and cabbage yield was reduced, in no-tillage compared to conventional-tillage treatments. We also found evidence of greater soil compaction and less nitrate–nitrogen (NO3–N) availability in no-tillage than conventional-tillage treatments. These results suggest that Tartary buckwheat is not a suitable summer cover crop alternative to buckwheat for weed suppression prior to cabbage production.