Organic Mulch and Nitrogen Affect Spring and Fall Collard Yields

Fall and spring collards (Brassica oleracea L. Acephala Group) were grown under one of three mulches (black plastic, ground newspaper, wood chips) and in a bare soil control. Mulch treatments were arranged in a factorial design with five rates of N fertilizer : 0, 67, 134, 201, or 268 kg N/ha. All fertilizer was preplant-incorporated into the bed before applying mulches and transplanting collards. Season did not affect collard yield, and there was no significant season x N rate interaction. Collard yields increased with increasing rates of N, with a maximum yield at 163 kg N/ha. Mulch type significantly affected collard yield, with fall collard yields highest under bare ground or wood chip mulches and spring yields highest under black plastic mulch. Collards produced under newspaper mulch produced the lowest yields in the fall and yields equal to bare soil and wood chips in the spring. Collards produced under newspaper mulch had less tissue N at harvest than those of any of the other treatments in both seasons. Collards produced on black plastic produced the lowest plant populations in both seasons. Wood chips and newspaper offer some appeal as low-input, small-scale mulches, but additional research to explore fertility management is necessary.