404 Cowpea Cover Crop Mulch Controls Weeds in Transplanted Bell Peppers

A 2-year field project was conducted in Thermal, Calif., on cowpea ( Vigna unguiculata ) mulch as an alternative weed control option in pepper ( Capsicum annuum ) production. Treatments included a bare ground production system with hand weeding, bare ground with no weeding, a cowpea mulch production system with hand weeding, and cowpea mulch with no weeding. Cowpea was seeded in July in 76-cm beds and irrigated with a buried drip line. In September, irrigation water was turned off to dry cowpea plants. The cowpea plants then were cut at the soil-line to form mulch. Pepper plants were transplanted into mulch and fertilized through the drip line. Every 2 weeks, the number of weeds emerged and pepper plant heights were recorded. In December, fruit production, pepper plant dry weight, and weed dry weight were recorded. Fewer weeds emerged in the cowpea mulch than the conventional bare ground system. At harvest, weed populations in nonweeded cowpea mulch were reduced 80% and 90% compared to nonweeded bare ground for 1997 and 1998, respectively. Weed dry weights in nonweeded treatments were 67% and 90% less than weed dry weights in nonweeded bare ground over the same period. Pepper plants in cowpea mulch produced 202% and 156% more dry weight than on bare ground in 1997 and 1998, respectively. Pepper plants in cowpea mulch produced more fruit weight than in bare ground with similar fruit size. Cowpea mulch provided season-long weed control without herbicides while promoting plant growth and fruit production.