Cover crops and organic mulch to improve tomato yields and soil fertility
Cover crops and organic mulches (OMs) have been reported as a means to reduce inputs and increase soil quality. A field experiment was conducted to elucidate the effects of summer cover crops and organic compost on winter fresh market tomato (Lycopersicon esculentum Mill.) yields and quality. Cover crops were sunn hemp (Crotalaria juncea L.), velvetbean (Mucuna pruriens var. utilis), cowpea (Vigna unguiculata L.), and sorghum sudangrass [Sorghum bicolor x S. bicolor var. sudanense (Piper) Stapf.], and compost was applied at 25, 50, and 75 t ha–1. Sunn hemp accumulated up to 190–319 kg ha–1 of N, which was greater than that by sorghum sudangrass (38–110 kg ha–1). The tomato total marketable yields increased 49–82 and 71–85 t ha–1, respectively, in 2 yr. The application of OM at 75 or 50 t ha–1 increased tomato yields compared with that at 25 t ha–1. Yields of extra-large tomato fruits, especially at the first harvest during the early winter, were improved by growing sunn hemp or applying the composts. However, no interaction between cover crops and OM was observed for tomato marketable yields or quality. Soil organic C increased when OMs were applied compared with the plastic mulch (PM), whereas total soil N and organic C:N ratio were unaffected by any treatment. These results suggest that either the production of cover crops, especially sunn hemp, or the application of compost at high rates can improve winter fresh market tomato yields and quality and advance organic farming.