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Summer Cover Crops for Tomato Production in South Florida
Yuncong Li, Herbert Bryan, Renuka Rao and Nolan Heckert
University of Florida, IFAS, Tropical Research and Education Center
18905 SW 280 Street, Homestead, Fl. 33031
Teresa Olczyk
Miami-Dade Cooperative County Extension Service
18710 SW 288 Street, Homestead, Fl. 33030
ABSTRACT
Cover crops have become an integral part of vegetable production practices in south Florida for weed control, disease and insect suppression, and retaining nutrients during the heavy summer rains. A wide variety of plants can be used as cover crops in south Florida. Some are legumes that fix nitrogen and some are nematode resistant crops. The objective of this study was to select the best cover crop(s) for vegetable production in south Florida. We have evaluated ten cover crops, and eight of them were legumes in 1997. In 1998, only sunn hemp (Crotalaria juncea L.) sorghum-Sudan, sesbania (Sesbania exaltata Raf.), and aeschynomene (Aeschynomene evenia) were evaluated. Sunn hemp and aeschynomene were superior to other
cover crops tested and reduced weed cover to 1% or less in 1997 and 1998. Sunn hemp produced 7,700-10,300 lb dry weight per acre and fixed or retained up to 248 lb N/ac, while sorghum-Sudan retained only 27-33 lb N/ac. All legumes contributed more nitrogen compared to nonlegumes, such as sorghum-Sudan, a common cover crop in Florida. Tomato plants from sunn hemp plots produced more marketable and extra large fruit than those from sesbania and control (weeds). Marketable fruit yields from the fumigation treatment were significantly higher than those from non fumigation treatment. The higher marketable tomato yield from fertilizer treatments with or without cover crops indicated that fertilizer application is still critical for cover crop and tomato production system.
INTRODUCTION
Summer cover crops are used for weed control (Li, 1998), disease and insect suppression (McSorley et al., 1994; Stansly et al., 1999) during the vegetable off-season (May to September) in south Florida. Cover crops are also important to improve soil physical properties, increase soil organic carbon, conserve soil water, reduce surface runoff and recycle nutrients during the heavy summer rains (Hubbell and Sartain, 1980; Reeves, 1994; Mansoer et al., 1997). Planting summer cover crops have become an integral part of vegetable production practices in south Florida. Moreover the use of cover crops continues to increase as farmers seek to improve soil quality, reduce chemical input and replace methyl bromide. A wide variety of plants can be
used as cover crops during late spring and summer in south Florida. Sunn hemp (Crotalaria juncea L.) and aeschynomene (Aeschynomene evenia) provide great ground coverage (Mansoer et al., 1997; Li, 1998, 1999). Nematode resistant cover crops such as ‘Iron&Clay’ cowpea (Vigna unguiculata L.) reduce nematodes for successive crops (Stansly et al., 1999). Obviously, legumes contribute more nitrogen by N fixation compared to nonlegumes such as sorghum-Sudan, which is a common cover crop in this area. In order to select the best cover crops for vegetable production in south Florida, we conducted experiments to evaluate suitability of eleven potential cover crops in south Florida and the effects of four cover crops on tomato growth and yield.
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