Paper presented at the 52nd CFCS Annual Meeting, Guadeloupe, July 10-16, 2016 INNOVATING AGROECOLOGICAL FARMING SYSTEMS IN THE CARIBBEAN
IMPLEMENTING CROPPING SYSTEMS TO IMPROVE SUSTAINABLE AGRICULTURE IN TROPICS AND SUBTROPICS Qingren Wang, University of Florida, IFAS Miami-Dade Extension Keywords : cover crop, crop rotation, nematodes, sunn hemp, sustainability
Abstract Under tropical and sub-tropical climates, a sustainable development of agriculture is challenging because of the pest pressure with favorable weather conditions. Implementation of appropriate cropping systems including growing cover crops and crop rotation plays a critical role, which can break up the food chain and life cycles of field pests. Some field trials have demonstrated that among all tested summer cover crops, sunn hemp (Crotalaria juncea L. cv. Tropic sun) can grow vigorously during the rainy summer, cover the land quickly and densely, and it can produce a large quantity of biomass in two to three months. More importantly, sunn hemp can suppress soil root-knot nematodes via releasing some nematicides through its roots and through the decomposition of plant residues. Therefore, growing cover crop â sunn hemp during the crop off season and rotating with valuable vegetable crops in the growing season has become a promising cropping system under the subtropical climate. Such a result may have a potential to be implemented in Caribbean countries to improve the sustainable development of agriculture. Materials and methods A number of summer cover crops were tested in field trials under subtropical climate in Homestead, Florida, U.S.A. The cover crops are sunn hemp (Crotalaria juncea L. cv. ‘Tropical Sun’), velvetbean (Mucuna deeringiana ‘Bort.’ Merr.), cowpea (Vigna unguiculata L. cv. ‘Iron Clay’), sorghum sudangrass (S. bicolor X S. bicolor var. sudanense ‘Piper’ Stapf.), and Japanese millet (Echinochloa esculenta ‘A. Braun’) vs. fallow. The seeding rates were 25 lb/ac for sunn hemp and sorghum sudangrass, 20 lb/ac for velvetbean and cowpea, and 15 lb/ac for Japanese millet. All these cover crops were planted in May or June, flail-mowed and incorporated into the soil in August. The land was prepared, i.e., disked and formed beds to grow vegetables, such as tomatoes and okra, etc. Crop yield and quality were recorded and evaluated with different treatments. Soil samples were collected for nutrient analyses and nematode assay. Main results Vegetable yields were increased with all cover crops grown as compared to the fallow, especially with sunn hemp and cowpea (Figure 1). Okra yield was improved significantly as well by growing cover crops, especially by velvet bean (Table 1). Moreover, sunn hemp can suppress soil nematodes effectively. For instance, the rate of root galls after growing sun hemp was statistically insignificant difference as compared with the treatments of fallow or methyl bromide (Figure 2).
Figure 1. Tomato marketable yields affected by growing cover crops.
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