2019 ASHS Annual Conference

Haitian farmers are still very dependent on tillage and hand-weeding for managing weeds in vegetable crops even though tillage can cause soil erosion and long-term decline in soil productivity and soil fertility. Because of limited financial resources for purchase of herbicides and loss of laborers to urban migration, farmers can benefit from nonchemical weed management approaches. The use of cover crops was proposed as a means of suppressing weeds and nematodes during the off-season prior to vegetable crops. The objective of the study was to evaluate the efficacy of different legume cover crops for management of weeds and plant-pathogenic nematodes for eggplant production in Haiti. In summer 2018, three legume cover crops were evaluated in field trials at two locations (Ducis and Camp-Perrin) in the valley of Les Cayes, Haiti. The cover crops used were: velvet beans (Mucuna pruriens), cowpea (unguiculata cv. Iron Clay), and sunn hemp (Crotalaria juncea cv. Tropic Sun), with a fourth treatment being a no cover crop control. The trials were stablished in late June with seeding rates of 45, 78, 56 kg·ha^-1, respectively. The experimental design was a split plot with main plots arranged in a randomized complete block with four replications. Cover crop treatments were assigned to the main plots and eggplant was grown in subplots with or without supplemental mineral fertilizer. During the cover cropping period data were collected on cover crop shoot biomass accumulation, weed density, and weed biomass; and soil was sampled and extracted for nematodes. Eggplant growth and yield were assessed during the cash crop period as well as persistence of weed and nematode suppression. In both locations, fresh shoot biomass was higher with sunn hemp than with cowpea and velvet bean. Sunn hemp and cowpea cover crops suppressed weeds more effectively than velvet bean at Camp Perrin whereas only sunn hemp resulted in significant weed suppression at Ducis. Our results indicated that the suppressive performance of cover crops on weeds depends on the amount of biomass produced by the cover crops. Poor velvet bean germination resulted in low cover crop biomass and thus inadequate weed suppression. Sunn hemp appears to have the best potential as a weed suppressive cover crop. However, increasing the cowpea seeding rate, and use of velvet bean with higher seed viability may improve the performance of these cover crops. Results on plant-parasitic nematodes and eggplant growth and yield will also be presented.