5.1.9
TOMATO PRODUCTION USING MINIMUM TILLAGE IN BAHIAGRASS PASTURE AS AN ALTERNATIVE TO FUMIGATION WITH METHYL BROMIDE FOR SOIL DISINFESTATION

DO CHELLEMI1, FM RHOADS2, SM OLSON2 and JR RICH2

1United States Department of Agriculture, Agricultural Research Service, Horticultural Research Laboratory, 2199 South Rock Road, Fort Pierce, FL 34945, USA; 2University of Florida, North Florida Research and Education Center, Quincy, FL 32095, USA

Backround and objectives
Field production of fresh market tomatoes in Florida is dependent upon methyl bromide for soil disinfestation and accounts for 18% of the total methyl bromide consumption in the USA. Methyl bromide has been identified as an ozone-depleting compound and, beginning in January 2001, production and sale will be banned in the USA. One approach to the development of alternatives to methyl bromide is to redesign the production system to minimize the impact of soilborne pests. Florida has ca 1 million ha of improved bahiagrass pasture which can serve as an excellent rotational crop to minimize the impact of soilborne pests. The objective of this study was to develop and validate an alternative production system for fresh market tomato utilizing existing bahiagrass pasture. The production system was designed to achieve multiple goals, including avoiding damage form soilborne pests, minimizing agricultural inputs, improving soil conservation and optimizing yields.

Materials and methods
No-till and strip tillage were used to transplant tomato seedlings into existing bahiagrass pasture. Grass in the row middles was maintained as a natural mulch through chemical or mechanical mowing. Field experiments were conducted to optimize tillage procedures, fertility rates, cultivar selection and plant spacing. Following several preliminary experiments, a 3-ha field trial was established by a commercial tomato producer to validate the alternative system.

Results and conclusions
Highest yields were obtained with maximum suppression of bahiagrass growth in the planted strips. High nitrogen rates increased vegetative growth, shifted more production to second and third harvest, and did not increase total yield where bahiagrass growth was suppressed. An interaction was observed between bahiagrass management and fertilizer rates. Failure to eliminate broad leaf weeds from the pasture resulted in root galling from Meloidogyne spp. Marketable yields of 44 million t/ha were obtained using this production system. In the field validation trial, marketable yield in the alternative system was 36 million t/ha as compared to 42 million t/ha in the conventional system using methyl bromide and plastic mulch. However, due to the reduced inputs the net return per ha was $2890 in the alternative system, as compared to $2322 in the conventional system. The incidence of tomato spotted wilt was 20% in the alternative system as compared to 10% in the conventional system, indicating the potential for increased levels of insect-transmitted plant viruses. The results indicate that an alternative production system designed to achieve several economic and ecological goals can be developed for commercial production systems.