Long-term effect of fumigation and a sorghum cover crop on broadleaf and grass weeds in plastic-mulched tomato.

Abstract

Broadleaf and grass weeds can adversely affect growth and productivity of plastic-mulched tomato (Solanum lycopersicum L.). Two, four-year research trials were conducted in Florida to evaluate the effect of repeated fumigation and chemical fallow versus a sorghum [Sorghum bicolor S. bicolor var. sudanense (Piper) Stapf.] cover crop on broadleaf and grass weeds in tomato plasticulture. 1,3-Dichloropropene (1,3-D) + chloropicrin (Pic), dimethyl disulfide (DMDS) + Pic, and DMDS + metam potassium effectively controlled broadleaf weeds in-crop and reduced densities by 79-98% compared to the non-fumigated control but provided inconsistent control of grass weeds. DMDS + metam potassium was generally the most effective fumigant. During the fallow period, a sorghum cover crop effectively reduced broadleaf weed density than the chemical fallow, while chemical fallow effectively reduced grass weed density than the cover crop. The fallow program did not affect in-crop densities of broadleaf and grass weeds. In some measurements, the evaluated fumigants resulted in taller tomato plants and higher yield compared to the non-fumigated control. We conclude that the evaluated soil fumigants effectively control broadleaf and grass weeds. Planting a sorghum cover crop effectively suppresses broadleaf weeds but not grasses during the fallow period. However, this suppression does not result in reduced weed density in-crop despite the fact that similar weed species were observed in both time periods. © 2020 Society of Chemical Industry.