Winter Cover Crop Mixes: Effects on Strip-tilled Plasticulture and No-till Watermelon Production in Arkansas

Watermelon, Citrullus lanatus (Thunb.) Matsum. & Nakai, producers in Arkansas grow watermelons in either plasticulture or bare-ground systems. Both systems can benefit from the use of winter cover crops for weed control and to supply nitrogen (N) to the watermelon crop. Currently, the use of cover crops in watermelon production in AR is mostly limited to either cereal rye (Secale cereale L.) or winter wheat (Triticum aestivum L). The objective of this research is to evaluate the potential benefits of growing a mix of a legume and grass cover crops before watermelon production in both a strip-till plasticulture and a no-till roller crimped system. Specifically, we compared the following winter cover crop treatments: Austrian winter pea (Pisum sativum L. ssp. arvense), crimson clover (Trifolium incarnatum L.), mustard (Brassica cretica), black-seeded oats (Avena sativa L.), cereal rye, winter wheat, and mixed combinations of Austrian winter pea + black-seeded oats, Austrian winter pea + cereal rye, Austrian winter pea + winter wheat, black-seeded oats + crimson clover, black-seeded oats + Austrian winter pea + mustard. These cover crops were compared to a fallow ground control with preemergence herbicide applied at transplant. The test to evaluate a plasticulture system was conducted in Hope, AR from 2017-2019, and the test in no-plastic cover, no-till system was conducted in Kibler, AR from 2017-2020. ‘Jubilee’ watermelon was planted in both locations. Data collected included: cover crop biomass (kg·ha-1), winter weed biomass (kg·ha-1), cover crop C to N ratio and N content (kg·ha-1), petiole nitrate-N, summer weed biomass (kg·ha-1), and watermelon yield and fruit quality. Overall, a mix of cereal rye + Austrian winter pea is a suitable choice for a strip-till plasticulture system or for a no-till roller-crimped system. In both production systems the mix of cereal rye + Austrian winter pea produced consistent amounts of cover crop biomass, occasionally increased watermelon petiole nitrate-N content, had summer weed suppression similar to a preemergence herbicide in the early season, and resulted in numerically higher watermelon yields. Arkansas farmers should avoid growing winter wheat as a cover crop for watermelon production because winter wheat could reduce yields in both no-till and strip-till systems.