Evaluation of cover crops and mowing as alternative approaches for weed control in organic tomato production

RaeLynn A Butler, Purdue University

Abstract

Organic tomato growers rely heavily on tillage, manual weeding, and plastic mulch for weed control in fresh market tomato production. Tillage can increase soil erosion, disrupt soil aggregates and microbial communities, and may promote weed emergence by breaking weed seed dormancy. Manual weeding and the application and removal of plastic mulch are time consuming and can lead to increased labor expenses. Weeds are controlled during a critical period, usually 4 to 6 weeks after transplanting tomatoes. Controlling weeds during this period helps prevent yield losses and weeds that emerge after the critical period have little effect on crop yield. Although crop yields are conserved, weeds that emerge after the critical period can produce seed that increases weed seed banks following a tomato crop. Alternative weed management strategies are needed to help improve current weed management practices employed by growers and to reduce the use of cultivation and manual weeding in fresh market tomato production. The objectives of our research were to evaluate the use of cover crops to suppress weeds in fresh market tomato and to evaluate the effect of mowing height and frequency on summer annual weeds. Field experiments were conducted in 2010 and 2011 and four treatments were examined: 1) tomatoes transplanted into plastic beds (ORG); 2) tomatoes transplanted into plastic beds plus clover sown between crop rows after the critical period (CLOVER); 3) tomatoes transplanted in no-till roller-crimped rye beds plus clover sown between crop rows (MIX); 4) tomatoes transplanted in no-till roller-crimped rye beds (RYE). We found that clover grown as a living mulch between tomato rows after the critical period reduced weed biomass in both years and weed inflorescence in 2010 compared to all other treatments. However, tomato yields were also lower in the CLOVER treatment than in the ORG treatment. Substituting plastic mulch with roller-crimped rye resulted in considerably higher weed biomass and lower yields. Greenhouse experiments conducted in 2011 evaluated the effect of mowing frequency (single and repeated clippings) and mowing height (5, 10, 20 cm) on five summer annual weeds (large crabgrass, barnyardgrass, giant ragweed, common lambsquarters, and velvetleaf). We found that mowing frequency and height reduced the total dry weight of all weed species compared to uncut plants. Weeds cut once were generally able to survive and produce weed seed. Our results suggest that frequent mowing can help suppress summer annual weed growth and seed production but mowing alone may be insufficient for adequate weed control. By addressing these issues, our research contributes to efforts that reduce cultivation and manual weeding while also improving the viability of organic vegetable production in order to help growers meet increasing consumer demands.

Degree

M.S.

Advisors

Gibson, Purdue University.

Subject Area

Agronomy|Plant sciences

COinS