Influence of periods of coexistence of weeds on organic okra production

Abstract

Weed management in okra grown in organic system minimizes crop yield losses. Thus, the objective of this study was to determine the period prior to weed interference in okra grown in organic system during the rainy and dry seasons in the state of Maranhão, northeastern Brazil. Experiments were conducted in the rainy and dry seasons in randomized block design with seven treatments and four replications. The treatments were T1 = weeds coexistence with okra for 7 days; T2 = coexistence for 14 days; T3 = coexistence for 21 days; T4 = coexistence for 28 days; T5 = coexistence for 35 days; T6 = coexistence for 42 days and, T7 = coexistence for 74 days). In addition to these treatments, we kept a control treatment with weed free until harvest to obtain maximum yield. At the end of each period of weed coexistence with the crop, three weed samples were collected in 0.25 m² to evaluate density, dry mass and to analise phytosociological parameters. The main weeds in both seasons were Commelina benghalensis, Cynodon dactylon, Eleusine indica, Alternanthera tenella and Amaranthus spinosus. The coexistence of weeds with the crop until harvest caused losses of 51% in the rainy season and 67% in the dry season compared to weed free control. In the rainy season, the period before weed interference (PBI) on okra crop of organic system was 12 days after emergence (DAE). In the dry season, 5% yield loss was observed 4 days after transplanting (DAT). Weed management in organic okra should be carried out earlier in the dry season than in the rainy season to avoid high yield losses