Effects of mulching on the weed community and grain yield of upland rice cultivars

This study evaluated the effects of mulching on upland rice cultivars Comecru and Cambará and the weed community under four amounts of babassou (Attalea speciosa Mart. ex Spreng.) straw mulching namely: 0, 15, 20, 25 t ha-1 with a view to control weeds. The experiment was laid out in a randomized complete block design in a 2 x 4 factorial scheme with four replications. The rice plant height, percentage of fertile panicles, number of spikelets per panicle, weight of 100 grains and grain yield were assessed. We also assessed the weed community by computing the following phytosociological parameters: density, frequency and the importance value index (IVI) of each species. Babassou straw mulching reduced weed density and dry mass between rows of upland rice cultivars and increased the rice yield. The weed species with the highest Importance Value Index (IVI) in the treatments with no mulching were Cyperus iria, Fimbristylis dichotoma and Digitaria ciliaris. Rice grain yield was increased with the increase in the amount of straw. Comecru cv. had the highest suppressive effect on weeds with significantly higher grain yield (1,214.85 kg-1) than Cambará cv. (878.72 kg ha-1). We conclude that the higher amounts (20 and 25 t ha-1) of babassou straw mulching suppressed weeds, providing less competition with the rice cultivars, which resulted in an increase in the number of rice panicles, weight of 100 grains, spikelet fertility and grain yield in both rice cultivars