Impact of ryegrass cover on lowland rice establishment.

This study aimed to analyze the impact of ryegrass as a soil cover on soil moisture level, initial rice establishment, grain yield and weed control in irrigated rice planted after ryegrass. The experiment was conducted under field conditions in randomized blocks design with four replications. Ryegrass (cv. BRS-Ponteio) was planted in autumn and glyphosate was used as a knockdown before rice planting. Ryegrass plants were cut at 0, 0.15, 0.30 or 0.45 m above ground, resulting in different mulching levels. Rice (cv. Irga-424-CL) was planted in spring and was managed according to local crop recommendations. Although positive to the overall cropping system, ryegrass mulching suppressed rice emergence, especially with ryegrass cutting heights above 0.30 m, thus increased seeding densities in rice fields with substantial ryegrass soil cover may be needed. Ryegrass mulching had no significant effect on weed suppression, with positive results being observed only with > 3000 kg ha-1 of ryegrass dry mass mulching. However, the rice yield in relation to the bare soil treatment was 14.3% less when straw quantity was 4500kg ha-1, reinforcing the need for evaluating the benefits and costs of ryegrass as a cover crop in rice production