Initial Establishment and Physiological Performance of Rice as Affected by Ryegrass Mulching Levels

Abstract

We aimed to evaluate the initial growth and physiological characteristics of rice planted following ryegrass in lowland areas. The experiment was conducted in Capao do Leao, Brazil, in Typic Albaqualf. Ryegrass was planted preceding the experiment installation. Prior to rice planting, the area was burndown with herbicide, when treatments were established: ryegrass plants were cut at 0, 15, 30 or 45 cm above ground, resulting in different mulching levels. Rice was then planted, being managed according to local recommendations for the crop. We evaluated the variation in soil moisture levels, rice establishment in density and seedling height, and physiological parameters: relative fluorescence, chlorophyll, flavonoid a nd nitrogen balance indexes. High mulching levels by ryegrass allowed rice five additional days on a dry season, before harmful soil water tension, compared to bare soil; seedlings able to emerge under the ryegrass mulching, grew without considerable barriers; plant physiology in fields with residual ryegrass mulching was little affected, and ryegrass cut up to 45cm height prior to planting rice seem not to affect it. This corresponds to a maximum of about 4500 kg ha-1 of ryegrass straw on soil surface prior to planting rice to avoid damages to crop establishment.