GREEN MANURE APPLICATION AND ITS EFFECT ON WEED MANAGEMENT AND GRAIN YIELD OF RICE CULTIVATE IN SRI LANKA

摘要

These studies compared the effect of different organic manures with, with out application of chemical fertilizer on nitrogen availability, weed bio-mass, and grain yields in wet land rice culture. Results revealed that application of green manure enhanced the mineral nitrogen content in the soil irrespective of the plant species. Combined application of green manure and chemical fertilizer recorded more mineral nitrogen than the application of both the sources individually. Weed dry weight of 64g/m2 of the plots treated with chemical fertilizer alone was significantly higher than that of the plots treated neither fertilizer nor manure. Effect of organic manure on weed bio mass was differ among organic manure sources. In the presence of chemical fertilizer, straw and Gliricidia sepium, recorded higher weed dry weight of 60g/m2 and 63g/m~2 respectively. With Tithonia diversifolia and Croton lacifer weed weight of 27 g/m~2 and 28 g/m~2 was recorded. There was a yield reduction of 29% due to competition of weeds in the plots treated with chemical fertilizer alone. Application of with Tithonia diversifolia and Croton lacifer significantly reduced the weed dry weight and as such there was a yield increment of 27% and 23% over the plots treated with chemical fertilizer alone and 11% and 6% over the plots treated with both Gliricidia sepium and chemical fertilizer. In this experiment it is proved that application of some green manures enhances mineral N content in soil while reducing weed biomass of the paddy filed which is an important factor to encourage farmers to apply organic manure application to paddy fields.