Stale seedbed and green manuring as an effective weed management strategy in dry-seeded rice (Oryza sativa)

摘要

Experiments to develop and refine stale seedbed technique for dry seeded rice (Oryza sativa L.) were conducted during 2006 and 2007 at Mannuthy, Kerala. Compared to normal seedbed, stale seedbed for 14 days with two shallow hoeings resulted in 80% reduction in the population and 40% reduction in the dry weight of weeds. Grass weeds were the most prominent group that germinated immediately after seedbed preparation, followed by broad leaf weeds. Maximum grain yields of 3.21 t/ha and 3.10 t/ha, during 2006 and 2007 respectively, were observed in plots with stale seedbed for 14 days with two shallow hoeings. The yield difference between normal seedbed and stale seedbed plots decreased with reduction in stale seedbed periods. The difference in grain yield between normal seedbed and stale seedbed for 7 days was only 0.25 t/ha and that with stale seedbed for 14 days with two shallow hoiengs was 0.58 t/ha. Concurrent growing of green manure crops or pre-emergence spraying of herbicide pretilachlor significantly reduced the population and dry weight of weeds resulting in better grain yield and weed control efficiency. Practising stale seedbed for 14 days gave the highest benefit: cost ratio during both years of the experiment.