Crop establishment of legumes in rainfed lowland rice-based cropping systems

Poor crop establishment is one of the major limitations to the production o f grain legumes after rice (Oryza sativa L.) in rainfed lowland lice-based cropping systems. The success of germination and emergence of mungbean (Vig na radiata (L.) Wilzek), soybean (Glycine max (L.) Merr) and peanut (Arachi s hypogaea L.) planted in zero tilled (ZT), zero tilled combined with mulch application (ZTM) and tilled soils (T) were investigated in a crop establi shment trial as a function of sowing delay. Sowing delay was used as a surr ogate for soil-water content. This experiment was conducted under a rain-sh elter to ensure continuous and progressive drying conditions. A dibbling tr ial using the same legumes was conducted concurrently and subjected to the: prevailing climatic conditions. Germination and emergence success rate of the traditional dibbling method was compared to dibbling incorporating dept h control and seed cover. Both experiments were conducted towards the end o f the 1994 rainy season in a Vertisol soil at Ngale and an Andosol soil at Jambegede, in East Java, Indonesia where the season gradually changes from wet to dry season. Mungbean emergence was 93-94% at Ngale and soybean emerg ence was 83-95% at Jambegede, both in the presence and absence of rain. Pea nut emergence was low (50-69%) at both sites. In all three species at both sites, the percentage of seeds that failed to germinate was greater than se eds that failed to emerge, indicating that germination rather than emergenc e was limiting. Seed rot caused by fungal attack and poor imbibition associ ated with poor seed-soil contact (observed as intact seeds) were the main c onstraints for the success of germination of mungbean, soybean and peanut. Thr failure to emerge was mainly caused by seedling rot and the failure of hypocotyl and radicle to penetrate the hard soil, observed as a culling of the hypocotyl, Cultivation at Ngale on a Vertisol resulted in excessively c loddy soil, which in turn resulted in a significant decrease in germination and emergence. The application of straw mulch had little effect on the eme rgence of legumes on this soil, The use of depth control and application of seed-soil cover did not have a significant effect. Hence the traditional d ibbling method where depth of planting ranged from 4 to 7 cm without seed c over was found to be appropriate for planting mungbean and soybean. Germina tion and emergence of peanut was improved with the application of soil cove r and the dibbling stick had a spike added to the tip to assist the root to penetrate the hard compacted soil. (C) 2000 Elsevier Science B.V. All righ ts reserved.