An evaluation of a no-tillage, unfertilised, direct-sown, wheat–rice cropping system in Korea

Abstract

A no-tillage, direct-sown, unfertilised, wheat–rice relaying cropping system has major advantages over a conventional transplanted-rice system. For example, when rice is sown simultaneously with the wheat harvest, there are savings in labor and costs as a result of eliminating the tillage required to prepare the seedbed and for transplanting. A field experiment was conducted between 1996 and 1998 at Hadong, Korea. The experiment compared the soil microbial-N status, the soil physical and chemical characteristics, and rice growth and yield in a long-term conventional rice system with those in a no-tillage, unfertilised, direct-sown, wheat–rice, relay cropping system. The wheat–rice system was imposed for 2, 4 and 7 years to identify the time course of responses in the soil and crop. Agricultural chemicals including fertilisers were not applied in the wheat–rice cropping system. Rice crop yields after 2, 4 and 7 years of a direct-sown, wheat–rice cropping system were similar to those in the conventional rice system. Rice yields were high, ranging from 4.7 to 6.9 t/ha. Since 110 kg N/ha was applied to the conventional rice system, a large amount of N was mineralised during the wheat–rice system. The pattern of rice growth and yield formation, however, differed between the 2 systems. Rice in the wheat–rice system generally had more panicles, fewer spikelets per panicle and heavier grains. These responses reflected temporal changes in the N content and greenness of the rice leaf and were related to soluble N levels in the soil. Generally the soil was fertile with a high initial organic matter content. Organic matter increased by 30% during the 7 years of wheat–rice cropping. Other soil physical measures, bulk density and permeability to air and water, indicated that soil structure improved in response to wheat–rice cropping. Problems of pathogens and perennial weeds associated with new cultural practices in the wheat–rice cropping were minor; however, a higher rate of seeding was necessary to achieve satisfactory seedling establishment. Benefits to weed control and soil moisture conditions during crop establishment were derived from the increased level of crop mulch. The wheat–rice cropping system was found to be high yielding and sustainable over the 7-year period of experimentation.