ABSTRACT
The traditional technique of rice cultivation involves puddling the soil to form a saturated root zone and the following wheat is grown after dry land preparation by sufficient plowing. The salient feature of the rice-wheat system is conversion of aerobic soil to anaerobic during rice and back to aerobic during wheat. Puddling breaks capillary pores, reduces the void ratio, destroys soil aggregates, disperses the fine clay particles, and lowers soil strength in the puddle layer (Sharma and De Datta, 1986). The destruction of soil aggregates by puddling leads to the formation of surface crusts, which crack on drying and delay land preparation for the following wheat crop. If the crust is broken by tillage, large clods result, leading to poor contact with seeds, thereby restricting germination. To overcome these disadvantages of puddling in rice and tillage in wheat, alternative practices such as zero-or minimum tillage have recently been researched. The use of mechanized equipment, in particular the Chinese seed drill, is being tested in Bangladesh, which favors rapid seeding after rice. The Chinese hand tractor (CHT) seeder was found not only to increase wheat yield over conventional tillage, but also to save the cost of land preparation (Nur-E-Elahi et aI., 2001). This paper reviews the impact of zero-or minimum tillage on yield, soil physical properties, and economics in Bangladesh.
