Physical Properties and Processes of Puddled Rice Soils

Abstract

In most Asian countries, wetland tillage for rice (Oryza sativa L.) puddling has become almost synonymous with rice culture (Sanchez, 1976), although in other parts of the world---the United States, Australia, parts of Europe, and some Asian countries---rice land is prepared dry and flooded later (Savant and De Datta, 1982). Puddling, in general, refers to the destruction of soil aggregates into ultimate soil particles at a moisture content near saturation. Buehrer and Rose (1943) defined puddling as ``the destruction of the aggregated condition of the soil by mechanical manipulation within a narrow range of moisture contents above and below field capacity (0.03 MPa), so that soil aggregates lose their identity and the soil is converted into a structurally more or less homogeneous mass of utlimate particles.'' According to Bodman and Rubin (1948) ``puddling is the mechanical reduction in the apparent specific volume of soil.'' From the farmer's point of view, however, puddling is simply the mixing of saturated soil with flood water to make it soft for transplanting and impervious to water (De Datta, 1981). Puddling, although a capital -and energy-intensive process, is practiced to achieve certain objectives such as weed control, ease of transplanting, and reduction in percolation losses of water and nutrients. The advantages and disadvantages of puddling in rice-based cropping systems are summarized in Table 1.