SOIL PHYSICAL-PROPERTIES IN RELATION TO RICE YIELD AND WATER-CONSUMPTION UNDER FLOODED AND UNFLOODED CONDITIONS

Four paddy soils from Thailand were included in this investigation. The soils are described as marine alluvial, fresh water alluvial, hydromorphic alluvial and hydromorphic non-calcareous brown soil. The hydraulic conductivity of water saturated soil was determined on puddled samples, and soil moisture retention curves were recorded for unpuddled samples. In a pot experiment rice variety RD-1 was grown on the soils under flooded and unflooded conditions. For the soils studied a negative relationship was found between the hydraulic conductivity and the ability of the soil to retain water against a given suction. The grain yield was higher under flooded conditions, while among the various soils studied in this experiment grain yield increased with decreasing water content in the suction range studied and increasing hydraulic conductivity of the soils. Better root development facilitated by more favourable physical conditions in highly permeable soils could be the possible reason for the yield increase. © 1979 Martinus Nijhoff.