A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science at the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Sc.) - Asian Institute of Technology, 1975

Effects of three water management practices namely, continuous flooding, intermittent irrigation and upland condition, were studied in pot culture experiment in different soils from four major Rice growing areas of Bangkok plain, viz, Bangkhen, Chainat, Klong Loung & Supanburi. It was observed that yield differences were nonsignificant between water management treatments, but increasing trend was noticed with the increasing water application, in terms of yield. Even though the yield components were showing favourable response in upland condition the causes for slightly lower yield as compared to other treatments were attributed to delayed flowering and ripening of grains, resulting in low dry matter partitioning to grain. The causes for increased concentration of P, Ca, Mg, and Fe in the plants grown under increased water supply condition were discussed. A clear antagonism was observed between concentration of Fe and Al in the plants. Concentration of K, Na, and Cu were also estimated and causes of dilution of various nutrients were analyzed, Coefficient of permeability and soil moisture characteristic curves were determined for various soils. The highest water requirement of paddy in Klong Luong soil was found to be related to its high permeability and low moisture holding capacity of the above soil, along with the development of high suction indicating rapid water depletion.