A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Environment, Resources & Development

Thesis (M.Eng.) - Asian Institute of Technology, 1978

A field experiment was conducted with maize in the acid sulphate soil of Bangkok Plain during the dry season (January-April) of 1978. Three levels of phosphorus fertilization -0, 50 and 100 kg/ha along with 100 kgN + 50 kgK/ ha (applied as basal dressing in band) and three irrigation regimes - always at field capacity (13), water applied upto field capacity when 35% (I2) and 70% (11) of the available moisture were depleted. The experiment was a double split-plot design with three replication. Increasing amounts of applied phosphorus increased the concentration of N, P & Na but no definite relation was found with that of K. The concentration of N, P, K & Na also increased with the increasing irrigation frequency. DM production and plant height increased with increasing amount of applied phosphorus and irrigation frequency. 432, 442 and 452 mm of water were required for I1, I2, and I3 treatments respectively and the crop-coefficient curve was developed on the basis of percent soil moisture depletion as estimated by gravimetric method. Significant variation in grain yield was found with irrigation, phosphorus and irrigation x phosphorus interaction at 99% level of significance. Maximum and minimum grain yields were 4.11 and 0.01 t/ha with I3P100 and I1Po treatments respectively. Preliminary diagnosis and yield prognosis models were developed on the basis of chemical composition of young plant. A good agreement between predicted and experimentally obtained yield showed the reliability and correctness of the model.