Response to Nitrogen Fertilizer of Rice in the Central Plain Region Of Thailand

Abstract

Responses of rice to nitrogen fertilization were measured for both wet and dry season cropping on the farmers field in the Central Plain Region of thailand between 1976 and 1983. Four soil groups were included in the study the groupings being based on surface soil (0-15 cm) texture; they were clay soils in the aeric and Typic Tropaquepts, clay-loam soils in teh Aeric Tropaquepts and Aeric Tropaqualfs, sandy clay - loam in the Aeric Plinthic Tropaqualfs, and acidsulfate-clay soil in the Typic Tropaquepts. Recommended non-photosensitive, photosensitive andmildly photosensitive rice varieties were used. Nitrogen fertilizer application rates varied from 0 to 225 kg N ha-1,
Response to nitrogen fertilizer level depended on soil type and rice variety. Response in relation to soil type was in decreasing magnitude for clay > clay-loam > sandy-clay-loam > acid-sulphate-clay. for any soil type the response was greater in teh dry season than the wet season. The amount of nitrogen needed to maximise yield increased in order of clay < clay-loam < sandy-clay-loam < acid-sulfate-clay. Yield potentials established for wet season cropping were 5794, 4688 and 4463 kgha-1 of paddy for non-photosensitive, mildly photosensitive and photosensitive varieties, respectively; for dry season cropping of non-photosensitive varieties the yield potential was 6031 kg ha-1 of paddy.
The maximum and optimum rates of nitrogen fertilizer application were able to be computed from the quadratic response equations.