Nitrogen supplying ability of paddy soils under field conditions in the Philippines

Abstract

Abstract The nitrogen supplying ability of paddy soil in the tropics was studied in a Maahas clay soil under field conditions in the Philippines and in two other soils in a pot experiment. The amount of soil nitrogen that was mineralized in one rice cropping season was estimated via incubation tests of these soils under laboratory conditions. The soil supplied nitrogen continuously throughout the period of plant growth, and this nitrogen played a crucial role in the growth and yield of the rice plant. The amount of nitrogen mineralized during a cropping season of rice was estimated to be between 60 and 80 kg/ha in Maahas clay soil depending on the season. The relatively lower mineralization rate during the dry season could be because the temperature was lower at the early stages of plant growth during this season than at the other times of the year. In both the wet and dry seasons, up to 27 kg N/ha was taken up by the plant between panicle initiation and the heading stage in both nitrogen-receiving and no...