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

Abstract

The nitrogen supplying ability of paddy soil in the tropics was studied in a Maahas clay soll under field con(tilions in the Philippines and in two other soils in a pot el(perimetlt. ThEl 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 thia nitrogen played a crucial role in the growth and yield of the rice plant. 111e amo'.lnt of nitrogen mineralized during It cropping srason of rice was clltimated to be between 60 and 80 kg/ha in Maahas clay soil df'pending on the season. The relatively. lower mineralization rate during the dry season could be brcause the temperature was lower at the early stages of plant growth during this season than at the other times of the year. 10 both the wet and dry seasons, up to 27 kg N/ba was taken up by the plant between panicle initiation and the heading 8tage in both nitrogen-receiving and no-nitrog!'n plots, Apparently, there are various types of patterns of mineralization of soil nitrogen in tropical regions. The incubation test using soils undrf similar conditions provad useful ill estimating' the Rmount of nitrogen mineralized and the pattern of mineralil!ation during a cropping season. © 1976 Taylor & Francis Group, LLC.