Residual Fertilizer Nitrogen in a Flooded Rice Soil1

摘要: in the soil-water-plant system was measured. ApproxiResidual effects of N-labelled fertilizer (ammonium sulfate) niy O^-half to two-thirds applied N trogen were measured during second cropping season rice recovered aboveground portion crop (grain and (Oryza sativa L.). During first season, labelled Straw). The grain contained 31-37% N, at 100 kg N/ha using different methods straw 18-24% with amount application. At end harvest obtained remaining soil ranging from 26-27% incorporated back into respective plots. N. half plots treated an isotopic enriched enough (8.810 additional nonlabelled as early atom % 15N) majntain jts identity top dressing. uptake residual (that present following season. Straw native organic matter straw) u i • * »u ^ j . , ' plots, a nee grown on growing time under t, *;, „^ ,,n-,,^ fertilized nonfertilized conditions. P^ts year (1976) determine recovery 2.7 Uptake In addition, effect 3.1 N/ha, large fraction (34.3 40.1 N/ha) still application release soil. Approximately 3 S also beginning not accounted for examined. any assumed be lost system. Over 2year period, about 66 82% could MATERIALS AND METHODS by plant or remainder plant-soil After 1975 chopped 5to 8-cm pieces depth Additional Index Words: stable isotope, ° °to -' f P provided aluminum fertilization, incorporation, waterlogged soil, nitrogen '"corporation moisture Table 1—The _____________________ THE STUDY reported this paper is continuation Trea, ££$$£%£, ££? Tota. £S£& ± field experiment Patrick Reddy (1976). ment that study ammonium sulfate metric tons/ha kg/ha i^/hl planted ., distribution placement 8.5 0.44 35.5 18.2 —————— B Half 'Contribution Laboratory Flooded Soils Sediments, Dep. + Napplied Agronomy, Louisiana Agric. Exp. Stn., State Univ., Baton atmidseason 7.4 0.46 33.8 24.1 Rouge, LA 70803. This conducted cooperatively Tennesc All see Valley Authority, Soil Fertilizer Research Branch, Div. 7.7 0.45 35.0 18.5 Develop. Received 10 May 1977. Approved 15 Dec. D No (check) 3.\ 0.5416.7 Associate Professor, respectively. senior author ————————————————————————————————————————— presently working post-doctoral research associate, Biological t does include roots plants orand Eng., North Carolina Raleigh, NC 27607. ganic pool. REDDY & PATRICK: RESIDUAL FERTILIZER IN A FLOODED RICE SOIL 317