各種畑土壌における作物吸収窒素に対する微生物バイオマスを経由した窒素の寄与

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We investigated the contribution of N through microbial biomass (biomass N and its debris N) to plant N uptake in upland soils with different physicochemical properties. Our experiment was carried out in concrete plots using different 5 types of upland soils (Light-colored Andosol, Humic Andosol, Brown Lowland soil, Dark Red soil and Sand-dune Regosol). Nitrogen fifteen-enriched ammonium sulfate was amended to the field soil in order to label microbial biomass N with ^<15>N. At 3 weeks after amendment, upland rice was sowed and cultivated in 15 weeks. Soil and plant samples were taken at every 3 weeks after sowing (WAS), and the ^<15>N abundance of soil microbial biomass N, soil total N and plant N were analyzed. The results we obtained are summarized as follows. 1) The amount of microbial biomass N in the soils was higher in the following order : Dark Red soil>Humic Andosol≒Brown Lowland soil≒Light-colored Andosol>Sand-dune Regosol. The amount of microbial biomass N in all of the soils was almost constant during the cropping period. 2) The amount of plant N uptake was higher in the following order : Brown Lowland soil>Humic Andosol>Dark Red soil>Light-colored Andosol>Sand-dune Regosol. The amount of plant N uptake in all of the soils was highest in the heading stage, suggesting that the amount of plant N uptake is high in the reproductive stage. 3) At 0-3 WAS, the ^<15>N abundance of plant N uptake in all of the soils was close to that of the microbial biomass N. At 6-15 WAS, however, it was close to that of soil total N. Based on this result, we assume that the N taken up by the plant is mainly derived from the N produced through the microbial biomass in the vegetative growth stage (0-6 WAS), and mainly organic N except for the microbial biomass N in the reproductive stage (6-15 WAS). 4) In all the soils except Dark Red soil, the amount of plant N uptake was closely correlated with the amount of microbial biomass N at the vegetative growth stage (R : 0.995^<**>, n= 4), supporting our hypothesis that the N through the micobial biomass is a major source of N for plants at this stage.
社団法人日本土壌肥料学会の論文
1997-08-05

各種畑土壌における作物吸収窒素に対する微生物バイオマスを経由した窒素の寄与

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