土壤不同粒级中C、N、P、K的分配及N的有效性研究

DISTRIBUTION OF C, N, P AND K IN DIFFERENT PARTICLE SIZE FRACTIONS OF SOIL AND AVAILABILITY OF N IN EACH FRACTION

本试验首先把７种采自不同省份的耕作土壤进行物理分级，然后测定了土壤Ｃ、Ｎ、Ｐ、Ｋ在不同粒级中的分布，同时还进行了不同粒级中Ｎ的有效性研究。结果表明：在不同粒级中Ｃ、Ｎ含量和分布均随土壤颗粒的加粗而逐渐下降，而Ｃ／Ｎ比则与此相反。在＜２μｍ粒级中Ｎ的有效性最高，随着土壤颗粒粒径的加粗有效性逐渐降低。在酸性土壤中Ｐ主要分布在较细的粒级中，而在石灰性土壤中则主要分布在较粗粒级中。土壤交换”性钾和缓效性钾主要分布在＜５０μｍ粒级中，表明该组分中Ｋ是作物吸收Ｋ的主要来源。

Summary Seven soils with a large range of soil organic carbon and nitrogen were fractionared according to particle size by ultrasonic dispersion and sedimentation, then the distribution of soil C, N, P and K in the clay, silt and sand fractiong was determined. At the same time, the availability of N in each fraction was also studied. The results showed that the C and N contents and their Percentages in the soil organic C and N decreased with the increase of particle size, but the C/ N ratio increased with the increase of particle size. The availability of N in < 2um fraction was highest and decreased with increase of the particle size. Soil P was mainly distributed in the fine fractions on the acidic soils, however on the calcareous soils in the coarser fractions. The exchangeable and non-exchangeable K was concentrated on the < 50pm fractions, indicating these fractions were the important K source to plant in the soil.