Effects of Fertilization Patterns on Chemical Forms of Nitrogen in Dark Brown Soil and Its Distribution in Different Aggregates

[Objective] This study was conducted to investigate the effects of tradition-al fertilization and formula fertilization by soil testing on the chemical forms of nitro-gen in dark brown soil and its distribution in different aggregates. [Method] A physi-co-chemistry method was adopted in a comparative study on the chemical forms of nitrogen and their distribution in different-sized aggregates of dark brown soil under traditional fertilization and formula fertilization by soil testing respectively. [Result] Compared with traditional fertilization in spring and autumn, the formula fertilization by soil testing averagely decreased, the total nitrogen in soil by 23.2% in spring and by 20% in autumn in the soil layer of 0-20 cm, by 48.8% in the layer of 20-40 cm. Ammonium nitrogen was so sensitive to the methods of fertilization that the content of ammonium nitrogen was reduced much more under formula fertitization by soil testing in autumn than under traditional fertilization. Nitrogen in soil under traditional fertilization pattern was mainly distributed in the aggregates of 0-0.25 and 0.5-1 mm, while in formula fertilization by soil testing it was mainly distributed in the aggregates of 0.25-0.5 and 0-0.25 mm. [Conclusion] The study proved that for-mula fertilization by soil testing helped to reduce the risk of nitrogen pol ution and had huge effects on the chemical forms and distribution of nitrogen in different ag-gregates in dark brown soil.

Hydrophobic effects on photophysical and photochemical processes——Ⅵ.Character of aggregates formed by hydrocarbon with long chain in poor solvents

Dodecyl β-naphthoate and 3-octadecyl pyrene were used as fluorescence probes for estimation of microscopic polarity in aggregates formed by long chain hydrocarbon C_n(n=10,12, 14,16,18)in dimethyl sulfoxide-water mixed solvent.The polarity in the aggregates is similar to that in cyclohexane.The average aggregation number(N)was determined by using time resolved fluorescence technique.N is dependent on substrate chain length and varies from 15 to 30.The microviscosity was also measured by fluorescence depolarization method.Above phase transition temperature,the microviscosity in aggregates is slightly larger than that in micelle,but below this temperature,the microviscosity in aggregates is as large as that in solid phase.