Effect Of CO₂ Partial Pressures On Formation And Transformation Of Soil Humus

In this paper ,incubation experiments were conducted to deal mainly with the chances on amounts and AlogK of humic acids(HA),fulvic acids(FA) during incubation time and the relations among the changes on the and incubation conditions (€02,62) in wind-blown soil. The objects are to provided scientific basis for clarifying the formation and transformation mechanism of soil humic substance, revealing the theoretical essence of Improving Soil Fertility by Organic Materials (ISFOM) and regulating soil fertility. Moreover, they also give new data for research on soil organic matter an d humic substances chemistry. The major results were as follows:(1) After the addition of corn stalk, amounts of SMBC increased, and then decreased gradually with prolonging of incubation time. Effect on SMBC of different incubation was different. In this experiment, high Oa was beneficial to multiplying and activity, therefore, amounts of SMBC were higher; low Oa and high CO2 restrained activity of soil microbe and were not beneficial to accumulation of SMBC.(2) The amounts of SOC and water soluble organic carbon (WSOC) increased in soils after the addition of corn stalk. They gradually decreased with prolonged incubation time, but still higher than CK at the end of incubation experiments(240th day ).the amounts of SOC were different under different incubation conditions. Generally soil microbe was quite active in high O2 which was beneficial to decomposition of SOC, but low O2 and high CO2 were beneficial to decomposition of SOC(3) During corn stalk decomposition, HEC, FAC and HuC decreased; HAC increased before 15th day, then decreased. But at the end of incubation experiments, HEC, HAC, FAC and HuC of all treatments were still higher than that of CK. As far as relative amounts, HE and FA increased before 15th day, and then decreased. But HA increased gradually. Effect on relative amounts was different under different condition of incubation. HAC and HuC were highest under high 02; FAC was the highest underhigh CO2 and low O2; The difference of HEC was not obvious under different O2 concentration incubation, however the difference of HEC was not obvious in prophase under CO2 incubation, and lower in anaphase under CO2 incubation.(4) After the addition of corn stalk, PQ of all treatments decreased rapidly. With prolonged incubation time, PQ gradually increased. But at the end of incubation experiments, PQ of all treatments were still lower than that of CK. PQ was higher under high 02 than under low 02 from 1th to 30th . It indicated that high O2 was beneficial to formation of HA, but not beneficial to formation of FA; low 02 was opposite to high O2. PQ was higher under low CO2 than high CO2 during the incubation(l-240d). It indicated that high CO2 was beneficial to formation and accumulation of FA.(5) After the addition of corn stalk, AlogK of HA or FA increased in all treatments, but RF decreased, which showed that molecular structure became simplified. With prolonged incubation time, AlogK of all treatments decreased gradually, and RF increased gradually which indicated that the degree of oxidation and aromaticity of HA and FA increased gradually, and molecular structure became complexed. From changes of AlogK, high O2 was beneficial to complexity of molecular structure of HA and FA; high CO2 was beneficial to simplility of molecular structure.