有机物料碳和土壤有机碳对水稻土甲烷排放的影响

基于30年水稻土长期施肥定位试验,在保证原有定位试验正常开展的前提下,将部分化肥处理变更为有机肥处理(或反之),通过观测一年水稻轮作周期内不同处理甲烷(CH_4)排放通量季节性变化,探讨不同肥力水稻土中外源有机碳及土壤有机碳含量对田间CH_4排放的影响。结果表明:施化肥处理和有机肥处理,水稻土全年CH_4累积排放量范围分别为1.73~4.72和35.09~86.60 g·m~(-2)。有机肥处理改施化肥后,田间土壤CH_4的排放量显著降低;化肥处理改施有机肥或有机肥处理增施有机肥后,田间土壤CH_4的排放量显著提高。外源有机碳的输入量是田间土壤CH_4年排放量的决定性因素,外源有机碳输入量(x)与水稻土CH_4年累积排放量(y)之间满足直线方程:y=0.087 7 x+3.265 7(R~2=0.965 9,n=21)。土壤有机碳同样也是影响稻田CH_4排放的因素,在不同有机碳水平的水稻土上施用等量相同化肥或有机肥,土壤有机碳含量高的水稻土都更有利于CH_4的产生。单施化肥稻田土壤CH_4排放的最主要碳源是土壤有机碳,有机碳含量(x)和水稻土CH_4年累积排放量(y)之间的指数方程:y=0.162 4 e~(0.162 2 x)(R~2=0.940 6,n=9)。有机肥可促进土壤有机碳分解释放CH_4,土壤有机碳含量相同的条件下,高量有机肥比常量有机肥的土壤有机碳分解比率高0.65%,等量相同有机肥但土壤有机碳含量不同的条件下,土壤有机碳分解比率无显著差异;同样,土壤有机碳也可促进有机物料碳分解释放CH_4,在常量有机肥或高量有机肥处理中,土壤有机碳含量高者比低者的有机物料碳分解比率分别多出3.57%和2.34%。

Effects of exogenous organic carbon and soil organic carbon on the CH4 emission in paddy soils with different fertilities

In this study, three red paddy soils have been cultivated under different organic fertilization treatments in a 30 years fertilizer experiment in Hunan Agricultural University. The soil organic carbon content of red paddy soils, which reported to be steady after 30 years' cultivation, was adjusted to the following seven treatments without compromising the original experiment:the chemical fertilization treatment changed from normal organic fertilization treatment ( NOM-CF) , the chemical fertilization treatment changed from high organic fertilization treatment ( HOM-CF) , the normal organic fertilization treatment changed from chemical fertilization (CF-NOM), the original normal organic fertilization treatment (NOM), the high organic fertilization treatment changed from the original normal organic fertilization treatment ( NOM-HOM) , the original high organic fertilization treatment ( HOM) , the original chemical fertilization treatment ( CF) . CH4 flux of the seven treatments was measured to stud-y the effects of the following-up fertilization reforming on the CH4 flux in red paddy soils with different fertilities and soil organic carbon (SOC) from 2012 to 2014. The results showed that the annually cumulative CH4 flux change of chemical fertilization treatment and organic fertilization treatment were respectively in the range between 1. 73~4. 72, 35. 09~86. 60 g·m-2 . The CH4 flux in the soils under long-term organic fertilization treatments decreased after the adjustment from organic fertilization to chemical fertilization. However, the CH4 flux in the soils under long-term chemical fertilization treatments increased remark-ably after the adjustment from chemical fertilization to organic fertilization. The organic fertilization had obvious impacts on the dynamics of CH4 flux. The organic fertilization ( x) had a significantly positive relationship with the total amount of annual CH4 (y) (y=0. 0877 x+3. 2657, R2 =0. 9659, n=21). CH4 flux also had a positive relationship with the increasing of SOC. Annual dynamics of CH4 flux in different fertilization paddy soils had significant correlation with SOC. Under same or-ganic fertilization treatment or chemical fertilization, CH4 flux with high SOC content was larger than those in the soils with low SOC content. The inherent SOC content ( x) had a positive relationship with the total amount of annual CH4 ( y) ( y =0.1624 e0.1622x, R2 =0.9406, n=9) in the paddy soils received chemical fertilization. Organic fertilization could promote decomposition of soil organic carbon and emission of CH4 . Comepared with the constants of organic fertilization in a given a-mount of organic carbon content, the decomposition rate of high amount of organic fertilization was 0. 65% higher. In same a-mount of organic fertilization but different soil organic carbon content, soil organic carbon decomposition ratio had no significant difference. Similarly, the soil organic carbon also promoted decomposition of organic material carbon and releasing CH4 . In constant organic fertilization or high amount of organic fertilization treatment, comparing higher soil organic carbon content to the lower, carbon decomposition ratio of organic material were 3. 57% and 2. 34% higher respectively.