长期施肥对中国3种典型农田土壤活性有机碳库变化的影响

Effects of Long-Term Fertilization on Change of Labile Organic Carbon in Three Typical Upland Soils of China

【目的】观测分析了中国3种典型农田土壤——黑土、灰漠土和红壤有机碳在时间与空间上对长期不同施肥措施的响应特征,为农田土壤培肥提供理论依据。【方法】通过有机碳分组对比分析了长期施肥后土壤总有机碳与活性有机碳的含量与比例变化。【结果】16年后,不施肥(CK)灰漠土总有机碳、活性有机碳含量均呈显著下降趋势,下降幅度分别为11.7%和34.9%,且活性有机碳占总有机碳的比例也显著下降了5.4个百分点;长期施用氮肥(N)3种土壤总有机碳含量基本保持不变,但活性有机碳所占比例显著下降,其中黑土下降幅度高达9.5个百分点;化肥配施(NP,NPK)后,黑土和灰漠土活性有机碳占总有机碳的比例仍显著下降,红壤则略呈上升趋势;有机无机配施(NPKM、1.5NPKM),3种土壤的总有机碳、活性有机碳及活性有机碳占总有机碳的比例均显著提高,其中红壤上升幅度最大,NPKM处理提高幅度分别为80.6%、146.2%和7.5个百分点,其次是灰漠土,分别提高了64.4%、138.0%和5.0个百分点;实施秸秆还田(NPKS)后,红壤的总有机碳、活性有机碳及活性有机碳占总有机碳的比例分别增加了21.6%、59.0%和7.5个百分点,黑土和灰漠土则相对较稳定。【结论】活性有机碳占总有机碳比例对施肥措施反应敏感,长期不施肥或只施氮肥多数导致土壤总有机碳含量和活性有机碳所占比例下降,有机无机配施能维持和提高土壤有机碳含量和活性有机碳所占比例,且效果优于秸秆还田,优于化肥(NPK)配施。

[Objective] Based on 3 long-term experiments, temporal and spatial responses of total soil organic carbon （TOC） and labile organic carbon （LOC） in red soil, black soil and grey-desert soil to various long-term fertilizations were discussed. [Method] Fractionation method of soil organic carbon was applied to determine the contents of LOC and the percentage of LOC to TOC in black soil, grey-desert soil and red soil, [Result] Results showed that the content of TOC and LOC and the percentage of LOC to TOC under 16 years of non-fertilization （CK） in grey-desert soil decreased significantly by 11.7%, 34.9% and 5.4 percentage points, respectively. After long-term application of chemical nitrogen fertilizer （N）, the content of TOC of the 3 soils kept no significant change throughout the studied period. However, the percentage of LOC to TOC for the 3 soils all decreased significantly. It decreased by 9.5 percentage points in black soil, which was the most of the 3 studied soils. After 16 years application of NP and NPK, the percentage of LOC to TOC in black soil and grey-desert soil decreased significantly. While there was increasing trend for red soil. There was significant increase in the contents of TOC and LOC and the percentage of LOC to TOC under long-term application of chemical fertilizers combinated with manure （NPKM, 1.5 NPKM）. After long-term application of NPKM, the contents of TOC, LOC and the percentage of LOC to TOC in red soil increased by 80.6%, 146.2% and 7.5 percentage points, respectively, which was the most. For grey-desert soil it was 64.4%, 138.0% and 5.0 percentage points, respectively. For long-term application of NPK with straw return （NPKS）, the contents of TOC, LOC and the percentage of LOC to TOC in red soil increased by 21.6%, 59.0% and 7.5 percentage points. However, it was stable in black soil and grey-desert soil. ~Conclusion] The percentage of LOC to TOC response sensitively to long-term fertilization and could be one of the indicators for the quality of soil organic carbon. Long-term non-fertilization and only chemical nitrogen fertilizers lead to decrease in the contents of total soil organic carbon and the percentage of LOC to TOC in most cases. Long-term application of NPKM could maintain and improve quality and quantity of soil organic carbon, The effect of long-term application of NPKM was better than that of NPKS, and they were both better than that of long-term application of NPK.