沼液还田对旱地红壤有机质及团聚体特征的影响

【目的】通过沼液还田试验,探明沼液对旱地红壤有机质含量、团聚体结构和稳定性的影响,为沼液合理应用及培肥旱地红壤肥力,提升土壤结构提供理论依据。【方法】通过红壤旱地2013—2014年沼液还田定位试验,按照不同沼液全氮还田比例设6个等氮量(N-P2O5-K2O量均为120-90-135 kg·hm-2,对照除外)处理:对照(不施肥,CK)、100%化学氮(NPK)、85%化学氮+15%沼液N(BS15)、70%化学氮+30%沼液N(BS30)、55%化学氮+45%沼液N(BS45)和100%沼液N(BS100),分析各处理下土壤有机质含量(OM)、0.25 mm机械稳定性(DR0.25)和水稳定性(WR0.25)团聚体含量、团聚体平均质量直径(MWD)、几何平均直径(GMD)、团聚体稳定率(AR,%)和分形维数(D)等团聚体稳定性指标。【结果】沼液化肥配施处理土壤有机质含量(OM)较CK、NPK、BS100处理分别增加16.21%—21.34%、2.94%—7.49%、7.69%—12.45%,而且随着沼液量增加呈先升高后降低趋势;沼液化肥配施处理显著提高土壤DR0.25和WR0.25团聚体含量,DR0.25较CK、NPK、BS100处理分别增加1.34%—6.66%、0.26%—5.52%、1.32%—5.25%,WR0.25较CK、NPK、BS100处理分别增加5.17%—10.37%、3.75%—8.88%、1.97%—4.94%,相关分析发现土壤有机质含量升高是土壤0.25 mm机械稳定性(DR0.25)和水稳定性(WR0.25)团聚体含量增加的主要原因;沼液化肥配施处理机械稳定性团聚体平均质量直径(MWD)、几何平均直径(GMD)显著升高,而水稳定性MWD和GMD无显著差异,同时,团聚体稳定率(AR,%)显著高于CK和NPK处理,机械稳定性团聚体分形维数(D)较CK和NPK处理显著降低,而水稳定性团聚体分形维数(D)无显著差异。【结论】沼液化肥配施还田对提高旱地红壤有机质含量、0.25 mm机械稳定性和水稳定性团聚体含量及团聚体机械稳定性具有显著作用,尤其是沼液全氮还田比例在30%—45%范围,适宜在红壤旱地地区推广。

Effects of Biogas Slurry on Soil Organic Matter and Characteristics of Soil Aggregates in Upland Red Earth

【Objective】 In order to provide a theoretical basis for soil structure control and a fertilization system establishment for arid area in south China, a field experiment was conducted to determine the effects of biogas slurry returning systems on concentrations of soil organic matter and structure and stability of soil aggregates in upland red soil. 【Method】 A field experiment was conducted with six treatments: no fertilizer (CK), chemical fertilizer (NPK), 85% chemical fertilizer N+15% biogas slurry N (BS15), 70% chemical fertilizer N+30% biogas slurry N (BS30), 55% chemical fertilizer N+45% biogas slurry N (BS45) and 100% biogas slurry N (BS100). Each treatment included the same amounts of N-P₂O₅-K₂O=120-90-135 kg·hm^-2 (except CK). Soil organic matter content, soil aggregate structure and stability were determined. 【Result】 After peanut harvest in 2014, soil organic matter contents and the amounts of ＞0.25 mm mechanical and water-stable soil aggregates were significantly higher in the treatments of BS15, BS30 and BS45 than those in the treatments of CK, NPK and BS100. The aggregate stability rate (AR), mean weight diameter (MWD), geometric mean diameter (GMD) and fractal dimensions (D) of mechanical stable soil aggregates were significantly higher in the treatments of BS15, BS30 and BS45 than those in the treatments of CK and NPK. 【Conclusion】 The contents of soil organic matter and soil aggregates could be improved efficiently by biogas slurry returning to field, especially in the treatments of BS15, BS30 and BS45, which could be expended in the upland red earth areas of south China.