不同轮耕模式对黄土高原旱作麦田土壤物理性状的影响

【目的】研究免耕、深松和翻耕两两组合而成的3种不同轮耕模式对黄土高原旱作麦田土壤物理结构与稳定性影响。【方法】于2007—2012年在陕西渭北旱塬麦田开展夏闲期免耕/深松、深松/翻耕和翻耕/免耕3种隔年交替的轮耕试验，测定土壤容重，并应用干筛和湿筛法分析土壤团聚体不同粒级含量、大小和分形维数。【结果】与耕作试验前相比，5年免耕/深松、深松/翻耕和翻耕/免耕处理在收获期0—60 cm土层土壤容重与孔隙度差异均不显著。3种轮耕处理的耕层团聚体性状变化差异显著，0—10 cm土层大于0.25 mm水稳性团聚体含量（R0.25）及稳定率表现为免耕/深松＞深松/翻耕＞翻耕/免耕；0—30 cm土层水稳性团聚体平均重量直径（mean weight diameter，MWD）大小表现为免耕/深松＞深松/翻耕＞翻耕/免耕。3种轮耕处理的团聚体分形维数（fractal dimension，D），干筛法下10—30 cm土层表现出差异，湿筛法下0—10 cm土层表现出差异，免耕/深松处理分形维数低于深松/翻耕和翻耕/免耕处理。【结论】3种轮耕模式对土壤容重的影响无显著差异。免耕/深松保护性轮耕模式能提高耕层团聚体含量与稳定性，改善旱地土壤结构；而深松/翻耕与翻耕/免耕的轮耕模式由于隔年翻耕对土壤的强烈扰动，对土壤结构改善效果不明显。

Effects of Different Rotational Tillage Patterns on Soil Physical Properties in Rainfed Wheat Fields of the Loess Plateau

【Objective】Effects of three different rotational tillage patterns, which were pairwise combined with no-tillage(N), subsoiling(S) and conventional tillage(C), on soil physical structure and stability were studied in rainfed wheat fields of the Loess Plateau.【Method】The experiments of N/S (no-tillage in the first year, subsoiling in the second year, again no-tillage followed by alternating the next year), S/C (subsoiling in the first year, conventional tillage in the second year, again subsoiling followed by alternating the next year) and C/N (conventional tillage in the first year, no-tillage in the second year, again conventional tillage followed by alternating the next year) rotational tillage were conducted in rainfed wheat fields of Weibei highland in summer fallow period from 2007 to 2012, soil bulk density, aggregates amount, size distribution and fractal dimension were observed and examined by dry and wet sieving methods.【Result】The results showed that, compared with pretreatment, soil bulk density of N/S, S/C and C/N rotational tillage treatments in harvest period had no significant differences at 0-60 cm. Soil aggregates properties changed significantly in three different rotational tillage treatments, N/S was higher in the macro-aggregate content (R0.25) and stability rate of water-stable aggregates than S/C and C/N treatments at 0-10 cm; N/S was also higher in mean weight diameter(MWD) of water-stable aggregates than S/C and C/N treatments at 0-30 cm. The fractal dimension of aggregates among these treatments were significantly different at 10-30 cm by dry sieving and at 0-10 cm by wet sieving, its value under N/S was lower than S/C and C/N treatments.【Conclusion】 The three different rotational tillage patterns had no significant difference in soil bulk density. N/S conservation rotational tillage pattern increased soil macro-aggregate content and stability, improved dryland soil structure. S/C and C/N rotational tillage patterns disturbed soil layer because of every other year plowing, so its soil structure had no significant improvement.