免耕条件下秸秆覆盖对旱地小麦田土壤团聚体的影响

设2个秸秆覆盖时期(全程覆盖、生育期覆盖)和3个覆盖量(3000、6000和9000kg·hm-2),以全程不覆盖为对照,研究陕西渭北旱塬免耕条件下秸秆覆盖对小麦田土壤团聚体的影响.结果表明:在0～40 cm土层,随土层的加深,＞5 mm径级的土壤团聚体含量逐渐增加,＜5 mm径级的土壤团聚体含量逐渐减小;各覆盖处理中,＞0.25 mm径级的机械稳定性团聚体和水稳性团聚体的含量均显著大于对照,分别增加13.0％～26.4％和18.6％～45.6％,其中,6000 kg·hm-2秸秆覆盖处理的增幅最大;秸秆覆盖提高了土壤有机质含量,土壤有机质含量与＞0.25 mm径级的土壤水稳性团聚体含量呈显著正相关;各秸秆覆盖量处理均降低了土壤不稳定团粒指数,以6000 kg·hm-2秸秆覆盖处理的土壤不稳定团粒指数最小.表明秸秆覆盖可显著增加0 ～40 cm土层＞0.25 mm径级的土壤团聚体和有机质含量,提高土壤结构稳定性,并且以6000 kg·hm-2覆盖量的处理效果最佳,该覆盖量可以作为渭北旱塬小麦田合理的秸秆覆盖模式应用于农业生产中.

Effects of straw mulching on the soil aggregates in dryland wheat field under no-tillage

A field experiment was conducted to study the effects of full period and growth period straw mulching with an amount of 3000, 6000, and 9000 kg x hm(-2) on the soil aggregates in a no-tillage dryland wheat field in Weibei Loess Pleateau of Shaanxi Province, taking no full period straw mulching as the control. In the 0-40 cm soil layer, the content of > 5 mm aggregates increased with depth, while that of <5 mm aggregates was in adverse. Under straw mulching, the total contents of > 0.25 mm mechanical stable aggregates (DR0.25) and of > 0.25 mm water stable aggregates (WR0.25) were significantly higher than the control, with an increase of 13.0%-26.4% and 18.6%-45.6%, respectively and the largest increment in the treatment 6000 kg x hm(-2) of straw mulching. Straw mulching increased the soil organic matter content, and the latter had a significant positive correlation with the WR0.25 content. All the straw mulching treatments decreased the soil unstable aggregate index (E(LT)) which was the lowest in treatment 6000 kg x hm(-2) of straw mulching. This study showed that straw mulching could increase the >0.25 mm aggregates and organic matter contents in 0-40 cm soil layer and improve the soil structural stability, and mulching with an amount of 6000 kg x hm(-2) had the best effect, being a reasonable straw mulching mode to be applied in the agricultural production in Weibei Loess Plateau.