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 · 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 o-40 cm soil layers, 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 (DR_0.25) and of >0.25 mm water stable aggregates (WR_0.25) 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 · hm^-2 of straw mulching. Straw mulching increased the soul organic matter content, and the latter had a significant positive correlation with the WR_0.25 content. All the straw mulching treatments decreased the soil unstable aggregate index (ELT) which was the lowest in treatment 6000 kg · 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 · hm^-2 had the best effect, being a reasonable straw mulching mode to be applied in the agricultural production in Weibei Loess Plateau. [ABSTRACT FROM AUTHOR]