Abstract:

To study the effects of agronomic improvement treatments on soil available nutrients, enzyme activities and physical structures of Yinbei saline-alkali land in Ningxia, this experiment adopted two treatments of applicating organic fertilizer (OM) and straw incorporation, with application of chemical fertilizer as control. The results showed that OM and straw return (RS) effectively increased the content of soil alkaline hydrolyzable nitrogen, available phosphorus and available potassium, and significantly enhanced the activities of soil urease and alkaline phosphatase. The proportion of mechanical stability aggregates with particle size over 5 mm treated with OM increased by 22.3%, while particle size ranging from 0.5 to 0.25 mm decreased by 3.8%; the proportion of mechanical stability aggregates with particle size over 5mm treated with RS increased by 19.1%, while particle size ranging from 0.5 to 0.25 mm and under 0.25 mm decreased by 3.1% and 3.2%, respectively. The proportion of water-stable aggregates with particle size over 5 mm treated with OM and RS increased by 29.0% and 43.3%, respectively, while particle size ranging from 0.5 to 0.25 mm treated by OM and RS decreased by 23.1% and 30.1%, respectively. The mean weight diameter (MWD) increased by 105.9% and 139.7%, the soil water stability coefficient (K) increased by 136.4% and 150.5%, and the percentage of aggregate destruction (PAD) decreased by 28.2% and 31.1%, respectively, under OM and RS treatments. The soil physical structure was also effectively improved with OM and RS treatment. The results indicate that organic manure and straw returning are effective measures to improve the quality of salinized soil in the Yinchuan Irrigation Area of Ningxia.

Key words: straw returning, organic fertilizer, saline-alkali land, soil nutrients, soil enzyme activity, soil physical structure