Effect of attapulgite addition on soil water availability of maize on Loess Plateau, China.

Water availability is the primary limiting factor for vegetation restoration and agricultural production in the arid and semi-arid regions of the Loess Plateau. The application of soil amendments is an effective approach for enhancing soil water use efficiency (WUE) in this area. The clay mineral of attapulgite (ATP) is a highly promising soil amendment due to its hydrophilic properties and adsorption capacity, which could improve soil water availability. In this study, we selected two soil types (dark loess soil and loess soil) with distinct soil textures from the Loess Plateau, and conducted an experiment with three levels of ATP application (0, 20, and 40 g·kg) and three water management strategies (drought stress group, drought-rewatering cycle group, and normal water condition group), resulting in a total of 18 experimental treatments. We measured photosynthetic parameters and WUE of maize, and investigated the impact of ATP on soil water availability. The results showed that across the entire growing season, both drought stress group and drought-rewatering cycle group significantly enhanced WUE. Additionally, the ATP-amended treatments exhibited significantly higher WUE compared to the non-amended treatments. The photosynthetic parameters of maize under different treatments all exhibited threshold response patterns based on change in soil relative water content (RWC). Both and WUE increased with rising RWC but decreased after exceeding the critical threshold value corresponding to each treatment. At the maximum ATP application rate (40 g·kg), the WUE of dark loess soil and loess soil reached their peaks at RWC of 73.7% and 98.3%, respectively. With and WUE as indicators of "productivity" and "efficiency" of maize production, the application of ATP enabled the achievement of high yield and efficiency even at the lower soil water conditions in loess soil. The application of ATP demonstrated superior efficacy in enhancing soil water availability in loess soil compared to dark loess soil.