Crushed plant matter postponed soil water leakage and enhanced soil water retention capacity of sandy soil

2.1. Collection and Preparation of Experimental Materials
The experimental materials, including soil and the crushed plant matter of maize straw, were collected and processed as follows:
Soil sample collection: The experimental soil was collected from the southeastern edge of the Mu Us Sandy Land (110°21′–110°23′E, 38°46′–38°51′N; elevation 1080–1270 m), a transitional zone between wind and water erosion with a continental monsoon climate. The region has a mean annual temperature of 7.8°C and an annual precipitation of 350 mm (concentrated from July to October). The soil type is aeolian sandy soil, with a sand content of 99.34% (particle size >0.053 mm), bulk density of 1.55–1.61 g/cm³, pH of 8.1–8.6, soil organic carbon (SOC) of 2.53–3.05 g/kg, total nitrogen of 0.42–0.53 g/kg (Fig. 1b).
The crushed plant matter sample collection and preparation: The crushed plant matter of maize straw was harvested in November 2024 from traditional maize fields (108°2′30E, 34°18′14N; elevation 1080–1270 m) near Yangling District, Xianyang City, Shaanxi Province, China. After collection, the straw was mechanically processed into dried shredded plant material using a dedicated straw crusher. The particle size distribution of the crushed straw was as follows: <0.053 mm: 0.73%, 0.053–0.15 mm: 2.87%, 0.15–0.25 mm: 5.58%, 0.25–0.5 mm: 21.61%, 0.5–1 mm: 40.49%, and 1–2 mm: 28.72% (Fig. 1b). The bulk density of the shredded material ranged from 0.14 to 0.16 g/cm3.
2.2. Experimental design
Based on the bulk density of the sandy soil and the mass density of the crushed plant matter of maize straw, four volumetric mixing ratios of the crushed plant matter-sandy soil were established: MS0% (100% sand, control), MS10% (the crushed plant matter: sandy soil = 10:90), MS20% (the crushed plant matter: sandy soil = 20:80), and MS30% (the crushed plant matter: sandy soil = 30:70). These treatments were designed to simulate the effects of varying crushed plant matter incorporation ratios on soil pore structure, hydro-physical properties, and hydrological processes, with further investigation into their impacts on soil water retention time and capacity.
2.3. Experimental procedure
2.3.1 Preparation of experimental materials
The test soil was passed through a 2-mm sieve to remove root residues and stones, followed by air-drying for experimental use. Similarly, the corn straw was mechanically crushed using the special plant branch shredder (ZNNJ-4T, Zhengzhou machinery factory, China; with a screen diameter of 20mm) to produce the crushed plant matters and stored as a reserve material. The gravimetric water content of the samples was determined, with the pure sandy soil exhibiting a moisture content of 5%, while the pure straw showed a moisture content of 1.77%.