Crushed plant matter postponed soil water leakage and enhanced soil water retention capacity of sandy soil
Description
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%.
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2.3.2 Material measurements The bulk density of the experimental materials was determined using a cutting ring with a volume of 200 cm³ (diameter: 70 mm, height: 52 mm). The upper cover of the cutting ring was removed, and a qualitative filter paper of the same size was placed on the bottom cover to prevent sand leakage. The prepared soil was then slowly poured into the ring while gently tapping it to ensure complete filling. Excess soil above the ring edge was carefully leveled using a straightedge to minimize experimental errors. This procedure was repeated to prepare three replicated soil core samples (pure sandy soil, MS0%). Similarly, three replicates of pure crushed plant matter of maize straw (MS) were prepared using the same method. After packing, the weight of each core was measured, and the bulk density was calculated. The bulk density of pure sandy soil (MS0%) was 1.582 ± 0.005 g/cm³, while that of pure crushed plant matter of was 0.1442 ± 0.003 g/cm³. 2.3.3 Preparation of composite samples Based on the bulk density of pure sandy soil and pure crushed plant matter (MS0%), composite samples with volumetric ratios of the crushed plant matter-sandy soil of 10%, 20%, and 30% were prepared. For each unit volume (100 cm³), the following quantities were homogenized: MS10% (the crushed plant matter: sandy soil = 10:90): 1.44 g of pure crushed plant matter + 142.38 g of pure sandy soil. MS20% (the crushed plant matter: sandy soil = 20:80): 2.88 g of pure crushed plant matter + 126.56 g of pure sandy soil. MS30% (the crushed plant matter: sandy soil = 30:70): 4.33 g of pure crushed plant matter + 110.74 g of pure sandy soil. 2.3.4 Determination of composite samples The mixed soil samples were prepared in triplicate according to the method described in Step 2, and their bulk densities were measured. Notably, the measured bulk densities of the composite samples exceeded theoretical predictions. For MS10%, the theoretical bulk density was 1.44 g/cm³, while the measured value reached 1.52 g/cm³, representing a 5.56% increase. Similarly, MS20% exhibited a theoretical bulk density of 1.29 g/cm³ versus a measured value of 1.45 g/cm³ (12.40% increase), and MS30% showed a theoretical bulk density of 1.15 g/cm³ compared to a measured value of 1.38 g/cm³ (20.00% increase). This discrepancy arose due to the larger particle size and high sand content (>0.053 mm, 99.34%) of the sandy soil, which resulted in elevated porosity (total porosity: 40.30%). The irregularly flattened fragments of the crushed plant matter of maize straw effectively filled the inter-particle pores within the sandy soil matrix, thereby increasing the mass per unit volume, reducing the theoretical porosity space, and ultimately enhancing the bulk density of the composite samples.
Institutions
- Shanxi Agricultural UniversityShanxi, Xiaodian
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Funders
- Project of Agricultural Science and Technology Innovation of Department of Agriculture and Rural Affairs of Shaanxi ProvinceGrant ID: 2025JCQY008
- Key Research and Development Plan of Ningxia Hui Autonomous RegionGrant ID: 2022BEG02002