Soil anti-erodibility at different growth stages of maize in hilly yellow soil areas

Mountainous yellow soil area is one of the most important agricultural production base in Sichuan province of southwestern China, as well as a serious soil erosion area. Since the slope farmland is the main cultivated land resource of hilly yellow soil area, the severe soil erosion has caused tremendous degradation in the slope farmland, and consequently posed negative effects in regional agricultural production and sustainable utilization of soil resource. Maize (Zea mays L.) is the dominant crop in this area, but the whole growth stages of maize overlap with the erosive period of regional rainfall on temporal scales. Thus, the soil erosion has inevitable impacts on the growth of maize in slope farmland. In this study, taking a slope farmland in hilly yellow soil areas as the object, the field experiments and lab analysis were combined to clarify the characteristics of soil anti-erodibility at the different growth stages of maize. The wet-sieving and pipe methods were employed to measure the composition and stability of soil water-stable aggregates and micro-aggregates, respectively. The model of soil anti-erodibility index (SAI) and the principal component analysis (PCA) were applied to evaluate the soil anti-erodibility. 10 evaluation indices were selected, including the content of soil organic matter (SOM), the content of <0.05 mm slit clay, the content of <0.001 mm clay, the content of >0.25 mm water-stable aggregate, mean weight diameter (MWD), percentage of aggregate disruption (PAD), mean weight specific surface area (MWSSA), fractal dimension of micro-aggregate (FD), aggregation degree (AD), and dispersion coefficient (DC). The characteristics of soil anti-erodibility can be determined using the comprehensive index F of PCA, and the soil anti-erodibility index SAI. The results indicated that: (1) The soil water-stable aggregates and micro-aggregates both showed a similar trend that micro-aggregates transformed gradually into macro-aggregates with advancing growth stages of maize. The content of >0.25 mm water-stable aggregates, MWD, AD, and SOM increased significantly with the maize growing (P<0.05), and all of them increased by 1.77%-6.85%, 2.11%-7.53%, 2.72%-8.29%, 1.09%-7.81%, respectively, compared with the seedling stage. However, the PAD, MWSSA, FD and DC exhibited an order of, seedling stage > jointing stage > tasseling stage > maturing stage, and these indices decreased by 1.17%-15.85%, 3.68%-14.89%, 0.39%-1.43%, and 3.96%-18.75%, respectively, compared with the seedling stage; (2) The 10 evaluation indices can be optimized to 5 indices by PCA, including The 10 evaluation indices can be optimized to 4 indices by PCA, including SOM, SL, PAD and AD. The F and SAI showed a similar trend that both increased with the maize growing, and decreased as the soil depth increased. Therefore, the soil anti-erodibility at the different stages of maize growth displayed an order of, maturing stage > tasseling stage > jointing stage > seedling stage, and the resistance of the 0-10 cm soil layer was stronger than that of the 10-20 cm soil layer; (3) The leaf area index (LAI) and root mass density (RMD) of maize showed a similar trend that both increased, and then decreased with the maize growing, peaked at the tasseling stage. The soil anti-erodibility was significantly and positively correlated with the LAI and RMD, where the correlation coefficients were 0.732 and 0.842, respectively (P<0.01). This correlation indicated that the growth of maize can significantly affect the soil anti-erodibility. The plantation of maize played a vital role in enhancing soil anti-erodibility in the slope farmland of the hilly yellow soil area. Therefore, the suitable patterns of maize planting can significantly reinforce soil anti-erodibility in topsoil layer. The finding can offer an effective approach to prevent and control the loss of soil and water in the regional slope farmland.