Alfalfa planting significantly improved alpine soil water infiltrability in the Qinghai-Tibetan Plateau

Abstract

The Qinghai-Tibetan Plateau is undergoing serious water and soil conservation problem resulted from grassland degradation, that is not conductive to the sustainability of grassland ecologicla function and agriculture productivity. The soil infiltrability has significance in reducing runoff yield and soil loss. However, characterization of the soil infiltration capacity of planted grasslands, such as alfalfa (Medicago Sativa), with different growing years in this high-altitude alpine region is still lacking. In this study, the variation of soil infiltration rate and characteristics were analyzed in alfalfa grasslands with three growth years (two-, four- and seven-year-old). A corn cropland was used as the control field, and the infiltration was monitored using the automatic soil infiltrability measurement system. To determine the influence factors on infiltration rate (IR), soil characteristics and root dry weight density (RDWD) at 0–30 cm soil depth were measured. The results indicated that the comprehensive index of soil water infiltration capacity (FIR) of the seven-year-old alfalfa grassland (0.69) was the highest, followed by the two- (0.05) and four-year-old (0.11) grasslands, being these values significantly higher than that of the corn field (-0.85, P < 0.05). SWC was positively correlated with IR during the fast infiltration stage (IR-I). The soil bulk density and organic matter were negatively correlated with IR, while RDWD was positively related to IR. Our results showed that alfalfa planting improved soil infiltrability, and this upgrade increased with the age growth. This study provided significant information to introduce soil-erosion-control practices for alpine soil and highlights the importance of ecological function of planted grasslands in alpine area of the Qinghai-Tibetan Plateau.