The contribution rate of stem‐leaf and root of alfalfa (Medicago sativa L.) to sediment and runoff reduction

Abstract

Seasonal changes in ground canopy and root density induced by the growth of alfalfa (Medicago sativa L.) may strongly influence the variation in runoff and sediment across alfalfa growth stages. In this study, eight alfalfa plots with and without ground canopy and two bare soil plots (CK) were used to investigate the effect of alfalfa growth on the regulation of runoff and sediment during one growing season (seedling stage, S1; budding stage, S2; flowering stage, S3; podding stage, S4). The experiments involved four slope gradients of 8.6%, 17.6%, 26.8%, and 36.4% and one rainfall intensity of 90 mm h−1. The time to runoff initiation (TR), runoff volume (RV), and sediment yield (SY) were recorded, and runoff reduction benefits (RRBs) and sediment reduction benefits (SRBs) were calculated. The results have shown that TR was delayed with the growth of alfalfa and advanced with an increasing slope gradient. From S1 to S4, compared with CK, alfalfa grassland reduced the runoff by 10.36% to 85.80% and the sediment by 15.34% to 94.48%. The root systems of alfalfa reduced the runoff by 1.29% to 34.86% and the sediment by 0.87% to 49.97%. RV and SY decreased exponentially with aboveground biomass and root density during the growing season. The SRBs were greater than the RRBs, and the contribution of stem leaves for SRBs and RRBs was higher than that for roots under the same growing seasons and slope gradient. This study deepens our understanding of herbaceous plants in regulating runoff and sediment at different growth stages and clarifies the contribution of vegetation components to soil and water loss control.

Mulch and Grass Cover Unevenly Halt Runoff Initiation and Sediment Detachment during the Growing Season of Hazelnut (Corylus avellana L.) in Croatia

“…The PCA results showed that lower soil compaction leads to postponed pond forming on the soil surface layer and the start of the Runoff, which was also observed previously [94][95][96][97]. Moreover, the WSA showed a positive relation with TP and TR because of (1) WSA's capability to create channels within the soil that will enable water to infiltrate and move down the soil profile, which will improve the soil's ability to store more water, thus reducing the water available for runoff [98,99], (2) higher aggregate stability will prevent crusting, since the soil particles are bounded into aggregates that are less prone to soil detachment during the raindrop impact [97,100], and (3) well-aggregated soil had a rougher surface texture due to the presence of clumps and particles, which will enlarge the surface area for rainfall catchment [101].…”