Selectivity of aggregate fractions for loess soils under different raindrop diameters

Abstract

Raindrop impact causes splash erosion, the initial form of water erosion, which splashes and disperses surface soil particles. To date, there have been several wide-ranging studies of the Loess Plateau; however, a single soil type was generally studied. This meant that the large differences in the characteristics of different soil types because of variation in topography and soil-forming conditions were disregarded. The objectives of this research were to clarify the soil aggregate splash characteristics of different soil types under different rainfall conditions on the Loess Plateau. This study analysed the soil aggregate mass and distribution of aggregate fractions from splash erosion under six rainfall conditions (raindrop size: 2.67–5.45 mm) at five splash distances (0–10, 10–20, 20–30, 30–40 and 40–50 cm). Five types of soil on the Loess Plateau were selected for this research. The results showed that soil properties had a greater effect on aggregate distribution in splash. With the increase in raindrop diameter, the mass from splash erosion of Lou, Linnamon and Dark loessial soils increased. The mass from splash erosion of Loessial and Aeolian sandy soils, however, showed a variable trend as the raindrop diameter increased to a peak at a diameter of 4.05 mm. Soil types with smaller clay contents were more likely to be transported under high rainfall intensity, and increasing raindrop diameter can transport more soil and also break down aggregates. For the same soil type, the distribution of splash aggregate fractions was similar at different splash distances, and the splash mass decreased exponentially as the splash distance increased (P < 0.001). The Aeolian sandy soil had the largest splash mass for each splash distance, and its resistance to soil erosion was poor. A model was developed to predict the splash mass using the soil erodibility factor, splash distance, raindrop diameter and raindrop intensity. Our findings indicated that compared with rainfall conditions, soil properties had a greater effect on aggregate distribution from splash, indicating that improved soil structure is the main factor that can reduce the water erosion damage.