waterArticleRaindrop Energy Impact on the DistributionCharacteristics of Splash Aggregates of CultivatedDark Loessial CoresYu Fu1, Guanglu Li1,2,*, Dong Wang2, Tenghui Zheng1and Mingxi Yang21Institute of Soil and Water Conservation, Northwest A&F University, No. 26 Xinong Road,Yangling 712100, China2College of Resources and Environment, Northwest A&F University, No. 3 Taicheng Road,Yangling 712100, China*Correspondence: [email protected]; Tel.:+86-029-87082376Received: 15 June 2019; Accepted: 18 July 2019; Published: 21 July 2019Abstract:To determine the effect of different rainfall energy levels on the breakdown of soil aggregates,this study analyzed the soil splash erosion amounts and the distribution of particle sizes under sixrainfall conditions (rainfall energy: 2.41×10-5–22.4×10-5J m-2s-1and 1.29×10-4J m-2s-1) at fivesplash distances (from 0–10 cm to 40–50 cm). Cores of the size 10×20 cm of undisturbed cultivateddark loessial soil were selected in tree replicates as the research subject. The results indicated thatsplashed aggregates were distributed mainly at splash distances of 0–20 cm, which accounted for66%–90% of the total splash erosion amount. The splash erosion amount significantly decreasedexponentially with increasing splash distance for the same rainfall energy (p<0.01). The splasherosion amount significantly increased in the power function relationship with increasing rainfallenergy at the same splash distance (p<0.05). A model was obtained to predict the splash erosionamount for rainfall energy and splash distance. The fractal dimension (D) of the aggregates showed adownward opening parabolic relationship with raindrop energy. The maximal value of the rainfallenergy was 1.286×10-4J m-2s-1, which broke the aggregates to the largest degree. Enrichment ratio(ER) values for fragments>2 mm were close to 0. A particle size of 0.25 mm was the critical particlelevel for splash erosion.Keywords:raindrop energy; soil aggregate; splash distance; fractal dimension; Loess Plateau1. IntroductionSoil erosion reduces land productivity and soil fertility, destroys farmland, exacerbates flooddisasters, and results in soil environment deterioration, which affects land exploitation and theprotection and utilization of soil and water resources [1,2]. Water erosion is the main type of soil erosionin the Loess Plateau. The aggregates caused by splash erosion are dispersed and broken, which is theinitial stage of water erosion [1–4]. Raindrops fall from the air and impact the surface soil particles at acertain speed under the action of gravity. Some soil particles are separated from the soil and becomeloose particles, which is conducive to the formation and flow of surface runoff. At the same time, theprocess provides abundant loose particles for subsequent runofftransport [5,6]. Additionally, soilparticle transport leads to reduced or blocked pores on the soil surface and reduced soil permeabilitydue to soil crust formation [7–9].