雨滴击溅对耕作层土壤团聚体粒径分布的影响

Effects of raindrop splash on aggregate particle size distribution of soil plough layer

为研究不同雨滴直径的降雨对耕作层团聚体的破碎及其粒径分布特征的影响,该文选取4个雨滴直径(2.67~3.79 mm)对耕层土壤(0~20 cm)团聚体进行雨滴击溅试验,每次试验各滴5 000滴,每1 000滴收集1次溅蚀团聚体。结果表明:1)所有收集次序中雨滴直径3.79 mm溅蚀量最大,累积雨滴数为2 000、3 000和4 000时,溅蚀量与雨滴直径均呈显著的指数函数关系。2)各雨滴直径的溅蚀量随粒径减小呈增大-减小-增大趋势,>2 mm粒径的溅蚀量几乎为0,<0.053 mm粒径的溅蚀量随雨滴直径增大而增大。3)相同雨滴直径不同累积雨滴数之间平均重量直径值差异不显著,相同累积雨滴数不同雨滴直径之间平均重量直径值差异不显著(P<0.05)。4)不同雨滴直径溅蚀团聚体富集率随粒径变化一致,>1 mm粒径溅蚀量团聚体富集率值接近0,0.053~1 mm粒径团聚体富集,>1 mm粒径团聚体主要破碎成0.053~1 mm粒径团聚体,且粒级越小,富集率越高。研究可为黄土高原地区水土保持提供理论依据。

Splash erosion, which is a main dynamic for the detachment and transport of soil aggregates, is the initial stage ofsoil water erosion. Soil aggregate is a crucial indicator determining the plough layer soil fertility. Destruction of the ploughlayer aggregate has a negative effect on the content of soil available water and soil fertility, destroying the soil structure andrestricting agricultural development of the Loess Plateau. To determine the effect of raindrop diameters on the breakdown ofsoil aggregates of plough layer and the characteristic of splashed fragment size distribution in the process of raindrop splasherosion, an artificially simulated raindrop splash experiment was conducted with 4 raindrop diameters （2.67, 3.05, 3.39 and3.79 ram） using a self-designed simulated device that had a circular room with a 10-cm diameter for placing soil samples. Thesoil sample was collected from the soil plough layer （0-20 cm） with a steel ring （10 cm in diameter）. The sampling site waslocated in a traditional agricultural planting region in Yangling of Shanxi Province （108°03＇29＂E, 34°18＇24＂N）. Each raindropdiameter splash test was replicated 3 times. For each raindrop diameter, 5000 raindrops were dripped from a generator deviceon sample, and splashed aggregate fragments were collected every 1000 raindrops. The splashed fragments were sieved withaperture （2, 1, 0.5, 0.25, 0.106, 0.053 mm） using an aggregate analyzer （HR-TTF-100）. All aggregate fragments were ovendried for 24 h at 105°C and weighed. The results showed that the splash amount among the collected order was notsignificantly different for raindrop diameter 2.67 and 3.05 mm, whereas, the splash amount of the II-V order was significantlylower than that of the I order for raindrop diameter 3.39 and 3.79 ram. An exponential function could be used to describe therelationship between splash amount and raindrop diameter when raindrop accumulation number was 2000-4000 （P〈0.05）. Forall the raindrop diameters, the total splash amount presented an up-down-up trend as the particle size decreased. The amount ofsplashed fragments 〉2 mm was almost 0 for each raindrop diameter test. However, the amounts of splashed aggregates 〈0.053 mm increased with the increase of raindrop diameter. There was no significant difference in mean weight diameter ofsplashed fragments among different accumulation raindrop numbers or different raindrop diameters （P〉0.05）. The variationin enrichment ratio with the fragment size was consistent under different raindrop diameters. Compared with the undisturbedsoil, the splashed fragments in particle size 〉1 mm and 〈 0.053 mm were decreased for all raindrop diameters. However, theenrichment ratios of splashed fragments of the other particle sizes were greater than 1. The results can provide valuableinformation for agricultural development in the Loess Plateau.