Effects of soil crusts on infiltration in slope land in the loess area
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    Abstract:

    Infiltration is a process of water penetration through the soil surface. During rainfall events, the amount of infiltration determines the quantity of water available for plant uptake, and abundant water helps increase crop yield. In the arid and semi-arid regions, water availability is one of the greatest factors affecting vegetation restoration and ecological environments, especially in the Chinese Loess Plateau area. Proper tillage practices can significantly alleviate certain soil-related constraints to crop production, such as compaction, crusting, low infiltration, poor drainage, and unfavourable soil moisture and temperature regimes. Traditional tillage practices used in the Loess Plateau, include contour tillage and artificial digging, can increase soil roughness and decrease runoff and soil erosion. However, the soil in the Loess Plateau has been reported to be poor in structure, susceptible to erosion and liable to form soil crusts during rainfall events. Soil crusts can reduce the amount of infiltration and hence soil moisture availability. The objective of this laboratory study is to explore characteristics of the formation of different types of soil crusts on slopelands different in soil micro-topography and effects of structural crusts and depositional crusts on soil water infiltration from the rainfall-infiltration perspective. For that end, an indoor experiment was designed to have simulated slopelands adjustable to 5°, 10°, 15° and 20° in slope gradient, three different tillage treatments (contour tillage, artificial digging and straight slope as control) and artificial rainfall events. Two rainfall events were simulated in the experiment. After the first rainfall event, structural crusts and the depositional crusts were formed on the slopeland 0° in gradient after 30 min of 80 mm h-1 rainfall, and then the slope lands were adjusted to 5°, 10°, 15° and 20° in gradient, step by step and each subjected to 30 min of 80 mm h-1 rainfall, to investigate rain water infiltration rates in the slopelands as affected by tillage pattern and slope gradient. Results show that soil crusts retarded water infiltration into the soil; consequently, runoff formed earlier on slopes with crusts than on slopes without crusts, and cumulative rain water infiltration was much lower on the former than on the latter. Infiltration rate decreased with increasing slope gradient regardless of the effect of soil crusts. Regression analysis of model simulation indicates that the Jiang Dingsheng model was optimal to describe variation of soil infiltration rate in this study. What type of soil crusts would be formed was significantly affected by tillage treatments. The structural crusts tended to form on ridges, which were directly impacted by rain drops while the depositional crusts formed in furrows between ridges as sediments in runoff deposited. Meanwhile, the structural crusts were lower in bulk density, but higher in porosity and in shear strength than the depositional crusts. The effects of the two types of soil crusts on soil water infiltration rate were different. Depositional crusts reduced accumulative water infiltration by 37.13%, while structural crusts did by 19.79% compared with the accumulative water infiltration on uncrusted slopes. It is quite obvious that the effect of depositional crusts reducing soil water infiltration is much higher than that of structural crusts.

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Wu Qiuju, Wu Jia, Wang Linhua, Wu Faqi. Effects of soil crusts on infiltration in slope land in the loess area[J]. Acta Pedologica Sinica,2015,52(2):303-311.

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History
  • Received:March 25,2014
  • Revised:October 28,2014
  • Adopted:October 31,2014
  • Online: December 25,2014
  • Published: