The Hole Type Control Technology Of The Deep Soil Moisture And Its Effect On The Slope Land On The Loess Plateau

Soil erosion is still one of major issues limiting agricultural and forestry productivity in Loess Plateau of China.A series of projects,such as comprehensive control of small watershed,silt dam and ‘Grain for Green',have been carried out successively.These projects have played a significant role in preventing soil and water loss.The loess plateau has a deep soil layer,which has a huge reservoir capacity for water accumulation.But at present,the reservoir is almost dried up because of less rainfall,more runoff,large evaporation and vegetation water consumption.On the basis of field location monitoring test and indoor soil column simulation test,the temporal and spatial distribution of soil moisture under the combination of infiltration holes and soil and water conservation measures is studied in this paper,which makes full use of this reservoir capacity to infiltrate rainfall in situ.The purpose is to provide theoretical basis and technical support for vegetation restoration and construction in the Loess Plateau.The results are as follows:(1)By comparing the soil water content and water retention effect of fish scale pits,it was found that the cover soil(0-60 cm)had the highest soil moisture content and better water retention and soil conservation effects.The rainfall runoff intercepted by the infiltration hole + fish scale pit combination measures is preferentially infiltrated into the deep soil through the infiltration hole,which can locally local soil moisture content,and can increase the maximum infiltration depth of soil moisture.In 2016-2017,the soil moisture content in fish scale pits has been restored,and the increase in soil moisture content is between 1.39% and 4.64%.The dynamic change of soil water storage in the fish scale pits over time was affected by rainfall.In the 0-70 cm soil layer,from the end of August to mid-November,the reduction of soil water storage in infiltration holes was lower than other treatments.After the rainfall(mid-to-late August),the increase in soil moisture content in the 70-120 cm soil layer of the infiltration hole was higher than that of other treatments,with an increase of 14.78 mm.(2)To study the water retention effect of infiltration holes in the horizontal ditch of Caragana korshinskii,it was found that the soil water storage decreased as the distance from the infiltration hole increased.The water content in the horizontal infiltration hole of Caragana korshinskii was the largest,and the soil moisture content was 50 cm in the horizontal ditch of Caragana intermedia.The water infiltration in the infiltration hole resulted in soil water content in the horizontal infiltration hole of Caragana korshinskii was higher than that in the sloping land.The water content of soil in the horizontal infiltration hole of Caragana korshinskii was increased by 29.34% and 11.38% compared with the sloping land,respectively.However,due to water consumption of Caragana korshinskii,soil water content at 25 cm and 50 cm from the infiltration hole was reduced by 1.69% and 4.49%,respectively,compared with the slope.(3)With the increase of infiltration hole depth(40 cm,60 cm and 80 cm),the average soil water content increased slightly,and the maximum depth of soil water infiltration increased.Comparing with stone covering,straw stalk and blank treatment,infiltration hole treatment increased the soil moisture content of the local soil,and for the entire soil,the effect of covering measures was more obvious.(4)As the depth of the infiltration hole increases,the daily evaporation of the soil decreases.The relationship between the daily evaporation of the treated soils and the evaporation time was related to evaporation.Within the 28 days of evaporation,the daily evaporation of the blank soil was the largest.However,after 28 days of evaporation,the daily evaporation of soil treated with straw and infiltration holes was higher than the blank.(5)Comparing the cumulative evaporation of each treatment,the effects of the cover measures to suppress soil evaporation are more pronounced.Infiltration hole treatment can reduce the accumulated evaporation of soil,and with the increase of the depth of infiltration hole,the cumulative evaporation of soil decreases.