Study On Characteristics Of Soil Moisture And Nutrients And New Regulation Techniques In The Thin Loess Covered Pisha Sandstone Area

Pisha sandstone area was located at the border of Shanxi,Shaanxi and Mongolia in China,which was an extremely fragile area of ecological environment.Due to the intense water and soil erosion for a long time,the upper eolian loess in this area was gradually eroded away,which exposed the overlying arsenic sandstone,and the ecological degradation and water and soil erosion in this area were intensified.Therefore,the residual soil thickness after soil erosion had become an important factor that restricted the ecological restoration in this area.In order to explore the variation of soil moisture and nutrients during the vegetation restoration process in the thin-layer soil Pisha sandstone area,so as to develop a new anti-erosion and growth-promoting regulation technical measure,this paper firstly studied the variation rules of soil moisture and nutrients in different soil covering thickness（0,20,50,120,300 cm）.Based on these data,the spatial distribution regularities and reserves of soil moisture and nutrients in different thickness of loess covering were obtained,and the causes affecting the slow growth of vegetation in thin overburden area were analyzed.At the same time,a new engineering technology to promote plant growth--nutrient water island engineering measure was innovated,and the change characteristics of plant growth and soil environment under the new engineering technology were discussed.In the Pisha sandstone area,we laid fish-scale pits+fertilizer+diversion holes,Fish-Scale Pits+diversion holes,Fish-Scale Pits and no fish-scale pit in Jungle Banner Warm Water Town.After the plot was set up,we monitored the growth of wild peach,soil nutrient change and soil water dynamic change in 0-180 cm profile,and studied the effects of fish-scale pits,fertilizer and diversion holes on the plant growth and soil environment in the soil-covered Pisha sandstone area,provided feasible theoretical support for the region to promote the restoration of vegetation.The preliminary results are as follows:1.With the deepening of soil depth,the soil water content of all treatment were boosted,but with the further deepening of soil depth,the soil water content were reduced.The loess layer showed the law of increase,ranging from 2.31-12.31%,while that of arsenic sandstone（P）layer showed a trend of first increase and then decrease,ranging from6.39-16.88%.As well as,the location of the maximum soil moisture content would deepen with the ascension of the thickness of loess overlying the soil,the maximum soil moisture of the L layer was 20 cm,50 cm,90 cm and 180 cm,respectively,and the maximum soil moisture of the P layer was 30 cm,60 cm,120 cm and 160 cm,respectively.In addition,with the increase of loess overburden thickness,the average soil water content and soil water storage gradually increased,while the average soil water content and soil water storage began to decrease with the further thickening of loess overburden thickness.2.With the deepening of soil depth,soil organic matter（SOM）,total nitrogen（TN）,total phosphorus（TP）,and total potassium（TK）decreased in all treatments.The contents of TP and TK began to rise to a certain depth and then continued to decline with the further deepening of soil depth,while the content of available phosphorus（AP）did not fluctuate.The contents of SOM,TN,TP,TK and AP in L layer were 1.58-15.75,0.01-0.74,0.21-0.77,7.63-14.43 g.kg^-1and 0.01-0.06 mg.kg^-1,respectively.The contents of SOM,TN,TP,TK and AP in P layer were 1.12-7.47,0.01-0.23,0.08-0.77,8.56-16.52 g.kg^-1and 0.001-0.1mg.kg^-1,respectively.As a result,SOM and TN content in all soil layers of each treatment were generally at a very low level,and only less than 20%were at a low level.Meanwhile,the TP content in all soil layers of all treatments was low and extremely low,and a few were medium to high and medium to low.The TK content of all soil layers in each treatment was in the medium-low level,and a few were in the upper or low level.Also,the content of AP in all soil layers was at an extremely low level.In addition,with the ascension of the thickness of loess overlying the soil,the contents of average SOM,TN,TP,TK began to decrease.With the further ascension of the thickness of loess overlying the soil,the contents of TN,TP,TK boosted,while the soil carbon storage（C）boosted.At the same time,the content of SOM,C in P layer began to decrease.With the further ascension of the thickness of loess overlying the soil,the content of SOM and C boosted,and the content of TP boosted.3.Through the study,we found that FTP,FT and F treatments could increase the soil total water storage（SWS）,promote the downward infiltration of water,and could transfer the surface soil water into the deep layer after the coming of the secondary rainfall.Meanwhile,the maximum value of soil water storage in each treatment was 468.5,412.2and 389.8 mm,respectively,which all occurred in August 2020.The infiltration depth of soil water in FTP and FT treatments could reach 70-80 cm,while the infiltration depth of soil water in F treatment was 30 cm.Also,FTP,FT and F treatments could increase the content of SWS by 26.42%,24.21%and 19.98%,respectively.After the rainfall,all treatments could quickly send rainwater to the deep soil layer,but the increase of soil moisture was mainly concentrated in the L layer.Compared with CK,FTP,FT and F treatments can all increase the total soil water storage.Among them,the soil moisture of L layer by FTP,FT and F significantly boosted by 84.73%,79.49%and 71.35%,and the the soil moisture of P layer by FTP,FT and F significantly boosted by 9.80%,6.56%and6.56%.4.It was found that the application of fertilizer,diversion hole and fish-scale pit could promote the growth of plants in the Pisha sandstone area,and significantly promoted the growth of wild peach crown width,tree height,ground diameter and new branch length.Among them,the increased plant growth under FTP treatment was 0.29 m,2.90 mm,0.15m and 19.8 cm;the increased plant growth under FT treatment was 0.14 m,1.12 mm,0.05m and 9.3 cm;the increased plant growth under F treatment was 0.03 m,1.02 mm,0.04 m and 8.12 cm.Meanwhile,the average soil organic contents of L and P layer in FTP treatment were significantly boosted by 19.13 and 1.25 g.kg^-1,and the soil carbon storage were significantly increased by 107.29 t.hm²and 5.65 t.hm²,respectively.Also,the average soil organic contents of L and P layer in FT treatment were significantly boosted by 1.90and 0.94 g.kg^-1,and the soil carbon storage were significantly increased by 4.15 t.hm²and2.56 t.hm²,respectively.In addition,the average soil organic matter content and soil carbon storage of L layer in F treatment were significantly decreased by 1.99 g.kg^-1and 15.90 t.hm²,and the average soil organic matter content and soil carbon storage of P layer in F treatment were significantly increased by 0.23 g.kg^-1and 1.30 t.hm².In general,In general,the addition of fertilization and diversion hole significantly increased soil organic matter and carbon storage,while the fish-scale pit significantly decreased soil organic matter and carbon storage in L layer.