Distribution And Availability Of Phosphors In Soil Profiles Of Slope Land Under Different Land Use Of Loess Plateau

According to the topography,vegetation and climate characteristics of Loess Plateau,we studied the soil nutrients in the slopes landof different vegetation and land use patterns under natural conditions in order to raise options for the ecological environment of the Loess Plateau in vegetation and land use,particularly P distribution and its effectiveness.This paper studied distribution and availability of phosphors of soil profiles under different land use of Loess Plateau.Meantime we analyzed availability of P with Correlation Analysis,Path Analysis and Stepwise Regression systemically.Results show as follows:1.Inorganic P was main proportion in total phosphors(TP)of soil profiles under different land use,and the order of iP forms of was Ca10-P＞O-P＞Ca8-P＞Fe-P＞Al-P＞Ca2-P,Land use were not the cause to change the order of inorganic P forms;The contents of HLOP were the most and the contents of LOP were the least among organic P forms.(1)The contents of available phosphors(AP)and TP in soil profiles under gramineae were less than them under non-gramineae,Ca2-P and LOP of soil profiles in farmland were the main resource of AP.(2)The contents of TP in bare land were high but the contents of AP were low,and the contents of surface layer were significantly more than other layers.Ca8-P,Al-P,LOP,HLOP and MROP of soil profiles in bare land were the main resource of AP.(3).The contents of TP in grassland were high but the contents of AP,OM and Hydrolysable N were low,their contents reduced as soli depth(0-60cm)decreased.Ca8-P,Al-P,LOP and MLOP were the main resource of AP.(4)Compared with bare land the contents of AP and TP in shrub land were high,but the contents of OM and Hydrolysable N were low,and their contents reduced as soli depth (0-60cm)decreased.Ca2-P,Ca8-P,LOP,and MLOP were the main resource of AP.(5)Compared with Zizyphus jujuba cv.land the contents of AP,TP and OM in Prunus armeniaca L.land of economic forest land were low.Ca2-P,Ca8-P,LOP and MLOP were the main resource of AP.(6)The contents of AP,TP and Hydrolysable N in soil profiles under leguminosae high wood were less than under non-leguminosae.The contents of AP and TP reduced as soli depth (0-60cm)decreased.Ca2-P,LOP and MLOP were the main resource of AP.2.The conclusions of distribution of P in soil profiles of different slope position under grassland in fertilization condition.(1)The contents of AP and OM in soil profiles of grassland in fertilization condition had a trend of the bottom of slope＞the middle slope＞the top of slope,and the order of the contents of TP and Hydrolysable N had a trend of the top of slope＞the middle slope＞the bottom of slope.The contents of nutrients reduced as soli depth decreased,and available nutrients decreased most.Compared with non-fertilization land the nutrition contents in fertilization condition increased,and the contents of Hydrolysable N increased most.(2)Fertilization increased the contents of Ca2-P,Al-P,Fe-P and O-P,and promoted Ca8-P to transform into Al-P and Ca2-P.Inorganic P and all the inorganic P forms enriched in the bottom of the slope.(3)Compared with non-fertilization land the contents of total organic P,LOP and HLOP of soil profiles in fertilization condition increased significantly.The contents organic P forms had a trend of the bottom of slope＞the top of slope＞the middle slope except MLOP.The contents of LOP reduced as soli depth decreased.3.The conclusions of comparison of distribution of P of soil profile under different land use.(1)The contents of AP and TP reduced as soli depth decreased under different land use expect shrub land.The contents of AP of soil surface layer in grassland and shrub land was more than that in other land use.Variation of the contents of TP under different land use was not obvious.(2)Compared with bare land the contents of Ca2-P increased and enriched in soil surface layer under other land use,the grassland and shrub land was Optimum among all the land use. The grassland was Optimum to Ca8-P and Al-P.Fe-P and O-P in grassland enriched in the surface layer.The contents of Ca10-P under different land use were not obvious.(3)The contents of LOP in grassland,shrub land and high wood enriched in the soil surfaced layer.The contents of LOP in farmland increased most.The contents of MLOP in shrub land and high wood accumulated in the soil surfaced layer.Compared with bare land the contents of MROP and HROP increased under other land use.