Study On Spatial Variability Of Soil Nutrients In Different Land Types In Xunyangba Area, Southern

Soil nutrients is necessary for plant growth, the deficiency or excess of which not only affects the plant growth, but also affects the food security and ecological health; Land use is a comprehensive reflection of human activities towards land use, the changes of which can cause many changes of natural phenomena and ecological processes. The study of abundance or shortage as well as spatial variability of soil nutrients under different land use types, has the important meaning to understand the spatial distribution of soil nutrients, define soil fertility situation clearly, and reveal coupling relationship between land use and soil nutrient distribution.Take Xunyangba, in Ningshan county, Shaanxi Province as an example, this text selected five land use types-terrace farmland, slope farmland, terrace grassland, slope grassland, forestland, to analyze the spatial variation of soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total kalium(TK), at the same time, compared the soil nutrients between farmland and grassland, terrace and slope land. The data was from the measured section in the field and laboratory soil analysis. We also use the method of classical statistical and geostatistics, with the SPSS19.0, GS+7.0, and Arcgis9.3to analyze the data. The main conclusions were as follows:(1) For SOM, the average content was level1(abundant), forestland has the maximum average value, slope farmland has the minimum average value, the level3(medium level) focused on slope farmland, the2level(slightly abundant) focused on slope grassland. Variation coefficient of soil nutrients from high to low was forestland>slope grassland>terrace farmland>terrace grassland>forestland, all of the land use types had moderate variability except terrace grassland, which has weak variability; range of different land use types from high to low was:slope grassland>slope farmland>terrace farmland>terrace grassland>forestland, the maximum is about five times as the minimum.(2) For TN, most of which focused on level6(very lack level), the average value from high to low was:slope grassland>forestland> terrace grassland>slope farmland>terrace farmland; the top two of variation coefficient were terrace farmland and terrace grassland, forestland was the minimum value, and in addition, all of the land use types had the moderate variability. The range was between35.51-134.10, forestland and slope farmland were the top2, terrace grassland was last. (3) For TP, across five grades-level5(lack level), level4(slightly lack level), level3(medium level), level2(slightly abundant level), most were level3or below. The average value from high to low was:terrace grassland>terrace farmland>slope farmland>slope grassland>forestland. Terrace grassland, terrace farmland and slope farmland were level3, slope grassland and forestland were level4; the variation coefficient of terrace grassland approach weak variability, however, others were moderate variability. All of the land use types has the weak spatial correlation expect slope farmland, which had the medium spatial correlation; The range of different land use types from high to low was:slope farmland>terrace farmland>forestland>slope grassland>terrace grassland, in other words, grassland lower than farmland, terrace lower than slope land.(4) For TK, across four grades-level4(slightly lack level), level3(medium level), level2(slightly abundant level), most were level3or above. The average value from high to low was:slope farmland>slope grassland> forestland>terrace farmland>terrace grassland, terrace grassland was level3, others four were the level2; variation coefficient from high to low was:slope grassland>slope farmland>terrace grassland>forestland>terrace farmland, and the terrace farmland had the weak variability, others approach weak variability. Slope grassland had strong spatial correlation; others four had weak spatial correlation. The range was between30.31and131.98, terrace grassland was the maximum value, and forestland was the minimum value.(5) From the perspective of the comparison between farmland and grassland, terrace and slope land:For the comparison between farmland and grassland:the grassland had more SOM and TP, the spatial variation of TK was mainly caused by structural factors, for example, climate, parent material, topography and so on, however, the spatial variation of SOM was mainly caused by human factors; the range of TK and SOM was relatively small in the grassland.For the comparison between terrace and slope land:the terraces had more TP, and expect the SOM in terrace had moderate spatial variation, others spatial variations were weak. The range of different nutrients in terrace vary greatly (both maximum and minimum of the range were appeared in terrace). In addition, as the soil nutrients at high geographical position were brought to the low by rain wash and transportation, thus making the space distribution of soil nutrients was related to topography.