Spatial Variability And Abundance Evaluation Of Soil Nutrients In Loess Hilly And Gully Region

The loess hilly and gully region is characterized with complicated topography, severesoil erosion and fragile ecological environment, the change of soil fertility in this regiondirectly affect the level of soil productivity and the way and direction of soil ecologicalrestoration. Thus, making a full understanding about the spatial variability and distribution ofsoil nutrients has important theoretical and realistic significance for revealing soil fertility,improving fertilizer utilization ratio and protecting soil ecological environmental. Ansaicounty which is located in loess hilly and gully region was selected for this research.Geostatistics combined with geographical information system (GIS) technique were appliedto analyze the spatial variability and distribution of soil organic matter, macronutrients(available nitrogen, available phosphorus and available potassium) and availablemicroelements (Fe, Mn, Cu and Zn) in this region. After that, the distribution maps of thecontents of soil nutrients were created, the controlling factors of soil nutrients were analyzed,the condition of abundance or deficiency of soil nutrients were evaluated and the feasibility ofdivision management of soil nutrients were discussed. This paper can provide scientific basisand reference for eco-agricultural construction, reasonable fertilization and soil ecologicalenvironment protection. The main conclusions of this research are as follows:(1) The variation coefficient of eight kinds of soil nutrients was between14.14%and26.84%, every soil nutrient had medium variability; The nugget effect value was between11.76%and46.94%, the spatial correlation of available potassium and Zn were highlydependent, may be they were related to the different parent material of local soils, the othersix kinds of soil nutrients were moderately dependent; The range was between0.84km and31.60km, the theoretical model of available nitrogen was Gaussian model, Fe and Cu wereSpherical model, the other five kinds of soil nutrients were Exponential model. The spatialdistributions of the contents of soil organic matter and macronutrients were significantlydifferent, the contents of them were relatively high in southwest area, but relatively low innorth area, especially available nitrogen and available phosphorus; The spatial distribution ofthe contents of available microelements showed the trend of diminishing, which from north and south to the central area, the contents of them were relatively high in north and south area,but relatively low in central area.(2) The soil type remarkably influences the contents of available nitrogen, availablephosphorus, Mn and Cu, indicating that their contents in gray-cinnamon soils were higherthan those in loessial soils. Relative elevation (Hr) mainly influenced organic matter,available nitrogen, available potassium, Fe, Mn and Zn, the area with higher relative elevation,the contents of these soil nutrients were lower; Gradient (β) mainly influenced organic matter,available phosphorus and Cu, the area with higher gradient, the contents of these soil nutrientswere lower; Roughness of terrain (QFD) mainly influenced Cu, the area with higherroughness of terrain, the contents of Cu were lower. Soil organic matter, available nitrogen,available phosphorus and available potassium mainly influenced Cu and Zn, the area withhigher contents of these soil nutrients, the contents of Cu were lower, but the contents of Znwere higher; available potassium mainly influenced Fe and Mn, the area with higher contentsof available potassium, the contents of Fe and Mn were also higher; Soil pH mainlyinfluenced available microelements, the area with higher soil pH, the contents of theseavailable microelements were lower.(3) The content of available nitrogen for apple planting was still scarce, most parts of thereaserch area were in deficiency grade, but basicly meet the growth needs of maize, potatoand millet; In order to avoid excess soil nitrogen in first divided region of available nitrogen,the nitrogen application must be controled, the second divided region needs stable nitrogenapplication so as to maintain the content of soil nitrogen, the third divided region needsincreased nitrogen application so as to improve the content of soil nitrogen. The contents ofavailable phosphorus was lower in the reaserch area, most parts of this area can not meet thegrowth needs of four kinds of crops; The first divided region of available phosphorus needsstable phosphorus application in order to maintain the content of soil phosphorus, the seconddivided region needs increased phosphorus application so as to improve the content of soilphosphorus. The reserch area was abundant in available potassium, the content of availablepotassium in some area can not meet the growth needs of apple, but most areas were ingeneral or rich grade, these areas can completely meet the growth needs of maize, potato andmillet; In order to avoid excess soil potassium in first divided region of available potassium,the potassium application must be controlled, the second divided region needs stablepotassium application so as to maintain the content of soil potassium.