| Spatial variability of farmland soil nutrients is widely existent and very complex. As thenutrient sources of the plants, the soil’s nutrient variation definitely influences the growthvariation of the plants. The research on soil spatial variability, one of the soil features, provideseffective avenues for predictions and simulations of soil process, whereby the predicted results canbe more approximate to the real condition, and the importance of spatial effect, imposing on therelation between soil and plant growth is better understood. Therefore, accurate mastery offarmland soil spatial distributions and determination of rational nutrient management units are thefoundation for implementing precise management in tobacco field.This experiment, chooses the typical mountain tobacco field in Huili County, LiangshanPrefecture, Sichuan Province; employ25-meter-interval grid method in sampling88soil samples;take advantage of GPS to locate each sample point. By comprehensively utilizing the new methodcombined GIS with geostatistics, this dissertation analyzes the spatial variation discipline of soilnutrients in tobacco field in mountainous regions. In addition, making use of a diversity of datasources on soil nutrient and terrain elevation to execute fuzzy c-means clustering, it partitions soilmanagement units in tobacco field as well as establishes recommendatory fertilization model viafield experiments. In conclusion, the results of this dissertation can be summarized as follows:(1) The soil in the research region has such characteristics: soil pH5.36, organic matters (OM)8.89g/kg, available N (AN)26.76mg/kg, available P (AP)1.92mg/kg, available K (AK)130.23mg/kg, total P (TP)0.28mg/kg, total K (TK)12.76mg/kg, available Fe10.86mg/kg,available Mn34.12mg/kg, available Cu0.3mg/kg, available Zn1.13mg/kg. That is, the soil isslightly acidic with a pH variation coefficient9.03%; OM content is low, AP content and ANcontent are extremely low; AK content is moderate, TP content and TK content are low; availableCu content is moderate, Fe, Mn and Zn content are affluent. There exists different degrees ofvariations in other nutrients, in the range between22.89%to86.72%.(2) By K-S test, apart from available Zn and AP of the soil property data in the researchregion, the others are all in accordance with normal distribution, and after logarithmictransformation, available Zn and AP also conform with normal distribution, so the stationary hypothesis satisfies. The geostatistic result shows that, the semi-variance functions of soil pH, OM,AK, TK, available Fe and available Zn are in line with exponential model; the models of AN, AP,TP, available Mn, available Cu are spherical model. The nugget/still ratios of available Cu andavailable Zn, which have a intense spatial correlation, are20%and23.7%respectively, while theother nutrients’ nuggest/still ratios are among25%~27%, with a moderate spatial correlation.Under the25-meter sampling scale of this study, various nutrient indices, which are among37.5~221.4m, have large degree diversities and all the spatial auto-correlation distances are greaterthan the sampling distance, illustrating that the sampling scale in this study is reasonable.The soil pH, AN and AK in the research region have the most wide range in isotropy, pHrepresenting weak anisotropy only in the45°, AN representing anisotropy in90°direction, AKrepresenting anisotropy in15°direction. Soil AP and OM represents strong anisotropy in0°and45°. The anisotropy ratios of Fe in15°and60°are0.7and0.605respectively, while in105°and150°, the anisotropy ratios are both0.999, very close to1. Mn represents isotropy in20°,70°and165°, while in120°direction, it represents anisotropy with an anisotropy ratio of0.662.Cu, represents isotropy in105°and160°, and anisotropy in10°and60°. Zn representsisotropy in0°and135°directions, and anisotropy in45°and90°directions.Trend analyses indicate that soil pH in the research region has a weak trend in the twodirections. TP represents U-shape in northeast-southwest, while in the northwest-southeast, itsvariation becomes slower. AK has a similar trend to pH, which is gentle. OM and AP have a strongglobal trend. AN and AK both represent a weak trend and a large variation in the middle areas. Inthe northeast-southwest direction, the four microelements represent accordant varied trend that alldecreased firstly and increased subsequently.(3) Soil nutrients mostly have correlations. With any other nutrient except pH, AP gets anotable or highly notable positive correlation. Soil pH has a highly notable negative correlationwith AN, but a highly notable positive correlation with OM, which has a notable or highly notablepositive correlation with most of the nutrients. Available Fe, Mn, Cu, Zn have close relations withmajor nutrients, namely, existing a notable or highly notable positive correlation.(4) This study takes various soil nutrients and terrain elevations as the data sources andutilizes fuzzy performance index (FPI) and normalized classification entropy (NCE) to be theindices, to partition the region into four management sections. After partition, within the section,the nutrient content trends to homogeny, while between the sections the variance notablyrepresents.(5) According to the filed experiments in2009and2010, this dissertation determines theparameters for Truog-Stanford equation and preliminarily builds the recommendatory fertilization equation for N, P and K fertilizer. |
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