| Soil is the important carrier, material basis and main environmental of agricultural production. Because of various factors, soil nutrients and crop yield have spatial within-field variability, changing with the time. Agricultural production is based on the family as the basic unit of small-scale production in China. It often regards soil as symmetrical, uniform integer to deal with and ignores the variation of soil nutrient inside soil, so caused fertilizer insufficiently in some areas or fertilizer amply in the others field. This is not only casued the waste of the fertilizer but also constituted a threat to ecological environment, therefore the production efficiency and economic benefits are low. Therefore, it is the basic for the accurate nutrient management of tobacco field which the management zones （MZs） were determined based on accurately understood the spatial distribution of soil nutrients; the fertilization models were established based on field experiment, and the amount of recommended fertilizer was given for each MZs.In this study, the distinguishing tobacco plantation field of PingDingShan was selected for exploring the site-specific nutrient management. Soil samples were collected in March 2009. The samples were taken from the topsoil （0 20 cm） on an approximate 20 m grid sampling design （n = 111）. A real-time kinematic global positioning system （GPS） survey was used to identify sampling locations. The spatial variability of soil nutrients in a tobacco-planted field was studied and spatial distribution maps of soil nutrients was generated by geostatistics and geographic information system （GIS）, the key quality-limiting factors for tobacco in the study area was determine by stepwise multiple regression analysis, the MZs were delineated by fuzzy clustering algorithm. The fertilization models were established by the data from field experiment and the amount of recommended fertilizer was given for each MZs. Simultaneity, the fertilization models were evaluated by the quality of tobacco. This study provides a basis of information for site-spcific fertilizer management in tobacco-planted field. The primary conclusions were as follows:（1） The soils are weakly alkaline with pH levels ranging from 7.39 to 8.44. These pH conditions are not conducive to the production of high-quality tobacco growth. The content of soil OM, TN, AN and AP have low levels, and their mean were 17.19 g kg-1, 0.95 g kg-1, 74.97 mg kg-1, and 7.39 mg kg-1, respectively. The high content of AK and Zn were 161.4 mg kg-1 and 1.79 mg kg-1, respectively. Soil Fe, Cu, and Mn have medium content with mean of 8.56 mg kg-1, 0.93 mg kg-1, and 7.37 mg kg-1. The soil nutrient holding and delivery capacity was medium according to the CEC content (cmol kg-1). Coefficients of variation ranged from approximately 3.22% for pH to almost 43.85% for available AP. Soil pH, OM, CEC, Cu, Sand, and Silt had low CV （3.22% 13.95%）, suggesting the relative stability. All other soil properties exhibited a medium variation （CV, 17.9% 43.85%）, indicating the heterogeneity of soil properties. Thus, differentiated management may be necessary to achieve maximum economic and environmental benefits. The Kolmogorov-Smirnov test revealed that all variables were normally distributed （P > 0.05） and did not require transformation.（2） The results of geostatisitical analyses are shown that the sand and clay ideally matched an exponential model, whereas the rest of the soil properties best fit the spherical model. The coefficients of determination （R2） of all the soil nutrients, expect for TN, OM, and Zn, were greater than 0.91, indicating a good fit. The value nugget-sill ratio is used to qualitatively define spatial dependence values. The nugget-sill ratios for TN, Zn, CEC, and silt were 3.39%, 13.61%, 17.01%, and 23.43%, respectively, suggesting strongly spatial dependence. Meanwhile, all other soil variables were moderately spatially dependent, with the nugget-sill ratios ranging from 30.48% to 49.99%. The range, expressed as distance, can be interpreted as the zone of in?uence diameter. This represents the average maximum distance over which the soil properties of the two samples are related. The range of Zn and silt were 34.3 m and 35.3 m, respectively, much smaller than the other nutrient. The smaller range suggests that smaller sampling intervals are needed for Zn and silt. The distributionmaps of all variables are shown that all soil properties have obvious spatial pattern.（3） In this study, the different sampling intervals were obtained artificially by deleting soil-sampling points from the actual sample figure, and the best models were modeled in different sampling intervals. The best models were used to obtain the content contour maps of soil properties in different sampling intervals. To evaluate the accuracy of the estimates, the performance of each interpolation under different intervals was assessed by comparing the deviation of estimates from the measured data through cross-validation. In this region, the interpolation errors of soil organic matter and available copper were lowest in the 60-m sampling interval. In the 20-m sampling interval, alkaline hydrolyzable N, available phosphorus, available potassium, available iron, and available zinc had the least errors of interpolation. Available manganese had the least interpolation error at the 40-m sampling interval. Overall, the sampling efficiency could be further improved. The method can be applied in a practical and cost-effective manner to facilitate soil sampling.（4） Through stepwise multiple regression analysis of the relationship between tobacco and soil nutrients showed that soil AK, OM, AP, and CEC were the key quality-limiting factors for tobacco in this area. To attain high-quality flue-cured tobacco, the four soil properties should be reasonably regulated. The four soil properties were aggregated into management zone （MZ） using a clustering algorithm.（5） The classification of data on the four soil properties for the delineation of the MZ can be carried out to effectively characterize the spatial variation of the soil nutrients and manage fertilizer application in the tobacco fields. The data on the four soil variables were imported into the MZA software through which clustering analysis was performed. Results of clustering analysis clearly indicated that grouping the data into four classes allowed both FPI and NCE indexes to be minimized. Clustering the four soil properties resulted in an optimum number of four cluster classes. Analysis of variance and CV indicated the heterogeneity of the soil properties and flue-cured tobacco quality among the four MZs. This study may provide a method for variable-rate fertilization management in tobacco-planted fields, and the application of MZ should improve the quality of ?ue-cured tobacco.（6） The rational fertilization models were building with Truog-Stanford equation. The models for nitrogen, phosphorus and potassium fertilizers recommendation were established based on four years field experiments. The result shown that the best relationship between soil nutrients and correction factors were power function. When the content of soil nutrients increased, their correction factor decreased. Using the three-fertilization model, the fertilizer application for four management zones were recommended, respectively. This study may provide a method for variable-rate fertilization management in tobacco-planted fields, and the application of MZ should improve the quality of ?ue-cured tobacco.（7） The fertilization recommendation for each MZs were generated by fertilization models and management zones, and using the quality of tobacco evaluate the effect of fertilization recommendation. The results indicated that the quality of tobacco in fertilization recommendation zone was better than the conventional fertilization with the chemical components and content of aroma constituent in flue-cured tobacco leaves. Recommended fertilizer reduced the amount of fertilizer application and the cost of agriculture. Based on the study, we conclude that tobacco-planted fields can be managed in a site-specific manner by these methods. |
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