| Lacking of the understanding in spatial variability of regional soil ecological conditions will affect the pertinence and rationality in fertilizer application, and decrease the production efficiency and economic benefits in tobacco planting. Thus, study on reasonable fertilization zone is with vital importance to regional management and scientific fertilization in tobacco growing area. Wushan County, the typical mountain area with high-quality tobacco growing in Chongqing, was chosen for case study. Based on GIS and geostatistics, together combined with5-10years tobacco planting data and fertilization habits investigation and analysis, spatial distribution and its impact factors on geographic conditions and soil fertility were carried out. Fuzzy c-means clustering algorithm was employed to delineate the fertilization zone, and fuzzy performance index and normalized classification entropy were used to select the optimal cluster numbers. Based on which, fertilizer recommendations for each fertilization zone were also discussed.The main results are as follows:(1) According to the analysis of5-10years tobacco planting data in Wushan County, area of tobacco growing, average yield and proportion of upper-middle tobacco was4331hm2,2064.8kg/hm2, and78.8%, respectively. In2009, increased fertilizer use resulted in higher yield than before, while its quality was not significant changed. However, fertilizer use was decreased from year2010to2012, but the yield was still around2050kg/hm2, while proportion of upper-middle tobacco showed an increasing tendency.(2) According to the investigation on farmers’ fertilization habits, application ration of nitrogen, phosphorus and potassium was reasonable, but the application amount was slightly higher, especially in nitrogen. Dressing ratio was also reasonable, while it exhibited significant differences among farmers.(3) Soil property had intermediate variability and intermediate or strong spatial correlation. Among all cases, coefficient of variation in soil pH was the lowest, exchangeable calcium was the highest. The soil properties had correlation, and the soil properties correlated with altitude. According to geostatistics analysis, values of Co/(Co+C) for soil pH, AP, Ca, Mg, B, Zn, Mn and Cl were among0.04%-14.66%, with strong spatial correlation. The other factors were among35.56%-49.99%, with intermediate spatial correlation. In addition, range of the soil properties was among1.68-68.67km.(4) The tobacco growing area was classified into3zones through principal component analysis and fuzzy clustering. Result of significant of difference test showed that the difference was significant between each zone and not significant within each zone, which tends to homogenate with relatively consistency of elevation.(5) The first zone was tagged as low nitrogen-middle phosphorus-high potassium, and its AN, AP and AK were99.27mg/kg,30.09mg/kg and251.11mg/kg, respectively. The second zone was tagged as middle nitrogen-high phosphorus-middle potassium, and its AN, AP and AK were139.21mg/kg,23.23mg/kg and205.54mg/kg, respectively. The third zone was tagged as low nitrogen-middle phosphorus-middle potassium, and its AN, AP and AK were82.96mg/kg,17.78mg/kg and184.24mg/kg. The second zone should be emphasized on nitrogen control, while the first and third zones should be emphasized on nitrogen supplement. |
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