重庆丰都岩溶区植烟土壤肥力特征及综合评价研究

以重庆市丰都县植烟区石灰岩土壤为研究对象，通过野外调查采样和室内分析方法，并采用主成分分析法和模糊数学隶属度函数模型估算出土壤适宜性指数（SFI），进而对土壤养分状况进行综合评价。结果表明:（1）该岩溶区植烟土壤pH多呈弱酸性至中性，有23.08 %的土壤样品pH低于5.00，这些土壤酸化问题较为突出；（2）有机质和氮含量丰富，78.85 %的土样有机质含量处在植烟所需的最适宜范围（15～30 g/kg）内，全部土样的碱解氮含量均在植烟所需的适宜范围（65～100 mg/kg）内，且变异系数仅为0.92 %；（3）土壤全磷表现出中至高含量水平（＞0.6 g/kg），但土壤有效磷供应不足，20.93 %土样有效磷含量处在缺乏水平（＜10 mg/kg）以下；（4）土壤钾元素供应充足，全钾含量全部处于丰富或极丰富水平（＞25 g/kg），超过81.84 %土样其速效钾含量处于植烟所需的适宜范围(＞150 mg/kg)内；（5）该岩溶区土壤肥力整体水平不高，仅15.38 %土样的综合肥力为较高水平（0.70＞SFI≥0.60)，57.69 %为中低等水平（0.60＞SFI≥0.40)，26.93 %为低水平(SFI≤0.40)，这与岩溶地区土壤贫瘠且侵蚀退化严重、施肥不合理等因素有关。为此，建议科学耕作，抑制土壤侵蚀退化，同时通过撒施生石灰等调节土壤pH，并适当提高复合肥中磷素比例。 

Study on characteristics and comprehensive evaluation of the fertility of tobacco cultivated soil in Fengdu karst area,Chongqing

The fertility of limestone soil cultivated with tobacco in karst areas of Fengdu county,Chongqing was studied through field sampling and lab analysis.Methods of principal component analysis and membership function of fuzzy mathematics were used to estimate soil fertility by means of estimating SFI（Soil Feasibility Index）.The results showed that：（1） The soil in the area was weakly acidic to neutral.23.08%of soil samples had pH less than 5.00,thus there are obvious soil acidification problems in the region.（2） The soil was rich in organic matter and nitrogen.78.85%of the soil samples had OM content in the optimum range for planting tobacco（15-30 g/kg）.All soil samples had available nitrogen content in a suitable range for planting tobacco（65-100 mg/kg） with a coefficient of variation of only 0.92%.（3） Total phosphorus content was medium to high（〉0.6 g/kg）,but there was insufficient supply of available phosphorus in the soil.Phosphorus was absent（〈10 mg/kg） in 20.93%of the soil samples.（4） The soil had an adequate supply of potassium.All samples had rich or extremely rich total potassium content（ 〉25 g/kg）.81.84%of the soil samples had available potassium content in the proper range for planting tobacco（〉150 mg/kg）;（5） The area＇s overall soil fertility level was not high.Only 15.38%of samples had medium-high soil fertility（0.70〉SFI≥0.60）,57.69%had medium-low fertility（0.60〉SFI≥ 0.40）,and 26.93%had low fertility.Obviously the karst areas are affected by factors including soil erosion and severe degradation,and irrational fertilization.Therefore,in karst areas attention should be given to scientific farming,reduction of soil erosion and degradation,the application of lime to regulate soil pH,and proper increase of the ratio of phosphorous in fertilizer.