Differences Of Fertilization Effects Of Sweet Potato In Different Landform Areas Of Chongqing And Influence Factors Research

Sweet potato is thought of as the third largest food crop in Chongqing,which has become the one of advantaged agriculture in Chongqing at present.Meanwhile,it is also supporting the industry with developmental economy,increased yield of food and elevated income for farmer.However,the factors that affect the yield of sweet potato include fertilization,varieties,soil nutrients and so on.The harms with far-flung diseases,decreasing yield quality were caused with unreasonable Fertilization.In the past,a great deal of efforts had been conducted to investigate the effect of certain factor to increasing yield of sweet potato.However,the effects of fertilization must be affected with terrains,soil nutrients and climate in Chongqing with complicated topography.Therefore,Investigate the relationship between yield for sweet potato and factors is of great concern,which could solve the problems with blind and incorrect fertilization,as well as increase yield of sweet potato.In this paper,the study area was divided to two regions with mountainous and hilly area,which are distributed in southeast,northeast of Chongqing and midland,westward of Chongqing,respectively.During the years of 2007-2010,the records of?3414?field trial were collected,including yield of sweet potato,rates of fertilizer with nitrogen,phosphorus and potassium,and soil nutrients.Meanwhile,daily climate data recorded at 34 stations in Chongqing were obtained from the National Meteorological Information Center?NMIC?.In addition,elevation was generated from digital elevation model in Chongqing.The affects that terrains,climate,soil nutrients and fertilization to sweet potato were analyzed and the frequency distribution diagrams were generated for yield increase and yield increase rate to investigate the distribution rule of fertilization effect for sweet potato.The important factors affecting the yield of sweet potato were analyzed by CART model and multiple linear regression model.In the end,the accuracies of two models were compared to find the optimal model and determine the most important factor affecting yield increase rate of sweet potato.The results of the study are as follows:?1?Frequency distribution diagrams showed that the field trials for mountainous areas were mainly distributed in the southeast and northeast of Chongqing,and the altitude is about 400-800m.The field trials for hilly areas were mainly distributed in the westward and midland of Chongqing,the altitude is about 200-400m.?2?The average increase yield of the hilly sweet potato planting area was 10560kg/ha,with an increase rate of about 71%,and the increase yield of the mountain sweet potato planting area was10202kg/ha,and the increase rate was only 53%.Hills in sweet potato fertilizer contributed more than 20%,basically reached 98%of the total sites,the average is 39.2%,and mountain sweet potato fertilizer contributed most between 30-40%,and most of the sites in below 40%;In the hilly area,the utilization rate of fertilizer agriculture is about 32%between 20-40%,and the utilization rate of agricultural science of mountain fertilizer is mostly under 60%,occupying about 98%of the test points.It can be seen that there are obvious differences between the yield rate,fertilizer utilization rate and fertilizer agronomic utilization rate of sweet potato in different ecological areas.In addition,the hills and mountain sweet potato growing areas with no fertilizer production yield coefficient of the regression equation between the decision are 0.6284 and 0.4032 respectively,indicating that there are 62.8%and 40.3%of the variation from the soil,other variants are derived from the environmental factors?the terrain,climate and so on?,and the slope of the regression equation was 1.1357 and 1.1357,respectively,showed that hilly yield of sweet potato fertilization on soil foundation soil fertility and environment dependence is bigger.?3?Among all factors,elevation belongs to medium variation with the range of 224-1299m,the mean value of organic matter,available nitrogen,available phosphorus,available potassium were 14.9g/kg,96.4mg/kg,13.6mg/kg,81.1mg/kg,respectively,which belong to medium variation.In terms of climate variables,the coefficient of variation were ranked in order of rainfall,sun hours,lowest temperature,mean temperature,highest temperature,which belong to low variation.Fertilization factors belong to medium variation.However,in terms of affecting factors in every area,elevation,rainfall,P₂O₅ were obviously more than that in hilly area,while the mean temperature,lowest temperature,highest temperature were lower than that in hilly area.?4?Obvious correlations between yield increase rate and affecting factors were found in study area.In hilly planting area for sweet potato,yield increase rate was negatively correlated with elevation and available nitrogen,while positively correlated with N,P₂O_5,K₂O,sun hours,mean temperature,highest temperature and lowest temperature.In mountain planting area,no significant correlations were observed between yield increase rate and factors.In addition,terrain variable was positively correlated with available nitrogen,available phosphorus and rainfall,while negatively correlated with mean temperature,highest temperature,lowest temperature,the determination coefficient was above 0.85.?5?The relationship between the observations and the estimated yield increase rate was generated by CART regression tree,and the most important factors were showed.Specifically,variables affecting hilly area were ranked in order of sun hours>highest temperature>mean temperature>lowest temperature>available potassium>organic matter>P₂O₅>available nitrogen>N>available phosphorus>K₂O>rainfall>elevation.The relative importance of sun hours,highest temperature,mean temperature,lowest temperature,available potassium,organic matter and P₂O₅ were more than 60%.The three most important factors include sun hours,highest temperature and mean temperature.Among the factors affecting yield increase rate in mountain area,the relative importance of highest temperature,mean temperature,rainfall,available potassium,K₂O,elevation were more than 60%.Highest temperature,mean temperature,rainfall became the most important factors.