Evaluation Of Forest Soil Fertility By Digital Soil Mapping

Soil fertility is an effective reflection of soil quality.The grade of soil fertility will directly affect the environment needed for crop growth,and will also affect the production structure,application layout and economic benefits of agriculture and forestry industry.Soil fertility index is an important index to evaluate soil fertility.Since the end of last century,with the continuous development of modern digital application technology,the existing backward agricultural production methods and corresponding technologies have been gradually replaced by advanced production methods and technologies.In recent years,with the advance of precision agriculture,the precision of predicting soil fertility has put forward higher requirements.How to improve the precision of soil fertility database of woodland and farmland and the matching accuracy of digital soil attribute mapping is a new research direction of soil digital mapping.The development of computer technology and 3s technology brings a new development opportunity to soil fertility digital attribute mapping.With the development of the close-range remote sensing technology,the application of 3s technology in the field of soil fertility assessment is more and more extensive.Remote sensing,digital elevation model DEM image and so on can improve the precision of soil fertility mapping.Digital mapping of soil fertility can provide information support for cultivated land conservation.In this study,the peak forest farm of Nanning City,Guangxi Province was used as the study area,and the sampling points were selected according to the Latin hypercube sampling method.In addition,according to the topographic map,the digital elevation of the study area is extracted from GIS.Then,the topographic factors such as slope,slope direction,plane curvature,profile curvature and topographic humidity index are extracted from DEM,and then digital soil attribute mapping is carried out based on fuzzy C-means clustering.The p H value of organic matter,total nitrogen,available phosphorus,available potassium,alkali-hydrolyzed nitrogen were forecasted and mapped according to membership degree.Finally,the soil fertility of peak forest farm in Nanning was evaluated and analyzed according to the comprehensive index method(IFI).It consists of two parts:1)based on the soil landscape model,the fuzzy c-means(FCM)clustering method was used to predict and map the main soil properties in the study area.The terrain factors such as elevation,slope,slope direction,plane curvature,profile curvature and topographic humidity index are taken as landscape parameters,and the watershed topographic combination is divided into 10 categories according to the corresponding clustering parameters.According to the fuzzy c mean value(FCM)clustering,the fuzzy membership map was obtained.The high value area of soil landscape type was selected as the typical area of this kind of landscape type.Finally,the p H value of organic matter,total nitrogen,alkali-hydrolyzed nitrogen in the study area were obtained by weighted average.Spatial distribution of available potassium and available phosphorus.The results show that FCM is a low cost and high efficiency mapping method with high prediction accuracy and good model stability.2)based on the results of soil attribute digital soil mapping,the soil fertility of peak forest farm in Nanning city was evaluated and mapped by using the comprehensive index method(IFII),and the soil attribute map was used to analyze the soil fertility.Available potassium and organic matter are secondary to vegetation supply.