Changes in Soil Nutrients of Farmland with Different Cultivation Years of Panax ginseng

Results indicated that the vertical structure was obvious in soil nutrients of farmland with different cultivation years of P. ginseng; in most cases, the soil nutrient content gradually declined with the fibrous roots of P. ginseng spreading downward; the soil electrical conductivity (EC) . total nitrogen (TN) . total phosphorus (TP) . total potassium (TK) , available nitrogen, available phosphorus were manifested as surface layer > root layer > bottom layer, while the available potassium was manifested as surface soil and bottom layer > root layer; the soil pH changed in the range of 5.69 - 6.22, suitable for growth of P. ginseng.Felling large area of trees leads to soil erosion and loss and reduction of biological diversity, and it has poseti a great threat to the ecological environment1 " ul.Since 1998, it has strictly restricted the cultivation of P. ginseng through felling trees.Soil pH and EC were determined at 5-1 soil-water ratio by pH meter and electrical conductivity meter; soil nitrate and ammonium nitrogen were determined by UV spectrophotometry; soil available phosphorus was determined by sodium hydrogen carbonate solution extraction-colorimetry; soil available potassium was determined by ammonium acetate extraction-flame spectrophotometry; soil total phosphorus ( TP) was sodium hydroxide melting molybdate-tartaric emetic-ascorbic acid colorimetry; soil total potassium (TK) was determined by sodium hydroxide melting flame spectrophotometry; soil loial nitrogen (TN) was determined by Kjeldahl method; soil organic mailer was determined by loss on ignition method, with reference to Soil Agrochemislrical Analysis (edited by Bao Shidan. 3 Results and analyses 3.1 Soil pH As shown in Fig. 1 , the soil pH varied in the range of 5.[...]soil pH decreased year by year with the increase in cultivation years.