Nutrient Input,Soil Nutrient Contents And Their Spatial Distribution Characteristics In The Main Apple Producing Areas Of The Loess Plateau

The Loess Plateau is one of the main apple producing areas in China,with the planting area and yield accounting for about half.Apple production has promoted local economic development and increased farmers’income.Compared with creal crops,excessive input of nutrient is common in apple orchard,which pose huge riske of environment and apple production development.Therefore,field survey（1028 apple orchards）,sampling（247 apple orchards）and literature analysis were combined to study the nutrient inputs,nutrient surplus,soil nutrient contents（organic matter,total nitrogen,available phosphorus,available potassium）and nitrate accumulation and controlling factors in the main apple production area of the Loess Plateau.Moreover,the Arc GIS geostatistical analysis was used to study the spatial distribution characteristics of nutrient inputs,nutrient surplus,soil nutrient contents and nitrate accumulation.The main conclusions are as follows:（1）The average annual inputs of nitrogen（N）,phosphorus（P₂O₅）and potassium（K₂O）were 941±240 kg·hm^-2,559±168 kg·hm^-2 and 638±275 kg·hm^-2,respectively.The surpluses of nitrogen（N）,phosphorus（P₂O₅）and potassium（K₂O）were 819±208 kg·hm^-2,498±137kg·hm^-2 and 516±190 kg·hm^-2,respectively.Thus,the problem of excessive inputs of nutrient in the main apple producing areas of loess plateau issevere.（2）The average contents of organic matter,total nitrogen,available phosphorus and available potassium in 0-20 cm soil were 11.10±1.58 g C kg^-1,0.78±0.15 g N kg^-1,40.20±16.85mg P kg^-1 and 236.10±57.52 mg K kg^-1,respectively.The average contents of those nutrient in 20-40 cm soil were 7.62±1.60 g Ckg^-1,0.50±0.12 g N kg^-1,27.12±17.40 mg P kg^-1,156.7±57.87 mg K kg^-1,respectively.The soil nutrient content in 20-40 cm soil was lower than those in 0-20 cm soil,which was related to the lower fertilization depth.Moreover,there was a significant positive correlation between each nutrient content in 0-40 cm soil.（3）The spatial distribution characteristics of nutrient input and apparent surplus in the main apple producing areas of the Loess Plateau showed that the nutrient input and surplus in Yan’an city,northern Shaanxi province and Qingyang city,Gansu province were low,and the nutrient input and surplus in Yuncheng city,southwestern Shanxi province and Sanmenxia city,western Henan province were high.nutrient input and surplus in semi-humid area were higher than those in semi-arid area.（4）Excessive nitrogen inputs resulted in nitrate accumulation in soil profile.The accumulations of nitrate nitrogen Nitate accumulation in 0–200 cm,0–500 cm and 0–800 cm soil profiles in the main apple producing areas of the Loess Plateau were 33315±1279 kg N hm^-2、4776±1473 kg N hm^-2、8130±1852 kg N hm^-2,respectively.The peak value of nitrate content in 0-800 cm soil profile were occurred in 120-140 cm and 200-240 cm,respectively.The nitrate accumulation in 0-800 cm soil profile of semi-arid and semi-humid area were6912±1328 kg N hm^-2 and 9349±2003 kg N hm^-2,respectively.It indicated that rainfall and fertilization affected the nitrate distribution andaccumulation in in the main apple producing areas of the Loess Plateau.