Nutrient Input And Soil Nitrogen Accumulation Characteristics Of Apple Orchard In Loess Plateau

The Loess Plateau is one of the two major production areas of apples in China.The apple industry has developed for a long time and has become a characteristic advantage industry that increases farmers'income and promotes regional economic development.Because the irrational fertilization of fruit farmers in the process of fertilization is very serious,not only the fertilizer resources are wasted,but also the ecological environment is affected,which limits the green and healthy development of the apple industry in the Loess Plateau.Based on the combination of field survey sampling and data collection,this paper analyzed the changes of nutrient input,balance and soil nutrient status in the apple orchard of the Loess Plateau,the accumulation characteristics of NO₃^--N in the soil profile and its relationship with orchard nitrogen input.In order to reveal the environmental effects brought about by the unreasonable fertilizer input in the development of the apple industry,it provides a scientific theoretical basis for the sustainable development of the apple industry in the Loess Plateau.The main findings and conclusions are as follows:?1?Through the field investigation of fertilization and irrigation of 588 orchards in the main apple producing areas of Shaanxi Province on the Loess Plateau,combined with relevant literature,the nutrient inputs of 14,129 orchards in 44 main producing counties were analyzed.The results showed that the nutrient input of apple orchards in different areas of the Loess Plateau was different.The average application rates of nitrogen,phosphorus and potassium fertilizers were:N:876±325 kg/hm²,P₂O₅:565±255 kg/hm²,K₂O:594±321kg/hm²,and the input amount exceeded the recommended amount.Fertilizer input showed a growth trend from 1990 to 2018.The average input of nitrogen,phosphorus and potassium fertilizer increased by 135.17%,107.23%and 311.97%in 2015-2018 compared with1990-1995.?2?Analysis and collection of 100 orchard soil samples and literature data in the main apple producing areas of Shaanxi Province,the results showed that the average content of soil organic matter in the 50,804 orchards distributed in 68 counties of the Loess Plateau was11.60 g/kg,and the average total nitrogen content was At 0.76 g/kg,the average contents of soil alkaline nitrogen,available phosphorus and available potassium were 63.53,38.08 and259.11 mg/kg,respectively.The ratios of alkaline nitrogen,available phosphorus and available potassium in the higher levels were 56.6%,52.3%,and 56.4%,respectively.The ratios of available phosphorus and available potassium were 20.2%and 23.0%,respectively.?3?The relationship between nutrient input and yield in the apple producing areas of the Loess Plateau,soil nutrient balance in different ecological regions and the deep accumulation and migration characteristics of nitrogen were studied.The results showed that the yield of apple orchard increased with the increase of nutrient input.The trend of increasing and decreasing,the excessive input and surplus of orchard nutrients is very serious,and the average surplus of nitrogen?N?,phosphorus?P₂O₅?and potassium?K₂O?nutrients is 721±363,551±301,488±412 kg/hm²,the nutrient input and surplus surplus in the southern producing areas are more serious than in the northern and central producing areas.The excessive nitrogen input caused nitrogen accumulation in the deep soil profile.From the north to the south,the nitrate-nitrogen accumulation peak of the orchard soil profile gradually moved to the deep layer,and the accumulation of nitrate nitrogen gradually increased,and the difference was significant.The average accumulation of nitrate nitrogen in the 0-500 cm soil layer in different ecological regions was 2785 kg/hm² in the northern producing area,6128 kg/hm² in the central producing area,13604 kg/hm² in the southern producing area,and 0-800 cm in the southern producing area.The accumulation of nitrate nitrogen in the soil profile reached 18914 kg/hm²,and the accumulation of nitrate nitrogen was very serious.The environmental risk is worthy of attention.