| Since the reform and opening up to the outside world,China's agricultural planting structure has undergone tremendous changes,with the growing area and output of apples increasing continuously.In 2016,the planting area of apples in China was 2323.8 thousand hectares,with a total output of about 40.393 million tons.Accounting for 46% and 49% of the world's total apple area and output,respectively,ranking first in the world.shaanxi Province,because of its superior geographical and climatic conditions,has become China's national apple production base,apple planting has also become the local farmers out of poverty to become rich,all-round well-off healthy road.However,in recent years,apple planting is faced with many difficulties,simply to increase the nutrient input to improve the yield has been The development of apple industry has been severely restricted.In addition,excessive nutrient input also reduced fertilizer use efficiency,aggravated environmental damage,and serious agricultural non-point source pollution.In this study,Luochuan County,an important apple producing area in Shaanxi Province,was taken as the research object.Through the combination of nutrient balance method and field sampling,the point-to-surface method was used.The nutrient input in apple orchard and nitrate nitrogen accumulation in apple orchard in Luochuan county were analyzed and the leaching risk was analyzed.Further expand the scope of the study,five major apple planting cities in Shaanxi Province(Yan'an,Tongchuan,Baoji,Xianyang,Weinan)as the research object,to study its two different water and fertilizer tubes.In order to provide theoretical basis for nutrient resource management and agricultural non-point source pollution control in Shaanxi apple orchard,the characteristics of leaching accumulation of nitrate nitrogen in apple orchard soil under rational model(irrigation,dry cropping)were studied.The main findings of the study are as follows:(1)Taking Luochuan County as the research object,112 fruit farmers in 15 villages of Fengxi Town,Luochuan County were investigated by visiting and investigating,and their nutrient input and apple yield were investigated in detail.Nutrient balance method was used to analyze the nutrient surplus of apple in Luochuan County.The results showed that the overfertilization of apple orchards in Luochuan County was serious,and the proportion of over-fertilized apple orchards was about 91.1%.The average amount of N,P and K in apple orchards was 1262.3kg / ha,1065.6 kg / ha and 1203.1 kg / ha,respectively.The proportion of organic fertilizer input was 4.90%,6.72%,8.03 respectively.In Luochuan County,the ratio of fertilizer nutrient input to organic fertilizer nutrient input was unbalanced,N,P,K nutrient input ratio was 1 ~ 0.84 ~ 0.95,P,K nutrient input ratio was higher than that of organic fertilizer input ratio,and the ratio of K nutrient input was higher than that of organic fertilizer input ratio.(2)Taking Lubai small watershed,Fengxi Town,Luochuan County,Shaanxi Province as the research object,30 apple orchards with the same age of different slope sites were selected to determine the content of 0-400 cm nitrate nitrogen in apple orchards.The results showed that the accumulation of nitrate in apple orchard was mainly dominated by nitrate nitrogen(98%)in the study area,and the accumulation peak of nitrate nitrogen in soil ofapple orchard at different slope positions was in 0~400 cm,all of which were at 120 cm.The content of nitrate nitrogen in the soil of apple orchard in the depth of 80-120 cm soil layer was significantly higher than that in the apple orchard on the tableland and the bottom of the ditch.The accumulation of nitrate nitrogen in the soil of 0~400 cm apple orchard had the order of slope land > tableland surface > gully bottom.Not for 3355.7kg / ha,3126.0kg / ha,2199.2kg / ha.For the whole small watershed apple orchard soil nitrate nitrogen mainly involved in the range of 100~160 cm and could be used by plants(within 0~100 cm)accounted for only 25%.Because of the formation of dry layer at 200 cm,the content of nitrate nitrogen in soil layer below 200 cm decreases,and the content of nitrate nitrogen in soil near zero point to the depth of 400 cm soil layer.In the three slope apple orchards,the risk of leaching from the apple orchards on the slope is small,and the apple orchards at the bottom of the ditch are leached due to the influence of factors such as river course,soil texture and so on.There is a great deal of risk.(3)0~800 cm soil samples were collected from 41 apple orchards in 11 counties of Yanan,Tongchuan,Baoji,Xianyang and Weinan in the major apple producing areas of Shaanxi Province,and the water and fertilizer management and apple yield of the orchards were investigated.The accumulation of nitrate nitrogen in two different modes in Shaanxi Province was compared and analyzed.The results showed that the soil moisture of apple orchard in irrigated area was significantly higher than that in dry area,but there was no significant difference between the two models.Compared with the content of nitrate nitrogen in apple orchard soil under two different irrigation modes,the depth and content of accumulation peak of nitrate nitrogen in dry area were lower than those in irrigated apple orchard.Soil of apple orchard in arid area Nitrate nitrogen was close to zero in 500 cm soil depth,while nitrate nitrogen content in apple orchard soil was still higher than that in 800 cm soil depth in irrigated area.There was a significant difference in the nitrogen accumulation between the two types of apple orchards,and the nitrate accumulation in the irrigated apple orchard was significantly higher than that in the dry-growing apple orchard.The accumulation of nitrate nitrogen in Liquan soil was the highest,as high as 24380 kg / ha,that in Ganquan was only 1200 kg / ha,which was 4.9% of that in Liquan soil,and the average nitrate accumulation in apple orchards in 11 counties was as high as 10484.2 kg / ha.The entire scope of the study(major apple producing areas)Nitrate nitrogen accumulation in Yan'an,Tongchuan,Baoji,Xianyang and Weinan showed the law of low in the north and high in the south,low in the east and high in the west. |
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