| Soil nutrient is an important factor affecting the growth and development of apple trees and the yield and quality of apples.Dwarfed apple orchards mostly use a water-fertilizer integrated drip irrigation system in cultivation and management.The water and fertilizer are directly dripped on the root soil of the apple tree to improve water and fertilizer use efficiency and further to promote the increase of apple production.However,the fertilization treatment has a great impact on the spatial distribution and loss of soil nutrients.The dwarfed apple orchard in Qianyang County,Shaanxi Province was selected as the research object,to study the distribution characteristics of soil nitrogen and phosphorus in dwarfed apple orchards and the loss of nutrients with surface runoff,based on the combination of field test and laboratory analysis,aiming to provide a scientific basis for the formulation of reasonable water and fertilizer management plans for dwarfed apple orchards.The main conclusions are as follows:(1)On the field scale,the total amount of soil available nutrients in the 0-100 cm soil layer of dwarfed apple orchards has strong variability,with the coefficient of variation of37.88%.The content of soil nutrients except total nitrogen in the Fuji apple area is higher than those in the Gala apple area,but it is not significant.Additionally,in the Fuji and Gala apple areas,when the distance to the trunk(dripper)is closer,the contents of soil available phosphorus and alkali-hydrolyzable nitrogen increase significantly(P<0.05)affected by fertilization.(2)On the soil profile,the soil nitrogen and phosphorus nutrient content in different soil layers of the dwarf Fuji and Gala apple areas are significantly different(P<0.05).With the increase of soil depth,the nutrients content gradually decrease and tend to become steady,and they are mainly concentrated in the soil layer within the depth of 0-30 cm.(3)Affected by the overland flow,the total nitrogen,total phosphorus,available phosphorus and alkali-hydrolyzable nitrogen nutrient components in the soil on different slope positions of the dwarfed apple orchard have the same changing trend,and accumulate at the bottom of the slope,which is significantly higher than those at the top and middle of the slope(P<0.05).The total nitrogen and total phosphorus content were in the order of the slope bottom>the middle of the slope>the top of the slope.The content of available phosphorus and the alkali hydrolyzed nitrogen showed as the slope bottom>the top of the slope>the middle of the slope.There was no significant difference in the nutrient content between the middle and top slopes(P>0.05).(4)On the soil profiles of different slope positions,the difference in soil nitrogen and phosphorus nutrient content among the soil layers reaches reaches a significant level(P<0.05).At the top and middle of the slope,the soil nutrient contents are mainly concentrated in the 0-20 cm and 0-30 cm soil layers,respectively,whereas at the bottom of the slope,the soil nutrient contents of each soil layer are relatively higher,and the accumulation depth is complicated(5)There are significant differences in runoff and sediment yield as well as nitrogen and phosphorus nutrient loss in the runoff plot under water and fertilizer drip irrigation and mixed soil fertilization(P<0.05).With the increase of rainfall duration,runoff,sediment yield,and loss of nitrogen and phosphorus showed a downward trend.After 20 minutes of runoff-yielding,the loss was basically stable.The form of nitrogen loss in surface runoff is mainly ammonium nitrogen,and the form of phosphorus loss is mainly dissolved phosphorus. |
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