Effects Of Different Emitter Flow Rate,Nitrogen Concentration And Frequency On Growth And Nitrogen Absorption And Utilization Of Apple

In this experiment,we used 4-year-old‘Fuji’/M.hupehensis Rehd as the test material and used ¹⁵N isotope labeling technology to study the effects of different dripper flow,drip nitrogen concentration,and drip nitrogen frequency on apple growth and development,soil nitrogen distribution,and tree nitrogen.The influence of the absorption and utilization characteristics of the element.The main findings are as follows:1.The different water dropper flow rates significantly affected the shoot length,leaf area,chlorophyll,photosynthetic rate and transpiration rate of apple.When the water dropper flow rate is 4 L/h,all the indexes reach the maximum value.They are 74.27 cm,2837.33 cm²,38.37mg·g^-1,18.37μmol/（m²·s）and 361.5 mmol/（m²·s）,respectively.When the water dropper flow rate is 8 L/h,all the indexes reach the lowest value,They are 71.33 cm,2700.67 cm²,37.17mg·g^-1,17.13μmol/（m²·s）and 347.33 mmol/（m²·s）,respectively.In the horizontal direction,the density of fine root length and the content of nitrate decreased with the increase of the radial distance from the tree trunk,while in the vertical direction,the two indexes showed a trend of increasing at first and then decreasing.In 0～20 cm soil layer,fine root length density and nitrate nitrogen content were the highest at 8 L/h.In the soil layer of 20～40 cm and 40～60cm,the root length density and nitrate nitrogen content of fine roots were the highest at 4 L/h.In conclusion,the water dropper flow rate of 4 L/h can promote plant growth and reduce the loss of nitrogen fertilizer leaching in deep layer.2.Different nitrogen concentration significantly affected the growth and development of apple and nitrogen absorption and utilization.The treatment of 4 g/L had the highest leaf area,chlorophyll,photosynthetic rate,transpiration rate and plant biomass,while the treatment of 10g/L had the lowest.Under different treatments,the NDFF value of each organ decreased with the increase of nitrogen dripping concentration,and reached the highest value at 2 g/L treatment（0.87,0.99,0.41,0.21 and 1.50,respectively）.The utilization rate of ¹⁵N in 2 g/L was 18.27%,which was significantly higher than that in 8 g/L（16.1%）and 10 g/L（15.1%）.The utilization rate of ¹⁵N in 2 g/L was 18.27%,which was higher than that in 10 g/L（15.1%）.In conclusion,4 g/L was the optimum nitrogen concentration for apple drip irrigation while ensuring high nitrogen use efficiency.3.The growth and development of apple and the distribution of soil nitrogen were significantly affected by different nitrogen dropping frequencies.The maximum values of leaf area,chlorophyll,shoot length,photosynthetic rate and transpiration rate of new shoots were3121 cm²,39.63 mg·g^-1,76.4 cm,13.9μmol/（m²·s）and 303 mmol/（m²·s）,respectively,under the treatment of high-frequency nitrogen application every 5 days.In addition,the plant biomass under high frequency N drops（every 5 days）was significantly higher than that under medium and low frequency N drops.Under different treatments,the length density of fine roots,nitrate nitrogen content and spatial distribution coincidence degree of each soil layer all showed high frequency nitrogen dripping>medium frequency nitrogen dripping>low frequency nitrogen dripping.Therefore,high frequency nitrogen drops（every 5 days）can promote root growth,reduce nitrogen loss,and promote nutrient growth of the aboveground part of the tree body.