Effects Of Subsurface Trace Infiltration Irrigation And Application ABA Into Root On Tree Growth And Fruit Quality Of Apple In Arid Area

Weibei of Shaanxi is China’s apple eugenic area.However,the rainfall in this area is small and the evaporation is large.The lack of water in the dry area has become the main factor limiting the long-term healthy development of the apple industry in northern Shaanxi.In order to improve the water use efficiency of the apple orchard in the arid area,and to achieve water and fertilizer adjustment,the experiment in 2018 was based on the 7-year-old‘Changfu 2’apple in Luochuan(the base anvil is Xinjiang wild apple and the intermediate anvil is M26).In contrast to the non-irrigation,the experiment has studied the effects of the underground trace amount of seepage irrigation(trace unilateral alternating infiltration,bilateral infiltration)and root abscisic acid(ABA)on the growth of fruit trees and fruit quality under the condition of 40%water-saving drip irrigation,aiming to explore an efficient irrigation system for apple orchards in the dry area.The research results are as follows:1.Comparing with the irrigation-free treatment,drip irrigation,unilateral alternating infiltration and bilateral infiltration can increase the chlorophyll content,leaf weight and leaf area,and the effect of unilateral alternating infiltration is the best.The content of nitrogen in the leaves increased by 0.36%,8.60%,and 5.53%respectively,and the phosphorus content increased by 4.12%,10.04%,and 2.25%respectively.The germination rate of fruit trees in the next year increased by 4.17%,8.50%and 7.20%.The net photosynthetic rate increased by 5.89%,6.74%and 9.74%.The short-branched ratio of fruit trees less than 5cm increased by 2.00%,3.34%and 6.00%respectively.The germination rate in the next year increased by 0.28%,4.98%and 1.12%,and the flower bud rate increased by 1.16%,1.51%and 2.09%.The inflorescence fruit set rate increased by 0.38%,5.23%and 4.86%,and the fruit weight per fruit increased by 3.34%,9.69%and4.64%respectively.The fruit shape index increased by 1.21%,3.24%and 4.64%.The content of nitrogen in fruits increased by 0.94%,11.76%,6.22%,and the content of potassium in fruits increased by 3.70%,18.09%and 11.62%respectively.The unilateral alternating infiltration can significantly increase the content of nitrogen and phosphorus in the leaves of fruit trees,the growth of spring shoots,the short branch rate of less than 5cm,the fruit set rate of inflorescence,the fruit weight and the fruit shape index.Bilateral irrigation can significantly increase the net photosynthetic rate of leaves,the content of potassium in leaves,the short branch ratio of less than 5cm,the fruit set rate of fruit trees in inflorescence,fruit shape index,etc.,and the effect is remarkable.These results show that although the rainfall in Luochuan was relatively abundant in 2018,the flowering period suffered from cold damage,and the fruit setting rate was not high,the reasonable irrigation in the dry period could promote the growth of the trees and improve the fruit quality.2.In the new shoot growth period,50μmol/L ABA solution was applied for 1-4weeks,and the growth of new shoots was significantly inhibited.Comparing with the control group(untreated group),the inhibition efficiency of new shoots growth was 74.34%,56.93%,55.28%and 36.07%respectively.After 4 weeks of root application,the transpiration decreased by 27.29%and the short-branched ratio of fruit trees increased by7.67%.The difference was significant.The content of phosphorus elements in leaves and phosphorus and potassium in fruits also increased significantly.There was no significant difference in fruit weight and soluble solids and there was also no significant change in the germination rate and flower bud rate of fruit trees in the following year.The root application of 50μmol/L ABA solution in the new shoots growth period can significantly inhibit the growth of new shoots of fruit trees.However,it does not hinder the growth and development of fruit trees.3.The root application of ABA solution 50μmol/L,100μmol/L,150μmol/L and 200μmol/L during the period of fruit trees maturation can significantly improve the fruit coloration.The value of fruit coloring L*(brightness)increased by 0.83%,4.82%,7.49%and 10.44%.The value of a*(red and green values)increased by 15.07%,15.21%,18.59%and 27.45%respectively.The value of H~0(chromaticity angle)decreased by 6.24%,9.15%,9.52%and 15.18%respectively.At the mature stage,root application ABA had no obvious effect on fruit quality indexes,such as hardness and soluble solids,and at the same time,there was no significant change in the germination rate,flower bud rate and fruit set rate of the fruit trees in the next year.ABA solution can significantly increase fruit coloration within the root application of 200μmol/L at the stage of fruit ripening,having no influence on the growth of fruit trees.