Effects of drip fertigation technical parameters on apple fruit quality and

Abstract: 【Objective】In order to explore the impact of different drip irrigation and fertilization technical parameters on apple fruit quality, the comprehensive evaluation method was used to evaluate the quality of apples, aiming to select the optimal combination of drip irrigation technology parameters and provide a basis for apple water and fertilizer management.【Methods】Two capillary tube arrangementsin one row (P1) or two rows (P2) were set up, and the distance between two drippers of 30 cm (D1) or 50 cm (D2) was set. Two fertilization cycles of 15 days (T1) or 30 days (T2) and two nitrogen fertilizer forms of urea (U) or urea ammonium nitrate solution (UAN) were applied. The anthrone colorimetric method was used to determine the soluble sugar content, the handheld refractometer was used to determine the soluble solid content, the GY-1 hardness tester was used to determine the fruit hardness, the UV spectrophotometer was used to determine the vitamin C content, and the sodium hydroxide titration method was used to determine the fruit titratable acid content. An electronic balance was used to measure the single fruit weight, and a vernier caliper was used to measure the length and breadth of the fruit. The apple fruit weight, soluble sugar content, vitamin C content and other quality indicators were analyzed with different drip irrigationchanges in technical parameters. Fruit shape index was the ratio of the longitudinal diameter to the transverse diameter of the fruit, the sugar-acid ratio was the ratio of the soluble sugar content to the titratable acid content, and the solid-acid ratio was the ratio of the soluble solid content to the titratable acid content. The statistical software SPSS 24.0 was used to perform variance analysis and Pearson correlation analysis on the experimental data, which were used to calculate the weight of the TOPSIS model of CRITIC method, entropy weight method and CRITIC- entropy weight method.【Results】The results showed that the arrangement of capillary tubes and the distance between the emitters had a significant influence on the weight and vertical and horizontal diameters of a single fruit, but had no significant influence on the fruit shape index. The capillary tube arrangement had a significant effect on Vc and soluble sugar contents, but had no significant effect on quality indicators like soluble solids and titratable acid contents. There was also a significant interaction between the capillary tube arrangement method and the drip irrigation spacing in terms of the influence on the single fruit weight, the vertical and horizontal diameter and the vitamin C content. The results also showed the soluble sugar content with two tubes in one row was higher than that with one tube in one row. The distance between the emitters had a significant effect on titratable acid content, soluble sugar content, vitamin C content, sugar-to- acid ratio, and fruit hardness. The indicators with a 50 cm distance between emitters were higher than those with a 30 cm distance between emitters (except for titratable acid content and hardness). The fertilization cycle had a significant effect on the titratable acid content, sugar-acid ratio, solid-acid ratio and fruit hardness. The 15-day fertilization cycle was higher than the 30-day fertilization cycle (except for titratable acid content). The form of nitrogen fertilizer had significant influence on the four indexes of single fruit weight, soluble sugar content, sugar to acid ratio, and fruit hardness. Compared with U, UAN increased the four indicators by 9.71%, 42.27%, 47.37% and 5.25%, respectively. The form of nitrogen fertilizer had no significant effect on the other appearance quality of apples, but the UAN treatment had a tendency to increase the longitudinal diameter, transverse diameter and fruit shape index. Using the subjective and objective combination weighting method, the weight value obtained by vitamin C accounted for the largest proportion in the evaluation of apple fruit quality, and the others were soluble solids> hardness> titratable acid> sugar to acid ratio> fruit shape index> solid acid ratio> soluble Sugar> single fruit weight> longitudinal diameter> transverse diameter. The Pearson correlation analysis between the comprehensive quality ranking of apple fruits with different treatments and the ranking of single quality indicators obtained by using the TOPSIS method showed that, except for the shape index and hardness, the ranking of other quality indicators was positively correlated with the comprehensive quality ranking. Fruit diameters, soluble sugar content and sugar-acid ratio were significantly and extremely correlated with the overall quality ranking, and were significantly positively correlated with single fruit weight, soluble solids content, and solid-acid ratio. There was a significant positive correlation with the sugar-acid ratio. It showed that the TOPSIS method can be used for the comprehensive evaluation of apple quality. The quality ranking was suitable for the comprehensive evaluation of fruit quality.【Conclusion】The TOPSIS model based on subjective and objective combination weighting was used to sort the comprehensive evaluation indexes of apple quality, and the technical parameters of drip irrigation and fertilization with the best comprehensive quality were that, one row and two tubes were appropriate, the distance between drippers was 50 cm, the fertilization period was 15 days, and the form of fertilizer was urea ammonium nitrate.