| This study investigated the effects of artificially added small molecule organic acids on the growth and development of apple seedlings and soil acidity and alkalinity,as well as the application of different water harvesting and percolation control techniques in the orchards of the Loess Plateau in Shaanxi Province.The results of the study indicate that:(1)The artificial addition of different concentrations(I: 0.5 mol/L,II: 0.1 mol/L,III: 0.05 mol/L)of small molecule organic acids of different types(A: citric acid,B: malic acid,C: butanedioic acid,D: levulinic acid,E: acetic acid,F: formic acid)can effectively improve the growth and development of plants.The combined effect of formic acid at 0.05 mol/L concentration was the best,with 111.88%,137.15%,42.31%,53.58%,91.54%,24.46% increase in height,stem thickness,biomass,root crown ratio,root length and root vigor,respectively,compared with the control(CK);low concentrations of small molecule organic acids had a better effect on the growth and development of the plants;citric acid,malic acid and succinic acid mainly increased the growth of the aboveground part of apple plants,while levulinic acid,acetic acid and formic acid mainly increased the root morphology and root vigor of the underground part of apple plants.(2)artificially add different concentrations of different kinds of small molecule organic acids,can effectively reduce the vermiculite matrix,vermiculite-soil interfacing and soil pH.The citric acid at 0.5 mol/L concentration was the most effective,reducing the pH of the vermiculite matrix,the vermiculite-soil interface and the soil by 7.23%,9.67% and 0.84%,respectively.High concentrations of small-molecule organic acids had a better effect on pH,but the growth and developmental status of the plants was relatively inhibited,and medium and low concentrations of small-molecule organic acids did not have a better effect on pH than high concentrations,but the growth and developmental status of the plants was enhanced.(3)The starting film treatment(I),the impermeable layer treatment(II)and the starting film plus impermeable layer treatment(III)can all increase the water content and storage of 0-300 cm of soil and reduce the nitrate nitrogen content.The combination of the two treatments has the best overall effect,which can increase the soil water content by 9.60% and reduce the nitrate nitrogen content by 57.15%;the treatment(I)can evenly increase the soil water content of 0-200 cm soil by 7.73% by pooling rainfall and runoff,and evenly reduce the nitrate nitrogen content by 60.08% as the water percolates to the deep layer;the treatment(II)can increase the soil water content of 0-40 cm soil by 7.37% by reducing water infiltration,but the effect on the deep soil is less effective,which can increase the accumulation of nitrate nitrogen in 0-40 cm soil and reduce the water percolation in 40-200 cm soil by preventing water infiltration.(4)The single fruit weight,yield per hectare,longitudinal diameter and soluble sugar content of apples treated with starting monopoly film(I),impermeable layer(II)and starting monopoly film plus impermeable layer(III)were significantly higher than those of the control(CK)(P<0.05),among which the highest single fruit weight,yield per hectare(32.85%),longitudinal diameter(4.63%),transverse diameter(5.73%)and soluble sugar content(18.53%)of apples treated with starting monopoly film plus impermeable layer(III)was 8.77% higher than the control(CK).From the consideration of growth and development indicators such as apple seedling height,stem thickness,crown width,number of leaves,amount of growth,root morphology and root vigor and soil pH change,0.05mol/L concentration of acetic acid was the most effective under this experimental treatment.From the improvement of soil moisture content,reduce soil moisture fluctuations,improve fruit quality in three aspects of comprehensive consideration,starting monopoly coating plus impermeable layer treatment in the experimental conditions of the best effect. |
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