Effects of soil conditioner and irrigation method on the yield, quality of fruit and soil chemical properties in apple orchards with acidified soils

Abstract:【Objective】Both soil conditioner and irrigation play important roles in the growth of fruit trees. However, so far, there are few studies on the interaction between soil conditioner and irrigation, and the interaction between them on the growth of apple tree is not clear. The objective of this study was to investigate the effects of soil conditioner and irrigation and their interaction on soil chemical properties and the growth of apple trees in acidified orchards.【Methods】A field experiment with differ- ent types of soil conditioners and irrigation methods was carried out in the study in two years. The experiment consisted of three soil conditioner treatments, including no soil conditioner (CK), chemical soil conditioner (ZD) and organic fertilizer conditioner (BOM), in combination with two irrigation meth- ods including flood irrigation (FD) and drip irrigation (DI). A split-plot design, with the type of soil con- ditioner as the main plot and the irrigation method as subplot, was used to study their interaction effects on the yield, fruit quality, mineral element content and soil nutrient element content. Nine similar fruit  trees were selected as a plot, and each treatment had three replicates. The test data were processed by Microsoft Excel 2010 software, and SAS 8.2 software was used for two factor difference significance analysis (p < 0.05) and interaction effect analysis; the data were plotted by SigmaPlot 12.5 software.【Results】Both the soil conditioners and irrigation methods could affect the yield, while there was a sig- nificant positive interaction between them. The apple yields in ZD and BOM treatments were signifi- cantly increased by 4.9%-22.1% compared with CK, and the yield in DI treatment was 3.7%-3.8% high- er than FI treatment. The single fruit weight in BOM treatment was the highest, which significantly in- creased by 5.2%-9.4% compared with the other treatments in two years. In 2015 and 2016, the yield and single fruit weight DI increased significantly compared with those in FI. Different soil conditioners and irrigation methods had significant effects on the contents of soluble solids and vitamin C and solid to acid ratio in the fruit, and there was significant interaction between soluble solids and solid to acid ra- tio. Compared with CK and ZD treatments, BOM treatment significantly increased soluble solid by 5.1%-10.7% and solid to acid ratio by 11.9%-15.5%. The soluble solid content, Vc content and solid to acid ratio in the fruit in DI treatment were significantly higher than in FI treatment. There were signifi- cant positive interactions between soil conditioners and irrigation methods on the total nitrogen and to- tal potassium contents in leaves and fruit. The total nitrogen content inf leaves in ZD treatment was 34.7% and 12.2% higher than CK and BOM treatment, respectively. The total calcium content in ZD treatment was 22.1% and 19.0% higher than CK and BOM treatment, respectively. BOM treatment in- creased the total potassium in leaves by 9.4%-11.5% compared with CK and ZD treatments. Compared with CK treatment, BOM and ZD treatment increased total nitrogen content in fruit by 8.4% and 9.5%, respectively, and increased total potassium content in fruit by 12.7% and 15.7%, respectively. The total nitrogen, total potassium, and total magnesium of fruit in DI treatment were increased significantly by 6.7%, 5.1%, and 4.2% compared to FI treatment, respectively. The soil pH with soil conditioners was in- creased by 6.7%-10.0% compared with CK, and the soil pH in drip irrigation was higher than that in flood irrigation. There were also significant interactions between soil conditioners and irrigation meth-ods on soil pH. The BOM treatment increased available nitrogen and available potassium by 15.9% and 7.3% respectively compared with CK. DI treatment increased them by 8.8% and 8.1%, respectively, compared with FI treatment. In 2016, compared with CK-FI and CK-DI, BOM-DI increased soil pH, or- ganic matter, alkali hydrolyzable nitrogen and cation exchange capacity by 8.3%-9.2%, 12.2%-14.3%, 16.1%-27.7% and 16.5%-35.4%, respectively. Compared with ZD-DI treatment, BOM-DI treatment in- creased the organic matter content by 9.3%. There were also significant interactions between soil condi- tioners and irrigation methods on soil exchangeable calcium and cation exchange capacity. It was found that apple yield was significantly positively correlated with soil pH, alkali hydrolyzable nitrogen, and exchangeable calcium and magnesium (p < 0.01), and with cation exchange capacity (p < 0.05). The sol- uble solid content in fruit was positively correlated with soil pH, available phosphorus and exchange- able calcium (p < 0.05), and with soil organic matter, available nitrogen, available potassium and cation exchange capacity (p < 0.01).【Conclusion】Soil conditioner and drip irrigation significantly increased soil pH, and there was a significant positive interaction between them. Organic fertilizer conditioner sig- nificantly increased the content of alkali hydrolyzable nitrogen and available potassium in soil, and had significant interaction with irrigation methods on cation exchange capacity. Both soil conditioner and drip irrigation significantly improved the yield and quality of apple, with significant interaction. In summary, the interaction of BOM and DI treatment not only improves soil quality effectively, but also in- crease yield and quality of apple.