Effects of alkaline humic acid fertilizer amendment on cherry tomato yield and quality and soil improvement

【Objective】In order to provide theoretical and practical basis for application of alkaline humic acid fertilizer amendment substituting chemical fertilizer in acified soil improvement and high quality cherry tomato production, the effects of humic acid fertilizer amendment substituting chemical fertilizer on soil physical and chemical environment, cherry tomato plant growth, fruit yield and quality were studied.【Method】Pot experiments were conducted and acid soil was as test soil. Five treatments were established:0.30‰ compound fertilizer(0.30‰ CF), 0.30‰ humic acid fertilizer amendment treatment(0.30‰ FDG), 0.20‰ humic acid fertilizer amendment treatment(0.20‰ FDG), and 0.16‰ humic acid fertilizer amendment treatment(0.16‰ FDG), with an unfertilized treatment as the control(CK). Soil pH was monitored regularly during planting. The leaf SPAD, plant height, stem diameter, fruit yield and quality were investigated at harvest period(transplanting 120 d), soil conductivity, effective nutrients, cation exchange properties and enzyme activity were detected, and cherry tomato quality, correlation analysis on yield, and soil physicochemical properties was conducted.【Result】The soil pH treated by 0.20‰-0.30‰ humic acid fertilizer amendment was >5.60 at fruit maturity stage, while soil pH treated by compound fertilizer was <5.00. Compared with unfertilized treatment(CK), 0.20‰-0.30‰ humic acid fertilizer amendment increased soil organic matter by 6.8%. Humic acid fertilizer amendment decreased soil electrical conductivity when compared with the compound fertilizer treatment. In addition, soil cation exchange capacity, soil exchangeable calcium and magnesium, acid phosphatase, sucrase and polyphenol oxidase activity were higher than that treated with compound fertilizer. Although the content of available N, P and K in soil treated with humic acid fertilizer amendment were decreased to different levels, it was still at a high level according to the classification index of available nutrient content in top soil, which could meet the demand of soil nutrient for cherry tomato plant growth. The plant height, stem diameter and biomass of cherry tomato treated with 0.20‰-0.30‰ humic acid fertilizer amendment were higher than those treated with other treatments, and the nutritional quality of fruit was superior to or equal to those treated with compound fertilizer. Compared with compound fertilizer treatment, 0.30‰ humic acid fertilizer amendment increased fruit yield by 2.2%. Cherry tomato fruit yield was significantly(P<0.05, the same below) or extremely(P<0.01, the same below) positively correlated with organic matter, alkali-hydrolyzable nitrogen, and cation exchange capacity. In addition, most indexes of cherry tomato fruit quality were significantly or extremely positively correlated with soil pH, exchangeable calcium, acid phosphatase, and sucrase activities, and significantly negatively correlated with soil electrical conductivity.【Conclusion】Humic acid fertilizer amendment can be employed with 0.20‰-0.30‰ for the best benefits with regard to the improvement of acid soil pH and fruit yield and quality of cherry tomato.