Effects of reducing chemical fertilizer use on apple tree growth and development in Beijing and Tianjin orchards

Abstract:【Objective】Chinese apple production is largest in the world and also apple industry hasmade great contributions to Chinese growers, while it is also faced with a series of problems such as excessiveuse of chemical fertilizers in orchards. In this research in Beijing and Tianjin region, experimentswith treatments by either reducing chemical fertilizers or reducing chemical fertilizers with thelaboratory-made bioactive agents were conducted to probe into their effects on soil nutrition, fruit treegrowth and fruit quality. It is hoped to provide a theoretical basis for the reduction of chemical fertilizersapplication, so as to achieve the goal of increasing yield and quality of apple trees and applyingchemical fertilizer reasonably and therefor to promote the healthy and sustainable development of appleindustry.【Methods】This test is arranged in two pilot projects in Beijing and Tianjin region. Before thetest, the basic situation of each pilot project is investigated. And then in the spring of 2018 four normallymanaged‘Fuji’orchards (5 years old, 15 years old in Beijing orchard and 6 years old , 8 years old inTianjin orchard) were selected for field trials. Tthree treatments were set for each trial: 30% reductionof chemical fertilizers, 30% reduction of chemical fertilizers combined with applying bioactive agents,and the control (normal application of chemical fertilizers and no bioactive agents). Then the treegrowth was investigated, and the nutrition indexes of the soil, the fruit quality were determined. The indexesof the apple tree growth included the growth length of new shoots, the chlorophyll content, thebranch types proportion, the number of flower buds and the inflorescences number of branches. The nutritionindexes of the soil included the pH, the total nitrogen content and the available nutrients content.The indexes of of the fruit yield and quality included the yield of per plant, the fruit hardness, the solublesolid contents of the fruits. The effect of bioactive agents and the feasibility of reducing fertilizer ap plication in apple orchards were explored according to the determination of the above indexes. 【Results】The results showed that the treatment of reducing 30% chemical fertilizers reduced soil pH by 2.3%,2.4% and 5.2% respectively in the three trials. No significant effect of the treatment was found on thesoil nutrient contents, the apple tree growth, the yield per plant and the fruit quality. The treatment of reducingchemical fertilizers with applying bioactive agents reduced the soil pH value by 1.6%, 2.4% and4.6% respectively in BJ-1, BJ-2 and TJ-1 test plots, and significantly increased, the number of flowerbuds by 25.56%, 78.73%, 87.32% and 67.82% respctively in all the four trial plots. The inflorescencenumber increased by 48.7% and 61.7% respectively. in BJ-2 and TJ-1 due to the treatment of reducingchemical fertilizers and applying with bioactive agents as well. In summary, the two treatments could reducethe soil pH value and modif the alkaline in the soil and increase the amount of flower buds and inflorescence,while the two treatments did not affect the apple growth, the yield and the quality of applefruits. The test results were consistent in Beijing and Tianjin regions, and the reduction of chemical fertilizerwith applying the bioactive agents would be beneficial to the flowering initiation of the appletrees. However, the effects of the reduction of chemical fertilizers with the application of bioactiveagents needs to verify by long term experiments.【Conclusion】According to the above results, we cansee that both treatments of reducing 30% chemical fertilizers and reducing 30% chemical fertilizerswith applying bioactive agents could be beneficial to the apple trees by reducing the pH of the soil andincrease the number of flower buds. The amount of chemical fertilizers for apple orchards could be reducedby 30% in Beijing and Tianjin regions, In the future, we will further to evaluate the effects of theapplicaton of the bioactive agents and the reasonable amount of the reduction of the chenical fertilizersto use in the apple orchard.