[Effects of Different Fertilization Treatments on Bacterial Community and Citrus Quality in Yellow Soils of the Yunnan-Guizhou Plateau]

Abstract

To investigate the intrinsic driving mechanism of citrus yield and quality enhancement under different fertilizer applications, a field experiment was conducted to study the effects of biochar （SW）, organic fertilizer （YJ）, farmyard manure （NJ）, chemical fertilizer （HF）, and no fertilizer as the control （CK） on soil physical and chemical properties, bacterial community characteristics, and citrus quality of citrus orchards in the yellow soil area of the Yunnan-Guizhou Plateau. The results showed that compared with those in the CK treatment, the yield, single fruit weight, edible rate, juice rate, vitamin C content, and soluble solids of citrus increased under the different fertilization treatments. In contrast, the titratable acid content of citrus decreased, resulting in an increase in the solid-acid ratio of citrus. Among the different fertilization treatments, the most significant effective treatment was SW. The SW and YJ treatments significantly increased the soil pH value, while the HF treatment decreased soil pH. Different fertilization treatments could increase the contents of soil organic matter, hydrolyzable nitrogen, available phosphorus, and available potassium. The SW treatment exhibited the most obvious effect on the contents of soil hydrolyzable nitrogen, available phosphorus, and available potassium. The YJ treatment exhibited the most obvious effect on the soil organic matter content. The different fertilization treatments significantly affected soil bacterial community diversity and community structure, among which the SW treatment significantly increased the soil Chao1 index, observed species index, and Shannon index； optimized soil bacterial community structure； and made the bacterial symbiotic network simple and stable. By contrast, the HF treatment significantly decreased the soil Chao1 index, observed species index, and Simpson index and had less effect on bacterial community structure. Redundancy analysis showed that soil available potassium （96.47%）, Chao1 index （73.80%）, and Chujaibacter （55.92%） were the key factors in improving citrus yield and quality. Variance decomposition analysis indicated that the soil bacterial community structure was the largest contributor （17.00%） to the improvement in citrus yield and quality. In conclusion, fertilization can effectively improve soil physical and chemical properties, increase soil nutrient supply level, optimize bacterial community structure, and improve citrus yield and quality. Of these, biochar can be used as a priority for the fertilization and improvement of the soil in citrus orchards in the yellow soil area of the Yunnan-Guizhou Plateau.

Keywords: bacterial community structure; bacterial diversity; citrus yield and quality; fertilization; nutrient characteristics; yellow soil.