Combining organic materials with conventional fertilizers may help citrus growers improve yields, fruit quality and soil health, according to a study published recently in Scientia Horticulturae.
The study evaluated three citrus cultivars — Ehime, Haruka and Orah — in orchards in Chongqing, China, from 2022 to 2024. Researchers compared conventional inorganic fertilizer with fertilizers combining inorganic nutrients and organic materials derived from animal manure or plant straw.
Compared with conventional inorganic fertilization, the animal-derived organic-inorganic treatment increased yields by 20.3% to 26.7% in several orchard-year comparisons. A modified version, using a different application schedule and rate, increased yields by 16.9% to 28.7%.
The animal-derived treatment also improved fruit quality. Vitamin C increased by 8.4% to 20.4%, soluble solids by 17.6% to 22.3% and total sugars by 20.3% to 27.1%. Fruit acidity decreased in several cases, potentially improving flavor. Results varied by cultivar and growing season.
The benefits extended below ground. Trees receiving organic-inorganic fertilizers generally developed longer roots, greater root surface area and more fine roots, which are important for absorbing water and nutrients. Soil organic matter increased by 17% to 34.8% in reported comparisons, while available nitrogen, phosphorus and potassium also improved.
For citrus growers, the findings suggest that combining organic materials with mineral fertilizers could support production while improving the soil environment. However, the treatments differed in nutrient inputs, organic matter content and application timing, so the results do not establish that manure alone caused the improvements.
Further testing under local growing conditions is needed before applying the results directly to other citrus-producing regions. Growers should consider soil testing, nutrient budgets and locally recommended fertilizer practices when evaluating similar programs.
The authors of the study are Jiale Wang, Yu Zhang, Shangyan Hao, Huaye Xiong, Yuheng Wang, Jie Wang, Xiaojun Shi and Yueqiang Zhang, all with Southwest University; Furong Kang with Changshou District Agricultural Technology Research Service Center; and Jingkun Zhao with Chongqing Agro-Tech Extension Station. Read the full study, titled “Multicultivar field evaluation of organic and inorganic fertilizer formulations for improving citrus productivity, fruit quality, root architecture, and soil fertility.”
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