Application and environmental effects of organic materials in orchard ecosystem: research status and prospects

The addition of exogenous organic materials is important for ameliorating soil structure, improving soil fertility, and enhancing fruit quality in orchards. Organic materials originate from diverse sources and exhibit complex compositions. The effects of alterations to the type, quantity, and method of application on their effectiveness and concomitant environmental implications in orchard ecosystems are noteworthy. This study systematically summarized the sources and properties of organic materials and their effects on fruit tree growth and development, soil physical structure, soil nutrient cycling, and biological properties. Emphasis was placed on greenhouse gas emissions and the accumulation and transformation characteristics of heavy metals and new pollutants (persistent organic pollutants, antibiotics, and microplastics) in orchards with the addition of organic materials. The main effects of organic material application on orchard ecosystems are as follows: 1) the rational application of organic materials can efficiently improve the physical structure, physicochemical properties, and biological activity of orchard soil; enhance its ability to maintain and supply nutrients; create favorable conditions for the growth and development of fruit trees; and improve yield and fruit quality. 2) The type, quantity, and application method of organic materials notably affect the concentration of carbon and nitrogen substrates and related enzymatic and microbial activities in orchard soil, which alter the characteristics of soil nutrient cycling and N₂O emissions. 3) The composition and structure of organic materials, soil properties, and functional microorganisms concurrently influence such accumulation. However, the potential environmental impact of organic materials remains uncertain. In addition, the formation and influencing mechanisms of associated composite pollutants in orchard soil are complex and deserve comprehensive attention. Further studies are required concerning the internal connections between the addition of organic materials and environmental change processes in orchards, the mechanisms of which also need to be elucidated. Finally, important directions for research regarding the relationship between the application of organic materials and environmental effects in orchard ecosystems are proposed.