Organic Fertilization and its Effects on Storage of Carbon and Nitrogen in Apple Orchard soil: A meta-analysis

This meta-analysis quantified the impact of organic fertilizers on carbon and nitrogen availability in apple orchard soils in China and Pakistan. The research questions were: (1) Do organic fertilizers increase soil nutrient availability and crop productivity? and (2) Does the impact vary by region?

A literature review using scientific databases identified 144 eligible studies from 6 regions in 2 countries, including Shaanxi and Shandong provinces in China and Balochistan, Khyber Pakhtunkhwa, Punjab provinces in Pakistan. Meta-analytical methods included programming for statistical analyses and visualization and mixed-effects models for effect size estimates. Significance was p ≤ 0.005.

Organic fertilization significantly increased availability of nitrogen ((Odd ratio) OR: 1.25), phosphorus (OR: 1.30), and carbon (OR: 1.45) compared to controls (p < 0.05). The impact varied regionally, with the most substantial increases observed in year 3 in Balochistan (OR: 1) and the Loess Plateau (OR 1.1) and in year 2 for Khyber Pakhtunkhwa (OR: 1.2), Punjab (OR: 1.1), Shaanxi (OR: 1.1), and Shandong (OR 1). Environmental concerns were significant for Shaanxi (OR: 0.0061), Punjab (OR: 0.0062), and Loess Plateau (OR: 0.0059) (all p < 0.005).

Organic fertilizers increased nitrogen, phosphorus, and carbon in apple orchard soils in both countries over 2–3 years. The degree of increase depended on the region, with varying soil compositions, climate conditions, and orchard management practices influencing the extent to which nitrogen, phosphorus, and carbon levels were enhanced. Significant environmental concerns continue to surround the potential long-term effects. Further research should investigate region-specific and sustainable best practices for organic fertilization. Characterizing environmental impact over longer time horizons is critical.