Contrasting responses of wheat and maize to organic fertilizer substitution in the Huang-Huai-Hai Plain: a meta-analysis

The Huang-Huai-Hai Plain, one of China’s most important grain-producing regions dominated by winter wheat–summer maize rotation systems, has experienced soil degradation and compromised agroecological sustainability because of long-term intensive chemical fertilization. Organic fertilizer substitution has been widely recognized as a key strategy for improving agricultural productivity and soil restoration. However, existing global meta-analyses mask critical region-specific divergent responses arising from crop rotation systems and soil factors, resulting in a conspicuous gap in quantitative evidence for this vital rotation system. To address this knowledge gap, data from 73 field studies comprising 541 paired observations were synthesized to quantitatively evaluate the effects of organic fertilizer substitution on crop yield, nutrient uptake, soil properties, and enzyme activities. Organic fertilizer substitution increased maize yield by 16.45% but showed no significant effect on wheat. Yield benefits were greatest in loam soils, fluvo-aquic soils, and under alkaline conditions, whereas neutral soils exhibited a negative yield response. Substitution consistently enhanced soil organic matter, available nutrients, and enzyme activities (e.g., nitrate reductase + 64.01%), with bidirectional pH buffering. The contrasting crop responses stem from phenological nutrient-demand mismatches modulated by soil texture and pH. We thus recommend targeted application, prioritizing maize in loam and fluvo-aquic soils and under alkaline conditions (initial pH ≥ 7.5), while adopting more cautious and site-specific management for wheat and neutral soils. This condition-specific strategy offers a practical reference for sustainable intensification in medium–low yield fields. These results collectively indicate that organic fertilizer substitution in the winter wheat–summer maize rotation system of the Huang-Huai-Hai Plain should be tailored to crop type and soil conditions, as it not only enhances maize productivity under favorable conditions but also improves soil fertility and biological activity, thus providing valuable insights for targeted fertilizer management and sustainable intensification in this major grain-producing region.