Intercropping increases land use efficiency and reduces soil salinity in salt-affected soils, but has minimal effect on pH
Song Ying, Jineng Sun, Zhi Li
Abstract
Context Soil salinization remains a significant form of soil degradation that restricts crop productivity in agricultural ecosystems. Intercropping has emerged as a sustainable solution to mitigate this issue. Research question However, the effects of intercropping on land-use efficiency, soil electrical conductivity (EC), and pH in saline-alkali soils, and how these effects vary with different intercropping practices (intercropping crop types, duration, distance between main crop and intercropping crop, nitrogen application rate) and environmental conditions (soil salinity, pH, soil organic matter , mean annual temperature (MAT), mean annual precipitation (MAP)), remain unclear. Methods This study conducted a meta-analysis using 51 published articles (693 paired observations) to elucidate the effects of intercropping on the land equivalent ratio (LER), soil EC, and pH changes under different intercropping managements and environmental conditions. Results Overall, intercropping significantly increased the LER by 1.5 (95 %CI: 1.2–1.8) and reduced soil EC (-33 %, 95 %CI: −32.9 % to −33.1 %), with a minimal effect on pH (-0.3 %, 95 %CI: −0.4 % to −0.3 %) compared to monocropping. The LER consistently exceeded 1 across all intercropping practices. In particular, when the intercropping crop type was woody plants , intercropping led to a significant reduction in both soil pH and EC simultaneously. Optimal reduction in soil EC and pH was achieved with an intercropping distance of 20–50 cm and a duration of 2–3 years. Regarding environmental conditions, the highest LER was observed in areas with MAT < 10℃, MAP between 300 and 500 mm, and mild salinization . When MAT < 20℃, intercropping significantly reduced soil EC, whereas MAT > 20℃ had the opposite effect. Notably, in severe salinization and saline soils , intercropping can simultaneously reduce soil EC and pH. Model selection results indicated that initial soil salinity , pH, and intercropping distance were key factors influencing LER, while initial soil salinity and soil organic matter are critical in regulating soil EC. Conclusions Intercropping can serve as a sustainable strategy to enhance land use efficiency and reduce soil EC in saline-alkali soils. Adopting appropriate intercropping practices can further enhance the benefits of intercropping. Implications This study highlights the potential benefits of intercropping for improving land use efficiency and soil health, providing scientific evidence to support the sustainable improvement and utilization of saline-alkali land.