Positive effects of amendments on crop yield and organic carbon in sandy soils are regulated by aridity: A global meta-analysis

Organic and inorganic amendment application is regarded as an effective management strategy for improving sandy soil health, thus enhancing agricultural productivity and ensuring food security. However, the comprehensive assessment of changes in crop yield and its association with soil organic carbon (SOC) induced by amendments into sandy soil has been poorly quantified. Herein, a global meta-analysis based on 843 observations from 151 field-based studies was conducted to evaluate the patterns and key controlling factors of crop yield and its linkage with SOC in response to organic and inorganic amendments into sandy soil. Results showed that amendment application strongly increased crop yield by 39 % and SOC by 62 % on average in sandy soils, with the greatest yield increase by composite amendments (+92 %), followed by inorganic amendments (+62 %) and organic amendments (+36 %). The inorganic amendment led to the highest increase in SOC (+133 %), followed by composite (+59 %) and organic amendments (+48 %). The linkage between the responses of crop yield and SOC was climate–dependent, with a strongly positive correlation in humid regions (aridity index < 0.5), while no significant relationship was observed in arid regions. The crop yield response positively correlated with mean annual temperature, amendment amount, and initial contents of soil sand and SOC, but decreased with aridity index, amendment duration and soil pH. Random forest analysis revealed that climate (aridity index) and soil properties (initial SOC and pH) were key factors regulating crop yield response, collectively explaining 48 % of the variation. Moreover, aridity index was the key driver indirectly affecting crop yield response via regulating SOC and nutrient availability. Crop yield increase by amendment application was significantly larger (50–56 %) under humid regions with high SOC relative to cold and arid regions with low SOC (30–35 %). Our findings suggest that crop yield response to amendment application strongly depends on soil properties and climate, highlighting the importance of site choices for prioritizing the use of appropriate amendments, so as to maximize the beneficial strategies for improving the fertility and productivity of sandy soils.