Heterogeneous impact of soil acidification on crop yield reduction and its regulatory variables: A global meta-analysis

Abstract

Context

Soil acidification poses a severe threat to both global food security and sustainable agriculture. However, a quantitative assessment of its impact on crop yield reduction across different soil conditions and crop varieties is still lacking.

Objectives

This study aims to evaluate how soil acidification affects crop yields, root length, crop nutrient uptake, soil nutrients availability, soil microbial biomass carbon, soil microbial biomass nitrogen, and soil microbial biomass phosphorus. Additionally, key factors contributing to yield reduction were identified through random forest model.

Methods

A meta-analysis was conducted, involving 1760 observations from 101 peer-reviewed studies.

Results

Soil acidification led to an average yield reduction of 13.7 %. Among crops, vegetables are most sensitive to soil acidification, with a reduction in yield of 33 %, while maize and wheat yields decrease by 18.2 % and 18.3 %, respectively. The yield of rice is unaffected by soil acidification. Similarly, in the present study, the yield of leguminous crops is also not affected by soil acidification because the soil pH mainly studied for leguminous crops is slightly acidic (pH ranging from 5.5 to 7.0). Additionally, soil acidification results in a 25.4 % reduction in root length and a 3.1 %-13.6 % decrease in nutrient uptake (nitrogen, phosphorus, potassium, calcium). The soil total nitrogen content, available phosphorus, soil organic matter, and exchangeable calcium were observed to decrease by 11.4 %, 18.1 %, 16.3 %, and 76.8 %, respectively, as affected by soil acidification. The microbial biomass carbon, nitrogen, and phosphorus decreased with pH reduction. The inhibitory effect of acidification on crop yield showed a decreasing and then increasing trend along with the elevated soil organic matter. Quantitative analysis revealed that yield was not inhibited by acidification within a soil pH range of 6.03–6.85. Specifically, for maize and wheat, this range that ensured crops yield was between 6.3 and 7.4, while yields of vegetable crops showed a reduction following soil acidification across all tested pH levels. The random forest prediction model indicates that the annual average rainfall is the main factor affecting the reduction of crop yields due to soil acidification.

Conclusion

Severe soil acidification can significantly impede crop yields, especially for vegetables, maize, and wheat. The decline in yield is attributed to the inhibition of root development, and reduced effectiveness of soil nutrients caused by acidification.

Implications

The findings provide crucial insights for global strategies aimed at managing acidic soils. It is recommended that soil pH should be maintained near the optimal acidity levels for specific crops to enhance crop yields and ensure global food security.