Effect of plant hedgerows on agricultural non-point source pollution: a meta-analysis

Eutrophication has been a critical environmental issue due to soil nitrogen (N) and phosphorus (P) loss in runoff from agricultural lands. Plant hedgerow is an important measure to prevent soil erosion and reduce agricultural non-point source pollution (NPSP). In the present study, we searched 3683 research papers on plant hedgerows published from 1980 to March 2020. After screening, we used 53 effective papers on plant hedgerows for the meta-analysis by using Stata 15.1. The results showed that plant hedgerows significantly increased soil organic matter (SOM) (standardized mean difference (SMD) = 1.46; 95% confidence interval (CI) = 1.12-1.80 > 0), total N (TN) (SMD = 1.33; 95% CI 0.98-1.68 > 0), total P (SMD = 0.73; 95% CI 0.26-1.20 > 0), alkali N (SMD = 0.86; 95% CI 0.52-1.21 > 0), available P (SMD = 1.28; 95% CI 0.75-1.81 > 0) and readily available potassium (K) (SMD = 1.20; 95% CI 0.75-1.65 > 0) concentrations but exhibited no significant effects on soil total K concentration (SMD = 0.17; 95% CI - 0.13-0.47 < 0). Plant hedgerows showed a greater effect on SOM increase than soil N, P, and K, and soil TN increase than the available state, but the opposite trend was observed for P and K. This meta-analysis can clarify the influence of plant hedgerows on soil nutrients and provide ideas for the prevention and control of agricultural NPSP.