Effects of manure application on paddy soil phosphorus in China based on a meta-analysis

Limited phosphorus (P) availability in paddy soil significantly constrains rice growth, which can be enhanced by manure amendments. Although the effects of manure on paddy soil P fractions and availability have been extensively studied, different studies have yielded inconsistent results. Therefore, we conducted a meta-analysis of 1,799 published experimental datasets from 58 references. The results demonstrated that manure application increased the total, available, and microbial biomass P (MBP) by 46%, 134%, and 78%, respectively. The enhancing effect of manure on different P fractions followed the order of labile-P (221%) > moderately labile-P (145%) > stable-P (53%). Manure also significantly enhanced the activity of soil phosphatase, particularly that of alkaline phosphatase, by improving soil properties and enhancing microbial activities. In terms of manure types, pig manure could more significantly enhance the soil P availability and labile-P. Soil available potassium (AK), soil total nitrogen (TN), and mean annual temperature (MAT) were significant factors influencing soil P availability. Compared with non-fertilization treatments, manure amendments also significantly increased TP loss. Under application rates of 2-6 t ha^- 1 yr^- 1, the runoff loss of TP (101%, 95% CI: 45 to 158%) was minimized. Overall, this study recommends applying pig manure at a rate of 2-6 t ha^- 1 yr^- 1 in southern China's paddy soils to enhance soil P utilization efficiency and reduce P runoff loss. These findings provide valuable insights for optimizing fertilizer application strategies to enhance soil P utilization and promote sustainable agricultural development.