Managing mineral phosphorus application with soil residual phosphorus reuse in Canada

With limited phosphorus (P) supplies, increasing P demand, and issues with P runoff and pollution, developing an ability to reuse the large amounts of residual P stored in agricultural soils is increasingly important. In this study, we investigated the potential for residual soil P to maintain crop yields while reducing P applications and losses in Canada. Using a P cycling model coupled with a soil P dynamics model, we analyzed soil P dynamics over 110 years across Canada's provinces. We found that using soil residual P may reduce mineral P demand as large as 132 Gg P year(-1) (29%) in Canada, with the highest potential for reducing P applications in the Atlantic provinces, Quebec, Ontario, and British Columbia. Using residual soil P would result in a 21% increase in Canada's cropland P use efficiency. We expected that the Atlantic provinces and Quebec would have the greatest runoff P loss reduction with use of residual soil P, with the average P loss rate decreasing from 4.24 and 1.69 kg ha(-1) to 3.45 and 1.38 kg ha(-1), respectively. Ontario, Manitoba, and British Columbia would experience relatively lower reductions in P loss through use of residual soil P, with the average runoff P loss rate decreasing from 0.44, 0.36, and 4.33 kg ha(-1) to 0.19, 0.26, and 4.14 kg ha(-1), respectively. Our study highlights the importance of considering residual soil P as a valuable resource and its potential for reducing P pollution.

Automated summary

The utilization of residual soil phosphorus in agricultural soils is important for reducing phosphorus applications and pollution. The potential for using residual soil phosphorus varies among Canadian provinces, with the highest potential in the Atlantic provinces, Quebec, Ontario, and British Columbia.