Agricultural phosphorus balance trends in Ontario, Michigan and Ohio

Bruulsema, T. W., Mullen, R. W., O'Halloran, I. P. and Warncke, D. D. 2011. Agricultural phosphorus balance trends in Ontario, Michigan and Ohio. Can. J. Soil Sci. 91: 437-442. Agriculture is one of the sources of phosphorus (P) that feeds into Lake Erie, impacting water quality. A substantial proportion of the agriculture in Ontario, Michigan and Ohio falls in the Lake Erie drainage basin. We examine trends in the balance of the major inputs and outputs of P to the soils of this region. Only a few decades ago, recommended rates of P application for optimum crop nutrition amounted to considerably more P than crops removed. In recent years, actual P applications have come much closer to balancing removals, while crop yields have increased. This trend has positive implications for both crop productivity and water quality. The P balance serves as an appropriate performance indicator for P management reflecting both economic and environmental aspects of sustainability. Depending on assumptions regarding the recoverability of manure and the current implementation of reduced-P feeding strategies in the livestock industry, estimates of the P balance for the region in 2008 range from a surplus equivalent to 1% of crop removal to a deficit amounting to 23% of the amount of P removed by crops.