How Much Phosphorus on Farm Lands Is Enough?

While phosphorus is an essential nutrient for all living things, too much of it in the wrong place can prove problematic. Excess phosphorus in a lake or stream can contribute to weed growth and algal blooms that choke off other life and degrade water quality. The Phosphorus Index (PI) is one of the principal tools for managing phosphorus in agricultural landscapes, but different versions of the PI have emerged from state to state, and concerns have been raised about consistency, accuracy, and the level of impact on farm practices and water quality.

Quirine M. Ketterings, Animal Science, Karl J. Czymmek, senior extension associate in Animal Science, and researchers in the Southern Extension-Research Activity Group 17 have been working with the Natural Resources Conservation Service (NRCS) to revise the NRCS 590 Nutrient Management Standard and to promote revision of PIs. The first phase of research included a considerable portion of the phosphorus-restricted Chesapeake Bay. The team is now expanding to the Northeast region, including the headwaters of the Chesapeake Bay, the Lake Champlain Watershed, and many important watersheds in New York, Pennsylvania, Vermont, Massachusetts and Connecticut.

Researchers are combining stakeholder-based feedback and farm-data collection with modeling-based evaluation of the most relevant best management practices. They are assessing whole-farm phosphorus balances as indicators of long-term sustainability and evaluating new PI approaches that include identification and quantification of inherent risk of phosphorus transport in a given location. Using these data, they will assign each field a score that is then modified by credits for implementation of best management practices—to provide farmers with incentives to improve and incorporate those practices. The work will result in more effective management practices in the Northeast region, with unified and consistent approaches that reflect the state-of-the-science of phosphorus management.

Cornell Researchers

Funding Received

$1 Million spanning 3 years

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