Confined animal feeding operations can produce more P in manure than is required by local crops, leading to local surpluses of manure P. As land application of manure is the primary method for disposal / use of manure, surpluses of manure P from confined animal operations can lead to increases in soil P concentrations. Recent publications have highlighted how P losses from agricultural land that has received surpluses of manure P can have a detrimental impact on water quality. Therefore, recent research has focused on decreasing the P concentration in animal feeds and hence in the manures produced. Several publications are now available that give the reductions in manure P that can be achieved through diet manipulation, but there is a need to evaluate how much surpluses of manure due to animal production can be decreased on a regional scale. The US Department of Agriculture ‘Census of Agriculture' reports county level animal and crop production statistics. We used these records to calculate crop P requirements and manure P production at the county scale. Using published results for the reductions in manure P that can be achieved through diet modification, we then calculated how the mass balance of P was affected if these reduced P diets were fully implemented. This mass balance approach is not perfect, as it assumes manure can be transported anywhere within the county to meet crop needs. However, it gives a useful guide of how much of the P surpluses associated with animal agriculture can be addressed by diet modification alone. The implications for sustainability of animal agriculture and the impact of diet modification, versus the need for other solutions to address P surpluses, will then be discussed.