Dietary changes helped reduce phosphorus intake an average of 25 percent in a study of four New York dairy farms.

All four farms were located in the Cannonsville Reservoir Basin — the third-largest source of water for New York City. Educators from Cornell University Cooperative Extension of Delaware County followed the farms for more than two years. During that time, they modified the diet on two of the farms to reduce phosphorus intake. In doing so, they reduced dietary phosphorus from 153 percent of requirement to 111 percent of requirement — an average reduction of 25 percent. Dietary changes also reduced manure phosphorus by 33 percent and the amount of phosphorus remaining on farm by 49 percent.

The researchers say that if phosphorus intake by all of the estimated 7,000 to 8,000 dairy cows in the Cannonsville Basin were lowered, it could reduce the amount of phosphorus from purchased feed and manure phosphorus excretions by more than 141,120 pounds per year.