What contributes to the largest source of phosphorus on the farm?
The rapid concentration of the animal industry in certain areas of the U.S. has been coupled with an intensification of operations. Current census information shows that while the number of dairies has decreased 40% over the last 10 years, dairy cow numbers have decreased only slightly more than 10%, and herd size has increased 50%. Prior to World War II, farming communities tended to be self-sufficient, in that enough feed was produced locally to meet animal requirements and the manure nutrients could be effectively recycled to meet crop needs. After World War II, increased fertilizer use in crop production made it possible to create specialized grain crop and animal operations and fragment animal agriculture. By 1995, some major animal producing states imported over 80% of animal feed from grain producing states. The potential for P surplus at the farm scale can be much greater in animal feeding operations, when nutrient inputs become dominated by feed rather than fertilizer, than cr
