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There was no direct link between P balance and milk production, and therefore some Virginia dairy farmers efficiently balanced P. Farms that fall outside the feasible zone of operation can improve P balance by changing management practices with the help of indicators in Table 2. There were two clear risk factors for surplus P balance: 1) excess use of poultry litter, and 2) excess P imported in purchased feed. While poultry litter is a good fertilizer in many situations, these excess P balances can be minimized by avoiding regular use of poultry litter, including exporting generated poultry litter on mixed dairy and poultry farms. Likewise, farmers with a P deficit could assist by importing poultry litter from local farms with excess P. It is also important to optimize homegrown feed production, and follow precision feeding practices with purchased feeds. Overall, farms can increase their P use efficiency for long-term sustainability while maintaining milk production by minimizing risk factors associated with increasing soil test P concentrations.
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March 15, 2021