Characterization of Nutrient Mass Balances on New York Dairy Farms.

A whole-farm nutrient mass balance (NMB) is a useful measure of the nutrient status of dairy farms. Currently, there are no feasible benchmarks NMB for milk production in NY. The objectives of this study were to (1) document the distribution of N, P, and K mass balances of several commercial dairies in NY in a given year, (2) establish initial NMB benchmarks based on what 75% of the farms achieved, and (3) identify opportunities to improve nutrient use efficiency and reduce NMBs over time. A total of 102 dairy farms were surveyed in 2006 in NY State. Nutrient mass balances per ha ranged from -39 to 237 kg N/ha without including N₂ fixation (N1), from -14 to 256 kg N/ha when including N₂ fixation (N2), from -7 to 51 kg P/ha, and from -46 to 148 kg K/ha. Seventy-five percent of the farms were operating with NMB below 118 kg N/ha for N1, 146 kg N/ha for N2, 13 kg P/ha, and 41 kg K/ha (75% benchmark). Farms with the highest nutrient use efficiencies per Mg of milk produced operated below 8.8 kg N/Mg milk for N1, 11.8 kg N/Mg milk for N2, 1.1 kg P/Mg milk, and 3.0 kg K/Mg milk. The animal density was positively correlated with NMB per ha. Farms operating with less than 2.4 AU/ha typically had NMB below the 75% benchmarks, whereas farms with >2.4 AU/ha needed to export manure or crops to meet the 75% benchmark. There are opportunities to reduce the NMB by more tightly managing feed and fertilizer imports, increasing the percentage of farm produced feed, implementation of precision feeding and by exporting crops or manure.