Nitrogen Balances for New York State: Past and Future.

Due to the size of the dairy industry in New York State and significant production of fruits and vegetables, large amounts of both manure and fertilizer are applied to cropland, raising concerns about potential nutrient losses to the environment. Our objectives were to (1) estimate state, regional, and county-level nitrogen (N) balances for NY in 2007, (2) evaluate N-balance trends over time (U.S. Census of Agriculture years 1987, 1992, 1997, 2002, and 2007), (3) quantify the potential impact of improved herd nutrition on N balances, (4) identify factors that most impact the N balance in NY. Nitrogen balances were estimated as N fertilizer sold + N excreted in manure - crop removal N from non-legume acres. Data sources included the U.S. Census of Agriculture and annual fertilizer sales data for NY. It was estimated that in 2007, 104.5 million kg N was excreted in manure, 62.9 million kg N from fertilizer was applied on farm, and non-legume crop removal accounted for 130.0 million kg N, resulting in an overall N balance of +37.3 million kg N or + 30.7 kg N ha^-1 at the state level. Nitrogen balances for individual counties ranged from -34.0 kg N ha^-1 to +111.7 kg N ha^-1. Improved management of milk cow dietary N intake has the potential to reduce the manure N excretion coefficient from 149 kg N cow^-1 yr^-1 to about 112 kg N cow^-1 yr^-1. Applying this new coefficient to the 2007 analysis shows there is potential for significantly lowering the state level N balance from +30.7 kg N ha^-1 to +16.2 kg N ha^-1. County N balances on a per hectare basis were most closely correlated with fertilizer N use. These results indicate that improvements can be made in both herd nutrition management and crop fertilizer management.