Nitrogen balances for New York State: Implications for manure and fertilizer management

Abstract

New York (NY) has dairy, cash grain, fruit, and vegetable industries located in close proximity to water, making it important to optimize manure and fertilizer use for both economic production of crops and protection of the environment. The gross phosphorus (P) balance for NY (manure and fertilizer P minus crop P removal) estimated for 2006 was +1.7 kg ha⁻¹ (+1.5 lb ac⁻¹), indicating that, on a statewide basis, P is in balance. Our objectives in this study were to (1) estimate state, regional, and county-level gross nitrogen (N) balances for NY for 2007; (2) evaluate N balance trends over time (1987, 1992, 1997, 2002, and 2007); (3) estimate nonlegume cropland (net) N balances for 2007; and (4) quantify the potential impact of improved herd nutrition and manure incorporation on N balances. The 2007 NY gross N balance for nonlegume cropland was +62 kg ha⁻¹ (+55 lb ac⁻¹). Long Island and western NY had the highest N balances (+101 and +77 kg ha⁻¹ [+90 and +69 lb ac⁻¹], respectively) reflecting N fertilizer use for horticultural and/or cash grain crops (both regions) and presence of a concentrated dairy industry (western NY). The Chesapeake Bay watershed and Lake Champlain Basin counties had gross N balances below +28 kg ha⁻¹ (+25 lb ac⁻¹). The statewide N balance decreased from +125 kg ha⁻¹ (+112 lb ac⁻¹) in 1987 to +62 kg ha⁻¹ (+55 lb ac⁻¹) in 2007, largely driven by a decline in N fertilizer use between 1987 and 1992. The statewide N balance dropped to −38 kg ha⁻¹ (−34 lb ac⁻¹) when manure N losses in the barn and storage system and at land application were taken into account. Given a nearly zero P balance, a negative N balance indicates the need for best management practices that increase N use efficiency of manure and fertilizer and/or add N from other sources (cover crops, greater reliance on N fixation, shorter rotations). Improvement in herd nutrition through precision feeding has the potential to increase N use efficiency of surface applied manure and thus reduce N loss to the environment. However, such improvements will also reduce the total amount of N excreted and decrease the N:P ratio of the manure. Best management practices that reduce N loss in the barn and storage system, increase manure and fertilizer N uptake efficiency, and/or reduce N needs will be essential in order to balance N and P for the long-term sustainability of NY agriculture.