TY - JOUR T1 - Past and future phosphorus balances for agricultural cropland in New York State JF - Journal of Soil and Water Conservation SP - 120 LP - 133 DO - 10.2489/jswc.64.2.120 VL - 64 IS - 2 AU - S.N. Swink AU - Q.M. Ketterings AU - L.E. Chase AU - K.J. Czymmek AU - J.C. Mekken Y1 - 2009/03/01 UR - http://www.jswconline.org/content/64/2/120.abstract N2 - New York State has a large dairy industry resulting in considerable amounts of manure being applied to cropland. Cropland phosphorus (P) balances (manure and fertilizer P minus crop P removal) combined with soil P assessments are illustrative of both challenges and opportunities for long-term sustainability of cropland management at the farm, county, and state scales. Our objectives were to (1) estimate state, regional, and county-level cropland P balances for NY in 2002, (2) evaluate P-balance trends over time (1987, 1992, 1997, and 2002), and (3) quantify the impact of improved herd nutrition and reduced fertilizer use on cropland P balances. Cropland P balances were derived from animal and cropland data from the Census of Agriculture and New York Agricultural Statistics Annual Bulletins and annual farm-use fertilizer sales data. In 2002, cropland P inputs were estimated at 12.7 and 20.9 million kg (28.1 and 46.1 million lb) of P for fertilizer and manure, respectively. Of the manure P, 69% originated from dairy cows. Crop P removal was 21.1 million kg (46.5 million lb), resulting in an overall P balance of +12.5 million kg (+27.6 million lb) or +8.0 kg P ha-1 (+7.2 lb P ac-1), a considerable improvement over 1987 when the statewide P balance was 24.4 million kg (+53.7 million lb) or 15.4 kg P ha-1 (+13.8 lb P ac-1). Without taking into account recent improvements in dairy herd nutrition (i.e., assuming a P excretion of 28 kg cow-1 [62 lb cow-1] per production period), the ratios of P in manure to P in crops were 1.10, 1.12, 1.00, and 0.99, for 1987, 1992, 1997, and 2002, respectively. Thus, the decrease in P balance from 1987 to 2002 reflected reduced fertilizer P use. When improvements in dairy nutrition were taken into account (a decrease in P excretion of dairy cows from 28 to 18 kg cow-1 [62 to 40 lb cow-1] per production period), the 2002 statewide P balance decreased from +8.0 to +4.8 kg ha-1 (+7.2 to +4.3 lb ac-1). This additional reduction illustrates the impact of precision feeding on overall cropland P balances. With a P excretion of 18 kg cow-1 (40 lb cow-1) per production period, increased yields in 2006 (reflected in crop P removal of 23,255 versus 21,104 Mg [25,639 versus 23,268 tn] in 2002) and reduced P fertilizer sales (10,508 versus 12,725 Mg [11,586 versus 14,030 tn] in 2002), the estimated P balance for 2006 amounted to +1.7 kg ha-1 (+1.5 lb ac-1). These assessments illustrate (1) the importance of precision feeding and cropland fertility management for the long-term sustainability of the dairy sector, and (2) the progress made through enhanced agricultural environmental management in New York. ER -