Larry Chase

A simple method for estimation of neutral detergent-soluble fibre

A method was developed to estimate the neutral detergent-soluble fibre (NDSF) content of feeds. Citrus pulp, sugar beet pulp, soybean hulls, separated leaves and stems from mature and immature alfalfa, red clover, reed canarygrass and timothy were analysed. Half-gram samples were stirred at room temperature for 4 h with 100 ml of 90:10 (v/v) ethanol/water to extract low molecular weight substances, crude protein (CP) and ash to produce ethanol-insoluble residues (EIR). Samples were refluxed for 1 h with neutral detergent solution and heat stable α-amylase to extract low molecular weight substances, NDSF, starch, CP and ash to produce neutral detergent residues (NDF). The EIR and NDF were analysed for organic matter (OM; EIROM; NDFOM) and CP (EIRCP; NDFCP), and EIR was analysed for starch. Values were expressed as proportions of the original sample dry matter. The NDSF was calculated as the difference in OM mass between EIR and NDF after correction for CP and starch by the equation: EIROM-NDFOM-EIRCP+NDFCP-EIR starch. Extractions with 90:10 (v/v) ethanol/water gave a higher yield of EIR and NDSF than did 80: 20 (v/v) ethanol/water. The method gave good precision and is convenient for assessing NDSF content of feeds.

Past and future phosphorus balances for agricultural cropland in New York State

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.