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Whole-Farm Perspectives of Nutrient Flows in Grassland Agriculture

^a USDA-ARS Pasture Systems and Watershed Management Research Unit, Building 3702, Curtin Road, University Park, PA
^b Univ. of Kiel, Germany
^c USDA-ARS Plant Science Research Unit and US Dairy Forage Research Center (Minnesota Cluster), St. Paul, MN
^d Plant Research International, Wageningen, the Netherlands
^e Univ. of Kassel, Witzenhausen, Germany

View larger version (47K): [in a new window]   Fig. 1. Schematic N cycle showing inputs, outputs (bold-faced), and transformations in a pasture. Dashed arrows indicate inputs most easily managed. Some minor pathways are not included (e.g., organic N excretion in urine).

View larger version (29K): [in a new window]   Fig. 2. Relationship between total N input and N output as products (milk, meat, and crops) and as losses (volatilization, denitrification, runoff, leaching, and transfer to unproductive areas) in dairy and beef production systems that involve some grazing. Data from on-farm and replicated large plot research in New Zealand, Europe, and the USA (Kaffka and Koepf, 1989; Granstedt, 1995; van der Werff et al., 1995; Klausner et al., 1998; Goh and Williams, 1999; Ledgard et al., 1999; Watson and Atkinson, 1999; Hilhorst et al., 2001; Table 4 in this paper) and modeled output for farms in northern Germany (Table 5 this paper) and De Marke (Table 6 in this paper). One data point for dairy (closed, dotted circle) likely underreported leaching losses.

View larger version (24K): [in a new window]   Fig. 3. The effect of total N supply (mineral fertilizer N + slurry N + N deposition + excreta N + residue N) on the proportion of white clover under different defoliation systems (mixed systems are one cut or two cuts in spring with subsequent grazing). Average of 1997 to 2001 at the Karkendamm experimental farm in northern Germany (Trott et al., 2004).

View larger version (28K): [in a new window]   Fig. 4. (a) The effect of total N supply (mineral fertilizer N + slurry N + N deposition + excreta N + residue N) on annual N surplus under different defoliation systems (mixed systems are one cut or two cuts in spring with subsequent grazing) at the Karkendamm experimental farm in northern Germany (Trott et al., 2004). (b) The relationship between annual N leaching losses and annual N surplus on grassland at the Karkendamm experimental farm in northern Germany (Wachendorf et al. (2004a).)

View larger version (24K): [in a new window]   Fig. 5. (a) Total N2O-N emissions from April 2001 to March 2002 and (b) mean N2O-N emission rates for the cutting period (April to July) and fertilizer-borne N2O (%) at the Karkendamm experimental farm in northern Germany (Kelm et al., 2004). C = Control; S = 15N-labeled slurry; F = 100 kg N ha–1 labeled with 15N; FS = nonlabeled slurry + 100 kg N ha–1 labeled with 15N; SF = 15N-labeled slurry + nonlabeled 100 kg N ha–1.

View larger version (59K): [in a new window]   Fig. 6. Average annual nitrogen inputs, outputs, and flows (kg N ha–1) through the major components of the De Marke experimental farm in the Netherlands for 1993 to 2002. Adapted from Aarts et al. (2000a) and Hilhorst et al. (2001).

View larger version (52K): [in a new window]   Fig. 7. Average annual phosphorus inputs, outputs, and flows (kg P ha–1) through the major components of the De Marke experimental farm in the Netherlands for 1993 to 2002. Adapted from Aarts et al. (2000b).

View larger version (22K): [in a new window]   Fig. 8. A comparison of simulated and actual nitrogen leaching losses from grass (a) and maize (b) plots at the Karkendamm Research farm over a wide range in fertilizer application rates and defoliation methods.

View larger version (20K): [in a new window]   Fig. 9. A comparison of simulated and actual nitrogen balances for the De Marke dairy farm for weather years 1996 to 2001.