|Rotz, Clarence - Al|
Submitted to: Grassland Science in Europe
Publication Type: Proceedings
Publication Acceptance Date: 3/22/2000
Publication Date: 5/22/2000
Citation: Sanderson, M.A., Ohlsson, C.M., Rotz, C.A., Moestrup, E. Whole farm modelling as a tool for integrated nutrient and farming systems management on dairy farms. Grassland Science in Europe. 2000. v. 5. p. 385-387. Interpretive Summary: Dairy farmers in Europe and the USA face environmental and economic pressures to manage nutrients as effectively as possible. Nutrient losses have economic as well as environmental (e.g., water quality) consequences. Addressing individual components of the whole farm system does not capture interactions among components. Therefore, whole-farm models are useful for revaluating alternative crop and animal management practices in a farming systems context and gauging their economic and environmental effects. We applied the Dairy Forage Systems Model (DAFOSYM) to simulate alternative farming systems and management practices on a Danish and a US dairy farm. In our model simulations, changing from a typical year-round confinement operation to a system where cows are grazed from April to October resulted in a 4% increase in net return and an 18% decrease in N leaching. The greater net return resulted from reduced manure handling and milking costs. .The amount of N lost by volatilization was not changed, but there was a slightly greater buildup of P in the soil with the grazing system. The standard deviation of net return of the grazing system was slightly greater than the confinement operation, indicating a slightly greater production risk. Our results suggest that management to reduce nutrient losses can also maintain or improve economic performance.
Technical Abstract: Whole-farm simulation models such as DAFOSYM provide tools to estimate the changes in economics and nutrient balances caused by changes in selected farm components. We used on-farm data from Denmark and USA. The Danish farm has 73 ha of crop and pasture land, 54 milking cows producing 8571 L milk year-1, and 60 young stock. The US farm has 100 milking cows producing 8790 L milk year-1, 85 young stock, and 81 ha of crop and pastur land. For the Danish farm, we simulated the effect of reducing the protein degradability of the protein supplement. Reducing the protein degradability did not affect net return but reduced N-volatilization by 19% and N-leaching by 8% compared to the base farm. Maintaining farm milk productivity by milking more cows of lower productivity resulted in negative economic returns and increased N-losses. The US scenario was changed from a year-round confinement operation to a system where cows were egrazed from April to October. This change resulted in a 4% increase in ne return and an 18% decrease in N-leaching. It is envisioned that DAFOSYM may be used on farms in Denmark and USA.