|Rotz, Clarence - Al|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2005
Publication Date: 9/23/2005
Citation: Rotz, C.A., Taube, F., Russelle, M.P., Oenema, J., Sanderson, M.A., Wachendorf, M. 2005. Whole-farm perspectives of nutrient flows in grassland agriculture. Crop Science. 45(6):2139-2159. Interpretive Summary: Prior to World War II, farms in the USA and northern Europe were diverse, integrated, and dependent upon grassland. Agricultural markets were primarily local and nutrients were cycled mainly within farms and among farms in local communities. With the advent of mechanization, fertilizers, improved seeds, and agrichemicals, farm size increased, agricultural markets became more national and international, and nutrient cycles became fragmented. Animal agriculture became specialized and concentrated, relying on annual crops and off-farm sources of feeds and fertilizers, which resulted in nutrient accumulation and loss from farms. At the beginning of the 21st century, forage and grasslands are being rediscovered for their multiple functions and the ecosystem services they provide. However, grassland systems are not necessarily environmentally benign. As in any managed ecosystem, nutrient management on grasslands must address multiple criteria, including water quality, nutrient use efficiency, and economics. Considering these multiple interacting forces, simple component analysis is inadequate; a broad approach addressing the whole farm is necessary. Experimental farm research combined with simulation studies are being used to demonstrate that major improvements in nutrient utilization and thus reduced losses to the environment can be achieved in forage-based animal production. A continuing challenge though, is to develop systems for realizing these improvements at an acceptable cost to the producer, or to develop policies that pass increased costs for environmental protection on to society as a whole. Computer simulation supported by field studies provides a powerful and cost-effective tool for developing, evaluating, and promoting more sustainable grassland systems for commercial livestock production.
Technical Abstract: Grassland agriculture is an important industry for livestock production and land management throughout the world. During the latter half of the 20th century, animal agriculture moved away from highly integrated forage-livestock systems toward specialized systems with fragmented nutrient cycles and attendant environmental problems. Nitrogen and phosphorus are the two major farm nutrients of environmental concern. Nitrogen transforms to different compounds as it cycles through the farm, and large losses occur to the atmosphere, groundwater, and surface waters. Although there are fewer pathways for phosphorus loss and losses are smaller relative to nitrogen, the environmental damage created by phosphorus-induced eutrophication of surface waters is an equally important concern. Comprehensive studies are being conducted at the Karkendamm experimental farm in northern Germany and the De Marke experimental farm in the Netherlands to monitor nutrient transformations and losses in grassland farming systems. Although the information generated in such experimental farms is not directly applicable to other climates and soils, it is being transferred to other regions through computer simulation. A whole-farm model calibrated and verified with the experimental farm data is being used to evaluate and transfer these technologies and strategies to commercial farms in other areas such as the USA. By integrating experimental farm data with whole-farm computer simulation, more sustainable grassland production systems can be developed, evaluated, and transferred to commercial production in a most cost-effective manner.