Forages Agronomy Journal  Volume 102, Issue 4  2010 1201 Published in Agron. J. 102:1201–1209 (2010) Published online 17 May 2010 doi:10.2134/agronj2009.0504 Copyright © 2010 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights re- served. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. M anagement-intensive rotational stocking as part of a livestock production system has been increasing in the United States (Casler and Undersander, 2005). his trend is primarily the result of increased net proits from decreased feeding and harvest costs (Dart et al., 1999). Rudstorm (2004) reported that use of management-intensive rotational stocking improved net proit of dairies in the north central United States. Studies in the northeastern United States show an increase in proits from $40 to $300 per cow for management-intensive rotational stock- ing compared to conined dairies (Aiello, 2004). Animal production (either milk or meat) in grazing systems depends on the combination of forage quantity and quality pro- duced. Research in natural grassland ecosystems has shown that environments with broader plant diversity tend to provide greater and more consistent plant community biomass (Tilman, 2001). Many researchers have explored the yield-diversity hypothesis in deliberately controlled plant diversity experiments with mixed results. Research in clipped plots has shown both a positive (Hec- tor et al., 1999; Bullock et al., 2007; Kirwan et al., 2007; Picasso et al., 2008) and a negative (Piano and Annicchiarico, 1995; Tracy and Sanderson, 2004) impact of increased mixture complexity (i.e., greater numbers of plant species) on dry matter (DM) yield. Similarly, research conducted under grazing has not yielded clear-cut results regarding mixed species pastures. In Canada, a study conducted with mixtures ranging in diversity from mono- culture to a complex six-species mixture found that the complex mixture yielded more consistently compared with less diverse mixtures (Clark, 2001). In the northeastern United States, research with dairy cows showed an increase in DM production for the more complex mixtures (composed of three- to six-species) compared with a two species grass–legume mixture (Sanderson et al., 2005). More recently, a study conducted with beef steers (Bos taurus ) in Illinois found that complex mixtures did not improve yield under grazing (Tracy and Faulkner, 2006). Although complex mixtures have not consistently produced top yields, their yields are usually more stable from year to year and outproduce simple mixtures in dry years (Sanderson et al., 2005; Skinner et al., 2004, 2006). Fluctuation in weather is a major reason for incon- sistent pasture production (Belesky et al., 1999). For instance, in the northern prairies of the United States drought reduced pasture yield by 50% (Dunn et al., 2005). Hence, the use of complex mix- tures could decrease environmental production risks. Even though much efort has been spent in clarifying the relationship between mixture complexity and DM production, little research has focused on the economic implications of using diferent mixture complexities and grazing strategies on a whole-farm scale. In a study conducted in Minnesota that con- sidered partial economic efects of mixture complexity, there was no economic beneit for dairy production associated with more complex mixtures (Wedin et al., 1965). In a more recent ABSTRACT Complex forage mixtures (mixtures of more than three species) have been researched as a means to increase yield and sustain forage production in pastures of the northeastern United States. However, little research has focused on the economic impact of forage mixture complexity and grazing strategy on a whole-farm scale. We used the Integrated Farm System Model (IFSM) to examine the short- (2-yr) and long-term (25-yr) performance and economic returns of four pasture mixtures (two, three, ive, and seven species of grasses and legumes) and grass monocultures grazed according to plant morphology or canopy height criteria. For both 2- and 25-yr analyses, reduced pasture production in the morphology-based grazing strategy led to a decrease in net return compared to the height-based grazing strategy. Both analyses showed that the diferences in net return were mainly due to seed, fertilizer, and feed costs, pasture production, and the income from excess forage sales. Production was more dependable for the height-based grazing strategy compared with the morphology-based strategy. Complex mixtures generated greater and more consistent net returns compared with either the simple mixtures or grass monoculture. More importantly, when comparing the diference in net return obtained by a particular forage treatment in dry and wet years, the net return using complex mixtures was reduced by only 25 to 27%. On the other hand, reductions in net return ranged from 36% for a three-species mixture to 55% for grass monoculture. For dairy pastures, complex mixtures are a useful alternative to reduce production variability in dry years. A. Deak, Monsanto Company, 6729 Newman, Corpus Christi, TX 78414; M.H. Hall, Crop and Soil Sciences, Penn State Univ., 116 ASI Bldg., University Park, PA 16802; M.A. Sanderson and A. Rotz, USDA-ARS, Pasture Systems & Watershed Management Unit, Bldg. 3702, Curtin Road, University Park, PA 16802-3702; M. Corson, INRA and Agrocampus Rennes, UMR 1069 Soil Agro and HydroSystems, Rennes F-35000, France. Received 9 Dec. 2009. *Corresponding author (atila.deak@monsanto.com). Abbreviations: CV, coeicient of variation; DM, dry matter; IFSM, Integrated Farm System Model. Whole-Farm Evaluation of Forage Mixtures and Grazing Strategies Atila Deak,* Marvin H. Hall, Matt A. Sanderson, Al Rotz, and Michael Corson