Duration: 10/01/2005 to 09/30/2010

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Dairy and beef production are major contributors to the economy of the US, but increasing costs of production, the decline of real prices towards a world market price, and environmental issues are jeopardizing the long-term sustainability of these farms. This is causing a continuing trend toward larger farms concentrated in certain geographic locations. More efficient, economical, and environmentally sound production systems are needed to maintain a viable agricultural industry. Integrated research and technology transfer programs are needed to help dairy and beef farmers manage their farms in a cost effective and environmentally acceptable manner and to comply with new farming regulations. Integrated crop, pasture, and livestock farms form very complex physical and biological systems. Most research focuses on one or relatively few components of the system, providing a narrow view of the potential effects of strategic production changes and an inadequate assessment of the farm-level issues of environmental impact and profitability. Modeling and computer simulation provide an effective research strategy for integrating component-level effects and interactions to predict farm level or higher outcomes.

Recently, attention has focused on animal production systems as non-point sources of pollution affecting the quality of air and water resources. In particular, nitrogen and phosphorus may contaminate water following the application of manure or chemical fertilizer to soils (Morse, 1995). Some nitrogen becomes volatilized as ammonia from manure or soils, and eventually contributes to acid rain that endangers forests and water bodies (Luebs et al., 1973). Some nitrogen may be lost from the farm by conversion to atmospheric N2 or nitrous oxides through denitrification, but the majority is normally lost through the other pathways. Phosphorus largely accumulates on farms, mainly as an accumulation in soil, which in turn contributes to accelerated P runoff and the eutrophication of surface waters. On many farms where manure is applied to soil surfaces without incorporation, such as in no-till or pasture fields, potential runoff loss of P can be substantially elevated because much of the manure P is water soluble and thus susceptible to subsequent loss to the environment (Dou et al., 2000, 2002, 2003).

Several technology and incentive programs are aimed at reducing the risk of environmental damage from animal agriculture while maintaining farm productivity. However, in order to better direct these resources, there is a need for routine assessment of which farm management practices are most effective on specific farms. Modeling supported by experimental research provides tools for such assessments. These tools may lead to farm management decision support aids that help producers and their consultants identify the most appropriate strategies for managing nutrients on a farm-by-farm basis. In addition, there is a need to collect and analyze data in the field, so as to identify the most appropriate technology transfer programs to address the problems associated with nutrient pollution in a cost effective manner.

Because the environmental impact of a farm management decision depends on farm characteristics (e.g., size, soil type, climate) and other management selections (e.g., crop rotations, tillage practices, manure storage), the only way to calculate the benefit of a farm practice is to model the changes in nutrient flows through the entire system. Development of integrated mathematical models enables calculation of the environmental benefit from one or more management or infrastructure changes in any management subsystem (crops, soils, feed, and animal). The development of such an integrated understanding of the farm nutrient cycle requires participation by scientists in a number of diverse disciplines.

The NE-132 project has brought together a broad range of disciplines, which led to the development of quantitative models including the GRAzing Simulation Model (GRASIM: http://danpatch.ecn.purdue.edu/~grasim/grasim.html), the Dairy Forage System Model (DAFOSYM : http://pswmru.arsup.psu.edu/software/dafosym.htm), a second generation model called the Integrated Farm System Model (IFSM: http://pswmru.arsup.psu.edu/software/ifsm.htm), the Dairy Nutrient Planner (DNP: http://library.scc.wa.gov/?viewCat=142), and the Whole Farm Balance Nutrient Education Tool (WFBNET: http://www.puyallup.wsu.edu/dairy/data/joeharrison/software/Dairy%20WFNBET%20ver%204.0%20with%20N%20&%20P%20linked%20protected.xls) and FarmSoft. These models are currently being used as tools to evaluate N and P flows through dairy farm systems by university extension and government regulatory agencies. These models integrate years of collaborative research and enable an enhanced understanding of nutrient flows in the farm system. These models need to be further evaluated, validated with real farm data, and adapted to address the immediate needs in the field across the nation related to nutrient management on dairy and beef farms. In the new project, models that were previously developed will be evaluated under diverse farm conditions to identify improved strategies for management of nutrients on farms. The collaborative modeling effort of the group has been critical in identifying knowledge gaps in our understanding of N and P flows in ruminant animal/cropping systems. The models have also helped identify directions for future field/lab research. The broad and diverse research background and expertise of the group has been and will continue to be integrated by the modeling effort.

To advance whole-farm model evaluation and application, a coordinated effort is needed at several levels. First, field studies of nutrient dynamics and cropping systems are needed to calibrate predictions for different geographic locations and to evaluate model components. Second, model refinements and software development are needed to enable use of the models on individual farms throughout the U.S. Third, model prediction capacity must be expanded to more accurately partition nutrient losses into those from volatilization, leaching, runoff and denitrification, and consequences of alternative feeding or crop management systems must be expanded. Finally, models must be applied to planning of dairy and beef production systems to reduce or eliminate problems associated with nutrient management and profitability.

Related, Current and Previous Work

The proposed work will build upon and integrate research in several disciplines to make maximal use of previous research. Major areas include crop growth, crop conservation, animal nutrient utilization, manure handling, pasture and grazing, and systems analysis of dairy and beef farms. Each of these areas is addressed in the attachment Related.doc.

Objectives

1. Enhance cropping, grazing, and feeding management systems to improve animal nutrient utilization and reduce nutrient excretion. . (Muck, ARS,WI; Fick, Cornelll, Dou, UPenn; Kohn, UMD; Knowlton, VaTech; Harrison, WA;Combs, WI; Mohtahr, Purdue; Rotz, ARS,PA; Sanderson, ARS;Felton, Wva). Additional details provided in the objectives.doc attachment.
   
2. Evaluate and develop efficient animal, manure, and cropping systems for reduced nutrient flow, cycling, transformation and loss to the environment. (Rotz, ARS,Pa; Herbert, UMass, Dou, UPenn,;Miller, UT; Harrison, WA; Powell, WI; Moreira, LA; Erickson, NE; Knowlton, VaTech). Additional details provided in the objectives.doc attachment.
   
3. Refine, evaluate, and apply integrated quantitative models of dairy and beef farms to predict profitability and nutrient losses to the environment. (Rotz, ARS, PA;Rayburn, WV, Karsten UPenn;Grabber, WI; Moriera, LA;Mohtahr, purdue; Randhir, UMass). Additional details provided in the objectives.doc attachment.
   
4. Develop science-based tools and educational materials to promote environmental stewardship in US dairy and beef industries. Additional details provided in the objectives.doc attachment.
   

Methods

To read the entire Methods section, please refer to the attachment 'Methods.doc.'

Measurement of Progress and Results

Outputs

• Completion of specified experiments in each cooperator state.
• Public release of new models or new versions of current models maintained by project collaborators.
• Publication of results in lay proceedings and scientific publications.
• Presentations at conferences and scientific meetings.
• Linkages with environmental agencies, NRCS, and conservation districts.
• Output 6 Funding to conduct research that meets these objectives.

Outcomes or Projected Impacts

• Increased awareness of whole farm nutrient management by producers, NRCS, conservation districts and environmental agencies.
• More economically and environmentally sustainable systems for dairy and beef production.

Milestones

(2005): Begin objective work in each cooperator state.

(2006): Begin reporting results of experiments and the development and validation of model components.

(2007): Continue with integration of research data and model development. Focus on outreach efforts.

(2008): Continue with integration of research data and model development. Focus on outreach efforts.

(2009): Finalize project objectives and plan for ongoing regional research activities.

Projected Participation

View Appendix E: Participation

Outreach Plan

Please refer to Objective 4: (Outreach) in the attachment Methods.doc, for specific outreach plans and activities. Outreach activities of this project will be targeted to dairy and beef producers, producer organizations, university extension, state and federal agricultural and environmental agencies, NRCS field staff, undergraduate and graduate education, agricultural professionals and elected officials.

The models, IFSM and GRASIM, are available and can be downloaded from the web. They will continue to be updated as new knowledge is integrated into the models. In addition, education and extension tools based on excel spreadsheets will be developed that will help producers and ag professionals better understand how nutrition, manure management, livestock housing and management, cropping decisions and herd expansion impact N and P dynamics on dairy and beef farms.
Spreadsheets that help producers understand better how forage quality affects profitability and nutrient flows on-farm will also be developed and made available. These tools will be made available through websites, journal publications and conference proceedings. Workshops and seminars will be held in cooperator states that highlight the integrated nature of nutrient management on farms.

The WPBNET has been selected as an educational tool to be incorporated into the National Comprehensive Nutrient Management Planning Curriculum project led by Robert Burns of Iowa State and a cooperative project with the Natural Resources Conservation Service.

The software and other publications generated in the proposed work will be useful to farmers, educators, policy makers, regulators, commodity groups, politicians, and other researchers. The information will aid farmers as they make strategic plans for crop production and manure management. Extension Specialists will obtain useful information for extension workshops and other forms of teaching or consulting with farmers on issues related to grazing, manure management, and cropping systems. The results will provide a better understanding of the costs, benefits, and potential impact of legislation on the dairy industry.

Organization/Governance

The voting membership of the technical committee consists of a technical representative from each participating USDA unit or state agricultural experiment station (SAES) as designated by the SAES director. Non-voting members include the regional administrative adviser, the CSREES representative, and additional representatives from participating SAES and USDA units.

All voting members are eligible to hold an office on the technical committee. These officers are the chair and the secretary. The chair, in consultation with the administrative advisor, notifies the technical committee members of the time and place of meetings, prepares the agenda, and presides at the annual meeting of the technical committee. The chair also prepares the annual report of the regional project.

The secretary records and distributes the minutes of the technical committee meeting. A new secretary is elected at the annual meeting of the technical committee and succeeds to chair position at the time the annual report is filed with the administrative advisor.

Literature Cited

Aarts, H.F.M., B. Habekotte and H. van Keulen. 2000. Nitrogen (N) management in the De Marke dairy farming system. Nutrient Cycling in Agroecosystems 56:231-240.

Allen, M.S. 1996a. Relationship between forage quality and dairy cattle production. An. Feed Sci. Tech. 59:51-60.

Allen, M.S. 1996b. Physical constraints on voluntary intake of forages by ruminants. J. Anim. Sci. 74:3063-3075.

Allen, M.S., M. Oba, and B.R. Choi. 1997. Nutritionists perspective on corn hybrids for silage. p. 25-36. In Silage: Field to Feedbunk, NRAES-99, Hershey, PA. Northeast Regional Agric. Engng. Service.

Armstrong, D.L., E.T. Shaudys, and J. H. Sitterly. 1962. Synthesis of optimum forage handling systems for a one-man dairy farm. J. Dairy Sci. 35(7):865-871.

Arnold, J.G., R. Srinivasa, R.S. Muttiah, and J.R. Williams. 1998. Large area hydrologic modeling and assessment Part 1: Model development. J. Am. Water Res. Assoc. 34:73-89.

Bal, M.A., J.G. Coors, and R.D. Shaver. 1997. Impact of the maturity of corn for use as silage in the diets of dairy cows on intake, digestion, and milk production. J. Dairy Sci. 80:2497-2503.

Ball, P.R., and J.C. Ryden. 1984. Nitrogen relationships in intensively managed temperate grasslands. Plant Soil 76:23 33.

Barzegar, A.R., S.J. Herbert, A.M. Hashemi and C.S. Hu. 2004. Passive pan sampler for vadose zone leachate collection. Soil Sci. Soc. Am. J. 68 (3):744-749.

Bergstrom, L. and N.J. Jarvis. 1991. Prediction of nitrate leaching losses from arable land under different fertilization intensities using SOIL-SOILN models. Soil Use Manag. 7:79-85.

Borton, L.R., C.A. Rotz, H.L. Person, T.M. Harrigan, and W.G. Bickert. 1995. Simulation to evaluate dairy manure systems. Appl. Eng. Agric. 11: 301-309.

Brye K.R., J.M. Norman, L.G. Bundy and S.T. Gower. 1999. An equilibrium tension lysimeter for measuring drainge through soil. Soil Sci. Soc. Am. J. 63: 536-543.

Buckmaster, D.R., C. A. Rotz, and R.E. Muck. 1989b. A comprehensive model of forage changes in the silo. Trans. ASAE, 32(4):1143-1152.

Buckmaster, D.R., C.A. Rotz, and D.R. Mertens. 1989a. A model of alfalfa hay storage. Trans. ASAE, 32(1):30-36.

Buttel, F.H. and D. B. Jackson-Smith, B. Barham, D. Mullarkey, and L. Chen. 1999. Entry into
Wisconsin Dairying: Patterns, processes, and policy implications. PATS Research Report No. 4. Program on Agricultural Technology Studies, University of Wisconsin-Madison.

Cherney, D.J.R., J.H. Cherney, and R.F. Lucey, 1993. In vitro digestion kinetics and quality of
perennial grasses as influenced by forage maturity. J. Dairy Sci. 76:790-797.

Cherney, J.H. and V.G. Allen. 1994. Chapter 14. Forages in livestock system. In: Barnes et al (ed.) Forages: The science of grassland agriculture. 5th ed. Iowa State Univ. Press.

Clark, S.G., J.R. Donnelly, and A.D. Moore, 2000. The GrassGro decision support tool: Its effectiveness in simulating pasture and animal production and value in determining research priorities. Australian J. Exp. Agric. 40(2): 247-256.

Cuttle S.P., and D. Scholfield. 1994. Management options to limit nitrate leaching from grassland. Trans. 15th World Congress of Soil Science. Acapulco, Mexico. p. 138-150.

Dado, R.G. and M.S. Allen. 1993. Intake limitations from rumen fill for cows challenged with high fiber diets and inert rumen bulk. J. Dairy Sci. 76(Suppl. 1):210.

Dado, R.G. and M.S. Allen. 1995. Intake limitations, feeding behavior, and rumen function of cows challenged with rumen fill from dietary fiber or inert bulk. J. Dairy Sci. 78:118-133.

Dado, R.G. and M.S. Allen. 1996. Enhanced intake and production of cows offered ensiled alfalfa with higher neutral detergent fiber digestibility. J. Dairy Sci. 79:418-428.

Demaine, D.C., and G.W. Fick. 2003. Device calibrated to help farmers manage pastures. What?s Cropping Up (Dep. of Soil, Crop and Atmos. Sci., Cornell Univ., Ithaca, NY) 13(2):10-11.

Deswysen, A., M. Vanbelle, and M. Focant. 1978. The effect of silage chop length on the voluntary intake and rumination behaviour of sheep. J. Brit. Grassland Soc. 33:107-115.

Dou, Z., J.D. Ferguson, J. Fiorini, J.D. Toth, S.M. Alexander, L.E. Chase, C.M. Ryan, K.F. Knowlton, R.A. Kohn, A.B. Peterson, J.T. Sims, and Z.Wu. 2003. Phosphorus feeding levels and critical control points on dairy farms. J. Dairy Sci. 86:3787-3795.

Dou, Z., J.D. Toth, D.T. Galligan, C.F. Ramberg, Jr., and J.D. Ferguson. 2000. Laboratory procedures for characterizing manure phosphorus. J. Environ. Qual. 29:508-514.

Dou, Z., K.F. Knowlton, R.A. Kohn, Z. Wu, L.D. Satter, G. Zhang, J.D. Toth, and J. Ferguson. 2002. Phosphorus characteristics of dairy feces affected by diets. J. Environ. Qual. 31:2058-2065.

Dou, Z., L.E. Lanyon, J.D. Ferguson, R.A. Kohn, R.C. Boston, and W. Chalupa. 1998. An integrated approach to managing nitrogen on dairy farms: evaluating farm performance using the dairy nitrogen planner. Agron. J. (???in press???).

Dou, Z., R.A. Kohn, J.D. Ferguson, R.C. Boston and J.D. Newbold. 1996. Managing nitrogen on dairy farms: An integrated approach I. Model Description. J. Dairy Sci. 79:2071-2080.

Ebeling, A.M., L.G. Bundy, J.M. Powell, and T.W. Andraski. 2002. Diary diet phosphorus effects on phosphorus losses in runoff from land-applied manure. Soil Sci. Soc. Am. J. 66:284-291.

Fisher, D.S., J.C. Burns, and K.R. Pond. 1987. Modeling ad libitum dry matter intake by ruminants as regulated by distension and chemostatic feedbacks. J. Theor. Biol. 126:407-418.

Garden, D.L. and T.P. Bolger, 2001. Interaction of competition and management in regulating composition and sustainability of native pasture. In: P.G. Tow and A. Lazenby (eds): Competition and succession in pastures (edition 1). pp.213-232

Gauch, H.G., Jr., J.T.G. Hwang, and G.W. Fick. 2003. Model evaluation by comparison of model-based predictions and measured values. Agron. J. 95:1442-1446.

Gupta, M.L., T.A. McMahon, R. H. Macmillan, and D.W. Bennett. 1990. Simulation of hay-making systems: part 1 - development of the model. Agr. Systems 34:277-299.

Hanrahan, G., M. Gledhill, W.A. House, and P.J. Worsfold. 2001. Phosphorus loading in the Frome catchment, UK: Seasonal refinement on the coefficient modeling approach. J. Environ. Qual. 30:1738- 1746.

Harrison, J. J. and L. Johnson. 1997. Mechanical processing of corn silage: our current understanding of the benefits. Pacific Northwest Animal Nutrition Conference, Oct. 15-17, Boise, ID.

Harrison, J.H., L. Johnson, D. Davidson, D. Huot, M. Horn, L. Morgan, K. Shinners, D. Linder, A. Rotz, R. Muck, and B. Mahanna. 1998. Effect of maturity, chop length, mechanical processing, and silo type on packed density of corn silage. J. Anim. Sci. 76(Suppl. 1):199.

Herbert S.J., S. Ou and M. Hashemi. 2001. More efficient nutrient management planning with
FarmSoft. In Agron. Abst. CD ROM. Amer. Soc. Agron. Madison, WI.

Holt, N.W. and P.G. Jefferson, 1999. Productivity and sustainability of four grazed grass - Alfalfa mixtures. Canadian J. Animal Sci. 79(1): 83-89.

Hutson, J.L. and R. J. Wagenet. 1991. Simulating nitrogen dynamics in soils using a deterministic model. Soil Use Manag. 7:74-78.

Hyer, J.C., J.W. Oltjen, and M.L. Galyean. 1991. Development of a model to predict forage intake by grazing cattle. J. Anim. Sci. 69:827-835.

Illius, A.W. and I.J. Gordon. 1991. Prediction of intake and digestion in ruminants by a model of rumen kinetics integrating animal size and plant characteristics. J. Agric.. Sci., Camb. 116:145-157.

Illius, A.W. and M.S. Allen. 1994. Assessing forage quality using integrated models of intake and digestion by ruminants. In: Forage Quality, Evaluation, and Utilization. G.C. Fahey, (ed.) Amer. Soc. Agron., Crop Sci. Soc. of Amer., Soil Sci. Soc. of Amer., Madison, WI.

Jarvis, S.C., D.J. Hatch, and D.H. Roberts. 1989. The effects of grassland management on nitrogen losses from grazed swards through ammonia volatilization, the relationship to excretal N returns from cattle. J. Agric. Sci. Camb. 112:205 216.

Jemison J.M. and R.H. Fox. 1992. Estimation of zero-tension pan lysimeters collection efficiency. Soil Sci. 15:85-94.

Johnes, P.J. 1996. Evaluation and management of the impact of land use changes on the nitrogen and phosphorus load delivered to surface waters: The export coefficient modeling approach. J. Hydrol. 183:323-349.

Johnes, P.J. and A.L. Heathwaite. 1997. Modelling the impact of land use change on water quality in agricultural catchments. Hydrol. Proc. 11:269-286.

Johnes, P.J., B. Moss, and G. Phillips. 1996. The determination of total nitrogen and total phosphorus concentrations in freshwaters from land use, stock headage and population data: Testing of a model for use in conservation and water quality management. Freshwater Biology 36:451-473.

Johnson, T.R. and D.K. Combs. 1992. Effects of inert rumen bulk on dry matter intake in early and midlactation cows fed diets differing in forage content. J. Dairy Sci. 75:508-519.

Kleinman, P.J.A., A.N. Sharpley, B.G. Moyer, and G.F. Elwinger. 2002a. Effect of mineral and manure phosphorus sources on phosphorus runoff. J. Environ. Qual. 31:2026-2033.

Knowlton, K.F., and J.H. Herbein. 2002. Phosphorus partitioning during early lactation in dairy cows fed diets varying in phosphorus content. J. Dairy Sci. 85:1227-1236.

Koegel, R.G., R.J. Straub, K.J. Shinners, G.A. Broderick, and D.R. Mertens. 1992. An overview of physical treatments of lucerne performed at Madison, Wisconsin, for improving properties. J. Agric. Engr. Res. 52:183-191.

Kohn, R.A. 1998. Utilization by cattle of the nitrogen in forage crops. In: Fate of N-Containing
Macromolecules in the Biosphere and Geosphere, B. A. Stankiewicz and P. Van Bergen (eds) American Chemical Society Symposium Series 707.

Kohn, R.A., Z. Dou, J.D. Ferguson, and R.C. Boston. 1997. A sensitivity analysis of nitrogen losses from dairy farms. J. Envir. Mgmnt. 50:417-428.

Krause, K. M., D. K. Combs and K. A. Beauchemin. 2002. Effects of forage particle size and grain fermentability in midlactation cows. I. Milk production and diet digestibility. J. Dairy Sci. 85: 1936-1946.

Krause, K. M., D. K. Combs and K. A. Beauchemin. 2002. Effects of forage particle size and grain fermentability in midlactation cows. II. Ruminal pH and chewing behaviour. J. Dairy Sci. 85:1947-1957.

Lord E.I. and M.A. Shepherd. 1993. Development in the use of porous ceramic cups for measuring nitrate leaching. J. Soil Sci. 44: 435-449.

Lovering, J. and J.A. McIsaac. 1981. A forage production model. J. Dairy Sci. 64:798-806.

Luebs, R. E., k. R. Davis, and A. E. Laag. 1973. Enrichment of the atmosphere with nitrogen
compounds volatilized from a large dairy area. J. Environ. Quality 2: 137-141.

Marsh, R., and P.B. Hamilton. 1978. A review of the effects of mechanical treatment of forages on fermentation in the silo and on the feeding value of the silages. N.Z. J. of Experimental Agric. 6:271-278.

McGechan, M.B. 1989. A review of losses arising during conservation of grass forage: part 1, field losses. J. Agr. Eng. Res. 44:1-21.

McGechan, M.D. 1990a. A review of losses arising during conservation of grass forage: part e, storage losses. J. Agr. Eng. Res. 45:1-30.

McGechan, M.D. 1990b. Operation research study of forage conservation systems for cool, humid upland climates, part 1: description of the model. J. Agr. Eng. Res. 45:117-136.

McGuckin, J.T., R.A. Schoney, R.J. Straub, and R. Koegel. 1982. Wet fractionation system: an
economic analysis. Trans ASAE 25:1400-1404.

Mertens, D.R. 1987. Predicting intake and digestibility using mathematical models of ruminal function. J. Anim. Sci. 64:1548-1558.

Mertens, D.R. and L.O. Ely. 1979. A dynamic model of fiber digestion and passage in the ruminant for evaluating forage quality. J. Anim. Sci. 49:1085-1095.

Miller, W.F. and G.E. Rehkugler. 1972. A simulation: the effect of harvest starting date, harvest-ing rate and weather on the value of forage for dairy cows. Trans. ASAE 15:409-413.

Mohtar, R.H., D.R. Buckmaster, and S.L. Fales. 1997a. A grazing simulation model: GRASIM, A: model development. Trans. ASAE 40(5):1483-1493.

Mohtar, R.H., J.D. Jabro, and D.R. Buckmaster. 1997b. A grazing simulation model: GRASIM, B: field testing. Trans. ASAE 40(5):1495-1500.

Mohtar, R.H., T. Zhai, and X.W. Chen, 2000. A world wide web-based grazing simulation model (GRASIM). Computers and Electronics in Agriculture. 29:243-250

Mooney, C.S. and M.S. Allen. 1997. Effects of whole linted cottonseed neutral detergent fiber
substituted for alfalfa silage neutral detergent fiber at two lengths of cut on performance and feeding behavior of lactating Holstein cows. J. Dairy Sci. 80:2052-2061.

Morse, D. 1995. Environmental considerations of livestock producers. J. Anim. Sci. 73: 2733.
Muck, R.E., and R.W. Hintz. 1996. Effects of breeding for quality on lucerne ensilability. p. 168-169. In: D.I.H. Jones, R. Jones, R. Dewhurst, R. Merry and P.M. Haigh (eds.) Proceedings of the XIth International Silage Conference, University of Wales, Aberystwyth, UK. IGER.

Muck, R.E., D.R. Mertens, and R.P. Walgenbach. 1996. Proteolysis in different forage silages. ASAE Paper No. 961031, ASAE, St. Joseph, MI.

Muck, R.E., R.G. Koegel, K.J. Shinners, and R.J. Straub. 1989. Ensilability of mat-processed alfalfa. p. 2055-2061. In: V.A. Dodd and P.M. Grace (eds.) Agricultural Engineering. Vol. 3, Agricultural Mechanisation. A. A. Balkema, Rotterdam.

Nagel, S.A. and G.A. Broderick. 1992. Effect of formic acid of formaldehyde treatment of alfalfa silage on nutrient utilization by dairy cows. J. Dairy Sci. 75:140-154.

National Research Council. 1987. Predicting Feed Intake of Food Producing Animals. Washington, D.C.: National Academy Press.

National Research Council. 1989. Nutrient Requirements of Dairy Cattle, 6th rev. ed. Washington, D.C.: National Academy Press.

Oltjen, J.W., R.D. Sainz, A.B. Pleasants, T.K. Soboleva and V.H. Oddy. 2005. Representation of fat and protein gain at low levels of growth and improved prediction of variable maintenance requirement in a ruminant growth and composition model. In: Nutrient Digestion and Utilization in Farm Animals: Modelling Approaches (E. Kebreab, J. Dijkstra, W.J.J. Gerrits, A. Bannink and J. France, Eds.) pp. xx-xx. CAB International, Wallingford, UK (in press).

Ostrom, M. R., and D. B. Jackson-Smith, 2000 The use and performance of management intensive rotational grazing among Wisconsin dairy farms in the 1990?s. PATS Research Report No. 8. Program on Agricultural Technology Studies, University of Wisconsin-Madison.

Parke, D., A.G. Dumone, and D.S. Boyce. 1978. A mathematical model to study forage conservation methods. J. British Grassland Soc. 33:261-273.

Parsch, Lucas D. 1982. DAFOSYM: A system simulation model for analyzing the economics of forages on commercial dairy farms. PhD dissertation, Dept of Agric Econ., Mich. St. Univ. DAI-A 43/12, p.3985.

Peters, C.J., G.W. Fick, and J.L. Wilkins. 2003. Cultivating better nutrition: Can the food pyramid help translate dietary recommendations into agricultural goals? Agron. J. 95:1424-1431.

Pienaar, J.P., C.Z. Roux, P.J.K. Morgan, and L. Grattarola. 1980. Predicting voluntary intake on medium quality roughages. S. Afr. J. Anim. Sci. 10:215-225.

Rees, D.V.H. 1982. A discussion of sources of dry matter loss during the process of haymaking. J. Agric, Eng. Res. 27:469-479.

Reis, R. B., F. San Emeterio, D. K. Combs, L. D. Satter and H. N. Costa. 2001. Effects of corn particle size and source on performance of lactating cows fed direct-cut grass-legume forage. J. Dairy Science 69:429-441.

Reis, R. B. and D. K. Combs. 2000a. Effects of corn processing and supplemental hay on rumen environment and lactation performance of dairy cows grazing grass-legume pasture. J. Dairy Sci. 83: 2529-2538.

Reis, R. B. and D. K. Combs. 2000b. Effects of increasing levels of grain supplementation on rumen environment and lactation performance of dairy cows grazing grass legume pasture. J. Dairy Sci. 83: 2888-2898.
Robertson, J.A. 1983. Influence of harvesting and conservation practices on forage quality. Can. J. Plant Sci. 63:913-925.

Rom, H.B. and C.G. Sorensen. 2001. Sustainable Handling and Utilization of Livestock Manure from Animals to Plants. Proc. NJF-Seminar no. 320, Denmark, January 16-19, Danish Instit. Agric. Sci., Research Centre Foulum, Tjele, DK.

Rotz, C. A., L. M. Johnson, and J. H. Harrison. 1998. Economics of corn silage processing on North American Dairy Farms. ASAE Annual International Meeting, Orlando, FL.

Rotz, C.A. 1995. Loss models for forage harvest. Trans. of ASAE 38(6):1621-1631.

Rotz, C.A. and Y. Chen. 1985. Alfalfa drying model for the field environment. Trans. ASAE 28
(5):1686-1691.

Rotz, C.A., D.R. Buckmaster, D.R. Mertens, and J.R. Black. 1989b. DAFOSYM: A dairy forage system model for evaluating alternatives in forage conservation. J. Dairy Sci. 72:3050-3063.

Rotz, C.A., L.D. Satter, D.R. Mertens, and R.E. Muck. 1999b. Feeding strategy, nitrogen cycling, and profitability of dairy farms. J. Dairy Sci. 82: 2841-2855.

Rotz, C.A., D.R. Buckmaster, and J.W. Comerford, 2004. A beef herd model for simulating feed intake, animal performance, and manure excretion in farm systems. J. Animal Sci. (in press)

Russelle, M.P. 1992. Nitrogen cycling in pasture and range. J. Prod. Agr. 5:13-23.

Ryden, J.C., P.R. Ball, and E.A. Garwood. 1984. Nitrate leaching from grassland. Nature 311:50-53.

Savoie, P., L.V. Parsch, C.A. Rotz, R.C. Brook, and J.R. Black. 1985. Simulation of forage harvest and conservation on dairy farms. Agric. Systems 17:117-131.

Shinners, K.J., R.G. Koegel, and R.J. Straub. 1988. Consolidation and compaction characteristics of macerated alfalfa used for silage production. Trans. ASAE 31:1020-1026.

Steenhuis T.S., K. Vandenheuvel, K.W. Weiler, J. Bell, J. Daliparthy, S.J. Herbert and K.J.S. Kung. 1998. Mapping and interpreting soil textural layers to assess agro-chemical movement at several scales along the eastern seaboard (USA). Nutrient Cycling in Agroecosystem 50: 91-97.

Stout, W.L., J.E. Delahoy, L.D. Muller and L.S. Saporito. 2001. Evaluating Nitrogen Management Options for Reducing Nitrate Leaching from Northeast U.S. Pastures. TheScientificWorld JOURNAL VOL 1, page number???

Stout, W.L., S.A. Fales, L.D. Muller, R.R. Schnabel, W.E. Priddy, and G.F. Elwinger 1997. Nitrate leaching from cattle urine and feces in northeast U.S. Soil Sci. Soc. Am. J. 61:1787-1794.

Stout, W.L., S.L. Fales, L.D. Muller, R.R. Schnabel, G.F Elwinger and S.R. Weaver. 2000a. Assessing the effect of management intensive grazing on water quality in the northeast U.S. J. Soil and Water conserv. 55:238-243.

Unruh, L.J., and G.W. Fick. 2002. Correcting measurements of pasture forage mass by vacuuming the stubble. Agron. J. 94:860-863.

Valk, H., J.A. Metcalf, and P.J.A. Withers. 2001. Prospects for minimizing phosphorus excretion in ruminants by dietary manipulation. J. Environ. Qual. 29:28-36.

van Es H.M., K.J. Czymmek and Q.M. Ketterings. 2002. management effects on nitrogen leaching and guidelines for nitrogen leaching index in New York. J. Soil Water Conservation 57: 499-504.

Whitehead, D.C. 1995. Nitrogen Leaching from Soils. p. 59-81. In D.C. Whitehead (ed.) Grassland Nitrogen. CAB International. Oxon, UK.

Wilkinson, J.M. 1981. Losses in the conservation and utilization of grass and forage crops. Ann. Appl. Biol. 98:365-375.

Wu, Z., L.D. Satter, A.J. Blohowiak, R.H. Stauffacher, and J.H. Wilson. 2001. Milk production, estimated phosphorus excretion, and bone characteristics of dairy cows fed different amounts of phosphorus for two or three years. J. Dairy Sci. 84:1738 - 1748.

Young, R.A., C.A. Onstad, and D.D. Bosch. 1995. AGNPS: An agricultural nonpoint source model. p. 1001-1020. In V.P. Singh (ed.), Computer models of watershed hydrology. Water Resources Publication, Highlands Ranch, CO.

Young, R.A., C.A. Onstad, D.D. Bosch, and W.P. Anderson. 1994. AGricultural Non-Point Source Pollution Model, Version 4.03 AGNPS USER'S GUIDE. July 1994. USDA-NRS-NSL, Oxford, MS.

Zhai, T., R. H. Mohtar, X.W. Chen, and B.A. Engel, 1999. Optimization of pasture system with Grazing Simulation Model (GRASIM). Written for Presentation at the 1999 ASAE Annual International Meeting Sponsored by ASAE, Paper number 993091, Toronto, Ontario, Canada. July 18-21, 1999

Zhai, T., R. H. Mohtar, H. Karsten, and M. Carlassare, 2004a. Modeling growth and competition of multi-species pasture system. Trans. ASAE 47(2):617-627

Zhai, T., R. H. Mohtar, F. El-Awar, W. Jabre, and J.J. Volenec, 2004b. Parameter estimation for process-based crop growth models. Accepted by Trans. ASAE with minor revision.

Zhu Y., R.H. Fox and J.D. Toth. 2002. Leachate collection efficiency of zero-tension pan and passive capillary fiberglass wick lysimeters. Soil Sci. Soc. Am. J. 66: 37-43.

Attachments

Land Grant Participating States/Institutions

CA, IL, LA, MA, MD, MI, NJ, NY, OR, UT, VA, WA, WI, WV

Non Land Grant Participating States/Institutions

University of Pennslyvania, USDA-ARS/Pennslyvania, USDA-ARS/Wisconsin