Duration: 10/01/2009 to 09/30/2014

Administrative Advisor(s):

NIFA Reps:

Non-Technical Summary

Statement of Issues and Justification

Title: Nitrogen cycling and plant-livestock use efficiency in grassland agroecosystems


STATEMENT OF ISSUES AND JUSTIFICATION


The amount of nitrogen (N) applied annually to forage production systems of the Midwest exceeds plant uptake (Mosier 2001) and relatively little of the N consumed by grazing animals is removed from the ecosystem (Jarvis and Ledgard 2002). Significantly greater N is removed via mechanical harvesting for feed but the same problem occurs when the forage is fedthe animals consume forage N, but then excrete most of this N into the environment. Because N is usually the primary limitation to plant production in temperate ecosystems, significant manure and inorganic fertilizer N is applied to agroecosystems. Nitrogen fixation by legumes and purchased feed supplements contribute additional N to the system. Unless soil organic matter increases significantly over time, there is little potential for highly mobile N to accumulate in soils, so the fate of this surplus N is deposition in waterbodies, groundwater, the atmosphere, and adjacent terrestrial ecosystems where it can have undesirable effects (Jenkinson 2001, Janzen et al. 2003, Eickhout et al. 2006). Surplus N from agroecosystems throughout the Midwest has been identified as the primary cause of periodic hypoxia in the Gulf of Mexico (Rabalais et al. 2002, Turner and Rabalais 2003). Gaseous N emissions from soils contribute to the greenhouse effect (Robertson et al. 2000, Mosier 2001) and eutrophication of terrestrial and aquatic ecosystems (Vitousek et al. 1997, Carpenter et al. 1998, Ferm 1998). The magnitude of N loss and subsequent negative impacts on ecosystems are influenced by the frequency, intensity, and timing of management practices within the agroecosystem.


From an agronomic perspective, much is known about fertilizer type, amount, and timing of application for maximizing crop yields (Jenkinson 2001, Addiscott 2005). Likewise, forage quality and animal nutrition research is targeting ways of improving N use efficiency by plants (Singer and Moore 2003) and livestock (Scholefield et al. 1991). A previous project (NC-189 Forage Protein Characterization and Utilization for Cattle) of this committee focused on the ruminal degradation characteristics of forage proteins in commonly cultivated forages and also provided a solid understanding of the protein degradation characteristics of native prairie and range grasses found throughout the northcentral region. While mechanisms and pathways for N transformation and loss have been determined for grasslands and pastures (Ledgard 2001, Kroeze et al. 2003), major gaps exist in our knowledge of the relationships between management and harvest strategies and N pathways on managed cool-season pastures of the central US and elsewhere. For example, while empirical relationships between N applied as fertilizer and N loss from the ecosystem exist (Rotz et al. 2005), tradeoffs in N retention and carbon (C) cycling, hence forage production, are less well understood. A recent review of grazing effects on C and N cycles concluded, There is major uncertainty in the quantification of N2O emissions, in particular with regard to different livestock production systems as well as their feeding and waste management practices, which need to be underpinned by more accurate modeling of soil N2O fluxes (Steinfeld and Wassenaar 2007).


Many scientists are focused on improving N use efficiency (NUE) of the products, i.e., crop plants and livestock, in order to reduce the amount of N going to the environment and to reduce fertilizer costs to farmers. Unfortunately, tradeoffs exist between NUE and forage quality, e.g., C4 grasses have greater N use efficiency, but this translates to lower crude protein content and lower livestock production on these grasses. Current research directed at improving NUE of livestock centers on manipulating the ratio of urine to feces N because urine-derived N is more volatile and labile in the environment. Researchers are examining tannins and other secondary compounds in feed, but the same forage quality tradeoffs are in play here. On the other hand, some forages contain more degradable protein than animals require but insufficient undegradable protein. The excess degradable protein is excreted in the urine. Strategies to increase forage production (e.g., N fertilization and interseeding legumes) often result in forages that contain N far in excess of animal needs. Identification of optimal grazing management and/or supplementation strategies offers opportunities to increase N utilization. There is a voluminous literature on confinement feeding of beef and dairy cattle for maximum production. However, very little work has been directed towards developing strategies for precisely meeting animal requirements for metabolically protein and amino acids without overfeeding crude protein in grazing situations Energy supplements with low degradable protein content may be an option, including byproduct sources of highly digestible fibers. Other protein supplements that resist degradation and have amino acid patterns that are complementary to ruminal microbial protein also have promise.
Mounting demand from consumers in the last decade has pushed ranchers and farmers to produce high quality foods at low prices with fewer environmental impacts while remaining profitable (Tilman et al. 2002). Hence, there is a pressing need for scientifically sound information to make decisions about how best to manage rural landscapes to simultaneously produce agricultural commodities and maintain, and develop ecosystem services such as biodiversity and soil, water, and air quality. Our project will quantify the effect of pasture management on both within-system and downstream environments, and the ability of those environments to provide ecosystem services that optimally benefit human well being. We also will determine the effect of these pasture management practices on N use efficiency in terms of animal production and economic returns. Realization of these objectives will help farmers, policymakers, and agency personnel manage for better quality of life in rural areas.


Many efforts and resources are aimed at staunching the flow of N into the atmosphere or waterbodies, including establishment of riparian buffer strips and restoration of wetlands where physical impedance or biogeochemical transformation of N can occur (Tate et al. 2000, Borin and Bigon 2002, Sabater et al. 2003). While these landscape mitigation strategies may be effective from the downstream ecosystem perspective, the farmer still loses N that otherwise might improve productivity. Further, the loss of nutrients from farm systems puts a spotlight on the farmer for the negative costs his enterprise places on society. Efforts to increase N retention within the productive agroecosystem should improve the standing of the farmer as a land steward.
In our current project (NC-1021 Nitrogen Cycling, Loading, and Use Effiency in Forage-Based Livestock Production Systems), we analyzed the N efficiency of grassland ecosystems managed for beef cattle production in Wisconsin and Nebraska. Based on estimates of N inputs (e.g., fertilization, fixation, and deposition) and outputs, we calculated that 18% or less of the N entering the system was leaving as product. While these grassland ecosystems may not have been at a long-term equilibrium, our analysis indicates that these grassland/beef cattle systems were not highly efficient with respect to product. Further, unless soil organic matter was accumulating at a high rate (and our data do not suggest this), much of the N entering as fertilization, deposition, and/or fixation is likely finding its way out of the agroecosystem. These studies and others in the NC-1021 states also have demonstrated the effect of management practices on N2O fluxes. For example, management intensive rotational grazing appears to enhance N2O fluxes from grassland soils in comparison to continuously grazed, hayed, or rested grasslands.
We propose to continue to conduct complementary experiments and simulation modeling to help stakeholders make informed decisions about rural landscapes. Multifunctional farming systems provide multiple ecosystem services. These services can include provisioning (i.e., meat, milk, and fiber production) as well as supporting, regulating, and cultural services. Supporting services include soil building and nutrient retention whereas carbon sequestration and water storage are regulating services, and cultural services include spiritual, aesthetic, and educational factors. Perennial grasslands vary greatly in their ability to provide these types of ecosystem services because of differing environmental and management characteristics. We will assess tradeoffs amongst these services, which should allow more informed decision-making and long-range improvements in U.S. agriculture as a result.


Our expected outcomes and predictions include ranking of management strategies in terms of N use efficiency, particularly as it relates to the capture and excretion of N in the environment, ultimately with the goal of adopting strategies/practices that ensure efficient use of N in order to positively influence environmental quality. In addition, this work will facilitate the identification of management strategies and forage systems that minimize N inputs and production costs. Minimizing expensive N inputs (e.g., fertilizers) in forage-based livestock production systems has tremendous potential to enhance their profitability. These impacts are most likely achieved through the development and implementation of a multiple state project. The members of our proposed project represent a geographically diverse set of states from the Southeast through the Midwest and Great Plains and to the Intermountain West. Our objectives of analyzing N efficiency of grassland production systems will be based on a wide range of vegetation types, environments (humid to semi-arid) and levels of management intensity (irrigated pasture to low-input pastures). The expertise, facilities and other resources required to design and conduct the proposed research in the grassland ecology and management area are not found at a single institution. The synergy coming from a multiple state effort in this area greatly enhances the likelihood of success in characterizing N use and developing appropriate management strategies for grassland agroecosystems. Furthermore, the technical feasibility of this type of research is questionable for a single university but becomes realistic when several institutions combine resources and expertise.


Literature Cited


Addiscott, T. M. 2005. Nitrate, agriculture and the environment. CABI Publishing, Cambridge, MA.


Borin, M., and E. Bigon. 2002. Abatement of NO3-N concentration in agricultural waters by narrow buffer strips. Environmental Pollution 117:165-168.


Carpenter, S. R., N. F. Caraco, D. L. Correll, R. W. Howarth, A. N. Sharpley, and V. H. Smith. 1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications 8:559-568.


Eickhout, B., A. F. Bouwman, and H. van Zeijts. 2006. The role of nitrogen in world food production and environmental sustainability. Agriculture Ecosystems & Environment 116:4-14.


Ferm, M. 1998. Atmospheric ammonia and ammonium transport in Europe and critical loads-a review. Nutrient Cycling in Agroecosystems 51:5-17.


Janzen, H. H., K. A. Beauchemin, Y. Bruinsma, C. A. Campbell, R. L. Desjardins, B. H. Ellert, and E. G. Smith. 2003. The fate of nitrogen in agroecosystems: an illustration using Canadian estimates. Nutrient Cycling in Agroecosystems 67:85-102.


Jarvis, S. C., and S. Ledgard. 2002. Ammonia emissions from intensive dairying: a comparison of contrasting systems in the United Kingdom and New Zealand. Agriculture Ecosystems & Environment 92:83-92.


Jenkinson, D. S. 2001. The impact of humans on the nitrogen cycle, with focus on temperate arable agriculture. Plant & Soil 228:3-15.


Kroeze, C., R. Aerts, N. van Breemen, D. van Dam, K. van der Hoek, P. Hofschreuder, M. Hoosbeek, J. de Klein, H. Kros, H. van Oene, O. Oenema, A. Tietema, R. van der Veeren, and W. de Vries. 2003. Uncertainties in the fate of nitrogen I: An overview of sources of uncertainty illustrated with a Dutch case study. Nutrient Cycling in Agroecosystems 66:43-69.


Ledgard, S. F. 2001. Nitrogen cycling in low input legume-based agriculture, with emphasis on legume/grass pastures. Plant & Soil 228:43-59.


Mosier, A. R. 2001. Exchange of gaseous nitrogen compounds between agricultural systems and the atmosphere. Plant & Soil 228:17-27.


Rabalais, N. N., R. E. Turner, and W. J. Wiseman. 2001. Hypoxia in the Gulf of Mexico. Journal of Environmental Quality 30:320-329.


Robertson, G. P., E. A. Paul, and R. R. Harwood. 2000. Greenhouse gases in intensive agriculture: Contributions of individual gases to the radiative forcing of the atmosphere. Science 289:1922-1925.


Rotz, C. A., F. Taube, M. P. Russelle, J. Oenema, M. A. Sanderson, and M. Wachendorf. 2005. Whole-farm perspectives of nutrient flows in grassland agriculture. Crop Science 45:2139-2159.


Sabater, S., A. Butturini, J. C. Clement, T. Burt, D. Dowrick, M. Hefting, V. Maitre, G. Pinay, C. Postolache, M. Rzepecki, and F. Sabater. 2003. Nitrogen removal by riparian buffers along a European climatic gradient: Patterns and factors of variation. Ecosystems 6:20-30.


Scholefield, D., D. R. Lockyer, D. C. Whitehead, and K. C. Tyson. 1991. A model to predict transformations and losses of nitrogen in UK pastures grazed by beef cattle. Plant and Soil 132:165-177.

Singer, J. W., and K. J. Moore. 2003. Nitrogen removal by orchardgrass and smooth bromegrass and residual soil nitrate. Crop Science 43:1420-1426.
Steinfeld, H., and T. Wassenaar. 2007. The role of livestock production in carbon and nitrogen cycles. Annual Review of Environment and Resources 32:271-294.


Tate, K. W., G. A. Nader, D. J. Lewis, E. R. Atwill, and J. M. Connor. 2000. Evaluation of buffers to improve the quality of runoff from irrigated pastures. Journal of Soil & Water Conservation 55:473-478.


Tilman, D., K. G. Cassman, P. A. Matson, R. Naylor, and S. Polasky. 2002. Agricultural sustainability and intensive production practices. Nature 418:671-677.


Turner, R. E., and N. N. Rabalais. 2003. Linking landscape and water quality in the Mississippi river basin for 200 years. Bioscience 53:563-572.


Vitousek, P. M., J. D. Aber, R. H. Howarth, G. E. Likens, P. A. Matson, D. W. Schindler, W. H. Schlesinger, and D. G. Tilman. 1997. Human alteration of the global nitrogen cycle: Source and consequences. Ecological Applications 7:737-750.

Related, Current and Previous Work

The principle objectives of the NC-1021 Multistate Project have focused on the N use efficiency of alternative forage-based systems, identifying and manipulating the management and environmental variables that influence this efficiency, and characterizing/quantifying the forms and amounts of N inputs into forage-based systems. The committee has been successful in coordinating research projects in these areas of study and several manuscripts are in preparation or submitted to scientific journals (e.g., Greenquist et al. 2008). Research proposed for the new project will focus on identifying and managing N inputs and outputs for improved ecosystem services in cool-season pastures.

Nitrogen Use Efficiency
Ecosystem perspective. Nitrogen that is applied to agroecosystems but not removed in livestock or crop biomass is surplus N (Jarvis and Ledgard 2002) because it performs no beneficial agronomic function. Estimates of surplus N in grazed temperate grasslands range from 30 to 50% of N inputs (Caet al. 1995, Ledgard 2001, Janzen et al. 2003), which include fertilizer, exogenous manure, biological fixation, and atmospheric deposition. Surplus N from agroecosystems throughout the Midwest has been identified as the primary cause of periodic hypoxia in the Gulf of Mexico (Rabalais et al. 2002, Turner and Rabalais 2003). Gaseous N emissions from soils contribute the greenhouse effect (Robertson et al. 2000, Mosier 2001) and eutrophication of terrestrial and aquatic ecosystems (Vitousek et al. 1997, Carpenter et al. 1998, Ferm 1998). Janzen et al. (2003) estimated that ~52% of the N entering Canadian agroecosystems was leaving as either plant or animal product, while ~39% entered the environment in ways that facilitated N loss to future agricultural productivity. These authors estimated a relatively even distribution of that lost N to atmospheric and aquatic sinks. Many agronomists are focused on improving N use efficiency of the products, i.e., crop plants and livestock, in order to reduce the amount of N going to the environment and to reduce fertilizer costs to farmers. Unfortunately, tradeoffs exist between N use efficiency and forage quality, e.g., C4 grasses have greater N use efficiency, but this translates to lower crude protein content and therefore lower livestock production on these grasses (Anderson and Matches 1983, Barbehenn et al. 2004).

NC-1021 related research. We calculated a back-of-the-envelope N budget for rotationally grazed plots at the Franbrook Farm in southern Wisconsin. In 2005, these were unfertilized cool-season grass/legume pastures. We estimated forage utilization, which coupled with assumed plant N content, was used to predict the amount of N consumed by grazing beef cattle on rotationally grazed pastures. Assuming 2% plant N content, and that beef cattle return 90% of ingested N as excreta, we estimated that 0.48 g N m-2 y-1 leaving the ecosystem as animal product. Since no fertilizer was applied to these pastures in 2005, we needed only to estimate atmospheric deposition of N and leguminous N fixation. The most recent estimates of N deposition come from a 2004 report by the National Atmospheric Deposition Program, where southern Wisconsin was in the moderately high deposition zone of 0.5 to 1.5 g N m-2 y-1. Nitrogen fixation by legumes is likely important in this system because significant amounts of clover (Trifolium spp.) are found in these pastures. We conservatively estimated that about 10% of the total aboveground net primary productivity (ANPP) (420 g dry biomass m-2 y-1) was clover. Given that estimates of N fixation range from 5 to 10 g N m-2 y-1, we conservatively estimated 2 g N m-2 y-1. We built a N balance calculator to estimate the N efficiency of this agroecosystem based on these N inputs and outputs and calculated ~18% off the N entering the system was leaving as product. While we realize that this was not an ecosystem at any sort of long-term equilibrium, our cursory analysis demonstrates that even low N-input systems are not highly efficient with respect to product. Further, unless soil organic matter was accumulating at a high rate (and our data do not suggest this), much of the N entering as deposition and fixation is likely finding its way out of the ecosystem.

N Input to Pastures
Fertilizer. Differences in the form and amount of fertilizer can significantly alter the amount and fate of N loss from the terrestrial environment (Ledgard et al. 1999, Dobbie and Smith 2003). Perennial crops receive less N as fertilizer and the soils on which they grow retain greater amounts of N than annual row crops (Randall et al. 1997, Huggins et al. 2001). In general forage production in the Midwest is improved with addition of N fertilizer (Jenkinson 2001). Recommendations of 50 to 200 kg N ha-1 by university extension services are common and N fertilizer is usually applied as synthetic ammonium nitrate, ammonium sulfate, or urea.

Historically, most of the recommendations for fertilization of grasses with commercial sources of N have been based on expected increases in forage production relative to the cost of application. Hall et al. (2003) recently reported economically optimum N rates of 26, 32, and 29 kg N Mg-1 of forage harvested for orchardgrass (Dactylis glomerata L.), tall fescue, and timothy (Phleum pratense L.), respectively. Other factors also can influence the appropriate use of N fertilizers. Osborne et al. (1999) found that N source and timing affected recovery of fertilizer N for bermudagrass [Cynodon dactylon (L.) Pers.] fertilized once annually at high rates (112 to 1344 kg N ha-1). Early spring applications of ammonium nitrate at a rate of 112 kg N ha-1 resulted in recoveries in excess of 85%, but recoveries were much lower with late-summer applications. For cool-season grasses, Zemenchik and Albrecht (2002) reported apparent N recoveries of only 17 to 50% for Kentucky bluegrass (Poa pratensis L.), smooth bromegrass, and orchardgrass receiving spilt applications of ammonium nitrate at annual rates ranging from 0 to 336 kg N ha-1. In addition to economic loss, one undesirable aspect of poor recovery of fertilizer N is the potential for leaching below the effective rooting zone (Stout and Jung 1992), and possible contamination of ground water
Supplemental feed. The practice of supplementing livestock diets on pasture with relatively inexpensive co-products, such as distillers grains (DG), is becoming another significant N input into grazing land systems. Supplementing diets of grazing livestock with concentrated feeds (e.g., cottonseed meal) has generally been restricted to the dormant season when nutrient density of the forage limits nutrient intake and performance of the animal. These concentrates are fed at relatively low amounts, generally not greater than the nutrient requirements of the animal. The co-products of grain milling (e.g., distillers grains) are nutrient dense and are an important source of livestock feed. The supply of DG will double or triple in the next few years in such states as Nebraska as the ethanol industry continues to grow. Largely because of the high availability of DG, it is relatively inexpensive and the cost of feeding it on pasture to cattle on a per unit nutrient basis is comparable to the rental cost of grazing land. Research at the University of Nebraska-Lincoln (Klopfenstein et al. 2007) indicates that it is economical to supplement it to yearlings on grass during the growing season. The crude protein content of DG is as high as 32%, far exceeding the crude protein requirements of grazing cattle even when fed as only a portion of the diet on grass pasture. Research at UNL indicates that yearling cattle grazing smooth bromegrass (Bromus inermis Leyss.) pasture excrete as much as 42 kg N/ha more than non-supplemented yearlings over a 5-month grazing season when fed about 2.5 kg DG head-1 day-1 (Greenquist et al., 2008).

Leguminous fixation. Plant species composition is known to affect N dynamics directly, primarily via N2-fixation by legumes (Ledgard 2001, Le Roux et al. 2003). Furthermore, legumes and non-legumes differ in their capacity to take up soil N (Ridley et al. 1990). Legumes contribute to the production of forage within mixed legume-grass swards by recycling biologically fixed N to grass species, and by production of legume biomass (Farnham and George 1994, Zemenchik et al. 2001). Nitrogen replacement values can be calculated as the amount of N fertilizer required for a grass monoculture to yield as much dry matter as the same grass grown in a mixture with a legume. Zemenchik et al. (2001) reported N replacement values of 251 and 269 kg N ha-1 for kura clover (Trifolium ambiguum M. Bieb.) and birdsfoot trefoil (Lotus corniculatus L.), respectively, when grown with orchardgrass in Wisconsin. This is obviously attractive to many forage-livestock enterprises because the need to purchase N fertilizer is reduced or eliminated. Furthermore, the nutritive value of legume-grass mixtures is often improved relative to monocultures of the same grass (Sleugh et al. 2000, Zemenchik and Albrecht 2002). However, these assessments of nutritive value have been confined primarily to estimates of crude protein, and further quantification of N fractions of nutritional significance is critical to efficient use of these forage mixtures.

Deposition. Nitrogen is deposited in wet and dry forms from the atmosphere. For example, N deposition in southern Wisconsin is estimated to be ~5 kg N ha-1 y-1. While the magnitude will differ from site to site in our study, within sites and across treatments N deposition should be constant.

N output from pastures
Surface water, groundwater, and the atmosphere are undesirable N sinks because the forms in which N is found in these environments can contribute to O3 production (Holland and Lamarque 1992), acidic deposition (Ferm 1998), the greenhouse effect (Schlesinger 1997, Robertson et al. 2000), eutrophication of aquatic systems (Carpenter et al. 1998), and human health concerns (Fan and Steinberg 1996). The exception to this is the emission of dinitrogen gas to the atmosphere, which itself is 78% N2. In soils, the potential exists for excreta N to be taken up by plants or microbes for recycling, thereby conserving N within the terrestrial environment.

Gaseous loss pathways. About 40 to 80% of cattle excreta N is in urine, which is 10 to 95% urea (Rodhe et al. 1997). Contact with water and the enzyme urease, which is found universally in feces and soils (Hoult and McGarity 1986), causes rapid conversion to gaseous ammonia (NH3). Ammonia is a strong base whose atmospheric concentrations are highly correlated with a strong odor (Pain and Misselbrook 1991). Once NH3 is airborne, either it quickly dissolves in water forming NH4+ that is redeposited on the landscape (Asman et al. 1998, Aneja et al. 2001) and available for biotic uptake or it is taken up directly by plants from the atmosphere (Ferm 1998).

Nitrous oxide (N2O) is a greenhouse gas whose atmospheric concentration has been rising at an alarming rate since the Industrial Revolution and concomitant intensification of land use for agricultural production (IPCC 2001). Tropical lowlands are generally considered the largest terrestrial source of N2O to the atmosphere (Schlesinger 1997, Silver et al. 2005), but significant emissions come from upland soils in temperate regions (Ambus and Robertson 2006, Flechard et al. 2007), especially agricultural systems where N inputs are high and labile C is available to act as an electron donor for microbial metabolic needs (Robertson et al. 2000, Scheehle and Kruger 2006, Verge et al. 2007). Managed grasslands have received much attention for their ability to sequester C (Conant et al. 2001, Follett et al. 2001, Conant and Paustian 2002, Allard et al. 2007), but tradeoffs in CO2-equivalents via N2O loss may reduce their ability to buffer global climate change (Conant et al. 2005, Flechard et al. 2005, Oenema et al. 2005). Alternatively, grassland soils may serve as a sink for N2O when it is the only electron acceptor remaining under very low redox conditions (for a review see Chapuis-Lardy et al. 2007).

Aqueous loss pathways. Nitrogen returns in animal urine have been shown to have an impact on nitrate (NO3-) leaching (Stout et al. 1997). A recent review ranked grazed pastures similar to arable cropping systems with respect to this phenomenon (Di and Cameron 2002). Work in the northeastern U.S. has shown that NO3- levels can be relatively high in leachate below intensively grazed pastures (Stout et al. 2000a, Stout et al. 2000b) with concentrations exceeding the U.S. EPA maximum surface water standard of 10 ppm NO3-- N. Nitrate concentrations beneath restored native prairie in southern Wisconsin were quite low (<1 ppm NO3-- N) compared to adjacent corn fields (>30 ppm NO3--N) (Brye et al. 2001). Again, rankings among grazing systems have not been made, hindering the ability to make informed management decisions. Stout et al. (2000b) have compared N leaching under various cool-season forage mixtures subjected to MIRG. They found lowest soil NO3- concentrations under orchardgrass compared to ryegrass , while white clover (Trifolium repens L.)-grass mixtures tended to have lower leachate N than alfalfa (Medicago sativa L.)-grass mixtures.
Related NC-1021 research. High stocking densities may promote gaseous losses of N2O from soils to the atmosphere via nitrification and denitrification. We compared N2O fluxes under rotational grazing, continuous grazing, harvesting forage for hay, and no disturbance during the 2005 growing season in southern Wisconsin. Bootstrapped mean N2O fluxes were significantly positive under rotational grazing (21.6 [se=10.3] ¼g N2O-N m-2 h-1), but not significantly different than zero under the other three pasture management treatments or rotationally grazed paddocks. The disparity in fluxes between treatments may be explained by the timing of sampling relative to grazing events, which suggests a brief pulse of N2O emissions post-grazing. To address this issue, we measured N2O fluxes from soils immediately before, during, and for several days after rotational grazing events in eastern Nebraska where three N treatments had been in place for 3 years. These treatments included replicated control plots where no N fertilizer was applied, plots fertilized with synthetic N, and plots where livestock were fed dried distillers grains (DDG)-a feed supplement containing high N. This sampling occurred during a particularly dry period, so results must be viewed cautiously. We found significant N2O consumption in control and DDG plots in the day prior to the grazing event, but no significant fluxes in these 2 treatments thereafter. Plots receiving inorganic N fertilizer had significant N2O emissions, but only 9 and 19 days post grazing, which corresponded to a brief period of rainfall. These preliminary results show how the quality of N inputs can potentially interact with management to affect the direction of N fluxes.

The presence or absence of grazing is known to affect ecosystem-wide N losses in Europe (Hyde et al. 2006, Schills et al. 2006, Allard et al. 2007), Oceania (Ruzjerez et al. 1994, Williams et al. 1998) and rangelands of the western U.S. (Risser and Parton 1982, Frank and Evans 1997), but large information gaps remain with respect to the question: What grazing systems, forage mixtures, and N inputs promote N retention in forage-based agroecosystems of the central U.S.?

Plant/Soil Influences on N Dynamics
Endophytic fungus and tall fescue. Tall fescue infected with the endophyte endophytic fungus N. coenophialum (wild-type endophyte; E+) is widely recognized as a superior and persistent forage (Bush and Burrus, 1988; Hill et al., 1990; 1991; Hoveland, 1993) that grows in areas previously occupied by even lower producing and less nutritious forages or weeds. Fungal endophyte symbionts of tall fescue are known to alter the physiology of individual plants, as well as effect changes in community structure and ecosystem function. Presence of the wild-type endophyte in tall fescue stands reduced soil microbial biomass and mineralization of C (Franzlubbers and Hill, 2005). Also, E+ appears to change the microbial community structure, because microbial biomass N and N mineralization were increased, while nitrate accumulation was reduced (Franzlubbers and Hill, 2005), and microbial activities were lower and soil C and N accumulations were greater under E+ than E- fescue (Franzluebbers et al., 1999). The inhibitory effects of E+ on soil microbial biomass were more pronounced at higher fertilization levels (Franzlubbers and Stuedemann, 2005), indicating the role of soil fertility that must be considered when interpreting effects of E+ in soil dynamics. In contrast, epigeic earthworms grew better on E+ leaf tissue than on E-leaves (Humphries et al., 2001). Thus, not only does E+ affect aboveground plant biomass and ecology, but it also affects belowground ecology and nutrient dynamics.

A recent focus has centered on selecting endophytes that produce low levels of ergot alkaloids, or none, and then matching these endophytes with tall fescue varieties to produce what are now called novel-endophyte infected fescues (Bouton et al., 2002; Roberts et al., 2002; Nihsen et al., 2004). Such NE+ have shown greater persistence than E-, but do not appear to produce symptoms of tall fescue toxicosis (Bouton et al., 2002). Digestibility of NE+ was greater than that of E+, and similar to that of E- (Matthews et al., 2005). Cows grazing NE+ gave birth to heavier calves with faster growth rates than those grazing toxic E+ (Watson et al., 2004); however, cows did not graze the treatment pastures during certain periods of the year. To date there have been no reported studies evaluating wild type vs. NE+ fescue for cows continually grazing those forages over multiple years and no reported studies evaluating using limited acreage of NE+ along with E+ in grazing systems for cows. Acceptance and adoption of NE+ products by cattlemen has been slow, primarily due to expense, but also because of soil type and slope limitations, limited definitive data on cow-calf performance, and the skepticism of long-term persistence of NE+ cultivars.

Objectives

1. 1. Quantify N harvest efficiency of grassland agroecosystems by determining N inputs such as fertilizer, manure, atmospheric deposition, and leguminous fixation and calculating N takeoff as food, fuel, or fiber.
   
2. 2. Evaluate supplementation practices, use of growth promoting compounds, and synchronization of plant nutrient supply and animal requirements to increase N capture or alter mode of excretion by livestock.
   
3. 3. Evaluate fertilizer regimens, harvesting practices, and grazing management interactions with plant communities and soils emphasizing N capture and forage quality.
   
4. 4. Determine the fate of excess N in grassland agroecosystems by estimating key components of nutrient cycles including aqueous and gaseous N losses.
   

Methods

OBJECTIVE 1 (WI, NE, OK, GA) Experiment 1: Nitrogen harvest efficiency in perennial grassland cropping systems. Participating stations (WI, NE) will compare the N harvest efficiency in perennial grassland cropping systems being managed for cellulosic biofuels. Systems to be evaluated may include, but are not limited to, native prairie (25 species or grasses, forbs, and legumes), native prairie grasses (5 species), switchgrass (Panicum virgatum L.) monoculture, Miscanthus monoculture, and an old field community. Each of these treatments is replicated five times as 0.25-ac plots in a randomized complete block design at UWs Arlington Agricultural Research Station. Nitrogen inputs as fertilizer will be tracked whether they are part of the treatment structure or simply part of the agronomic management. Nitrogen deposition will be measured with Whatman #5 filter papers placed at several locations around and within the experiment that are collected at monthly intervals throughout the year. These papers will be ground and analyzed for total N on an elemental analyzer. No manure will be applied and legume fixation of N will be estimated based on cover estimates of legumes and literature estimates of N-fixation by various species. All biomass harvested will be dried, weighed, and ground for total C and N analyses on an elemental analyzer. We will combine estimates of input N and offtake N to calculate N harvest efficiency. Experiment 2: Nitrogen dynamics as affected by grazing management and supplementation strategies (NE). A hypothesis to be tested by this study is that supplementation and management strategies can be used on smooth bromegrass pasture grazed by yearling beef cattle to increase N capture and N use efficiency. This study will be conducted as a continuation of the current NC-1021 project at Nebraska that is comparing the N-use efficiency on fertilized and non-fertilized pastures grazed by supplemented (dried distillers grains) or non-supplemented yearling cattle during the growing season. Supplementing the forage diets of grazing cattle with distillers grains nearly doubled their average daily weight gains but it did not have effect on forage consumption  there was no substitution of forage with distillers grains. Additionally, a considerable amount of N from the supplemented distillers grains passed through the animal to the pasture. Other research at Nebraska suggests that a mixture of distillers grains and wheat straw (a high fiber roughage) when supplemented to grazing cattle can replace a portion of pasture forage and reduce the amount of N excreted on the pasture. Treatments for the proposed study will be (1) smooth bromegrass pasture stocked with yearling cattle at the recommended rate (about 4 AUM/acre) and fertilized with 80 lbs. of N/acre (control), (2) non-fertilized smooth bromegrass pasture stocked at 60% of the control, and (3) non-fertilized smooth bromegrass pasture stocked at the same rate as the control and the cattle supplemented with DDGS, (4) non-fertilized smooth bromegrass pasture stocked at the same rate as the control the cattle supplemented with a mixture of 33% wheat straw and 67% wet distillers grains, and (5) non-fertilized smooth bromegrass pasture stocked at the same rate as the control with the cattle supplemented with a mixture of 67% wheat straw and 33% wet distillers grains. Daily gains of the cattle will be measured and N removal from the pasture estimated with NRC (1996) equations. Diet samples will be collected monthly with ruminally-fistulated cattle. Intakes will be estimated with the use of NRC (1996) energy equations. Intakes of forage and supplements will allow calculation of N use efficiency. The economics of supplementation practices also will be determined to estimate cost benefit ratios of reducing N losses to the environment. Experiment 3: Nitrogen use efficiency in grazing dairies (GA). A nitrogen budget will be created by measuring N inputs via feed and fertilizer and inorganic soil nitrogen. Records of the amounts of N fertilizer applied to each field and manure N coming from outside the field will be estimated based on the amount of time the animals spend outside the monitored field and the feed intake from outside the field. Nitrogen outputs from the field can be estimated by measuring N removed in the form of milk, as well as nitrate leaching and ammonia volatilization. Production records will be kept to measure the amount of milk leaving the farm. Subsamples of milk will be taken, a volume of milk freeze-dried to determine milk solid content and removal. The milk solid subsamples will be acid-digested and analyzed for nitrogen and N removal from milk calculated based upon milk yield and N concentration. Passive flux samplers consisting of two pairs of glass tubes (each tube 100 mm long, 10 mm outer diameter, 7 mm inner diameter) with a coating of oxalic acid on their inner surfaces will be used trap ammonia. The resulting ammonia oxalate is soluble in water, the concentration determined colorimetrically, and the horizontal ammonia flux calculated. To account for nitrate leaching, cup lysimeters will be installed and kept under vacuum to collect samples of water percolating through the 90-cm depth. Water samples collected in the lysimeters will be removed weekly and analyzed for nitrate by a colorimetric procedure. Estimates of water flux through the 90-cm depth will be used together with nitrate concentrations to calculate nitrate leaching losses (kg N ha-1) during the measurement period. Experiment 4: Legume management strategies and warm-season grass production (OK). A replicated field study will be conducted in Oklahoma to compare three different above ground legume biomass management strategies on subsequent annual warm-season grass biomass production. Red clover will be established in the fall on nine 1.3 ha plots. One plot in each block (n=3) will be assigned to one of the following treatments prior to establishment of BMR sorghum in June; 1) above ground red clover biomass will be mechanically incorporated into the soil as green manure; 2) above ground red clover biomass will be harvested as high moisture hay and remove from the plot; 3) above ground red clover biomass grazed by stocker calves to recycle N via feces and urine. The amount of plant biomass produced will be estimated by clipping five 1.0 m2 areas randomly selected/plot. Samples will be hand separated into legume, grass and other, weighed, dried in a forced air oven, weighed again and stored for chemical analysis. Soil samples will be taken at key times to determine changes in N, P and OM content. A N rich strip will be established in each replicate to estimate the amount of available N in each plot for annual warm-season grass biomass production. Within the grazing treatment, partitioning of dietary N into three pools (retained by the calf and excreted as feces or urine) will be estimates by NIRS analysis of feces, calf body weight and rate of growth. Plots within block will remain assigned to the same treatments for the three year duration of the experiment. Data will be analyzed using repeated measures as a randomized complete block design using the mixed model procedure of SAS. OBJECTIVE 2 (AR, ND) Experiment 1: N dynamics and capture in response to calving season and tall fescue type (AR). In Arkansas, a total of 197 Gelbvieh x Angus cows were allocated to five treatments in mid-January 2007. The overall experimental design is a randomized complete block with treatments structured in a 2 x 2 factorial arrangement with a positive control. The main effects are calving season (spring vs. fall) and forage (100% E+ vs. 75% E+ plus 25% NE). Three groups of fall-calving cows (early September  early November calving season; F-NE0) and three groups of spring-calving cows (late February through late April calving season; S-NE0) are grazing E+ throughout the year. Three other fall-calving groups (F-NE25) and three other spring-calving groups (S-NE25) are grazing pasture areas of which 75% is established to E+ and 25% of the area is established to NE. Two additional groups of spring-calving cows are grazing only NE pastures (S-NE100) and serve as positive controls. All E+ and NE pastures are approximately 10 ha. The F-NE25 and S-NE25 pastures have an additional 3.2 ha of NE. The stocking rate for each group is set at 0.8 ha/cow. The F-NE25 and S-NE25 groups graze E+ pastures for much of the year, but are placed on NE for about 60 d in the spring, beginning in mid-April. Moving F-NE25 and S-NE25 cow-calf pairs to NE+ in mid-April should minimize exposure to tall fescue toxins and allow the cows and calves ample time to recover from the minimal exposure prior to breeding (spring-calving) or weaning (fall-calving). Both groups also graze NE in the fall for about 30 d. The S-NE25 cows begin grazing NE near early-September to allow the calves to graze non-toxic forage for approximately 30 d prior to weaning. The F-NE25 cows begin grazing NE+ around the third week of October; approximately one month prior to the initiation of the breeding season to allow those cows to recover from the fall toxin peak prior to breeding. Breeding season should then occur when toxin levels in E+ are low or declining. This will also allow the remaining E+ paddocks to stockpile for grazing during the fall breeding season, thereby providing cows with a high plane of nutrition during breeding (Kallenbach et al., 2003). Each pasture is grazed rotationally using a six paddock system. Hay is harvested from within each replication and offered back to that group of cows during times of low available forage. We will sample 0.2 ha sections of the described pastures in early and late spring and fall. Eight 2.5-cm diameter cores (depth to be determined empirically) will be collected and composited per pasture for soil moisture, pH, microbial biomass C and N, dissolved organic C, dissolved total N, and inorganic N. Five 5-cm diameter cores will be collected for each replicate pasture for soil moisture, bulk density, water-stable aggregate determinations, and total C and N measurements. Dry aggregate stability will be determined first and then water stable aggregates will be determined using the method described in Franzlubbers and Stuedemann (2005). Depending on available resources, earthworm populations will be enumerated after electro-shocking or by excavating a 30 x 30 x 20-cm plot and counting organisms. Earthworms will be identified and then dried at 65oC for 72 hr to obtain biomass on a dry weight basis. Animal performance will be used to determine the economic benefits of NE+ technology using representative, long-term average cattle prices and input costs on an animal-by-animal basis. Using estimates of forage persistence, the economic useful life of NE technology will allow appropriate amortization of pasture investments and thereby allow for the determination of economically optimal investment strategies for cow-calf producers. Economic return comparisons will be used to make recommendations on the basis of expected profitability as well as production and price risk. Soils data will be used to determine the impacts of the different forages and management strategies on N-use efficiency. Experiment 2: Impacts of supplemental dried distiller grains with solubles (DDGS) on N digestion,efficiency of N capture by ruminal bacteria, and N excretion in beef cattle (ND). All animal care, handling, and surgical techniques will follow protocols approved by the North Dakota State University Animal Care and Use Committee before the initiation of the study. Five ruminally and duodenally cannulated steers will be used in a 5 x 5 Latin square. Steers will be weighed at the initiation of the trial and housed in a climate controlled room in individual housed during each adaptation and collection period. Diets will consist of a moderate-quality, smooth bromegrass hay chopped through a 10.16-cm screen, offered ad libitum, free access to water and trace mineralized salt and one of five levels of DDGS. Diet samples will be collected weekly and composited within period. Five days prior to and throughout collections, 8 g of chromic oxide will be dosed ruminally twice daily at 0700 and 1900 via gelatin capsule for use as a digesta flow marker. Total fecal collections will be done. Duodenal samples will be collected over 4 d in a manner that allowed for every other hour in a 24-h period to be sampled. In situ DM, CP, NDF, and ADF disappearance will be determined using Dacron bags containing 5 g of hay or DDGS. In situ forage DM and NDF disappearance will be calculated using the model of Mertens and Loften (1980). In situ forage CP disappearance will be calculated using the non-linear model of Ørskov and McDonald (1979). Liquid dilution rate will be estimated using Co-EDTA as a liquid flow marker. Ruminal fluid samples will be collected with a suction strainer at -2, 0, 2, 4, 6, 8, 10, and 12 h post-feeding, and pH immediately determined with a combination electrode. Samples will also be analyzed for ammonia and volatile fatty acid concentrations On d 7 of each collection period, prior to morning feeding, ruminal evacuations will be conducted to determine ruminal fill. Ruminal contents will be removed, weighed, and sub-sampled. Sub-samples will be obtained by hand mixing ruminal contents in 208 L tubs and taking samples from various locations. A grab sample will be taken for analysis of DM, OM, N, ADF, and NDF. A second ruminal content sample (4 kg) will be taken and 2 L of formalin/saline solution (3.7% formaldehyde/0.9% NaCl) was added for isolation of bacterial cells which was later analyzed for DM, ash, N, and purine. Samples will be analyzed in the laboratory and used to calculate site of digestion, efficiency of N capture by ruminal bacteria, and fecal N excretion as influenced by treatment. OBJECTIVE 3: (KY) Experiment 1: Comparing C storage, N retention, and gas fluxes of tall fescues and Bermuda grass (KY). The objective of this study is to determine differences between cool season tall fescue (endophyte-infected, endophyte-free, and two novel endophyte-infected) and warm season Bermuda forages with regard to aboveground production and carbon storage, nitrogen retention, and soil trace gas fluxes. In Kentucky, monoculture small plots (2m x 2m) of tall fescue (2 novel endophyte, endophyte-infected, and endophyte-free) and Bermuda grass will be established at the Spindletop Agricultural Farm in Lexington, KY. Moderate levels of rotational grazing will be simulated by mowing the plots. Measurements of above- and belowground production, soil trace gas fluxes, ecosystem carbon and nitrogen storage, and plant species richness and abundance will be made throughout the growing season for multiple years after plot establishment. A 15N tracer will be added to small sub-plots within the original plots to monitor nitrogen retention. We will couple this somewhat artificial grazing and small plot experimental design to an already funded, larger scale project being carried out by Drs. Glenn Aiken and Tim Phillips at the Woodford County farm. We will make all the same measurements in their 1 ha pastures of novel endophyte tall fescue and KY31 E+ and E- that will be continuously grazed by cattle at moderately heavy stocking rates. By coupling these two experimental designs, we will be able to determine if our small plot results are similar to larger-scale, more realistic conditions. OBJECTIVE 4 (UT, WI): Experiment 1: Determining N losses in coo-season grass pasture (UT). This study is based at the Utah State University Intermountain West Pasture Facility located near Lewiston, Utah. Tall fescue paddocks (12 meters x 24 meters) were planted in the fall of 2005. Eighteen zero-tension lysimeters have been installed using a hollow-core drill and 38.1 cm diameter PVC pipe to ensure undisturbed soil columns. Nutrient cycling under three grazing treatments: no grazing (NG); deferred grazing (DG); and standard management intensive grazing (MIG) with six replications, will be monitored. These irrigated plots will be grazed for 24 hours, approximately every 6 weeks. In the DG treatment, the last grazing event will be deferred until November, when it is the only treatment grazed. The non-grazed plots will be mechanically harvested for hay production. Ammonium sulfate fertilizer will be applied approximately every 30 days at a rate of 35 kg ha-1, per application. Composite soil samples, 1.8 meters deep, will be taken in the spring and the fall and divided into six samples; 0-15.24 cm, 15.24-30.48 cm, 30.48-60.96 cm, 60.96-91.44 cm, 91.44-121.92 cm, and 121.92-152.40 cm. Each soil sample will be analyzed for available nitrogen, nitrate/nitrite, and phosphorus. Bulk density measurement will be taken in the spring, prior to grazing, and in the fall after the growing season. Weather data will be recorded from a weather station located just outside of the treatment area. Soil water (leachate) samples will be collected using undisturbed monolith zero-tension lysimeters placed one meter deep (Persson and Bergstrom, 1991). This is below most of the roots thereby collecting the leachate as it moves past the root zone, but before it enters the groundwater. Zero-tension lysimeters allow for quantification of the nutrients lost through leaching. Leachate will be collected every two weeks during the growing season, and as close as possible to every two weeks during the winter months. Leachate samples will be collected using a vacuum pump connected to the PEX pipes. Samples will be analyzed for nitrate-nitrite and inorganic dissolved phosphorus. Ammonia emission measurements will be made using dynamic chambers and the equilibrium concentration technique developed by JTI, Sweden (Svensson, 1994). Dynamic chambers will be placed in the field immediately after each grazing event with emission measurements continuing for each plot for five days following. To document the effects of grazing on nutrient cycling, determination of the nutrients in each phase will be made. Herbage dry matter analyses and yield measurements will be utilized to calculate the nutrients being removed in the plant phase. Total nitrogen outputs (recovery in the plant, soil, air, and soil water phases) against the total amount of nitrogen inputs. Experiment 2: N loss in warm-season grasses (WI). Using the same Wisconsin study site as described in Objective 1, net N mineralization and dissolved organic N pools in the surface 15-cm will be estimated in each of the perennial grassland cropping systems [i.e., native prairie (25 species or grasses, forbs, and legumes), native prairie grasses (5 species), switchgrass monoculture, Miscanthus monoculture, and an old field community]. These data will be made on a twice monthly basis. At the same time points, we will sample greenhouse gases (CO2 , CH4 , and N2O) from each treatment using static chambers. Chambers will be fitted over the soil and 3-5 subsamples of the headspace will be made over a 30-min period with nylon syringes. Syringes will be downloaded to evacuated glass vials for transport to the laboratory, where an HP gas chromatograph outfitted with a 30-tray autosampler will be used to determine GHG concentrations. Mass fluxes of each analyte will be calculated by estimating slopes of GHG concentrations over time and scaling by the area and volume of the static chamber. Continuous measurement of soil water and temperature, along with inorganic and organic N estimates, will allow us to seek correlations between environmental and management drivers and N losses from the agroecosystem. To address N loss via leaching, we will install porous cup soil water samplers in one of the 5 blocks. Twice monthly, we will sample soil water and return it to the laboratory for analysis of nitrate, ammonium, and dissolved organic N on a microplate spectrophotometer.

Measurement of Progress and Results

Outputs

• We propose to continue to conduct complementary experiments and simulation modeling to help stakeholders make informed decisions about rural landscapes. Multifunctional farming systems provide multiple ecosystem services. We will assess tradeoffs among these services, which should allow more informed decision-making and long-range improvements in U.S. agriculture as a result. Here, we breakdown outputs from the proposed work by objective:
• Objective 1. We will estimate the harvest efficiency of N for various grassland agroecosystems. We will improve our understanding of how efficiently N applied as fertilizer or manure is used by crops. This should translate to improved management by indicating when and where N application can be reduced without significantly sacrificing crop production. These results will be compared to agroecosystem models for their ability to represent reality. If these models are adequate under a relevant range of conditions and management, they will be promoted as useful tools for farmers and policymakers wishing to fine-tune N management.
• Objective 2. Animal inputs will be measured and the animal response quantified in terms of N offtake and/or excretion. These results will generate important information about more effective management of nitrogen supply, capture, and loss in livestock based agroecosystems. This research should result in identification and management strategies and forage plants that increase N use efficiency and performance of the ruminant animal.
• Objective 3. We will manipulate vegetation communities and their management. Results will provide insight about soil-plant responses and feedbacks stemming from disturbance and nutrient inputs. Again, this is a key nested system within the agroecosystem.
• Objective 4. Loss pathways of N will be quantified, producing data describing the fate of applied N that was meant to be harvested from the systems as plant or animal biomass, but escaping the system. Adopting strategies/practices that ensure efficient use of N, including minimizing N loss, will have a positive influence on environmental quality in the region and the nation as a whole. These data also will be compared to modeled N loss using agroecosystem modeling tools.
• While the outputs for each objective are key to our projects success, perhaps the most important aspect of this iteration of our work is our plan to change our annual meeting agenda. Historically, we have convened our 1.5-d meeting and reported to each other on the past years progress and results. This is rewarding, but leaves little time for true integration of experiments, protocols, and research agendas from different states. Beginning in 2009, we will scrap the oral reports (maintaining written state reports) and engage in a concept modeling effort designed to find the connections, gaps and opportunities in our rather disparate research expertises. This is an effort to truly integrate our work and allow us to fine tune research questions we can address collaboratively. We submitted a collaborative extramural research grant to USDA-NRI Managed Ecosystems in 2007. Reviews indicated that our approach was remarkable in the geographic range but lacked in true integration across states. We believe a solid output of this proposed project will be more collaborative grant writing.

Outcomes or Projected Impacts

• Our expected outcomes and predictions include ranking of management strategies in terms of N use efficiency, particularly as it relates to the capture and excretion of N in the environment, ultimately with the goal of adopting strategies/practices that ensure efficient use of N in order to positively influence environmental quality. In addition, this work will facilitate the identification of management strategies and forage systems that minimize N inputs and production costs. Minimizing expensive N inputs (e.g., fertilizers) in forage-based livestock production systems has tremendous potential to enhance their profitability. These impacts are most likely achieved through the development and implementation of a multiple state project.
• The members of our proposed project represent a geographically diverse set of states from the Southeast through the Midwest and Great Plains and to the Intermountain West. Our objectives of analyzing N efficiency of grassland production systems will be based on a wide range of vegetation types, environments (humid to semi-arid) and levels of management intensity (irrigated pasture to low-input pastures). The expertise, facilities and other resources required to design and conduct the proposed research in the grassland ecology and management area are not found at a single institution. The synergy coming from a multiple state effort in this area greatly enhances the likelihood of success in characterizing N use and developing appropriate management strategies for grassland agroecosystems. Furthermore, the technical feasibility of this type of research is questionable for a single university but becomes realistic when several institutions combine resources and expertise.
• In addition to peer-reviewed journal articles, outreach publications and popular-press articles will be produced locally and regionally for an audience of forage/livestock producers, crop and nutrition consultants, advisors with federal and state agencies, managers of public and private agricultural lands, and policy makers in the state and federal governments. The publications will present strategies/methods of efficiently using N in forage-based livestock production systems.
• Results from these experiments will be synthesized and presented as a component of extant Cooperative Extension Programs located in the various states. Project results and tools/models will be presented in UWs Wisconsin Profitable Pastures program and the Wisconsin Grazing Conference, which attracts several hundred agency personnel and graziers, and UKs Master Grazier School and Master Cattleman programs. In Kentucky alone, 9 sessions of the Master Grazing program occur yearly throughout the state, each containing 30 to 50 producers interested in learning more about good grazing management practices. In Nebraska, results will be delivered to stakeholders through the Hay and Forage Minute (a weekly radio program on the main agriculture stations in Nebraska), the Nebraska Grazing Conference (annual conference that attracts over 300 producers), the Nebraska Ranch Practicum, and the Beef Cattle Production website. Arkansas also has several established conferences and venues for delivery of project results, including the Annual Cow/Calf conference and the Stocker Cattle conference.

Milestones

(2009): Establish new field trials to determine the N dynamics and N use efficiency in various grassland agroecosystems.

(2009): Perform conceptual model development at September meetings in effort to find synergies, overlap, and gaps in research projects. Use this session to work towards submission of extramural grant proposal.

(2010): Work towards standardization of protocols across projects where appropriate.

(2013): Data analyses completed so that manuscripts can be written and submitted for publication and the database developed.

Projected Participation

View Appendix E: Participation

Outreach Plan

The timing and purpose of the proposed project is extremely relevant because N use efficiency and the dynamics of associated soil nutrients are a major focus of production agriculture systems in both the North Central Region and entire country. Furthermore, there is a large audience needing research-based information for making decisions. Results of the project will be made available to intended users, listed in the Outputs section, through a number of avenues. Several of the participants have extension appointments and most participating research scientists work closely with extension specialists in the region.

Results of this project will be incorporated in extension programming of each participating state. Methods used will include extension publications available to producers and extension educators, publication of results in such journals as the Forage and Grazing Land Journal, Crop Management Journal, and Journal of Animal Science which are used by crop and livestock consultants, county/area training sessions, grazing workshops, field days, and individual consultations. Establishment of on-farm demonstrations also will be used in Arkansas and other states after data become available from the research effort. The Cooperative Extension Service in member states has extensive listings of fact sheets for livestock and forage production. Information from this work will be used to develop new fact sheets and to update existing fact sheets on forage and livestock systems. These fact sheets are distributed to producers region wide. Summaries of the research will also be included on the Extension Service websites and the projects website for use by producers and other clientele throughout the region and nation. The websites also will provide access to project updates and publications and other relevant resources. Finally, project results will be available through refereed publications. These publications should be particularly important to scientists and policy makers seeking the most current information on N dynamics and N use efficiency in livestock based agricultural production systems.

Organization/Governance

The technical committee will organize and function in accordance with the procedures described in "Manual for Cooperative Regional Research." The voting members will elect three officers (Chair, Secretary, and Secretary-elect). These officers plus the immediate past Chair (after the first year) will constitute the executive committee. Specific task subcommittees and coordinators will be appointed as necessary to help coordinate activities among states. The executive committee will conduct any necessary business between annual meetings of the technical committee. The Chair will be responsible for presiding over the annual meeting of the technical committee, preparing the meeting agenda, appointing any necessary subcommittees, and for preparing the annual project report for the year ending with the meeting at which he presides. The Secretary will record and distribute the minutes of the annual meeting. At the end of the annual meeting, the Secretary will become Chair and the Secretary-elect will become Secretary.

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