Autumn Management of Grass-legume Pasture

Duration of autumn grazing may affect the long-term balance of grass and legume in a sward. Effects of early and late autumn closing dates were studied on productivity and morphology of orchardgrass (Dactylis glomerata) and white clover (Trifolium repens) in replicated grazed swards. Early-closed paddocks continued to accumulate herbage during autumn, resulting in greater winter senescence than late-closed paddocks. Spring-cut herbage mass was not affected by autumn management; however, late closing had significantly more clover than early closing. Early-closed paddocks were grass domlnanl, with few relatively large tillers and few clover growing points compared with late-closed paddocks at the end of each grazing season. Late closing resulted in more than twice as many clover growing points as early-closed. Stolon mass was greater, but starch and total non-structural carbohydrate contents were less during autumn in late- than in early-closed paddocks. Improvement in clover growing point density and stolon mass in the late-closed treatment may favour clover persistence in mixed swards

Seedling Performance Associated with Live or Herbicide Treated Tall Fescue

Tall fescue is an important forage grass which can host systemic fungal endophytes. The association of host grass and endophyte is known to influence herbivore behavior and host plant competition for resources. Establishing legumes into existing tall fescue sods is a desirable means to acquire nitrogen and enhance the nutritive value of forage for livestock production. Competition from existing tall fescue typically must be controlled to ensure interseeding success. We used a soil-on-agar method to determine if soil from intact, living (L), or an herbicide killed (K) tall fescue sward influenced germination and seedling growth of three cultivars of tall fescue (E+, MaxQ, and E−) or legumes (alfalfa, red clover, and white clover). After 30 days, seedlings were larger and present in greater numbers when grown in L soil rather than K soil. Root growth of legumes (especially white clover) and tall fescue (especially MaxQ) were not as vigorous in K soil as L soil. While shoot biomass was similar for all cultivars of tall fescue in L soil, MaxQ produced less herbage when grown in K soil. Our data suggest establishing legumes or fescue cultivars may not be improved by first killing the existing fescue sod and seedling performance can exhibit significant interseasonal variation, related only to soil conditions

Testing terrain: exploring the computational design of natural systems in landscape architecture

While the use of computational design methods in landscape architecture is not uncommon, they are rarely used to develop performance-driven design strategies. Throughout this thesis, I argue that this shortfall stems from disciplinary differences in the design process and designed medium that are not reflected in common computational design tools. The scope for better reconciling these disjuncts is broad, but especially acute when employing design strategies that consider the performance of complex natural systems. Here, the overlap between disciplinary intent and computational capability is significant as natural systems have unique representational, scalar, and temporal complexities and their design forms a core concern of landscape architecture. Computation offers new approaches to managing these complexities, but also introduces new challenges. I investigate these using a design research methodology that foregrounds the tool development as a reflective practice that can span across specific design contexts and general disciplinary concepts. In discursive terms, I identify that the aims of computational design broadly align with those emphasised in contemporary landscape architectural theory: to pursue dynamism through generative systems. This seeming similarity masks a difference whereby the agency of computational design systems acts within the design process while the agency of landscapes systems acts within the world. Using the generative techniques of the former to help design the generative effects of the latter creates representations that posses a novel capacity for explicit precision and projection alongside a corresponding increase in implicit uncertainty. As a result, I suggest that traversing the solution space of these models requires a distinct design strategy that emphasises tendency and feedback over convergence. Framing the use of computational design methods in this manner highlights their value and purpose when modelling complex natural systems. In technical terms, I identify that current computational design platforms tend to employ geometry as the locus of design resolution and data propagation. In doing so they marginalise many informal or aformal landscape conditions and thus limit the scope of modelling. I explore alternatives through a process of tool-making that tests how to create interoperable procedures that each represent different aspects of landscape systems. In many cases, the encapsulation of computational procedures — as both machinic instructions and interface affordances — can enact existing landscape architectural theories of representation, ecology, and emergence. This form of instrumentality offers a distinct, valuable, and under-developed form of disciplinary praxis. However, as I highlight, its execution requires successfully negotiating between two modes of abstraction: the representation of computational procedures as software and the representation of landscape architectural design intent as computational procedures. The strategies I develop to align these two forms of representation help create more accessible and flexible computational methods for modelling complex natural systems

Establishment and production from thinned mature deciduous-forest silvopastures in Appalachia

Paper presented at the 11th North American Agroforesty Conference, which was held May 31-June 3, 2009 in Columbia, Missouri.In Gold, M.A. and M.M. Hall, eds. Agroforestry Comes of Age: Putting Science into Practice. Proceedings, 11th North American Agroforestry Conference, Columbia, Mo., May 31-June 3, 2009.Past research has not adequately addressed effective management and utilization of silvopastures developed from the ubiquitous mature woodlots which comprise 40-50% of small Appalachian farm acreage. While some grazing in woodlots is common, a set of guidelines for optimal utilization of these areas is not. We thinned a white oak dominated mature second growth forested area establishing two 0.5 ha, eight-paddock, orchardgrass-perennial ryegrass-white clover silvopasture replications for comparison with two nearby open pasture replications. After thinning trees, silvopastures were limed, fertilized and seeded. Sheep were fed hay and corn scattered across the area to facilitate removal of residual understory and incorporation of applied materials into surface soil. We measured soil moisture in the top 15 cm using TDR and photosynthetically active radiation (PAR) using a system of 16, 1 m line Quantum Sensors during the subsequent growing seasons of 2004, 2005, and 2006. Paddocks were rotationally grazed by sheep with two 1 m2 herbage mass samples taken prior to animal grazing. There was no significant difference in soil moisture between silvopastures and open pastures however, there was adequate rainfall to prevent drought all three years. The two silvopasture replications had residual tree stands of 14.1 and 15.6 m2 ha-1 diameter breast height allowing 42 and 51 [percent] of total daily incident PAR compared to measurements in the open field. Total forage mass yield from open pasture for 2004, 2005 and 2006 was 9.9, 10.5 and 10.2 t ha-1 respectively and for silvopasture 8.5, 6.7 and 6.7 t ha-1. Silvopastures received 47 [percent] of open pasture incident PAR yet yielded an average of 72 [percent] as much herbage mass as the open pastures. The silvopasture soils were managed for forage production only a few years unlike the open pastures which received roughly a century of better management. Soil limitations may have contributed to decreased forage yield in silvopastures in addition to reduced PAR.C.M. Feldhake, J.P.S. Neel and D.P. Belesky ; USDA-ARS Appalachian Farming Systems Research Center 1224 Airport Road, Beaver, WV.Includes bibliographical references

Winter Grazing in a Grass-Fed System: Effect of Stocking Density and Sequential Use of Autumn-Stockpiled Grassland on Performance of Yearling Steers

Winter grazing can help reduce the need for purchased feeds in livestock production systems, when finishing cattle on pasture. Our objective was to evaluate the influence of stocking density and grazing stockpiled forage on performance of yearling steers during winter. Three grasslands were winter grazed for two years: I, naturalized pastureland, and II and III, sown and managed for hay production during the growing season but grazed in winter. Two stocking densities were used: low 7.41 and high 12.35 steers ha−1. Herbage mass was estimated before and after each grazing event, and disappearance (consumption, weathering, and trampling) was the difference between both. Forage mass and residual differed by stocking density (SD), year (YR), and grazing interval (GI), and disappearance differed by YR and GI. Grass and dead constituents of botanical composition differed by YR and GI. No differences were found for legumes and forbs. CP differed by YR and GI, and NDF and ADF differed only by YR. Steer average daily gain was 0.15 kg d−1 in 2011 and 0.68 kg d−1 in 2012 and varied by YR and GI. Acceptable gains in 2012 may be a product of environmental conditions that influenced herbage mass and nutritive value during stockpile and animal behavior during winter

Epichloë (formerly Neotyphodium) fungal endophytes increase adaptation of cool-season perennial grasses to environmental stresses

Many cool-season grass species have evolved with asexual, nonsymptomatic fungal endophytes of the genus Epichloë (formerly Neotyphodium) of the family Clavicipitaceae. These associations range from parasitic to mutualistic and have dramatic effects on grass host chemistry, increasing resistance to abiotic (drought, soil mineral imbalance) and biotic (vertebrate and invertebrate herbivory, nematodes, plant pathogens, plant competition) stresses. Native endophyte strains produce a range of bioprotective alkaloid and other nonalkaloid secondary compounds, several of them known to have detrimental effects on grazing animals. In the past two decades, epichloid endophyte strains have been selected with marginal or no capacity of producing ergot and/or lolitrem alkaloids. These novel endophyte strains have been introduced to several grass cultivars with the idea to increase grass host resistance to abiotic stresses without hindering grazing livestock, and abiotic stresses to ensure high competitive ability of symbiotic grass cultivars. In this presentation, we discuss mechanisms underlying the competitiveness of epichloid endophyte/grass associations and consequences of endophyte infection for grassland ecosystem functions

Seedling Performance Associated with Live or Herbicide Treated Tall Fescue

Tall fescue is an important forage grass which can host systemic fungal endophytes. The association of host grass and endophyte is known to influence herbivore behavior and host plant competition for resources. Establishing legumes into existing tall fescue sods is a desirable means to acquire nitrogen and enhance the nutritive value of forage for livestock production. Competition from existing tall fescue typically must be controlled to ensure interseeding success. We used a soil-on-agar method to determine if soil from intact, living (L), or an herbicide killed (K) tall fescue sward influenced germination and seedling growth of three cultivars of tall fescue (E+, MaxQ, and E−) or legumes (alfalfa, red clover, and white clover). After 30 days, seedlings were larger and present in greater numbers when grown in L soil rather than K soil. Root growth of legumes (especially white clover) and tall fescue (especially MaxQ) were not as vigorous in K soil as L soil. While shoot biomass was similar for all cultivars of tall fescue in L soil, MaxQ produced less herbage when grown in K soil. Our data suggest establishing legumes or fescue cultivars may not be improved by first killing the existing fescue sod and seedling performance can exhibit significant interseasonal variation, related only to soil conditions

Managing soil fertility in organic farming systems

Complex relationships exist between different components of the organic farm and the quantity and quality of the end products depend on the functioning of the whole system. As such, it is very difficult to isolate soil fertility from production and environmental aspects of the system. Crop rotation is the central tool that integrates the maintenance and development of soil fertility with different aspects of crop and livestock production in organic systems. Nutrient supply to crops depends on the use of legumes to add nitrogen to the system and limited inputs of supplementary nutrients, added in acceptable forms. Manures and crop residues are carefully managed to recycle nutrients around the farm. Management of soil organic matter, primarily through the use of short-term leys, helps ensure good soil structure and biological activity, important for nutrient supply, health and productivity of both crops and livestock. Carefully planned diverse rotations help reduce the incidence of pests and diseases and allow for cultural methods of weed control. As a result of the complex interactions between different system components, fertility management in organic farming relies on a long-term integrated approach rather than the more short-term very targeted solutions common in conventional agriculture

Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland

Legumes play a crucial role in nitrogen supply to grass-legume mixtures for ruminant fodder. To quantify N transfer from legumes to neighbouring plants in multi-species grasslands we established a grass-legume-herb mixture on a loamy-sandy site in Denmark. White clover (Trifolium repens L.), red clover (Trifolium pratense L.) and lucerne (Medicago sativa L.) were leaf-labelled with 15N enriched urea during one growing season. N transfer to grasses (Lolium perenne L. and xfestulolium), white clover, red clover, lucerne, birdsfoot trefoil (Lotus corniculatus L.), chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), salad burnet (Sanguisorba minor L.)and caraway (Carum carvi L.) was assessed. Neighbouring plants contained greater amounts of N derived from white clover (4.8 gm-2) compared with red clover (2.2 gm-2) and lucerne (1.1 gm-2). Grasses having fibrous roots received greater amounts of N from legumes than dicotyledonous plants which generally have taproots. Slurry application mainly increased N transfer from legumes to grasses. During the growing season the three legumes transferred approximately 40 kg N ha-1 to neighbouring plants. Below-ground N transfer from legumes to neighbouring plants differed among nitrogen donors and nitrogen receivers and may depend on root characteristics and regrowth strategies of plant species in the multi-species grassland