A bonding and damage constitutive model for lightly cemented granular material

The behaviour of cemented granular material is complicated by the fact that the eventual cemented properties depend on the conditions under which cement hydration (curing) takes place. There are a number of situations in industry where granular materials are mixed with small quantities of cement and deployed in highly transient curing environments. Understanding and predicting the responses in these situations requires a constitutive model where cemented properties are an output, rather than a pre-determined input. This paper presents a constitutive model that is capable of representing the formation and destruction of bonding in weakly cemented granular material in a transient stress environment.</p

Herbage Characteristics as Affected by the Canopies of Dominant Trees in a Savanna of Southern Mozambique

This study surveyed the species composition, forage yield and forage nitrogen concentration of the herbaceous layer 50, 100 and 200% of the canopy radius from the trunks of many-stemmed false thorn, knob thorn, scented thorn and marula trees in a southern Mozambican savanna. Tree species did not affect herbaceous DM yield or species diversity. Neither direction nor distance from the tree trunk affected DM or specific diversity. Crude protein percentages were 15% higher for legumes and 9% higher for grasses at 50% canopy than at 200% canopy. Grasses under the marulas, the only non-legume tree in the study, had 18% lower CP than the average for the other three tree species. Green panic was the predominant grass species under the canopies while no single grass species predominated outside the canopy where common urochloa, Themeda triandra and Aristida spp. were the most common grasses. Vigna spp. and Stylosanthes fruticosa were evenly distributed whereas Tephrosia spp. was found predominantly outside the canopy

Tree Legumes as Sustainable Ecosystem Services in Livestock Systems

Arboreal legumes provide multiple uses in pastures and rangelands. Trees directly and indirectly feed, house, doctor, and warm humans at minimal environmental cost through forage (fodder), timber, biofuel, medicines, as well as edible leaves, pods, and seeds. Leguminous trees, because they foster biological nitrogen fixation (BNF) and acquire deep-soil nutrients and moisture, compete less with herbaceous plants for shallow-horizon soil moisture and nutrients. Their ecosystem services (ES) are generally less obvious and quantifiable. These include converting CO2 to sequestered C and released O2 in N-poor soils where trees without BNF do not thrive. Other ES include shade for animals (including humans), plants, and soil microorganisms that would not otherwise survive in direct sunlight, in dry seasons, or under human mismanagement (overgrazing). Arboreal legumes in semi-arid and arid environments also provide habitat and nutrition to insects (pollinators), mammals, and birds during crucial drought seasons and years, facilitating repopulation to the ecosystem when rainfall returns. Additional ES include crucial ecosystem biological diversity, climatic stability, as well as aesthetic and cultural values. Humans have long recognized their value in natural semi-arid and arid ecosystems such as rangelands but have been slower to incorporate them into cultivated pastures where herbaceous monocultures dominate. Incorporating arboreal legumes with greater regularity into restored rangelands or cultivated pastures would not only increase overall productivity by adding non-herbaceous aerial and deep-soil root biomass but also provide ES that herbaceous species cannot match

The Long Road to Developing Native Herbaceous Summer Forage Legume Ecotypes

Only a handful of well-adapted herbaceous summer forage legumes are currently marketed for drier regions of North America and even fewer are true natives. There is a growing demand for native germplasm in the region as a new generation of landowner attempts to return grasslands to a semblance of their original species and diversity. The objective of this paper is to describe preliminary research results of a grasslands team collecting, studying and promulgating native leguminous germplasm in Texas

Concentration and Bioactivity of Condensed Tannins and Total Phenolics of \u3cem\u3eLespedeza\u3c/em\u3e Species From a Germplasm Collection

Interest in ‘AU-Grazer’ sericea lespedeza (Lespedeza cuneata) as an anti-parasitic bioactive forage has been growing in the United States, but the concentration and bioactivity of tannins and other phenolics from additional accessions of L. cuneata, as well as other Lespedeza species, have not been evaluated. A study was completed to determine the concentration of extractable condensed tannins (ECT), total CT (TCT), total phenolics (TP), and protein-precipitable phenolics (PPP) of 32 accessions of L. cuneata and 16 additional Lespedeza species from a germplasm collection. The plants were established in small pots in a greenhouse and then transplanted into small field plots at the Fort Valley State University Agricultural Research Station in Georgia. Once established in the field, samples from each plot were collected, freeze-dried, and ground for analysis. The ECT and TCT for L. cuneata accessions averaged 6.6 ± 1.4% and 9.1 ± 1.8%, respectively, while TP were 114.8 ± 33.2 mg/g plant material and PPP averaged 81.5 ± 25.3 mg binding CT/g plant material. For other Lespedeza species, ECT ranged from 3.7 ± 1.3 (L. striate) to 8.8 ± 1.3 (L. frutescens) and TCT from 6.0 ± 0.5 (L. japonica) to 10.8 ± 1.3 (L. frutescens). Total phenolics ranged from 45.3 ± 24.0 (L. striate) to 185.8 ± 43.9 (L. virgata), and PPP from 22.1 ± 71 (L. tomentosa) to 89.0 ± 23.6 (L. virginica). All Lespedeza species evaluated in this study had relatively high levels of CT, with several species as high or higher in TP and PPP (bioactivity) than L. cuneata, suggesting potential increased use of these plants as nutraceutical forages for animals

Mechanics of Combining Divergent Herbivores in Cultivated Pastures

Sustainable intensification of cultivated pastures is needed in ruminant production if we are to feed a growing world population expected to exceed 9 billion by 2050. Planting pastures of diverse, and therefore more productive and resilient, plant species has been proposed and researched. Despite illustrative examples from wild grasslands (Hofmann, 1989) and rangelands (Glimp, 1988), very little research and even less application of multiple herbivore species (MHS) in cultivated pastures has followed. We review the specific mechanics of divergent domesticated ruminants and theorize how these could best be combined to sustainably intensify meat, milk and fiber production from cultivated pastures around the world

Habitat selection of the Black-shouldered Kite Elanus caeruleus in agroecosystems of Swaziland

A decline in many African raptor populations may contribute to loss of ecosystem services such as pest control. The Black-shouldered Kite (Elanus caeruleus) stands out as an exception, experiencing range expansions due to its proclivity for agricultural landscapes. We surveyed roads throughout Swaziland agroecosystems for Black-shouldered Kites and looked at habitat selection in a used versus available framework. We found that kites selected for savannahs and tall herbaceous vegetation but did not show preferences for or against land use types. We also found a significant relationship with kite presence and low tree densities in the immediate vicinity of a perch site. Singles, pairs and fledgling kites were observed in agricultural landscape, suggesting that although they are not selecting for these areas in proportion to its availability, they are foraging in it. This may be a boon for farmers who implement ecologically based rodent management programs.United States Department of Agriculture National Institute for Food and Agriculture and Tarleton State University.http://www.tandfonline.com/loi/tost202017-05-31hb2016Mammal Research Institut

Challenges to Domesticating Native Forage Legumes

If ruminant production from cultivated and natural grasslands is to depend less on petroleum-based products, forage legumes must serve as protein sources. Commercially available legumes for warm-dry climate grasslands are, however, very limited and resources available for developing such legumes are inadequate. Indeterminate flowering and dehiscent seed pods combined with the need for specialized seed harvesting equipment are major impediments (Butler and Muir 2012). Warm climates often present environmental challenges such as poor rainfall distribution, extended dry seasons, temperature extremes and aggressive grass species (Muir et al. 2011). Erosion of indigenous knowledge and replacement with inappropriate land management approaches from moist-temperate regions compound the challenges