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COVER CROPPING FOR SUSTAINABLE CO-PRODUCTION OF BIOENERGY, FOOD, FEED (BFF) AND ENHANCEMENT OF ECOSYSTEM SERVICES (ES)Brodrick L Deno (9867779) 18 December 2020 (has links)
Increasing food, feed, fiber, biofuel production on decreasing amounts of arable land while simultaneously enhancing ecosystem services is challenging. Strategic inclusion of winter rye (<i>Secale cereale</i>) for biomass, silage, grain and Kura clover (<i>Trifolium ambiguum</i>) living mulch into existing Midwestern cropping systems may offer alternative economic income for farmers without displacing or reducing yields of primary crops. Research was conducted at the Purdue Water Quality Field Station (WQFS) where net balances of water, carbon, nitrogen, and radiation can be measured, and greenhouse gas (GHG) emissions are monitored. The agronomic performance of a corn-soybean rotation and continuous corn (controls) were compared to novel systems that included the use of rye cover cropping and Kura clover co-cropping. Rye was harvested for biomass/silage at heading immediately followed by corn or soybean planting. Continuous corn receiving 69 kg N ha<sup>-1 </sup>was planted into an establishment of Kura clover sod. Controls included these same systems without the rye or clover. GHG samples were taken via the static chamber method and tile-drained water sub-samples were collected, analyzed for nitrate, and load losses calculated. Biomass composition was determined and used to calculate herbage theoretical ethanol (EtOH) yields. Cereal rye did not significantly decrease corn or soybean grain yield. Averaged across years, Kura clover significantly depressed corn grain yields by nearly 70%. Kura clover significantly reduced flow-weighted tile drainage nitrate (NO<sub>3</sub><sup>-</sup>) concentrations, however cereal rye did not. Reductions in flow-weighted tile drainage nitrate (NO<sub>3</sub><sup>-</sup>) concentrations were found to largely occur during Quarter two (April, May, June). Cover crops did not significantly reduce annual tile drained NO<sub>3</sub><sup>-</sup> load losses in most cases, however, they did significantly reduce annual N<sub>2</sub>O emissions. Cumulative annual CH<sub>4</sub> emissions were not significantly altered. Annual CO<sub>2</sub>emissions were higher after the introduction of Kura clover and not significantly altered following the introduction of cereal rye. Averaged across years, theoretical ethanol yields in the Kura clover system produced 2,752 L EtOH ha<sup>-1</sup>, whereas EtOH production in cereal rye systems ranged from 3,245 to 4,210 L EtOH ha<sup>-1</sup>. Theoretical ethanol yields of continuous corn and rotational controls ranged from 2,982 to 3505 L EtOH ha<sup>-1</sup> for these same systems without the cereal rye of Kura clover. These data suggest that a multipurpose approach to cover crop inclusion can provide both environmental and economic advantages worthy of consideration.
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Productivity and physiological responses of winter annual forage legumes to planting date and short-term rotation with forage sorghum for sheep production under no-till system in Limpopo ProvinceMotshekga, Lesego Minah January 2022 (has links)
Thesis (Ph.D. Agriculture (Plant Production)) -- University of Limpopo, 2022 / Livestock has evolved to serve as the foundation and backbone of human well-being, and it is an important component of South Africa's agricultural sector. The small stock such as sheep (Ovis aries) in Limpopo province has remained a significant and multifunctional livelihood strategy for the majority of the rural and resource-poor people. Factors such as population growth, urbanization, rising per capita income and changes in consumer tastes and preferences are all contributing to gradual increases in livestock product consumption and demand. According to the 2019 Abstract of Agricultural Statistics, South Africa is an importer of sheep and sheep products. If the sheep production industry in the province could pursue this opportunity and realize its full production potential then increased production could stimulate economic growth and development, particularly from the communal and smallholder sector. Objective one of the study seeks to describe the demographic and socio-economic characteristics of communal and smallholder sheep farmers, identify sheep feeding practices and describe the constraints that hinder the sustainable productive growth of communal and smallholder sheep systems.
Data were collected from one hundred and twenty (120) sheep farmers using a structured questionnaire across three agro-ecological zones of Limpopo province. Results revealed that overall, the majority of sheep farmers were males (78%) and farmers were above 60 years old (48%). Mean sheep flock size differed significantly between communal (24.74) and smallholder (62.36) farmers. Indigenous crossbreeds were the dominant breed kept by communal (86%) and smallholder (77%) farmers. The majority of communal and smallholder farmers (90% and 96%, respectively) reared their sheep under an extensive system with rangelands as the main source of feed. As a result, they experience a critical feed gap during June and September, the mid-winter to early spring until the first rains. The findings of the study revealed that feed shortages and diseases were ranked as the first and second production constraints by sheep farmers in both the production systems. In rangeland-dependent feeding systems, insufficient feed to meet animal demands create a feed gap, which is a critical factor that limits sheep productivity and causes
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land degradation through overgrazing. Improved forages have been widely advocated as a critical step toward resolving this challenge. However, the adoption and utilization of improved technologies such as on-farm forage legume production by these farmers have been very low, contributing to the province's low sheep productivity. An extension of objective one of this study used primary data which was collected from a sample of 120 sheep farmers to determine the factors that influence the adoption of on-farm forage legume production and the perceived barriers to adoption by communal and smallholder sheep farmers in the Limpopo province. A Probit regression model and Principal Component Analysis (PCA) were used to analyze the data. The study revealed that the adoption of on-farm forage production by communal and smallholder sheep farmers is influenced by several factors, including gender, farming experience, knowledge of forage legume production, source of income, membership in farmer associations, access to extension services and farm size. Farmer perceived barriers to adoption of on-farm forage legume production identified by this study were low institutional support, lack of resources, lack of knowledge, shortage of water and objectives of the farmer. It is therefore recommended that intensive and high-quality extension support in partnership with industry associations and stakeholders is required for communal and smallholder farmers to improve forage technology awareness, training and promote on-farm forage production to transform communal and smallholder sheep feeding practices.
In the face of climate change, identifying forage species with a high potential to mitigate winter feed gap challenges under more variable climatic conditions is critical. Trifolium and Vicia species are forage legumes well known for producing high-quality forage, particularly protein, which is deficient in the majority of feed resources used for sheep feeding during the winter season. Climate change-induced stresses from rising temperatures, which these winter annual forage legumes are likely to face, necessitate agronomic and breeding approaches to improve their adaptability. Lack of knowledge on how these climate change mitigation approaches influence the productivity of winter annual forage legumes in the Pietersburg Plateau of Limpopo province prompted objective two of this study. A three-year field experiment laid in a split-split plot design with four replications was conducted to measure the effects of planting date, cultivar and harvest stage on the physiological traits associated with biomass production, forage quality, nodulation activity and
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nutritive value of annual clover and vetch species. The results showed that the planting date and harvest stage had a significant effect on leaf gaseous exchange and biomass production. A non-significant effect of planting date on nutritive value was observed. Intercellular CO2 concentration, transpiration rate, stomatal conductance, instantaneous water use efficiency and intrinsic water use efficiency in cultivars increased with delayed planting, while a decrease in photosynthetic rate, shoot DM, root DM and nodule DM was observed. Overall among the cultivars, Resal, Alex, Elite, Laser and Dr Baumans showed more consistency in terms of leaf gaseous exchange, biomass production and quality traits under planting date 1 and varying harvest stages.
Investment in the year-round fodder flow establishment with high-quality forages is important in supporting sustainable sheep production. Forage legume-grass rotation systems are important not only for green fodder production of high crude protein, mineral and vitamin content throughout the year but also for enhanced soil fertility to reduce the nitrogen (N) fertilizer requirements. Accurate estimates of forage yields on the farm are required for fodder flow planning to ensure the seasonal distribution of fodder throughout the year. Objective three of the study was a no-tillage, short-term rotation experiment conducted to determine the growth and nutritive value of forage sorghum, planted after the winter annual forage legumes in combination with nitrogen application and to validate the performance of the APSIM-grain sorghum crop model in simulating forage sorghum growth and biomass production under different N rates. The treatments were planting date (January and February) and N source from inorganic N fertilizer (0 kg N ha-1, 60 kg N ha-1, 120 kg N ha-1, 180 kg N ha-1) and forage legume N residues (Alex, Capello, Dr Baumans, Elite, Hanka, Laser, Linkarus, Opolska, Resal and Timok) arranged in a randomized complete block design with four replicates. The findings of this study showed a significant response of forage sorghum growth and nutritive value to planting date. Delayed planting reduced plant height (11%), stem diameter (18%), LAI (6.7%), chlorophyll content (18%), NDVI (2.5%), photosynthetic rate (38%) and biomass production (8%). Delayed planting further reduced crude protein, acid detergent fiber and N yield. Nitrogen source from inorganic N at 60 kg N ha-1, 120 kg N ha-1, 180 kg N ha-1 and residual N from annual clover and vetch cultivars had a significant effect on morphological, physiological, yield and nutritive value parameters of forage sorghum.
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Generally, legume N residue effects on all the studied parameters of forage sorghum were similar to the inorganic N fertilizer of 60 kg N ha-1. However, the effects differed widely according to the species and cultivar of the legume. Resal, Laser, Elite Capello and Dr Baumans N residue consistently showed greater effects than other legume residues. They consistently outperformed inorganic 60 kg N ha-1 on the most measured parameters. The results confirm that annual clover-forage sorghum and vetch-forage sorghum rotation have huge potential to reduce the cost and negative environmental effects associated with inorganic N use in forage prediction systems. Regarding the evaluation of the potential of the APSIM grain legume model to simulate forage legume DM and plant height, in general, the model performed well and accurately in predicting the shoot dry matter accumulation and plant height under 0 kg N ha-1, 60 kg N ha-1 and 120 kg N ha-1. However, it underestimated both these parameters at 180 kg N ha-1 implying that the application of N up to 180 kg N ha-1 is not necessary. APSIM-grain module was able to accurately predict forage biomass production under N rates up to 120 kg N ha-1 and it is therefore considered reliable to support the N nutrition in the forage sorghum fodder production systems. / University of Limpopo, research office under the UCDP program and National Research Foundation-Thuthuka
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När kvinnan vinner : En filmanalys om maktrelationer / When the woman is the winner : A film analysis of power structuresLemark, Cajsa January 2024 (has links)
The purpose of this study is to examine in which way power structures are played out in the 2022 movie The Menu (2022). Five categories of scenes with the main focus on the main character have been selected to be analyzed through a narrative movie analysis with focus on intersectionality regarding class and gender in relation to the theory of the final girl. Every scene is to be explained and then, together with the main narrative, analyzed through theories of marxism, Bourdieu’s capital theory and Clover’s final girl in focus. The study concludes that the power structures of class and gender is played out through the main character by her using her looks as a beautiful and young woman as well as her working class background in the service industry as an escort to her advantage in getting to know the male antagonist. By doing so she can, unlike the other guests which are all upper class, escape the safe death they all face. / The purpose of this media production is to be used as a base for discussion during seminars regarding honor related violence and oppression. The mateiral is the be used during education for proffesionals in the field of social work.
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Detekce a identifikace virů pomocí sekvenování nové generace (NGS)PODRÁBSKÁ, Kateřina January 2017 (has links)
Next generation sequencing is a modern method applied in plant virology for sensitive detection of previously characterized and novel pathogens without any preceding knowledge of them. In this study three novel and two already described viruses were detected by de novo assembly of Illumina single-end reads ( Hi-Seq 2500 system) from total poly(A) enriched RNA of diseased red clover (Trifolium pratense) and indicator plant (Nicotiana occidentalis 37B). The complete genomic sequence of novel Red clover carlavirus A (RCCA) was determined from Illumina reads, 5´, 3´ RACE, cloning, RT-PCR and Sanger sequencing. The presence of RCCV was also confirmed in mechanically inoculated tobacco plant.
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Contamination atmosphérique par les hydrocarbures aromatiques polycycliques : toxicité et devenir du phénanthrène dans des systèmes sol-plante-microorganismes / Atmospheric contamination bu polycyclic aromatic hydrocarbons : toxicity and fate of phenanthrene in soil-plant-microorganism systemsDesalme, Dorine 22 June 2011 (has links)
Les hydrocarbures aromatiques polycycliques (HAP) sont des polluants organiques persistants potentiellement mutagènes et cancérigènes. Leur transfert de l’atmosphère vers les écosystèmes, notamment vers les plantes, conditionne leur entrée dans les chaines alimentaires mais les modalités de ce transfert restent encore mal connues. L’objectif de ce travail était donc de caractériser le transfert et d’identifier les effets biologiques des HAP atmosphériques sur un système sol-plante-microorganismes symbiotiques.Un dispositif expérimental a été conçu afin de recréer en laboratoire une pollution atmosphérique par les HAP avec comme HAP modèle le phénanthrène (PHE). Le dispositif a fait l’objet d’une validation et d’une calibration élaborée de manière originale par une double approche mêlant l’expérimental à la simulation mathématique. Les niveaux d’exposition en polluant (150 µg m-3), contrôlés par des échantillonneurs passifs, se sont avérés pertinents par rapport aux conditions in situ. Ce dispositif a donc été utilisé pour exposer durant un mois des microsystèmes sol-plante-microorganismes au PHE par voie atmosphérique.Les différentes études ont mis en évidence un transfert du PHE depuis l’atmosphère vers tous les compartiments du microsystème, avec une accumulation majeure vers les feuilles de trèfle ou de ray-grass (respectivement 170 et 70 µg g־ ¹MS) et un transfert phloémien vers les racines est suggéré. Chez le trèfle, la mycorhization n’a pas été affectée, tandis que le nombre de nodules actifs a diminué de manière significative. Contrairement aux racines, la biomasse aérienne du trèfle a été significativement affectée (environ – 25%) par l’exposition au PHE atmosphérique, suggérant un impact sur le métabolisme carboné de la plante. Une expérience de marquage des trèfles au ¹³C-CO2 a effectivement montré un impact négatif du PHE atmosphérique sur la croissance, l’allocation de biomasse et l’allocation carbonée. Pour conclure, ces études ont permis non seulement de caractériser les effets biologiques et physiologiques des HAP atmosphériques sur les végétaux mais également de proposer l’utilisation du potentiel mycorhizien comme indicateur de pollution atmosphérique par les HAP. / Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants potentially mutagenic and carcinogenic. Transfer from the atmosphere to ecosystems, especially to plants, conditioning their entry into food chains, but the terms of this transfer are still poorly understood. The aim of this study was to characterize the transfer and identify the biological effects of atmospheric PAHs on soil-plant-symbiotic microorganisms.An experimental device was designed to recreate in the laboratory air pollution with phenanthrene (PHE) as a model PAH. The device was been validated and a calibration developed in an original way by a dual approach combining the experimental mathematical simulation. The levels of exposure to pollutant (150 mg m־³), controlled by passive samplers, were relevant with field conditions. This device has been used to expose a month of the soil-plant micro-organisms in the PHE through the air.Various studies have demonstrated a transfer of PHE from the atmosphere to all compartments of the microsystem, with a major accumulation to leaves in clover or ryegrass (respectively 170 and 70 µg g ־¹ dry weight) and a phloemic transfer to the roots is suggested. In clover, mycorrhization was not affected, while the number of active nodules decreased significantly. Unlike roots, aboveground biomass of clover was significantly affected (approximately – 25%) by exposure to air PHE, suggesting an impact on the carbon metabolism of the plant. A labelling experiment with ¹³C- CO2 in clover has actually shown a negative impact of PHE air on growth, biomass and carbon allocation.In conclusion, these studies have not only characterized the biological and physiological effects of atmospheric PAHs on plants but also proposed the use of mycorrhizal potential as an indicator of air pollution by PAHs.
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Effet d'une sécheresse extrême sur le fonctionnement de l'écosystème prairial : évaluation du rôle tampon de la composition et de la diversité végétale par approche expérimentale / Extreme drought effect on grassland ecosystem functioning : assessment of buffering effect of plant composition and diversity by experimental approachHernandez, Pauline 29 November 2016 (has links)
Les prairies permanentes représentent l’une des principales formes d’utilisation des terres en Europe. En France, elles représentent près de 40% de la Surface Agricole Utile (SAU) et restent le support de nombreux systèmes d’élevage. Les scénarios actuels de changement climatique prévoient tous un accroissement de la variabilité climatique qui pourrait se traduire par un accroissement des évènements extrêmes, notamment en ce qui concerne les épisodes de sécheresses. Ces événements extrêmes sont de nature à altérer la structure et le fonctionnement des prairies et en conséquence la capacité de ces écosystèmes à rendre des services agricoles, écologiques et environnementaux. Une meilleure compréhension des mécanismes de résistance et de résilience des communautés végétales prairiales face à l’occurrence de sécheresses extrêmes s’avère donc cruciale pour évaluer la stabilité du fonctionnement de l’écosystème prairial et notamment du service de production qu'il supporte. Cette thèse a pour objectif principal d’évaluer la capacité des prairies permanentes à maintenir leur fonction de production face à un événement de sécheresse extrême. Elle s’appuie sur une démarche expérimentale en mésocosmes sous conditions semi-contrôlées permettant de caractériser le rôle de la composition et de la structure des communautés végétales prairiales dans la résistance et la résilience à la sécheresse des prairies. Pour évaluer l’importance de la composition et de la diversité fonctionnelle dans la réponse des communautés végétales, des monocultures et des mélanges associant graminées et une légumineuse ont été sélectionnés. L’originalité de ce travail réside dans une approche d’écologie fonctionnelle permettant d’appréhender l’importance des interactions entre espèces dans la réponse de la communauté via l’analyse de traits morphologiques et physiologiques mesurés conjointement dans les compartiments aérien et souterrain de la végétation. Cette étude a mis en évidence le rôle prépondérant du Trèfle blanc (Trifolium repens) dans la modulation de l’impact d’un événement de sécheresse extrême sur la production de biomasse de mélanges prairiaux. Si aucun effet tampon de la composition et de la structure de la communauté n’a été mis en évidence durant la sécheresse, la présence et l’abondance de Trèfle blanc a été reliée à une meilleure récupération à long terme de la production de biomasse des mélanges. Après l’extrême, une surproduction des mélanges associant graminée et Trèfle blanc a ainsi été attribuée à des mécanismes de facilitation azotée et de complémentarité verticale de niches au niveau racinaire pour l’acquisition de l’eau. Nous avons ainsi souligné l’importance de la croissance des racines profondes pour la mise en place de complémentarités fonctionnelles entre espèces et donc pour le maintien de la production sous sécheresse extrême. L’événement de sécheresse affecte durablement le comportement des racines et de ce fait les mécanismes sous-jacents de l’effet bénéfique du Trèfle blanc sur la production aérienne. Par ailleurs, notre étude a mis en évidence le rôle majeur des interactions hétérospécifiques dans l’expression de traits intraspécifiques liés aux stratégies d’acquisition des ressources et par conséquent dans la régulation de la performance des espèces sous sécheresse extrême. Nous montrons que la structure et la composition fonctionnelle de la communauté végétale apparaît essentielle dans la régulation de la réponse à un événement de sécheresse extrême. Dans notre étude, la récupération de la production de biomasse aérienne après sécheresse extrême repose essentiellement sur la présence de Trèfle blanc et la mise en place d’interactions positives entre espèces. La prise en compte de la modulation par les interactions interspécifiques du comportement des espèces en mélanges s’avère nécessaire dans la prévision de la production des prairies sous climat futur. (...) / Permanent grasslands are one of the main forms of land use in Europe. In France, permanent grasslands represent around 40% of Utilised Agricultural Land and support many animal-based farming systems. Current climate change scenarios predict increased climate variability that could result in an increase in extreme events such as drought episodes. These extreme events can significantly alter the structure and functioning of grasslands, with implications for their capacity to provide agricultural, ecological and environmental services. Improved understanding of the resistance and resilience mechanisms of grassland plant communities exposed to extreme drought is therefore critical in order to assess the stability of grassland functions, in particular that of biomass production. This thesis aims at assessing the capacity of permanent grasslands to sustain their production when exposed to an extreme drought event. The study uses an experimental approach and semi-controlled conditions to investigate the role of community composition and functional diversity for drought resistance and resilience in grassland mixtures. Monocultures and mixtures combining grasses and legumes were selected to test the importance of composition and functional diversity for plant community responses during drought and up to a year after the end of water stress. The originality of this work is the use of a functional ecological approach to assess the impacts of species’ interactions via measurements of plant morphological and physiological traits both above- and below-ground. This study demonstrates the importance of white clover (Trifolium repens) in modulating the impact of extreme droughts on biomass production of grassland mixtures. Community composition did not have a buffering effect on biomass production during the drought event but the presence and abundance of white clover in mixtures was linked to higher recovery of biomass production in the long-term. After the extreme drought event, overyielding in mixtures combining grass and white clover could be attributed to mechanisms of nitrogen facilitation and vertical root complementarity for water uptake. Results also show the importance of deep root growth for the establishment of functional complementarity between species and the maintenance of biomass production under extreme drought. Drought had lasting effects on the root system patterns and thus on the underlying mechanisms of the positive effect of white clover on aboveground production. Moreover, this work highlights the key role of heterospecific interactions in the expression of intraspecific traits related to resource acquisition strategies. Heterospecific interactions are thus an important driver of the species performance under extreme drought.We show that the structure and functional composition of the plant community in simplified mixtures are critical for modulating grassland responses to an extreme drought event. In our study, the recovery of aboveground biomass production is mainly related to the presence of white clover and the establishment of positive interactions between species. Changes of species behaviour in response to heterospecific interactions should be taken into account to better predict grassland biomass production under future climatic conditions. From an applied perspective, accounting for the key role of white clover and the inherent variability or neighbour-induced plasticity of intraspecific traits appears important to adapt mixtures of species or varieties to more intense and frequent drought events.
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Determinants of the introduction, naturalisation, and spread of Trifolium species in New ZealandGravuer, Kelly January 2004 (has links)
Two conceptual approaches which offer promise for improved understanding of biological invasions are conceptualizing the invasion process as a series of distinct stages and explicitly incorporating human actions into analyses. This study explores the utility of these approaches for understanding the invasion of Trifolium (true clover) species in New Zealand. From the published literature, I collected a range of Trifolium species attributes, including aspects of global transport and use by humans, opportunistic association with humans in New Zealand, native range attributes, habitat characteristics, and biological traits. I also searched historical records to estimate the extent to which each species had been planted in New Zealand, a search facilitated by the enormous importance of Trifolium in New Zealand's pastoral agriculture system. Regression analysis and structural equation modelling were then used to relate these variables to success at each invasion stage. Fifty-four of the 228 species in the genus Trifolium were intentionally introduced to New Zealand. Species introduced for commercial agriculture were characterised by a large number of economic uses and presence in Britain, while species introduced for horticulture or experimental agriculture were characterised by a large native range area. Nine of these 54 intentionally introduced species subsequently naturalised in New Zealand. The species that successfully naturalised were those that had been planted extensively by humans and that were well-matched to the New Zealand climate. A further 16 species (from the pool of 174 species that were never intentionally introduced) arrived and naturalised in New Zealand without any recorded intentional aid of humans. Several attributes appeared to assist species in unintentional introduction-naturalisation, including a good match to the New Zealand climate, a large native range area, presence in human-influenced habitats, a widespread distribution in Britain, and self-pollination capability. The 25 total naturalised species varied greatly in their current distributions and in the rates at which they had spread to achieve those distributions. Species that had spread quickly and are currently more widespread had been frequent contaminants in the pasture seed supply and have a long flowering period in New Zealand. Other biological traits and native range attributes played supporting roles in the spread process. Attributes facilitating success clearly varied among invasion stages. Humans played a dominant role at all stages of this invasion, although biological traits had increasing importance as a species moved through the invasion sequence. My findings suggest that incorporation of human actions and the stage-based framework provide valuable insight into the invasion process. I discuss potential avenues by which these approaches might be integrated into predictive invasion models.
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An agronomic evaluation of subterranean clover cultivarsScott, W. R. January 1969 (has links)
The permanent pasture based on a grass-clover association and utilised in situ by grazing stock is the basis of New Zealand's chief primary industries. Although white clover is the main legume species used for this purpose its production and persistence in the drier eastern areas of the South Island often leaves much to be desired. In such situations subterranean clover may provide a useful alternative. Subterranean clover has been a very useful species in the past and will probably continue to play an important role in the future, provided the most climatically adapted cultivars are grown. The aim of the field trials was to evaluate the productive performance of several subterranean clover cultivars in Canterbury. Because of the big influence of seed yield on subsequent production and persistence in annuals, this aspect was also investigated. The subterranean clover cultivars Geraldton, Yarloop, Woogenellup, Clare, Mt. Barker and Tallarook were evaluated under cutting in swards at two sites in Canterbury.
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Pasture responses to lime and phosphorus on acid soils in Natal.Miles, Neil. January 1986 (has links)
No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1986.
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Mixed grazing of sheep and cattle using continuous or rotational stockingKitessa, Soressa Mererra January 1997 (has links)
Two consecutive experiments were conducted to test a hypothesis that mixed grazing outcome is influenced by the type of stocking system applied. The objective of both experiments was to investigate the influence of co-grazing with sheep on cattle liveweight gain (LWG) under continuous (C) and rotational (R) stocking, where sheep weekly liveweight change under the two stocking systems was kept similar. In experiment I nine yearling heifers (266 ± 4.5 kg liveweight) and 27 ewe hoggets (54±0.9 kg liveweight) were continuously stocked for 19 weeks on an irrigated perennial ryegrass-white clover pasture (2.95 ha) maintained at a sward surface height (SSH) of 5cm by adding or removing additional animals in a fixed ratio (1: 1 W⁰.⁷⁵ cattle:sheep). An equal area of pasture was rotationally stocked by a similar group of animals where they received a new area of pasture daily and also had access to the grazed area over the previous 2 days. The size of the new area provided daily was such that the weekly liveweight change of rotationally co-grazed sheep was equal to that of those continuously co-grazed with cattle. Similar groups of animals were used in the second experiment with additional group of 9 heifers grazed alone on C and R pastures. Liveweight of animals was recorded weekly and final fasted weight was determined after 24-hour total feed restriction. SSH on both treatment swards was recorded daily. There were three intake measurement periods spread over the trial period. Organic matter intake (OMI) was predicted from the ratio of N-alkanes in faeces and herbage. Diet composition was determined by dissecting oesophageal extrusa samples. Grazing behaviour (bite rates and grazing time) were also recorded. The mean SSH for C pasture was 5.1±0.09 cm. Overall pre- and post-grazing SSH for R pasture was 15.9 ±0.12 and 5.6 ±0.07 cm, respectively. As determined by the protocol average daily LWG of sheep was similar between C and R (147 (±5.8) vs 138 (±6.7) g day⁻¹; (P>0.05). In contrast, cattle continuously stocked with sheep grew 200 g day⁻¹ slower than those rotationally stocked with sheep (800 (±41.6) vs 1040 (±47.7) g day⁻¹, P<0.0l). R heifers achieved 30 kg higher final fasted liveweight than C heifers (350 vs 381 kg; P<0.01). Overall LWG per ha was also 6 % higher under R than C stocking (674 vs 634 kg ha⁻¹). The OMD of both sheep (73.5 vs 75.8 %) and cattle (75.8 vs 78.0 %) diets was similar under continuous and rotational stocking. There was no significant difference OMI data also concurred with the L WG data (Cattle: 7.94 vs 6.31 (±0.32) kg day⁻¹ (P<0.05); sheep: 1.40 vs 1.44 (±0.04) kg day⁻¹ for Rand C treatments, respectively). There was no difference in clover content of cattle diet under C and R treatments. C heifers had higher number of bites per minute than R heifers (62 vs 56; P<0.05). Proportion of heifers seen grazing (every 15-minute) during four 24-hour observations was greater on C than R pasture (0.44 vs 0.31 (±0.03); P<0.05). The similarity coefficient between sheep and cattle diet was 0.61 and 0.76 under C and R stocking, respectively. The lower daily LWG of C heifers was attributed to (a) the lower SSH under C than R stocking and/or (b) the inability of cattle to compete well with sheep where there is small, continual renewal of resources (C) in contrast to a large periodic renewal under R stocking. This experiment showed that the outcome of mixed gruing can be influenced by the stocking system chosen. But it was not possible to apportion the difference in LWG of cattle between mixed grazing per se and the difference in mean grazed sward height (5.1 for C vs 10.8 cm for R). A second experiment was conducted to determine the relative performance of cattle co-grazed with sheep (CS) and grazed alone (CA) under each stocking system. Hence, there were four treatments. CA- continuous stocking (CA-C), CS- continuous stocking (CS-C), CA- rotational stocking (CAR) and CS- rotational stocking (CS-R). A total area of 4.42 ha was allocated to each stocking system. Under C stocking, 2.95 ha (2/3) was assigned to CS-C and 1.47 ha (1/3) to CA-C, and SSH on both treatments was kept at 4 cm by adding or removing extra animals. Under R stocking, CA-R and CS-R grazed side by side separated by an electric fence. They were given a fresh area daily, the size of which was varied such that the weekly LW change of R sheep was equal to that of the C sheep. CA-R received one-third of the new area though the size was adjusted regularly to achieve the same post-grazing SSH with CS-R. Measurements included: weekly liveweight change, OMI (two periods) and diet composition (using N-alkanes). The mean SSH of CA-C and CS-C swards was 4.27 and 4.26 (±0.02) cm, respectively. CA-R and CS-R swards had mean pre-grazing SSH of 14.9 and 15.2 (±0.08) cm and post-grazing heights of 4.87 and 4.82 cm (±0.03), respectively. The proportion of areas infrequently grazed was higher for CA-C than CS-C swards (0.22 vs 0.17, respectively). C and R sheep daily LWG: 155 (±0.6) and 147 (±0.7) g, and OMI: 1.96 and 2.04 (±0.ll) kg, respectively, were not significantly different. They also had similar diet composition. In comparison, CS-C heifers grew only at 69 % of the daily LWG achieved by CS-R heifers (706 vs 1028 (±72) g; P<0.05). LWG of CA-C and CA-R was 916 and 1022 (±72) g day⁻¹, respectively. The difference in LWG between CS-R and CS-C (D₁) heifers was due to difference in mean sward height, stocking system and mixed grazing, while D₂ (difference in LWG between CA-R and CAC) was due to difference in mean sward height and stocking system. D₁-D₂ (the effect of stocking system on mixed grazing) was 216 g and made up 67 % of the total difference between CS-R and CS-C. There was a significant stocking system-species mixture interaction in the final fasted LW achieved by heifers. Final fasted LW was significantly lower for CS-C than CA-C heifers (283 vs 323 (±9.7) kg), but did not differ between CS-R and CA-R (332 vs 330 (±9.7) kg, respectively). The digestibility of diet OM was similar for both continuously and rotationally stocked sheep (84.4 vs 83.2 %, respectively). Cattle diet OMO was 76.5, 74.7, 79.4 and 77.8 for CA-C, CS-C, CA-R and CS-R respectively (P>0.05). Differences in OMI followed a similar pattern to daily LWG. Mean daily OMI was 8.98, 6.24, 8.80 and 9.45 (±0.40) kg for CA-C, CS-C, CA-R and CS-R, respectively. Clover content of the diet of CA-C heifers was three times higher than that of CS-C heifers (30.7 vs 10.4 % OM; P<0.05); there was no difference in clover content of diets of CS-R and CA-R heifers (21.5 vs 23.9 % OM, respectively). In both stocking systems LWG per ha was higher on CA than CS treatments. These results suggested that the disadvantage of selective clover grazing by sheep outweighed the advantages of sheep grazing around cattle dung patches under continuous stocking. Under rotational stocking, rapid diurnal changes in sward conditions probably limited selective grazing by both sheep and cattle such that there was no disadvantage to CS cattle. The results do not provide a basis for recommending grazing cattle with sheep rather than cattle alone, but do provide some basis for recommending co-grazing of sheep and cattle using rotational rather than continuous stocking.
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