Nutrient exports, in particular phosphorus, are a major problem for Gippsland and many other regions of the world. This thesis investigates the export of phosphorus in overland flow from pasture-based grazing systems in south-eastern Australia. Initially, field-scale monitoring is used to investigate the forms of phosphorus in overland flow with a view to identifying the primary mobilisation process. It is shown that from a well-managed pasture, phosphorus was primarily mobilised as a result of dissolution rather than physical detachment (erosion) processes. Phosphorus in the overland flow is shown to be predominantly in the dissolved reactive form (DRP). It follows that remedial strategies that rely on physically trapping phosphorus entrained in overland flow (i.e. buffer strips and riparian zones) are unlikely to be effective. The field-scale monitoring data are then used to investigate the structure of phosphorus exports. It is shown that the data conforms to a base-plus-increments model. It is proposed that phosphorus exports can be divided into a base or systematic component that results from a particular land use management system, and an incremental or incidental (preventable) component that is the result of particular management decisions, activities or incidents. (For complete abstract open document)

Kikuyu is well adapted to the main milk producing areas of the Southern Cape region of South Africa. The strategic incorporation of different types of temperate grasses into kikuyu pastures can increase the seasonal dry matter production, pasture quality, and milk production attainable from these pastures. To determine whether there is production and economical differences between kikuyu based pasture systems, a trial was conducted on the Outeniqua Research Farm near George. The three pasture treatments, namely italian, westerwold, and perennial ryegrass over-sown into kikuyu, were tested. Forty-five Jersey cows were blocked and cows within blocks were randomly allocated to the treatments. The cows received 9 kilograms of pasture (on a dry matter basis) per cow per day, and four kilograms of concentrate per cow per day. Milk production was recorded daily, and milk composition was determined monthly. The cows were weighed and body condition scored monthly. The perennial ryegrass pasture treatment had a higher milk production per hectare (32288 kg/ha) than the westerwold ryegrass pasture treatment (29761 kg/ha) but did not differ from the italian ryegrass pasture treatment (30446 kg/ha). The italian ryegrass pasture treatment had a higher milk protein percentage than the perennial ryegrass pasture treatment (3.84% vs. 3.64%) but did not differ from the westerwold ryegrass pasture treatment (3.75%). When the three pasture treatments were economically compared, the italian ryegrass pasture treatment had the highest margin over specified costs per hectare (R 36,565.03), followed by the perennial (R 33,889.14) and westerwold (R 29,468.09) ryegrass pasture treatments. From the results it seems that the italian ryegrass pasture treatment is the best choice for a kikuyu based pasture system in the Southern Cape region of South Africa. A high level of concentrate supplementation could increase energy intake of grazing dairy cows, but might also reduce fibre digestion within the rumens of high producing dairy cows. To test this hypothesis, two trials were conducted, one during October and November 2007, and the other during March 2008. In both trials twelve rumen cannulated cows were allocated to four groups. Two groups were allocated to each pasture treatment, namely perennial and westerwold ryegrass over-sown into kikuyu. Within each pasture treatment, one group received 4 kg of concentrate per cow per day, and the other 8 kg of concentrate per day. Pasture was allocated at 9 kg per day (DM). Cows were adapted for ten days, after which ruminal pH, and ammonia nitrogen and volatile fatty acid concentration data was collected. An in sacco study was conducted to determine the neutral detergent fibre degradability. After the data was collected, the two groups within each pasture treatment swapped concentrate levels; were adapted, and the same data as described above was collected. During both trials reductions in ruminal pH were observed when a higher amount of concentrate was supplemented. During the first trial there was a significant increase in the time that the ruminal pH remained below pH 5.8 on the westerwold ryegrass pasture treatment (from 80 minutes when the cows received 4 kg of concentrate per day, to 375 minutes when it was increased to 8 kg of concentrate per day). A decrease in neutral detergent fibre degradability was also seen. During the second trial, the percentage of NDF disappearance decreased from 8.45% over a twelve hour period when 4 kg of concentrate was fed, to 4.51% when 8 kg of concentrate was fed on the perennial ryegrass pasture treatment. From the results it appears that feeding a higher level of concentrate supplementation to high producing dairy cows grazing kikuyu pasture systems has a negative effect on neutral detergent fibre digestion within the rumen. It appears that feeding a moderate level of concentrate supplementation when cows are on pasture based systems is more beneficial to the rumen environment and decreases the possibility of sub-clinical ruminal acidosis when cows grazed ryegrass dominant pastures, but had a less pronounced effect when the dominant pasture specie was kikuyu. Future research could examine the relationship between the level of concentrate supplementation and pasture specie more closely, as it would be interesting to find the optimal ratios for each pasture specie. Copyright / Dissertation (MScAgric)--University of Pretoria, 2009. / Animal and Wildlife Sciences / unrestricted

Tree clearing is practised for greater beef production and hence monetary gains from grazing systems of central Queensland. The high rates of clearing in the past and even recently (577, 000 ha/yr during 1999-2001) were mainly to develop land for pastures. The sustainability of cleared pasture systems over the long-term is questioned. Three major types of tree communities i.e. Eucalyptus populnea F. Muell., E. melanophloia F. Muell. and Acacia harpophylla F. Muell. ex. Benth. were selected on one property in central Queensland to quantify the impacts of clearing on pasture production and composition, and soil properties. The impacts were measured over time-since-clearing (recent (&lt5 years), medium (11-13years) and old (&gt30 years)) in unreplicated cleared pastures in comparison to their replicated uncleared/intact woodland pastures of each tree community. Measures of pasture above-ground biomass production on a single property over time-sinceclearing in cleared systems showed that gains were not sustained over the long-term. The difference in response to clearing between tree communities was evident and important to support the future policy decisions. The impact of clearing on soil properties (physicochemical and biological) was confirmed, and explained the lesser availability of nutrients with time of clearing in cleared pastures. The changes in some soil properties underscored the associated risks and changes in ecosystem functions due to clearing. Less litter was produced at cleared than uncleared pastures, but nutrient release was faster at cleared compared to uncleared systems. The overall effect of clearing in terms of pasture and litter production, and major soil parameters were analysed using multivariate analyses.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The objective of this research was to evaluate of three pasture-based systems with bermudagrass (BG) + 200 kg of N/ha; BG + 100 kg of N/ha and common vetch; BG + 100 kg of N/ha + forage peanut. The experiment was carried out from May 2011 to may 2012. Holstein cows receiving 4 kg-daily complementary concentrate feed were used in the evaluation. The actual mean value of forage on offer was 7.2 kg of dry matter/100 kg live weight. Herbage mass, botanical and structural composition, daily dry matter accumulation rate, forage production, disappearance of forage mass and stocking rate were evaluated. Nine grazing cycles were performed during the experimental period (365 days). The mean value of forage production and stocking rate were 21.05; 21.8 and 16.1 t/ha; 5.1; 5.3 and 4.5 animal units/ha/day for respective pasture systems. Superior result were found on BG + 100 kg of N/ha + common vetch and BG + 200 kg of N/ha pasture systems. / Objetivou-se com essa pesquisa avaliar três sistemas forrageiros constituídos por capim bermuda (CB) + 200 kg de N/ha; CB + 100 kg de N/ha e ervilhaca comum e CB + 100 kg de N /ha + amendoim forrageiro. O experimento foi realizado entre maio de 2011 e maio de 2012. Para avaliação foram utilizadas vacas em lactação da raça Holandesa, que receberam individualmente 4 kg/dia de concentrado. A oferta de forragem foi de 7,2 kg de matéria seca /100 kg de peso vivo. Foram avaliadas a massa de forragem, a composição botânica e estrutural, a taxa de acúmulo diário de matéria seca, a produção de forragem e o desaparecimento de massa de forragem e a taxa de lotação. Durante o período experimental (365 dias) foram realizados nove ciclos de pastejo. O valor médio da produção de forragem e a taxa de lotação foram de 21,05; 21,8 e 16,1 t/ha; 5,1; 5,3 e 4,5 unidades animais/ha/dia para os respectivos sistemas forrageiros. Resultados superiores foram encontrados nos sistemas forrageiros constituídos por CB+ 100 kg de N/ha + ervilhaca comum e CB + 200 kg de N/ha.

The objective of this research was to evaluate three grazing systems with Coastcross-1 (CC) + 100 kg N/ha/year + common vetch; CC + 100 kg N/ha/year + arrowleaf clover; and CC + 200 kg N/ha/year. The experiment was carried out from May 2013 to April 2014. Lactating Holstein cows were used in the evaluation. The grazing method was the rotative stocking, with one day of occupation. Thirteen grazing cycles were performed during the experimental period (313 days). The forage mass, botanical composition, leaf/stem ratio; daily accumulation rate, production and forage intake; grazing efficiency and stocking rate were evaluated. Experimental design was completely randomized with three treatments (grazing systems), three replicates (paddocks) in completely split-plot time (seasons). The average of forage production and stocking rate were 20.8, 17.6 and 19.7 t/ha/year; 7.0, 6.8 e 6.8 animal units/ha/day, respectively. Better results were found on CC + 100 kg of N/ha + common vech and CC + 200 kg of N/ha pasture systems. The presence of the legumes did not affect the structural composition of Coastcross-1, but implies delay in the development of this grass. / Objetivou-se com esta pesquisa avaliar três sistemas forrageiros constituídos por: Coastcross-1(CC) + ervilhaca comum + 100 kg de N/ha/ano; CC + trevo vesiculoso + 100 kg de N/ha/ano e CC + 200 kg de N/ha/ano. O experimento foi conduzido entre maio de 2013 e abril de 2014. Para avaliação foram utilizadas vacas em lactação da raça Holandesa. O método de pastejo utilizado foi o de lotação rotacionada, com um dia de ocupação. Durante o período experimental (313 dias) foram realizados treze pastejos. Foram avaliados a massa de forragem, composição botânica, relação folha/colmo; taxa de acúmulo diário, produção e consumo de foragem; eficiência de pastejo e taxa de lotação. O delineamento experimental utilizado foi o inteiramente casualizado com três tratamentos (sistemas forrageiros), três repetições (piquetes) e parcelas subdivididas no tempo (estações do ano). Os valores médios de produção de forragem e taxa de lotação foram de 20,8; 17,6 e 19,7 t/ha/ano; 7,0; 6,8 e 6,8 unidades animais/ha/dia, respectivamente. Melhores resultados foram encontrados nos sistemas forrageiros constituídos por CC + 100 kg de N/ha + ervilhaca comum e CC + 200 kg de N/ha. A presença das leguminosas não afetou a composição estrutural da Coastcross-1, mas implica em atraso no desenvolvimento dessa gramínea.