Kikuyu (Pennisetum clandestinum) is highly productive during summer and autumn and capable of supporting high cattle stocking rates., The winter and spring production of kikuyu, however, is low, while forage quality, and consequently milk production per cow, is also low compared to temperate grass species. The aim of this study was to determine the dry matter yield, botanical composition, nutritional value, grazing capacity and milk production potential of irrigated kikuyu over-sown with Italian ryegrass (Lolium multiflorum var. italicum), Westerwolds ryegrass (Lolium multiflorum var. westerwoldicum) or perennial ryegrass (Lolium perenne) under an intensive grazing system with Jersey cows. Calibrations for the rising plate meter (RPM) were developed for the kikuyu-ryegrass systems. These calibrations were evaluated for seasonal variation, linearity and were also combined over seasons, treatments and years to develop a calibration equation that could be used by dairy farmers in the region. The three kikuyu based pasture systems reached their peak growth rates during different months and seasons. All treatments experienced lower growth rates during winter, while peak growth rates occurred during spring for the Italian ryegrass treatment; summer for the Westerwolds ryegrass treatment and late spring/early summer for the perennial ryegrass treatment. All three treatments had similar total annual dry matter yields (kg DM ha-1) during the first year of the study. However, during year 2 the PR treatment had a higher annual DM production than IR and WR treatments. The ability of the PR treatment to maintain DM production during periods when the other treatments underwent a dip in production (WR during spring and IR during summer) enabled the PR treatment to maintain a higher annual DM production during year 2 than the systems based on annual ryegrass species. As the kikuyu component increased in kikuyu-ryegrass pastures from winter to summer, the DM and NDF content increased, while the ME content decreased. All three treatments were deficient in Ca throughout the study and deficient in P during summer and autumn for high producing dairy cows. The Ca:P ratio was below the recommended ratio of 1.6:1 for high producing dairy cows throughout the study. The grazing capacity of all three kikuyu-ryegrass systems was lower during winter and autumn than during spring and summer. The seasonal grazing capacity of the perennial ryegrass treatment, however, was more evenly distributed than that of the Italian and Westerwolds ryegrass treatments. The perennial ryegrass treatment had a lower butterfat and milk production per lactation than the Italian and Westerwolds ryegrass treatments during both years, but had the highest milk production per ha. The latter was a result of the higher annual grazing capacity achieved by the perennial ryegrass treatment. It was thus concluded that, because kikuyu over-sown with perennial ryegrass supported a higher number of animals and had a more evenly distributed fodder-flow, it allowed for higher animal production per ha than kikuyu over-sown with annual ryegrass varieties such as Italian and Westerwolds ryegrass. The pre-grazing and post-grazing regressions of all three the kikuyu based pastures developed for the RPM differed over seasons and years, primarily due to the change in botanical composition from ryegrass based pastures during winter to kikuyu-based pastures in the summer and the associated change in pasture structure. The post-grazing regressions developed during the study did not have a lower degree of accuracy (R2 values) than the pre-grazing regressions. The generalised RPM regression equations developed for kikuyu-ryegrass pastures (consisting of large data sets pooled over treatments and years) could be of use to farmers in the surrounding area, but are not recommended for research purposes due to the large errors and variation associated with such regressions. In the event that farmers employ these calibrations it is important that pasture type and pasture management practices be similar to those utilised during the study. The decision on which kikuyu-ryegrass system to utilize should be based on the specific conditions prevalent on a particular farm, an economic analysis on and a comparison between the three systems, as well as the particular fodder-flow program requirements within the pasture system. / Dissertation (MSc(Agric))--University of Pretoria, 2010. / Plant Production and Soil Science / unrestricted

Made available in DSpace on 2016-12-08T16:24:20Z (GMT). No. of bitstreams: 1 PGCA14MA150.pdf: 671118 bytes, checksum: 044e392b9e087c5b498a3cdbdfdf9d62 (MD5) Previous issue date: 2014-09-19 / The sustainable management of pastures is in evidence in academic circles, looking for a better association between animal performance and natural resources conservation. The aim of this work was to evaluate cattle pattern displament on kikuiu-grass submitted to different heights and the same level of defoliation of 50%. The experiment was carried out at CAV/UDESC during April and May 2013. The experimental design was a complete randomized block design with three replications and four treatments. The treatments were four pre-grazing heights: 25, 20, 15 and 10 centimeters associated which were associated with a level of defoliation of 50%. Animals stand longer on feeding stations in 20 and 25 cm swards during the initial stage of grazing without differences on the final phase of grazings down. At the early stage, on the lower pasture height (10 cm) the animals walked more and moved more quickly when compared to those managed at higher swards heights (5,25 e 4,0, respectively). There was no difference during the final stage of grazings process. The bite number in each feeding station had a linear reduction with the increase in sward height during the initial phase, being minor on the 25 cm height (27 bites.feeding station-1), with no differences at the final stage. Bite rate (bites. min-1) also presented a linear response by reducing according the increase in pasture height, from 42,02 to 35,18 bites.min-1 in pastures with 10 and 25 cm, respectively. During the initial phase of the grazing down the animals presented diferences in displacement patterns, suggesting that swards heights of 20 to 25 cm (in kikuygrass) present better conditions to foraging search. At the final phase, the animals did not present differences among treatments, suggesting that on using 50% of the grazing down is already over the limit when the objective is to minimize forage searching / O manejo sustentável das pastagens está ganhando cada vez mais espaço na pesquisa mundial, visando maior desempenho animal aliado à preservação dos recursos naturais. O objetivo deste trabalho foi avaliar os padrões de deslocamento de bovinos em pastos de capim-quicuio, submetidos a diferentes alturas de entrada e mesma severidade de desfolhação de 50%. O experimento foi realizado no setor de bovinocultura leiteira do CAV/UDESC, durante os meses de abril e maio de 2013. O delineamento experimental foi em blocos completos casualizados com três repetições e quatro tratamentos. Os tratamentos eram quatro alturas em pré-pastejo: 25, 20, 15 e 10 cm, associados com uma severidade de desfolhação de 50% destas alturas. O maior tempo de permanência dos animais nas estações alimentares foi encontrado nos pastos mais altos, com 20 e 25 cm de altura, na fase inicial de rebaixamento dos pastos, sem diferenças na fase final do rebaixamento. Os animais caminharam mais (P.min-1) e com maior rapidez (passos entre estações) nos pastos mais baixos (10 cm), durante a fase inicial de rebaixamento destes. Já na fase final não foram observadas alterações. O número de bocados em cada estação alimentar na fase inicial do rebaixamento apresentou uma redução linear com o aumento da altura, sendo menor na altura de 25 cm (27,02), permanecendo sem diferenças na fase final. A taxa de bocados (bocados. min-1) também apresentou uma resposta linear, reduzindo conforme o aumento na altura dos pastos, de 42,02 para 35,18 bocados.min-1, nos pastos com 10 e 25cm, respectivamente. Os animais na fase inicial de rebaixamento dos pastos apresentaram diferenças nos padrões de deslocamento, indicando que alturas de dossel de 20 e 25 cm (em pastos de capim-quicuiu) apresentam melhores condições ao processo de forrageamento. Já na fase final, os animais não apresentaram diferenças entre os tratamentos, sugerindo que utilizando a faixa de 50% de rebaixamento dos pastos os animais já encontram dificuldades no processo de busca por forragem, independente de metas de alturas em pré-pastejo

L’attività di ricerca ha previsto il confronto fra due siti inquinati da metalli pesanti e due siti controllo naturali. Contrariamente ai parametri chimico-fisici e ai contenuti in metallo dei suoli, le analisi vegetazionali non hanno evidenziato differenze significative tra i siti. E’ stata necessaria la messa a punto strumentale di tecniche ICP-OES, ED(P)XRF per la calibrazione empirica di un XRF portatile, per le osservazioni puntiformi in situ di suoli e flora ed è stata modificata la metodica ufficiale per le stime della biodisponibilità dei metalli pesanti nei suoli inquinati. 6 specie comuni ai 4 siti sono state valutate per i loro TF e BAF. Viene confermata la specie-specificità del TF e del BAF per il quale è stato elaborato un inedito algoritmo per un corretto confronto tra le specie. Tra le sei specie, Silene Alba ha i migliori TF e BAF. Successivamente, sono state valutate alcune caratteristiche del Pennisetum clandestinum, candidato per la fitodepurazione: tollera le concentrazioni di arseniato tipiche dei suoli inquinati, l’arseniato è un inibitore competitivo del trasporto del fosfato, possiede un’elevata velocità di assorbimento dell’arseniato che accumula nella radice, ma non lo trasloca nella frazione epigea, parte dell’As(V) viene ridotto ad As(III) che viene efflusso dalla radice / The research has provided a comparison between two heavy metals polluted sites and two natural control sites. Unlike physical-chemical parameters and metal content in the soils, vegetation analysis showed no significant differences between sites. The development and optimization of instrumental techniques ICP-OES and ED(P)XRF was necessary to calibrate empirically a portable XRF for soil and flora point observations in situ and the official method for estimation of bioavailability of heavy metals in polluted soil was changed. Six species, common to the four sites, were evaluated for their TF and BAF. Were confirmed the TF and the BAF species-specificity for which it was developed a novel algorithm to obtain a correct comparison among species. Among the six species, Silene Alba has the best TF and BAF. In the second stage, some characteristics of Pennisetum clandestinum, candidate for the phytoremediation, were assessed: it tolerates arsenate concentrations typical of polluted soil, arsenate is a competitive inhibitor of phosphate transport, it has a high uptake rate of arsenic that accumulates in the root, but it doesn’t move in the aboveground fraction and part of As(V) is reduced to As(III), which is efflux from roots.