Thesis (M.A.) (Language translation) --University of Limpopo, 2007. / See document, page 135. / N/A

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Use of biotechnology in agriculture has become beneficial for many farmers. However, growing of genetically modified crops has it's own specifics. Paper describes and evaluates specifics of use of biotechnologies in agriculture in the Czech Republic.

No Brasil, a área de pastagens ocupa cerca de 180 milhões de hectares. Desses, 70 a 80 % são formados por gramíneas do gênero Brachiaria. O desenvolvimento dos sistemas de produção animal gera a necessidade de novos espécies ou cultivares forrageiros que se adaptem em diferentes condições de clima, solo e manejo. A intensificação desses sistemas exige do produtor ferramentas que o auxiliem no processo de tomada de decisão. Dentre essas ferramentas os modelos de simulação podem auxiliar o controle das etapas de produção. O objetivo deste trabalho foi gerar informações sobre produção de forragem e características morfológicas de quatro genótipos de Brachiaria brizantha (Hochst. ex A. Rich) Stapf (cultivares Marandu, Xaraés, Arapoty e Capiporã) e parametrizar modelos simples de predição da produção de forragem para esses cultivares, buscando assim associar características agronômicas e variáveis ambientais no processo de tomada de decisão. Para isso, foram realizados dois experimentos com delineamento experimental inteiramente casualizado com quatro tratamentos (cultivares) e quatro repetições . No primeiro experimento com parcelas irrigadas, foram avaliados o acúmulo de forragem e a composição morfológica da forragem colhida a cada quatro semanas a 20 cm do nível do solo. No segundo experimento com parcelas em crescimento livre o acúmulo e a composição morfológica da forragem acumulada foram medidos aos 28, 42, 56, 70 e 84 dias de crescimento. No primeiro experimento, as maiores produções acumuladas em nove cortes foram de Arapoty e Capiporã com 8380 e 7130 kg MS ha-1 respectivamente, seguidos de Xaraés e Marandu, com 6210 e 5860 kg MS ha-1 respectivamente. Em crescimento livre, aos 84 dias, os cultivares não diferiram quanto à produção de forragem sendo que, após os 56 dias de crescimento o aumento de massa foi oriundo principalmente do maior acúmulo de hastes e material morto. Visando conciliar maior produção de folhas e menor produção de haste e material morto, Arapoty, Xaraés e Capiporã devem ser cortados quando apresentarem altura entre 45 e 50 cm. Marandu deve ser colhido com altura variando de 35 a 40 cm do nível do solo. O fotoperíodo foi um forte determinante da taxa de acúmulo de forragem dos cultivares. As temperaturas mínimas e médias do ar tiveram menor influência e a insolação não foi significativa. Os valores de R2 dos cultivares Arapoty e Marandu foram 0,64 e 0,59 para Tmin (temperatura mínima) e 0,50 e 0,41 para Tmed (temperatura média), respectivamente. Para os cultivares Capiporã e Xaraés, a influência da temperatura mínima e temperatura média na taxa de acúmulo de forragem foram mais pronunciadas, com R2 de 0,83 e 0,74 para Tmin e 0,53 e 0,63 para Tmed respectivamente. A análise comparativa dos modelos completos e reduzidos revelou coincidência entre os modelos de Tmin, Tmed, GD (graus-dia) e UF (unidades fototérmicas) para um nível de significância de 5%. Para os modelos de fotoperíodo (Nm) a análise demonstrou que os modelos não são coincidentes, indicando que para essa variável, a utilização de um modelo específico para cada cultivar fornecerá melhores estimativas para a taxa de acúmulo de forragem. No crescimento livre os modelos baseados em GD e UF mostram-se viáveis para estimativa do acúmulo de forragem, apresentando altos coeficientes de determinação. A análise comparativa desses modelos revelou que para as duas variáveis climáticas (GD e UF), os modelos específicos (completos) fornecerão melhores estimativas que os modelos genéricos (reduzidos). Quanto ao início do desenvolvimento reprodutivo, os cultivares podem ser classificados como: precoce (cv. Arapoty), médio (cv. Marandu) e tardios (Xaraés e Capiporã). Estudos devem ser conduzidos visando explorar as características morfológicas e fenológicas inerentes a cada genótipo, buscando acima de tudo, conhecer a ecofisiologia e entender os processos de crescimento, desenvolvimento e senescência. / Pastures make up for 180 million ha in Brazil. Of those, 70 to 80% are established with grasses of the Brachiaria genus. The successful development of new animal production systems would benefit from the availability of improved forages that are adapted to a range of conditions regarding climate, soil, and management. Intensification of these systems requires that decision-making tools are available to producers. Among these tools, simulation models may be useful in monitoring and controlling forage production. The objective of this research was to study forage productivity and morphology of four Brachiaria brizantha cultivars ('Marandu', 'Xaraés', 'Arapoty', and 'Capiporã') and to parameterize simple models to predict forage production, in an attempt to associate agronomic traits and environmental variables to support decision-making. Two experiments were carried out using a completely randomized experimental design with four treatments (grass cultivars) and four replications. In the first experiment, irrigated plots were harvested every four weeks at 20 cm and the accumulated forage was characterized in terms of mass and plant part composition. In the second experiment a single regrowth was monitored and both forage mass and plant part composition from these unharvested plots were characterized on days 28, 42, 56, 70, and 84 of regrowth. In the first experiment, total forage accumulation after nine harvests was greater for Arapoty (8380 kg DM ha-1) than for Xaraés (6210 kg DM ha-1) and Marandu (5860 kg DM ha-1), but not higher than that of Capiporã (7130 kg DM ha-1). In the unharvested plots, forage mass was not different across cultivars on the 84th day. After the 56th day, increases in forage mass were accounted for by increases in the stem and dead material components. In managing these grasses, if objectives include maximization of leaf proportion and minimization of stem and dead material, Arapoty, Xaraés, and Capiporã should be harvested at sward heights between 45 and 50 cm. Marandu should be harvested at sward heights of 35 to 40 cm. Daylength impacted herbage accumulation rates markedly, while the low and mean daily air temperatures affected that response to a lower degree. Solar radiation did not affect herbage accumulation rate. The R2-values of the prediction models for forage accumulation rates of Capiporã and Xaraés were 0.64 and 0.59 for the low-temperature (Tmin) model, and 0.50 and 0.41 for the mean-temperature (Tmed) model, respectively. On Capiporã and Xaraés, the impact of both Tmin and Tmed on the rates of forage accumulation was higher, with R2 of 0.83 and 0.74 for Tmin and 0.53 and 0.63 for Tmed, respectively. Comparative analyses of both full and reduced models showed coincidence among the Tmin, Tmed, GDD (growing degree-days), and PU (photothermal units), at the 5% significance level. The daylentgth (Nm) models were not coincident, suggesting that cultivar-specific Nm models are stronger predictors of forage accumulation rate than a single reduced Nm model. The GDD and PU models built with data from the unharvested plots were found to be good predictors of forage accumulation. Analysis showed that for both independent variables, cultivar-specific (full) models give better estimates than the reduced models. With regard to the initiation of reproductive development, Arapoty is an early cultivar, whereas Marandu is medium and Xaraés and Capiporã are late. Further research is needed in order to provide a better description of cultivar morphology and phenology, and, ultimately, to allow for a fuller understanding of the inter-relationships among growth, development, and senescence.

Thesis (M.Sc. (Agriculture)) --University of Limpopo, 2008 / The mineral nutrition of indigenous crop species is not well documented like other known crop species, thus making it difficult for one to know how to plant and maintain the crops. Mmupudu (Mimusops zeyheri), which, happens to be a wild crop, is one of the indigenous trees of interest to the Discipline of Plant Production, University of Limpopo. The current study gives baseline information that will be important in various environmental physiology studies of this plant. Physiological studies will be necessary to assess the importance of “limiting” mineral nutrients in the accumulation of certain mineral nutrients in Mmupudu in relation to its productivity. The experiment was arranged as a 2 x 3 factorial in RCBD, with the first and second factors being time of sampling and location, respectively. The three locations where data were collected were Chuenespoort, Bochum and Sekgosese. In each location, the experiment was replicated 10 times. Data were analyzed using ANOVA and means were separated using the least significant difference test. The two-factor interaction was nonsignificant (P ≥ 0.10) for both pH and electrical conductivity. Soil pH was not affected by time in all three locations suggesting that abscised flowers and fruitlets have no effect on pH. Leaf K experienced an increase of 65% at Chuenespoort and a decrease of soil K after fruiting by 44%. Leaf and soil P decreased after fruiting in all locations as was the case with Cu. Chuenespoort and Sekgosese experienced a decrease in leaf Mn after fruiting while soil Mn decreased in all locations after fruiting. Sekgosese experienced an increase of 25% soil Mg after fruiting, whereas leaf Mg decreased in all locations. / National Research Foundation and the Department of Water Affairs and Forestry

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2008. / Härtill 4 uppsatser.

Der Bericht gibt einen Überblick über den Umfang der bewässerten landwirtschaftlichen Fläche in Sachsen und die bewässerten Kulturarten. Verschiedene Bewässerungsverfahren und -techniken sowie Steuerungsmodelle werden vorgestellt und bewertet. Weiterhin sind die Ergebnisse von Wirtschaftlichkeitsuntersuchungen dargestellt. Die Bewässerungsfläche in der sächsischen Landwirtschaft entspricht nur 0,4 % der landwirtschaftlichen Nutzfläche, zeigt aber auf Grund verstärkter Frühsommertrockenheit eine steigende Tendenz. Gemüse, Obst und Kartoffeln sind die am häufigsten bewässerten Kulturarten. Mobile Beregnungsmaschinen (Schlauchtrommeln) mit Großregnern dominieren, Kreis– und Linearberegnungsmaschinen sind allerdings umwelt– und ressourcenschonender. Für die Optimierung hinsichtlich Wasserverbrauch und Wirtschaftlichkeit stehen Softwarelösungen und Beratungsdienste zur Verfügung. Die Bewässerung ist bei gezielter Steuerung und bei beregnungswürdigen Fruchtarten meist wirtschaftlich.

Diss. Alnarp : Sveriges lantbruksuniversitet, 2005.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.