Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. / Includes bibliographical references (leaves [182]-189). / Microfiche. / xv, 189 leaves, bound ill. 29 cm

Made available in DSpace on 2014-06-11T19:29:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-08-30Bitstream added on 2014-06-13T20:59:59Z : No. of bitstreams: 1 monteiro_s_me_ilha.pdf: 342717 bytes, checksum: ecc9b1356eb2348ccf36b9b0fe797088 (MD5) / O arroz de terras altas era tradicionalmente cultivado em áreas novas, na qual a cultura se estabelecia após a derrubada da vegetação nativa. A utilização deste sistema tende a desaparecer em razão dos altos impactos ambientais causados, obrigando a cultura a migrar para outros sistemas de cultivo, especialmente o sistema de plantio direto, porém, ainda não está adaptado a integrar este sistema. Assim, o experimento foi conduzido durante o ano agrícola 2009/10, em área experimental da Faculdade de Engenharia de Ilha Solteira - UNESP, localizada no município de Selvíria (MS). Os tratamentos foram constituídos pela combinação de plantas de cobertura (milheto, crotalária, guandu, milheto + crotalária, milheto + guandu e área em pousio com vegetação espontânea), fontes de nitrogênio (N-NH4+, N-NO3- e ½ N-NH4+ + ½ N-NO3-) e o fornecimento de molibdênio. O delineamento estatístico foi o de blocos ao acaso, disposto em esquema fatorial com quatro repetições. Foram realizadas as seguintes avaliações: massa seca das coberturas vegetais; cobertura morta do solo; teor de nitrogênio nas folhas; altura de plantas; grau de acamamento; número de colmos e panículas; número de espiguetas cheias por panícula; espiguetas chochas por panícula; massa de 100 grãos; produtividade de grãos; rendimento de engenho. Também os fatores econômicos foram avaliados, sendo eles: custo efetivo e custo total, lucro operacional, renda bruta e índice de lucratividade. As plantas de cobertura em cultivo consorciado (milheto + crotalaria) e solteiro proporcionaram as maiores produtividades de grãos. A aplicação de molibdênio não influenciou os parâmetros avaliados. A aplicação de N-NO3- como fonte de nitrogênio representou maior custo operacional. Os tratamentos com utilização de milheto e crotalária e o seu consorciamento, juntamente... / Upland rice used to be traditionally cultivated in new areas where the crop would establish after the native vegetation was cleared. The use of this system tends to disappear dive to its high environmental impacts, forcing farmers to use other cultivation systems especially no-till. However the crop is not adapted to integrate this system owing to means by which nitrogen is absorbed in the initial phase of the plant’s development, a decisive factor for the low crop’s development. The experiment was carried out during 2009/2010 in an experimental area of Ilha Solteira Engineer University – UNESP, Located in Selviria (MS) The treatments consisted of the combination of cover crops (millet, sunn hemp, pigeon pea, millet + pigeon pea, millet + sunn hemp and area in fallow ground with natural vegetation.), sources of nitrogen (N-NH4+, N-NO3- e ½ N-NH4+ + ½ N-NO3-) and molybdenum supply.. The fallowing evaluations were carried out: dry mass of the cover crops, dead cover of the soil, nitrogen content tenor of the leaves, plant height, lying rate degree, number of stems/stalks and panicles; number of spikelets full of panicle; mass of 100 grains; grains yield, mill yield. The economical factors were evaluated as will: effective cost and total cost operational profit, gross income and profitability index. Cover crops in consortium (millet + sunn hemp) and single (sunn hemp and millet) allowed a higher grains productivity. Molybdenium has not influenced the evaluated parameters. The and also indicated a higher operational cost with the use of N-NO3- as nitrogen source. The treatments using millet and crotalaria and their consortium, together with... (Complete abstract click electronic access below)

The effect of global warming on methane (CH₄) and nitrous oxide (N₂O) emissions from agriculture was investigated and simulated from a soil warming experiment. Experiments were designed and installed in a temperature controlled greenhouse. The relationships between elevated temperatures and CH₄ and N₂O emissions were determined and calculated as the Q₁₀s of production, emission and oxidation. A study of the populations of methanogens and methanotrophs at a range of soil temperatures was performed based on soil molecular DNA analysis. This study showed that global warming would increase CH₄ emissions from rice agriculture and that the resultant emissions will be potentially large enough to cause changes in the present atmospheric concentrations. This research also showed that this increase was most evident for soil temperatures below 30⁰C, above which emissions decreased with increasing temperature. The seasonal average Q₁₀s of CH₄ emission, production, oxidation, methanogen and methanotroph populations were found to be 1.7, 2.6 and 2.2, 2.6 and 3.8, respectively, over a temperature of 20-32⁰C. Considering that the processes of CH₄ production and emission are similar to those in natural wetlands, which is the largest source of atmospheric CH₄, the contribution of this feedback is likely to cause a significant increase to the present CH₄ atmospheric budget if the current global warming trend persists over the next century. The Q₁₀s of N₂O emissions and production were 0.5-3.3 and 0.4-2.9, respectively. The low Q₁₀ values found for N₂O suggest that although global warming will have a direct impact on the production and emission rates. Nevertheless, the magnitude of the impact of global on both CH₄ and N₂O emissions from agriculture is likely to vary from one region to another due to the spatial variations in agricultural soil temperatures and the likely changes in the global regional distribution of water resources (water tables, rainfall patterns), water management practices and the responses of terrestrial CH₄ and N₂O sources such as natural wetlands and plants.

Rice production in Sub-Sahara Africa is hampered by drought stress, low farmer adoption of improved varieties, un-adapted germplasm, problems of crossability between species and problems of efficient emasculation. This study was initiated to: (1) determine farmer preferences for rice varieties and production practices, (2) identify drought tolerant parental lines for use in interspecific crosses, (3) determine crossability between different rice species, (4) identify drought tolerant interspecific segregants from crosses, and (5) study the efficacy of ethrel and gibberrilic acid (GA3) as chemical hybridising agents. Participatory rural appraisal (PRA) was conducted in Sikasso region in the month of September 2005 to determine farmer preferences for varieties and production constraints. A total of 125 rice farmers from 10 villages participated. This study found that farmer preferences for rice traits did not coincide with the breeders' objectives and trait preferences varied across ecologies. In upland and lowland rice ecologies, the most preferred characteristic was short duration. In the lowland tall plants was most preferred and short duration trait ranked second. Long duration ranked as the second most preferred trait after yield in the irrigated rice ecology. The estimated grain yield reduction was 60% due to drought stress from all ecologies. Sixteen genotypes including seven Oryza glaberrima Steud, six interspecific (0. saliva x 0. glaberrima) inbred genotypes and two improved 0. saliva L. subsp Gaponica) genotypes, with OS 6, as drought tolerant check were screened for drought tolerance at the vegetative stage during the dry seasons of 2004 and 2005 at Samanko research station, in Mali. Most of the genotypes could be regarded as exhibiting drought tolerance and avoidance mechanisms for most of the morpho-physiological characters under study. High selection index was observed for WAB 450-I-B-P-103-HB in the two season experiments. Drought stress tolerance (little leaf drying) was significantly correlated with leaf rolling, leaf area index, and plant height. Fast drought recovery was significantly correlated with drought tolerance, tiller number and leaf area index. Effects of genotypes, environment and their interactions were significant for tiller number, root dry weight and relative leaf water content. The most stable genotype was RAM 3 for tiller number and relative leaf water content. Thirteen genotypes were selected on the basis of these traits for rice hybridisation. A factorial arrangement involving three levels of gametocide concentrations and five application stages of the female rice parent was undertaken for each gametocide ethrel and GA3 for two seasons. Per cent empty spikelets and male sterility increased with concentration of ethrel. Male sterility induction of 41.5% and 42.8% at 2000 ppm was achieved in 2004 and 2005, respectively, while at 4000 ppm male sterility induction was 40.5 % and 46.1% in 2004 and 2005, respectively. The best application stage of ethrel that induced highest male sterility was at P4 (panicle primordium differentiation + spikelet primordium differentiation) of 46.6% in 2004 and 49.2% at PI (panicle primordium differentiation) in 2005. There was no measurement on GA3 for sterility due to lodging. Total male sterility was not achieved therefore, these gametocides could not be recommended for use as hybridising agents. Crossability was studied in four groups: group A (0. glaberrima x 0. saliva), group B (0. glaberrima x Interspecific), group C (Interspecific x 0. saliva) and group D (Interspecifics x Interspecific). High percent seed set was obtained in group D of 19.08% and group A had 9.29%, in group B the seed set was 11.26% and group Chad 6.62 %. The three best combiners as female parents based on percentage seed set were CG 14 (0.glaberrima), WAB 450-IBP-I05-HB and WAB450-I-B-P-I03-HB (interspecifics), and for male parents were NERICA 3, NERICA 2 (interspecifics) and WAB 375-B-9-H3-2 (0. sativa). Genetic components of variance and heritability estimates were studied in F3 and F4 generation progenies from North Carolina II design mating scheme. General combining ability (GCA), manly due to female and specific combining ability (SCA) were significant for tiller number, plant height and specific leaf dry weight indicating that additive and non-additive genetic effects controlled these traits. Heritability estimates for drought tolerance and leaf rolling were highly significant for all the populations examined, ranging from 0.32 to 0.72 and 0.22 to 0.56, respectively. Drought tolerance expressed as little leaf drying was significantly associated with less leaf rolling, larger leaf area index, and taller plants. Some genotypes and progenies such as WBK 39-B-B-B, WBK 30-B-B and WAB 450-I-B-P-I03-HB were identified as being drought tolerant with the ability to recover quickly from drought stress. There was a strong desire for tall plants and short duration rice in upland and lowland ecologies, while high yield was preferred in irrigated ecology. Therefore, the best breeding strategy would be ecosystem breeding targeting each of the ecologies. Screening for secondary traits that have been identified to be significantly associated with rice grain yield could be used for direct selection for grain yield under drought stressed conditions. Progenies identified, as drought tolerant would be considered for use as source germplasm in breeding that target Sikasso region and any other similar ecologies. This study therefore suggested that participatory research approaches that involve all stakeholders in rice production would be valuable in identifying and generating drought tolerant and adoptable rice cultivars in the tropics of Africa with considerable impact on food security. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.