Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-06-22T17:46:39Z No. of bitstreams: 1 2015 - Wilk Sampaio de Almeida.pdf: 2008285 bytes, checksum: 164bf0a934ccde49c7e387496f6b7960 (MD5) / Made available in DSpace on 2017-06-22T17:46:39Z (GMT). No. of bitstreams: 1 2015 - Wilk Sampaio de Almeida.pdf: 2008285 bytes, checksum: 164bf0a934ccde49c7e387496f6b7960 (MD5) Previous issue date: 2015-02-23 / CNPq / Inadequate soil management practices associated with bare soil are the main factors that promote hidric erosion in tropical countries such as Brazil. In this study were evaluated soil and water losses, vegetation index, water infiltration into the soil and the adjusted Kostiakov-Lewis, Horton and Philip models to estimate soil water infiltration rate in four cropping systems on a Red Ultisol. The systems studied were exposed or bare soil (SE), soybeans grown under conventional tillage (PC), soybean grown under no-tillage (NT) and established pasture without cattle trampling (PA) in six seasons. Every 20 days after the soybean?s sowing digital photographs were taken to estimate soil coverage ratio. Also, simulated rainfall at the parcels was measured using a portable sprinkler infiltrometer (InfiAsper) calibrated to apply intensity of rainfall of 60 mm h-1. Soil losses ranged from 3.10 to 11.40 and 0.03 to 0.19 Mg ha-1 h-1 in the SE and PA, while water oscillated from 300.60 to 555 and 62.8 to 229.4 m3 ha-1 h-1 in the SE and PD, respectively. Soil losses decreased with increasing vegetation cover ratio, which at the PA had a maximum value of 98.1%. The initial effect of soil under conventional tillage in cropping systems is temporary, which makes them susceptible to erosion. The models were adjusted using the volume of water that was infiltrated during the corresponding time interval. In the PD system was obtained the highest infiltration rate (TIE). There was no difference between the SE and PC TIE. The best fit found is for the Horton?s model in systems with vegetal cover and without soil tillage. / As pr?ticas inadequadas de manejo do solo associadas ? condi??o de solo descoberto s?o os principais fatores que intensificam a eros?o h?drica em pa?ses de clima tropical como o Brasil. Neste estudo foram avaliadas perdas de solo e de ?gua, o ?ndice de cobertura vegetal, a infiltra??o de ?gua no solo e o ajuste dos modelos Kostiakov-Lewis, Horton e Philip para estimativa da taxa de infiltra??o de ?gua no solo em quatro sistemas de cultivo em um Argissolo Vermelho distr?fico. Os sistemas estudados foram solo exposto ou descoberto (SE), soja cultivada sob preparo convencional do solo (PC), soja cultivada sob plantio direto (PD) e pastagem estabelecida sem pisoteio animal (PA) em seis ?pocas. A cada 20 dias a partir da semeadura da cultura da soja foram tomadas fotografias digitais para estimativa do ?ndice de cobertura do solo e tamb?m simuladas chuvas nas parcelas em campo com o infiltr?metro de aspers?o port?til (InfiAsper) calibrado para aplicar intensidade de precipita??o de 60 mm h-1. As perdas de solo variaram de 3,10 a 11,40 e 0,03 a 0,19 Mg ha-1 h-1 no SE e PA, ?gua de 300,60 a 555 e 62,8 a 229,4 m3 ha-1 h-1 no SE e PD, respectivamente. As perdas de solo diminu?ram com o aumento do ?ndice de cobertura vegetal, que em PA teve valor m?ximo de 98,1%. O efeito inicial do preparo convencional do solo nos sistemas de cultivo ? tempor?rio, o que os torna suscept?veis ao processo erosivo. Os modelos foram ajustados com os dados de volume de ?gua infiltrada por intervalo de tempo correspondente. No sistema PD foi obtida maior taxa de infiltra??o est?vel (TIE). N?o h? diferen?a na TIE do SE e PC. O melhor ajuste verificado ? para o modelo de Horton em sistemas com cobertura vegetal sem revolvimento do solo.

Made available in DSpace on 2014-08-20T14:36:55Z (GMT). No. of bitstreams: 1 Dissertacao_ Noemi_ Lunkes.pdf: 245441 bytes, checksum: 4d602cb74ba37d804b403b79f628e9fa (MD5) Previous issue date: 2006-11-20 / The inadequate management of cultural tecnics as well as the continuous use of the soil, can alter soil physical, chemical and biological properties. In order to increase crop productivity and to lower production costs without changing the soil physical and chemical properties, a field experiment with alternative cropping systems is being conducted in an Albaqualf soil since 1985 in the Embrapa Clima Temperado lowland experimental field in Capão do Leão, Rio Grande do Sul State, Brazil. with the objective of evaluating soil fertility in the different cropping systems, after 19 years of experiment conduction, soil samples have been collected at 0.0 2.5; 2.5 5.0; and 5.0 20.0 cm deepness as well as at the top of the B horizon. The following systems have been evaluated: 1 Traditional system: one year rice (conventional soil preparation) and two years fallow; 2 Continuous system with rice (conventional soil preparation) and weed control with herbicide; 4 Rice x soy rotation with conventional soil preparation; 5 Rice x soy x maize rotation with conventional soil preparation; 6 Rice x with ryegrass rotation under no tillage; 7 Rotation of no tillage rice x soy under conventional preparation; and 8 Natural vegetation (control). The following parameters were analyzed: organic carbon by the Walkley-Black method, as described in Alison (1965); total nitrogen, exchangeable cations ( Ca, Mg, Na, and Al), water pH and SMP index, as described by Tedesco et al. (1995); the extractable phosphorus and potassium by the Mehlich method described by Tedesco et al. (1995); the potential acidity (H + Al) extracted with calcium acetate 1 N (pH 7), titrated with 0.0125 NaOH N, as described in Embrapa (1997); The total cation exchange capacity (CEC) and base saturation were calculated from the sum of exchangeable cations and potential acidy and % of base cations in the CEC. All the variables were submitted to variance analysis and Duncan test, using the Winstat software (Machado et al. 2001) for statistical Analysis. The results showed that the intensive use of the soil with annual cultures in rotation with flooded irrigated rice changed soil organic matter and nitrogen contents in the upper layers compared to the control; the affect of the liming in the acidity soil parameters (pH, V%, Ca, and Mg) after 14 years of application is being depleted, but it is still detectable; the systems exhibit the contents of extractable phosphorus and potassium by the Mehlich method proportional to the amounts of these nutrients applied along the years. / O manejo inadequado das práticas culturais como também o uso contínuo do solo pode provocar alterações nas propriedades físicas, químicas e biológicas do solo. Para tentar aumentar a produtividade e diminuir os custos de produção, alterando o mínimo possível às características físicas e químicas, estão sendo testados sistemas alternativos de cultivo, de um planossolo num experimento de campo na área experimental da Embrapa clima temperado, no Capão do Leão desde 1985. Assim, tendo por objetivo avaliar a fertilidade do solo nos diferentes sistemas de cultivo, após 19 anos de condução do experimento, foram coletadas amostras nas profundidades 0-2,5; 2,5-5; 5-20 cm e TB (topo do horizonte B). Foram avaliados os seguintes sistemas: 1 - Sistema tradicional de cultivo: um ano arroz (preparo convencional) e dois anos com pousio; 2 - Sistema de cultivo contínuo de arroz (preparo convencional) e controle de invasoras com herbicida; 4 - Sucessão arroz x soja com preparo convencional do solo; 5 - Rotação arroz x soja x milho com preparo convencional do solo; 6 - Sucessão de azevém x arroz sob plantio direto; 7 - Sucessão arroz sob plantio direto x soja sob preparo convencional do solo; e 8 - Solo mantido em condições naturais (testemunha). Nas amostras foram analisados os seguintes parâmetros: carbono orgânico foi determinado pelo método Walkley-Black conforme Alison (1965); nitrogênio total, cátions trocáveis (Ca, Mg, Na, Al, e Mn), pH em água e índice SMP determinados conforme os métodos descritos por Tedesco et al. (1995); fósforo e potássio extraíveis determinados pelo método Mehlich conforme descrito por Tedesco et al (1995); acidez potencial (H + Al) extraído com acetato de cálcio 1 N (a pH 7)e titulado com NaOH. 0,0125 N, conforme descrito por Embrapa (1997); capacidade de troca de Cátions e saturação por bases calculadas a partir dos cátions trocáveis e acidez potencial. Os dados foram submetidos à análise de variância e ao teste de Duncan, com o auxílio do programa estatístico winstat. (Machado et al. 2001). Os resultados evidenciaram que o uso intensivo de culturas anuais em sucessão ou rotação com o arroz irrigado por alagamento alterou os teores de matéria orgânica e nitrogênio na camada superficial em relação ao solo natural; o efeito da calagem nos parâmetros de acidez do solo (pH, V, Ca e Mg) após 14 anos de aplicação de calcário está se exaurindo, mas ainda é mensurável; os efeitos dos sistemas de uso do solo nos teores de fósforo e potássio extraíveis pelo método Mehlich são proporcionais às quantidades destes nutrientes aplicados ao longo dos anos.

Master of Science / Department of Agronomy / Scott A. Staggenborg / Irrigated cropping systems on the High Plains are dominated by water intensive continuous corn (Zea mays L.) production, which along with other factors has caused a decline in the Ogallala aquifer. Potentially demand for water from the aquifer could be decreased by including drought tolerant crops, like grain sorghum (Sorghum bicolor L.) and cotton (Gossypium hirsutum L.), in the cropping systems. This study calibrated the CERES-Maize, CERES-Sorghum, and CROPGRO-Cotton models for the High Plains and studied the simulated effects of different irrigation amounts and initial soil water contents on corn, cotton, and grain sorghum. Input files for calibration were created from irrigated and dryland research plots across Kansas. Information was collected on: soil physical properties, dry matter, leaf area, initial and final soil water content, management, and weather. CERES-Maize simulated grain yield, kernel number, ear number, and seed weight across the locations with root mean square errors (RMSE) of 2891 kg ha-1, 1283 kernels m-2, 1.6 ears m-2, and 38.02 mg kernel-1, respectively. CERES-Sorghum simulated grain yield, kernel number, head number, and seed weight with RMSEs of 2150 kg ha-1, 5755 kernels m-2, 0.13 heads m-2, and 4.51 mg kernel-1. CROPGRO-Cotton simulated lint yield and boll number with RMSEs of 487 kg ha-1 and 25.97 bolls m-2. Simulations were also conducted with CERES-Maize, CERES-Sorghum, and CROPGRO-Cotton to evaluate the effects of irrigation amounts and initial soil water content on yield, evapotranspiration (ET), water use efficiency (WUE), available soil water at maturity, and gross income per hectare. Simulations used weather data from Garden City, KS from 1961 to 1999. Irrigation amounts were different for all variables for corn and grain sorghum. For cotton, yield, WUE, soil water, and gross income were not different between the top two irrigation amounts. For corn and grain sorghum, initial soil water content was only different at 50% plant available water. Initial soil water had no affect on cotton, except for ET at 50%. Simulations showed that cotton yields are similar at lower irrigation. Also, cropping systems that include cotton have the potential to reduce overall irrigation demand on the Ogallala aquifer, potentially prolonging the life of the aquifer.

No description available.

Call number: LD2668 .T4 1986 H54 / Master of Science / Agricultural Economics

L'intensification et l'homogénéisation des paysages agricoles a rendu les agrosystèmes plus sensibles aux bioagresseurs. Pour limiter les impacts de ces bioagresseurs sans recourir de manière intensive aux pesticides, une solution efficace est l'utilisation de variétés résistantes. La durabilité de ces résistances peut être faible, en lien avec l'adaptation des populations pathogènes. Il est donc nécessaire de concevoir des systèmes de culture permettant le contrôle des bioagresseurs et la préservation des ressources variétales. Ces stratégies de gestion peuvent reposer sur la combinaison de pratiques agricoles et d'organisation spatiale de ces pratiques, pour des pathosystèmes dont les agents sont dispersés par le vent. D'une part, la conception de ces stratégies peut bénéficier d'une approche participative, prenant en compte les conditions de culture et l'organisation des acteurs locaux. D'autre part, l'évaluation de ces stratégies, dont l'expérimentation est délicate du fait des échelles spatiale et temporelle requises, peut bénéficier d'une approche modélisatrice. Dans ce cadre, ce travail de thèse a mis au point et testé, sur deux régions d'étude, une méthode participative de construction de scénarios d'organisation spatiale des systèmes de culture, évalués vis-à-vis du contrôle du phoma du colza et de la gestion des résistances. Les scénarios co-construits explorent les futurs agricoles possibles en identifiant les tendances possibles d'évolution du contexte (économique, politique, règlementaire, épidémique), de manière prédictive ou plus exploratoire. Ils ont ensuite été évalués numériquement à l'aide d'un modèle préexistant, vis-à-vis de trois critères pertinents pour les acteurs : les pertes de rendement, la taille de la population pathogène et sa structure. Ces scénarios ont ensuite été évalués à l'aide de régressions linéaires, de manière à identifier les pratiques agricoles les plus influentes sur les trois critères d'évaluation considérés. Cette analyse a été réalisée à deux échelles spatiales complémentaires : l'échelle d'une petite région agricole et l'échelle locale, considérant plusieurs centaines de mètres autour des parcelles de colza pouvant être infectées. Ces analyses ont permis de mettre en évidence la prépondérance des rotations, des variétés et de la gestion des résidus de colza dans l'évolution de la maladie et sur la durabilité des résistances. Elles ont également montré la nécessité de prendre en compte plusieurs échelles pour la gestion de la maladie : si la taille de la population pathogène et les pertes de rendement peuvent être déterminées à partir de la composition en termes de systèmes de culture à l'échelle du paysage, une échelle plus locale est nécessaire pour évaluer l'évolution de la structure génétique de la population. Cet indicateur est en effet très lié aux variétés et aux pratiques présentes dans les 500 mètres autour des parcelles porteuses de la résistance considérée. Finalement, l'exploration de règles spatiales (isolement) et temporelles (maximisation des surfaces un an sur deux) des parcelles de colza ou des types variétaux a mis en exergue le fort potentiel de stratégies basées sur ces règles pour la gestion des résistances. La mise en place de ces stratégies nécessiterait une coordination entre les différents acteurs, à l'échelle du territoire agricole, qui pourrait s'avérer nécessaire en cas d'épidémie importante de phoma. La méthode mise en place pourrait être utilisée pour explorer la gestion d'autres thématiques à composante spatiale, comme par exemple l'érosion ou la gestion d'autres bioagresseurs. Ceci pourrait permettre une évaluation multicritère, prenant par exemple en compte les bioagresseurs de différentes cultures composant une même rotation, identifiant ainsi les pratiques les plus à mêmes de gérer simultanément les différentes thématiques locales. / The intensification and the homogenization of agricultural systems led to agrosystèmes that are more sensible to pests and diseases. To limit the impacts of these pests and diseases without increasing pesticides use, an efficient solution is the use of resistant cultivars. Sustainability of these resistances can be low, in link with the adaptation of pathogen populations. It is thus necessary to design cropping systems allowing both the control of pests and diseases and preservation of cultivar resistances. Such management strategies can combine cropping practices and their spatial organization, for pathosystems whose agents are wind-dispersed. The design of these strategies can benefit from participatory approaches, taking into account the local cropping systems and stakeholders' organizations. The evaluation of these strategies, hardly testable in reality due to the spatial and temporal scales involved, can benefit from a modeling approach. Within this scope, this PhD thesis designed and tested, in two study regions, a participatory method of scenarios design, aiming at building with local stakeholders scenarios of spatial organization of cropping systems and to assess them with regards to their performances on phoma stem canker of winter oilseed rape and resistance durability management. Participatory designed scenarios explore agricultural futures that may happen by identifying the possible evolutions of the context (economic, political, regulatory or epidemic), in a predictive or more exploratory way. Scenarios are then evaluated numerically with a pre-existing model, for three criteria relevant for the stakeholders: yield losses, structure and size of the pathogen population. This analysis has been performed at two complementary spatial scales: the regional and the local scale, considering hundreds of meters around fields cropped with sensitive cultivars. These analyses showed the importance of crop rotations, cultivars and tillage for the evolution of the disease and resistance sustainability. These analyses also showed the necessity of taking into account different scales for disease management. Indeed, size of the pathogen population and yield losses are well related to the landscape composition in terms of cropping practices, but a more local scale is necessary for the assessment of the genetic structure of the pathogen population. This indicator is thus significantly linked with the cultivars and cropping practices in the 500 meters around fields cropped with the considered resistance. Finally, we explored spatial (isolation) and temporal rules for rapeseed spatial and temporal allocations that could be used to manage resistance. For these strategies to be applied, coordination between stakeholders at the agricultural territory would be necessary, which could be necessary in case of strong phoma stem canker epidemics. The method we applied could be used to explore other thematic with a spatial component, as for instance pests or erosion. This could allow a multi-criteria analysis, for instance taking into account pathogens of different crops included in a rotation, thus identifying the cropping practices that could promote management of these local problems.

A combinação de nove tratamentos (T) foi utilizada com o objetivo de fazer uma avaliação agronômica da disponibilização de nitrogênio (N) na produção de feijão, quando inoculado com Rhizobium leguminosarum bv. Phaseoly (RL), cobalto (Co) e molibdênio (Mo), conduzidos sob sistema de semeadura direta (SSD). T1 disponibilizou N através do solo, T2 através da inoculação das sementes com RL (400 g por 50 kg de sementes) imediatamente antes da semeadura, T3 através da inoculação das sementes com RL e adubação nitrogenada em cobertura (60 kg.ha -1 ) (ANC60), utilizando como fonte de N o nitrato de amônio (NA) contendo 33% de N, T4 através inoculação das sementes com Co e Mo (116 g.ha -1 ), produto formulado contendo 1,5% de Co e 10,0% de Mo, T5 através da inoculação das sementes com Co e Mo e ANC60, T6 através da inoculação das sementes com Co, Mo e RL, T7 através da inoculação das sementes com Co, Mo e RL e ANC60, T8 através de ANC60, T9 através da adubação mineral na semeadura com NA (20 kg.ha -1 ) e ANC60. A área escolhida localiza-se no município de Piracicaba, SP (22º42'30" Sul e 47º38'30" Oeste) pertencente ao Departamento de Produção Vegetal da Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, onde o SSD vem sendo usado desde 1993, sendo que as culturas implantadas nessa área nunca foram inoculadas com bactérias fixadoras de N. O solo foi amostrado na camada de 0,0-0,2 m anualmente, de 1994 a 1999, mostrando evolução dos atributos químicos do solo. Os parâmetros utilizados na análise foram: número de nódulos, massa de matéria seca de raízes, nódulos, e parte aérea, número de vagens por planta, número de grãos por vagem, massa de 100 grãos, teor de nitrogênio na planta, índice de utilização de nitrogênio (IUN), coeficientes técnicos e custo de produção total, índice de lucratividade (IL) e rendimento de grãos (Rg). Os resultados evidenciaram que o T7 é uma alternativa para disponibilizar N à cultura, dentro do SSD, obtendo o maior Rg. O SSD foi eficiente na manutenção do teor de matéria orgânica no solo, mas não foi eficiente para suprir totalmente a demanda da planta por N, evidenciando a necessidade da adoção de métodos alternativos para incrementar sua disponibilidade no SSD. / To evaluate the nitrogen (N) availability to common bean grain yield under no tillage system (SSD) after inoculation with Rhizobium leguminosarum bv. phaseoly (RL), cobalt (Co) and molybdenum (Mo), nine treatments (T) were used. T1 supplied N from the soil, T2 supplied N through the inoculation of the seed prior to sowing with RL (400 g per 50 kg of seeds), T3 supplied N through the inoculation of the seed prior to sowing with RL and additional N was also added using a top dressing with 60 kg.ha -1 of ammonium nitrate (NA) with 33% of N (ANC60), T4 supplied N through inoculation of the seed prior to sowing with Co and Mo (116 g.ha -1 ) using a formulated product containing Co (1.5%) and Mo (10.0%), T5 supplied N through inoculation of the seed prior to sowing with Co and Mo and ANC60, T6 supplied N through inoculation of the seed prior to sowing with Co and Mo and RL, T7 supplied N through inoculation of the seed prior to sowing with Co and Mo and RL and ANC60, T8 supplied N through using a top dressing, T9 supplied N using NA in the sowing (20 kg.ha -1 ) and ANC60. The field experiment was carried out at Crop Science Department, Esalq, University of São Paulo, Piracicaba, Brazil (22°42'30" South and 47° 38' 30" West), where the SSD has been practiced since 1993, and the crop had never been inoculated with N fixing bacteria. The soil was sampled annually at 0.0 to 0.2 m depth, from 1993 to 1999, showing evolution in the soil chemical attributes. The following agronomic parameters related to common bean crop were used for statistical analysis: the number of nodules, roots and nodules dry biomass, shoot dry biomass, number of pods per plant and grains per pod, and 100 grains mass, the plant nitrogen content, the nitrogen utilization index (IUN), the technical crop production coefficients, the total production cost, the profitability index (IL) and grain yield (Rg). The results showed that T7 was an alternative to make nitrogen available to common bean crop inside SSD, reaching the best productivity. No tillage system was efficient in the maintenance of the soil organic matter, but it was not efficient enough to supply the total demand of the plant for nitrogen, showing the need of alternative methods adoption to increment its availability to the system.

Orientador: Antonio Lázaro Sant'Ana / Banca: Maria Aparecida Anselmo Tarsitano / Banca: Leonardo de Barros Pinto / Resumo: Um assentamento rural pode ser definido como a criação de novas unidades de produção agrícola, gerados pelo surgimento de novas formas de organização. A compreensão da forma como os produtores familiares organizam a produção exige a utilização de categorias de análise que enfoquem o conjunto das atividades realizadas pela família, como é o caso dos estudos baseados nos sistemas de produção. Foi feito um levantamento de dados, por meio de um questionário, realizado no período de agosto a outubro de 2010, abrangendo 40 produtores que estavam realizando alguma atividade produtiva, residiam na área a mais de 6 anos e não apresentavam irregularidades junto ao Incra, visando levantar algumas características em relação à produção animal e vegetal, à tecnologia utilizada, à assistência técnica, ao acesso ao crédito e aos preços médios recebidos. As atividades rurais do assentamento Mutum são limitadas pela aptidão agrícola de seu solo (Neossolo Quartzarênico). A bovinocultura de leite está presente em quase todos os lotes e é também a principal fonte de renda desses produtores. A comercialização do leite é feita principalmente de duas formas, como subproduto queijo de salmoura (62,5%) e in natura (32,5%), mas este tipo de processamento do leite não tem resultado em agregação de valor ao produto. Outras atividades de importância dentro do assentamento são a bovinocultura de corte e a silvicultura. Com base nas principais atividades que envolviam a comercialização do produto foram identificados quatro sistemas de sistemas de produção (1. Bovinocultura de Leite; 2. Bovinocultura de Leite + Bovinocultura de Corte; 3. Bovinocultura de Leite + Silvicultura; 4. Diversificado), todos com a participação da pecuária de leite. Constatou-se que a adoção dos diferentes sistemas de produção, embora resulte a curto ou médio prazo em entradas monetárias ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: A rural settlement is defined as the creation of new agricultural production units, generated by the emergence of new forms of organization. The understanding of how family farmers organize production requires the use of categories of analysis that focus on all the activities performed by the family, as is the case of studies based on production systems. He conducted a survey of data through a questionnaire, conducted from August to October 2010, covering 40 producers that were doing some productive activity, resided in the area for more than six years and had no irregularities to the Incra order raise some features in relation to animal and crop production, the technology used for technical assistance, access to credit and average prices received. Rural activities of the settlement are limited by Mutum agricultural suitability of your soil (PSAMENT). The dairy cattle is present in almost all lots and is also the main source of income for these producers. The marketing of milk is done mainly in two ways, as a byproduct of cheese brine (62.5%) and fresh (32.5%), but this type of processing of milk has resulted in adding value to the product. Other activities of importance within the settlement are beef cattle and forestry. Based on the main activities involving the commercialization of the product were identified four systems of production systems (1. Dairy Cattle; 2. Dairy Cattle + Beef Cattle; 3. Dairy Cattle + Forestry; 4. Diverse), all with the participation of livestock for milk. It was found that the adoption of different production systems, although resulting in the short or medium term monetary differentiated inputs, is not associated with sharp differences in the level of technical conduct of farming systems and cultivation, nor the striking differences characteristics of the producer and the lot. However, the system more diverse activities and the sale of products with added ... (Complete abstract click electronic access below) / Mestre

Thesis (M.Sc. (Agricultural Management)) --University of Limpopo, 2004 / Identification of annual grass/legume intercropping or mixtures with superior nutrient traits and Dry matter (DM) production is critical to increasing productivity of the crop and animal production among small-scale farmers in the Limpopo Province. Three similar field experiments were established at different locations in the Province to determine the significance of the contribution of annual summer legumes, and cutting treatments on the nutritive value and dry matter accumulation of the popular forage sorghum (Sorghum spp) and pearl millet (Pennisetum glaucum) intercropped with cowpea (Vigna unguiculata) and dolichos (Lablab purpureus). The cropping systems evaluated were sole sorghum, sole pearl millet, sorghum + cowpea, sorghum + dolichos, pearl millet + cowpea and pearl millet + dolichos. The treatments sole sorghum and pearl millet significantly (P<0.05) outperformed the other treatments in terms of DM production at most cutting stages. The remaining four treatments though, inferior in DM in this study, yielded better than the average yield on farmers' fields in the Province. Higher protein content was obtained in mixtures than in sole cropping, and generally there was lower protein production and content at matured stages (CT3) in the study. The other chemical composition analyzed in the study was not significant for both mixtures and sole cultures.

Salsola australis is an introduced weed of crop and pasture systems in the Western Australian broad acre cropping and pasture region (wheat-belt). This thesis investigated the classification, biology and ecology of the genus Salsola in southwest Australia, as well as modelling the effectiveness of possible weed control practices. Prior to this research, S. tragus was the only recognised species of the Salsola genus within Australia. However, genetic analysis revealed that four genetically distinct putative taxa of the genus Salsola were found in southwest Australia, none of which were S. tragus. The taxa that is the most prevalent agricultural weed was classified as S. australis, but the other three putative taxa could not be matched to recognised species. All four taxa were diploid (2n = 18), as opposed to tetraploid (2n = 36) S. tragus. Within the agricultural system of southwest Australia, S. australis plants established throughout the year, although the majority of seed production occurred in late summer and autumn. Total seed production (138-7734 seeds per plant) and seed viability (7.6-62.8%) of S. australis were lower than that reported for other agricultural weed species of the Salsola genus. Seed dispersal occurred when the senesced plants broke free of their root system to become mobile. Wind driven plants travelled and shed seed over distances of 1.6 to 1247.2 m. Movement of approximately half the plants was restricted to less than 100 m by entanglement with other S. australis plants within the stand. Some seed was retained on the senesced plants, but the germinability of this seed fell to less than 2% in the two month period following plant senescence (i.e. a decline of 79%). Once seed shed into the soil seed bank, anywhere from 32.3 to 80.7% of the viable seeds germinated in the year following seed production, with the rest remaining dormant or degrading. A model of the life cycle of S. australis based on the population ecology data indicated that the dormant seed bank had very little effect on annual seedling recruitment, but seed dispersal from neighbouring populations had a large impact on population growth rate. Therefore, the most successful weed control measures were those that restricted seed dispersal from neighbouring populations, or those that were applied to all populations in the region rather than to a single population. Weed control techniques applied to a single population, without reducing seed dispersal, could not reduce population size.