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Tesis (Doctor en Ciencias Económicas)--Universidad Nacional de Córdoba, Facultad de Ciencias Econoḿicas, 1970.

Dissertaç̂ão (Mestre em Ciências Sociais Rurais)--Escola Superior de Agricultura "Luiz de Queiroz" da Universidade de São Paulo. / English summary: leaves 120-125. Bibliography: leaves [126]-134.

Thesis--Universidade Federal do Rio Grande do Sul. / Bibliography: leaves 77-81.

A series of experiments was carried out in the Department of Agriculture, University College of North Wales, Bangor, during October 1987 to September 1989. The purpose of these was to study the effects of water stress and salinity stress at different stages on long (Norman), medium (Fenman) and short duration (Wembley) wheat varieties in different environments. Effects of water stress were tested in large pots in different types of soil. Effects of salinity were tested by growing plants in solution culture. In both experiments water stress and salinity stress were imposed at three major stages, tillering to stem extension (TL-SE), stem extension to booting (SE-BG) and booting to maturity (BG-MT). These were tested in each variety in comparison with a control of each variety. Growth measurements, leaf number and area, stem area, shoot number, plant height, nitrogen %, nitrogen uptake, dry weight per plant were determined at the end of each stage. Soluble carbohydrates were determined at anthesis. This was done to find out how much these growth measurements were decreased during each stress period. Yield and yield components were determined at harvest. In these experiments the long duration variety took a long time in growth during TL-SE, in comparison to mid winter and spring wheat varieties. The long duration variety gave a higher plant, more straw dry weight production and more leaf number than the short duration variety. The long duration variety also gave a higher yield than the medium and short duration varieties, due to larger ears, more spikelets vi per ear, more grain number per ear and more grain number per spikelet. All varieties experienced higher temperatures and longer days during SE-BG and BG-MT in both experiments. The lengths of these stages therefore showed smaller variation between varieties. In water stress experiments the mixed peat-soil used in Experiment 2 dried out quicker than the normal field soil used in Experiment 1. The upper portion of the soil was dried before the lower portion of the soil during the stress period. With water stress at SE-BG and BG-MT the soil dried out quicker in both years. Gypsum blocks were used to give readings of water stress. with water stress at BG-MT the soil was completely dried out after the third week, in all varieties, due to higher plant height, higher temperature and more evaporation. Because of this water stress at BG-MT resulted in a short duration for ripening. In both water stress Experiments 1 and 2, in all varieties all water stress treatments decreased the growth measurements, decreased yield and yield components. In Norman water stress at TL-SE had a long stress period due to slow growth processes during cold winter. However, this stage had a similar effect on yield in Norman, Fenman and Wembley. In both water stress experiments in all varieties, water stress at SE-BG caused the largest reductions in growth measurements, because at this stage the plant had the greatest leaf area and temperature was higher, although the period of stress was only a few weeks. However, water stress at BG-MT caused the greatest decreases in yield. This stage showed the greatest vii decreases in yield and yield components, due to small grain size, fewer fertile spikelets, small size of ear, earlier leaf senescence, short duration for ripening, higher temperature, lack of soluble carbohydrate for grain f~lling from stem and pollination problems at anthesis time. In both salinity Experiments 1 and 2, all varieties had a larger green leaf area, more tillers and all varieties were much stronger after stem extension than in the water stress experiments due to the solution culture teChnique. Norman was more strong than the other varieties because of its long period grown in solution culture. Salinity at TL-SE was more damaging than other stages in all varieties. Salinity at TL-SE decreased the growth measurements, such as leaf area, stem area, plant height, dry weight per plant. Because of the growth measurement reduction, grain weight per plant, grain number per plant, grain number per ear, grain number per fertile spikelet and fertile spikelet per ear were decreased by salinity at this stage. Salinity at SE-BG and BG-MT also decreased growth measurements, decreased grain yield and yield components. Salinity at BG-MT decreased grain yield and yield components more than salinity at SE-BG. In Experiment 2 in all varieties with salinity at BG-MT plants were harvested a few days before other stages and the control. Norman was more sensitive with salinity at TL-SE than the other varieties because of its long period grown under salt stress. Norman was much stronger with salinity at SE-BG. Norman gave lower yield, yield components at BG-MT than other varieties at this stage.

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"Tesis presentada a la H. Facultad de Agronomía de la Universidad de Concepción para optar al título de Ingeniero Agrónomo." / eContent provider-neutral record in process. Description based on print version record. Bibliography: leaves 150-154.

Master of Science / Department of Agricultural Economics / Benjamin B. Schwab / Khat, a lucrative cash crop cultivated in and near the Horn of Africa, is gaining the interest of researchers around the globe. Despite its potential to provide excess income, economic opportunity, and access to technology to those who produce it, the conflicting legal status around the globe causes policy and trade disputes between countries. Research on the impact of khat production on household welfare is sparse. To address this, the purpose of this research is to determine what factors affect the decision to grow khat and subsequently determine the impact of khat production on labor, income, education expenditure, and food security. Data was extracted from a survey conducted in early 2017. A total of 365 households in the Amhara Region of Ethiopia were surveyed. We estimate the factors affecting the decision to grow khat by employing use of two logit models and one linear probability model to calculate marginal effects. We estimate the impact of khat production on labor, income, education expenditure, and food security through propensity score matching. Khat production appears to be adopted by households who are educated and apt to adopt improved technologies. These households are likely to own a donkey, own irrigation, and own more plots than a non-producing household. Practicing seed saving, conservation techniques, and growing more crops decreases the likelihood of growing khat. Regarding impacts, khat production increases on-farm male (41.8%) and female (62.1%) labor and income (41.7%), but decreases education expense (-10.7%), food consumption scores (-15.9%), and number of food shortage months (-16.2%). Overall, khat production uses more labor, generates higher incomes, and decreases food shortage months, but decreases expenditure on education and dietary diversity.

A number of foliar fertilizers were evaluated for their effects on yield and quality of both cantaloupes and honeydews. None of the treatments or treatment combinations resulted in statistical increases or decreases for numbers of cantaloupes or honeydews when compared with the untreated check. A highly significant increase of one treatment regimen (which contained calcium) was noted for cantaloupe weights when compared with the untreated check. Statistical differences were not noted for honeydew weights for this treatment although it also resulted in highest calculated weights of honeydew/area of treatments evaluated. All treatments resulted in numerically higher brix for cantaloupes than the untreated check, thought to be a response to pounds of melons/unit area as the untreated check had the least cantaloupe weight. No differences were noted for cantaloupe seed cavity diameters.

A series of replicated trials were conducted during the winter season of 2003 and 2004 to investigate the effect of pre-harvest applications of cytokinins on yield and postharvest quality of intact and fresh-cut lettuce. We report here only those results obtained at harvest. Cytokinins products were applied at different frequency and rates. The crops in the different trials were under different cultivation programs, including different nitrogen fertilization rates. Figures showing the performance of each individual cytokinin product versus the corresponding untreated controls are provided. Results obtained are mixed even for the same cytokinin product, however, some trends were observed. With the exception of products that also contain other plant growth regulators in their formula, high rates (or multiple applications) of the cytokinin products resulted in no effect or even in negative results. For example applications of Cytokin® did not improve yields as was the case with Cytoplex®, from the same manufacturer, under different conditions. The results from this study suggest that lettuce plants can respond to cytokinin applications, but factors to enhance positive response still need to be studied further. Single applications appear to be the most effective program for products containing only cytokinins, while products such as Cytoplex® can increase yield with multiple applications. A discussion addressing the different results obtained with nitrogen rates and the cytokinin products in yield and quality is included.