Master of Science / Department of Agronomy / Kraig Roozeboom / High soybean [Glycine max.] commodity prices in recent years have led to an increase in use of yield enhancing and protecting products. These products need to be evaluated to determine if the use of multiple inputs has a positive impact on yield and how these inputs interact with agronomic practices. The objectives of this study were to evaluate products individually and collectively in input systems, examine interactions between varieties and input systems (IS), seeding rates (SR) and IS, and row spacing (RS) and IS. Field experiments were conducted at high-yielding locations in Kansas and Minnesota in 2012 to 2014 to meet these objectives. Sixteen treatments consisting of individual inputs and inputs combined in systems were evaluated in one experiment. A second experiment evaluated the variety by IS interaction by constructing 18 treatments from a factorial combination of six glyphosate [N-(phosphonomethyl) glycine] resistant varieties and three IS’s: untreated control (UTC), SOYA (combination of possible yield-enhancing products representative of those currently being marketed), and SOYA minus foliar fungicide (SOYA – foliar F). A third experiment evaluated the SR by IS interaction by constructing 12 treatments from a factorial arrangement of six SR’s and two IS’s: UTC and SOYA. A fourth experiment evaluated the RS by IS interaction by constructing 12 treatments from a factorial arrangement of three RS’s and four IS’s: UTC, fungicide and insecticide seed treatment plus foliar fungicide (STFF), SOYA, and SOYA – foliar F. Very few interactions between IS and agronomic practices were detected in any of the experiments. Varieties had an effect on multiple growth parameters but yield differences were marginal; linear-plateau and non-linear models found that seeding rates that maximized yield in this study were similar to University recommendations; and in general, narrow rows produced the greatest yields. The use of inputs and IS’s typically increased seed mass and yield above the UTC across all experiments. However, given current costs and soybean prices, yield response to IS’s was not great enough to cover the additional costs. Overall, it appears producers would be better served by focusing on agronomic practices rather than implementing input systems.

Thesis (M. Agricultural Management (Agronomy)) -- University of Limpopo, 2018 / A survey study identified indigenous leafy vegetables (ILVs) utilized by rural communities in Limpopo Province in the three districts of Capricorn, Sekhukhune and Vhembe focusing on their availability, agronomic practices, marketing, medicinal and cultural roles, as well as their nutritional value. An ILV that was highly preferred and with good marketing potential was identified for further studies on its response to planting density and nitrogen fertilizer rate. A questionnaire survey was used to gather information about types of ILVs utilised, their production practices, marketing of ILVs and their importance in medicinal and cultural roles. Data collected were subjected to analysis using the Statistical Package for Social Sciences (SPSS) using descriptive statistics. Results showed that there were 45 different types of ILVs identified from the three districts in Limpopo Province. Farmers indicated that cultivation of these vegetables was mostly done from October to January in Sekhukhune and Capricorn district while in Vhembe it was practiced all year round. Most of farmers in Vhembe district used inorganic fertilizer during planting while farmers in Sekhukhune and Capricorn districts used organic fertilizers such as cattle manure. Irrigation was commonly used in Vhembe district through furrow irrigation system whereas in Capricorn and Sekhukhune districts most farmers relied on rainfall. Farmers indicated that harvesting was done at an early growing stage of the crop. Indigenous leafy vegetables were mostly marketed in local communities. Several ILVs were identified as preferred and regularly consumed as vegetables. Spider plant (Cleome gynandra) and nightshade (Solanum retroflexum) were identified as the most consumed ILVs in the three districts. Comparing the market potential of the two vegetables, S. retroflexum was chosen for further studies on its response to plant density and nitrogen fertilizer rate. The first study investigated the effect of varying plant density (inter and intra-row spacing) and the second study evaluated the response of intra-row spacing and nitrogen fertilizer (LAN-28%N) rate on growth and yield of S. retroflexum during 2014 (April to May) and 2015 (March to May) growing seasons. The plant density experiment was laid out as a 3 x 4 factorial arrangement in a randomised complete block design (RCBD) with three replications. The treatment factors were 3 inter-row spacings of 30, 45 and 60 cm and 4 intra-row spacings of vi 7.5, 15, 22.5 and 30 cm. The data collected included plant height, plant vigour, number of leaves and branches per plant as well as plant leaf yield. Data were subjected to analysis of variance (ANOVA) using STATISTIX 10.0 package and mean treatments were separated using Turkey HSD at 5% probability level. The results revealed that growth parameters (plant height, plant vigour, number of branches and leaves) and plant leaf yield were significantly influenced by the combined inter and intra-row spacings. Closer inter-row spacings of 30 cm and 45 cm, and intra-row spacings of 7.5 and 15 cm produced the highest values of parameters and plant leaf yield. The combined spacings of 30 x 7.5 cm produced the highest plant leaf yield. The second study was also laid out as a randomised complete block design (RCBD) with three replications. The treatments were 6 x 2 factorial arrangement: 6 levels of nitrogen (LAN-28%N) at 0, 20, 40, 60, 80 and 100 kg N/ha and two intra-row spacings of 15 and 30cm. Inter-row spacing of 30 cm was used. The nitrogen fertilizer was applied a week after transplanting and repeated a week after first harvesting. Data was subjected to analysis of variance (ANOVA) using STATISTIX 10.0 package. Where significant differences were detected, means were separated using Turkey HSD at 5% propability level. The results suggested that both nitrogen fertilizer and spacing can be used to enhance growth and leaf yield of S. retroflexum vegetable. Nitrogen fertilizer rate and plant density significantly (P≤0.05) affected plant growth and plant leaf yields. Growth parameters and leaf yield were optimised using closer spacing of 15 cm and applying nitrogen at 60 kg N/ha. The application of 60 kg N/ha and 15 cm spacing was therefore recommended for the production of S. retroflexum as a vegetable, if planted at 30 cm inter-row spacing. Key words: Indigenous leafy vegetables, agronomic practices, Solanum retroflexum, planting density, nitrogen fertilizer, planting date

Two field trials were conducted to determine the impact of water management on the efficacy of insecticide seed treatments against rice water weevil, Lissorhoptrus oryzophilus Kuschel, in rice at the Delta Research and Extension Center during 2011 and 2012. The performance of thiamethoxam, chlorantraniliprole, and clothianidin was evaluated when the permanent flood was established at different timings (6 and 8 weeks after planting) and the effect of flush number (0, 1, or 2) on seed treatment performance was evaluated. Seed treatment efficacy was not impacted by delayed flooding, but 2 flushes reduced efficacy of some seed treatments. Experiments were also conducted to determine the impact of reduced seeding rates found in hybrid rice production on the efficacy of insecticide seed treatments targeting rice water weevil. Efficacy was similar when comparing currently labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin with higher rates of these products.