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Thesis (M. Agricultural Management (Plant Production)) -- University of Limpopo, 2020 / Tomato is a major vegetable crop produced in Limpopo province by subsistence and commercial farmers. Biotic and abiotic factors such as diseases and drought affect its productivity and yield negatively. The most economically important tomato disease in Limpopo is early blight, caused by Alternaria solani. Early blight affects tomato growing under stressful conditions such as drought. The main aim of this study was to evaluate water management in tomato production and its effect on tomato yield, early blight occurrence and severity under smallholder farming systems in Giyani. A survey study and field experiments on early blight occurrence and severity were conducted in the Greater Giyani municipality in Limpopo province. Firstly, a survey of early blight was conducted in tomato fields selected from three service centres namely Guwela, Hlaneki and Mhlava Willem. Twenty five potential tomato grower’s farms were randomly selected for survey based on the location and production management strategies. A second study was carried out by establishing field experiments at two farms in the same area, namely: A hi tirheni Mqekwa and Duvadzi farms. The experiments were laid out in a randomized complete block design (RCBD) in a split plot arrangement, with irrigation as the main plot treatment and tomato variety as the subplot treatment. Each treatment was replicated four times. The irrigation treatments consisted of full irrigation up to field capacity and deficit irrigation. The tomato varieties planted were HTX14, Rodade, STAR9006 and Commander, and were irrigated with a drip irrigation system. The overall survey results showed that Guwela s/c had high disease incidence and the lowest disease severity as compared to the other two service centers. The lowest disease incidence was observed at Hlaneki s/c whilst Mhlava willem s/c had the highest disease severity. The two water treatments (full and deficit irrigation) in both farms have shown no significant pairwise differences among xx the volumetric water content means. There was no significant difference (P≥0.05) in early blight disease severity in both farms. Results shows that, all tomato varieties did not differ significantly (P≥0.05) in yield observed between treatments at Duvadzi and A hi tirheni Mqekwa Farm. Deficit irrigation can be used effectively to produce high yields in tomato production provided the cropping season window does not coincide with the hottest time of the year. Full and deficit irrigation did not have influence on the early blight disease incidence on tomato plants. Key words: Alternaria solani; disease incidence; disease severity and drip irrigation

Thesis (M. A. (Sociology)) -- University of Limpopo, 2017 / The study explored Mutoko community members’ perceptions of climate change and its impact on subsistence farming. Mutoko is a rural community situated in the eastern part of Zimbabwe. Focus group discussions were conducted to explore perceptions of climate change and its impacts on subsistence farming. The study findings show that the primary source of food is subsistence farming. The main crop grown in Mutoko is maize, followed by ground nuts (peanuts), and indigenous vegetables. Maize, ground nuts, sunflowers (for seed), sorghum and millet are grown for household consumption. The study reports community members’ perceptions and views of changes in the local natural environment. The changes are increased temperature and scarcity of rain. Observable impacts of these changes are decreased crop yields in times of drought. The findings are supported by observation that Zimbabwe lies in a semi-arid region with limited and unreliable rainfall patterns and temperature variations. Rainfall exhibits considerable spatial and temporal variability. Generally, the impact of climate change on subsistence farming was the major concern among the participants. Though the study was not aimed at documenting adaptation measures taken to lessen the negative impacts of increased temperature and rainfall scarcity on crop production, the study shows that adaptive measures have been developed and used to adapt and cope with climate change. Community members are adapting to the impacts of increased temperature and scarcity of rain through their culturally informed mechanisms. The mechanisms include change of crops, use of manure to improve soil structure and mulching. It is concluded that the impact of climate change on subsistence farming is real and is negatively affecting food security in the study area. Farmers gave different views on the following; knowledge about climate variations, changes in environmental conditions, changes in temperature patterns and changes in rainfall patterns. / Centre of Indigenous Knowledge Systems (CIKS) and National Research Foundation (NRF)

Previous research has shown that crop land application of alum sludge can be a valuable method of residuals disposal and has been demonstrated to cause no adverse effects on soil properties and crop yields. Studies have shown that with good soil management practices essential plant macronutrient levels can be maintained to support good crop growth. This study investigated the application of water treatment residuals in both field studies and greenhouse pot studies in order to determine the effects on soils properties and crop yields. Alum sludge collected from the Blacksburg-Christiansburg-VPI Water Authority and Radford Water Treatment Plant was land applied in the Spring of 1992. Two separate crop rotations, corn followed by wheat, were grown and harvested during the two-year field study. A greenhouse pot study using lettuce and radish plants was initiated in the Spring of 1993. Soil and plant tissue samples were collected and analyzed for the field and greenhouse studies. Harvest yields were also carefully monitored and recorded. The results of the laboratory analysis provided information on nutrient concentrations in soil and uptake by plants, and also soil and plant tissue elemental accumulations. Alum and PACI sludge at loading rates of up to 2.5% had no negative impacts on wheat yield. The growth study using lettuce and radish plants concluded that residual additions at low levels improved crop yield and that residual aging prior to land application was essential for good yield. / Master of Science

Dairy farming in Virginia could be more profitable if price and yield risks affecting the cost and availability of feed inputs such as corngrain, corn silage, alfalfa and ryelage are reduced. Price and yield risk facing dairy farmers in Virginia can be reduced through a marketing strategy like hedging and government commodity program participation. The overall objective of this study is to evaluate how the variability of price and yields of particular feed crops affect the variability of expected returns in dairy farming. Specific objectives include: 1) to evaluate the relationship between feed production risk and the level and variability of net returns for a representative dairy farm in Virginia; 2) to evaluate the relationship between price risks of purchased feed inputs and the variability of net returns; 3) to draw implications from the results that can be used to help dairy farmers better manage feed production risk. To accomplish these objectives, the target MOTAD risk analysis technique is used. The empirical model is developed in four steps. First, the model activities such as milking and feeding of cows, heifer and calf activities, crop production, harvesting, labor, and buying and selling activities were created. Second, variable yields based on probability elicitation from dairy farmers were generated. Third, variable prices based on commodity options were generated; and fourth a target income constraint was derived. Results from the analysis indicated that the target income constraint was exceeded in every state of nature for the representative farm resulting in an efficiency frontier of a single point. Increasing the assumed debt-asset ratio and annual debt service requirement, resulted in a risk-return tradeoff with lower levels of risk (measured as mean deviation below target or MDBT) being obtained at the expense of lower levels of expected returns. At a higher debt asset-ratio, when the mean deviation below target (MDBT) was varied over a range of values, the quantity of crops harvested also varied. The average harvested acres of alfalfa and corn silage increased as the MDBT increased while the harvested acres of corn grain and ryelage decreased. Alfalfa harvest is increased because less forage in terms of ryelage is harvested and the average quantity of corn grain decreases as the MDBT increases because more com silage is grown in place of the costlier but less risky ryelage. The results show that hedging and participation in the government feed grain program could lead to effective risk reduction and increases in expected returns for the dairy farmer. Government program participation increased expected returns at all debt-asset ratios. Both government programs and hedging reduced risks at higher debt-asset ratios. Government program participation led to larger gains in expected returns as the availability of land increased. / Master of Science

Thesis (M.Sc. (Horticulture)) --University of Limpopo, 2009 / Field experiments were conducted at the University of Limpopo experimental farm, Syferkuil during 2005/06 and 2006/07 production seasons. This was initiated to examine the effect of leaf removal on cowpea biomass, protein content and grain yield under sole and binary cultures. Treatments consisted of cowpea varieties (Pan 311 and Red caloona), cropping systems (sole and intercropping) and cowpea-leaf pruning regimes (pruning and un-pruned). Sweet corn was planted, as a component crop in the intercropped plots while sole sweet corn plot was included as a treatment. All treatment combinations were laid out as Randomize complete block design (RCBD) with four replicates. Supplementary irrigation was carried out during the plant growth period. Fully expanded leaves were harvested once on all cowpea plants in the two middle rows from designated plots at seven weeks after planting for each year. Growth and yield data were collected from component crops during the course of the trial while the protein content of harvested leaves and immature pods as well as the different cowpea plant parts at harvest were determined. Results of the study revealed that leaves of cowpea variety, Pan 311 harvested prior to the reproductive stage had significantly higher protein content than those of Red caloona. Protein content of immature Pan 311 pods had higher (18.8 to 25.1%) than Red caloona (17.9 to 20.7%) during both planting seasons. The percent protein content of cowpea stem obtained at harvest for Pan 311 varied between 9.3 and 9.4%, and between 9.9 and 12.3% for Red caloona during both planting seasons. Grain yield obtained for Pan 311 and Red caloona were 1703.7 kg ha-1 and 1479.8 kg ha-1, respectively during 2005/06 and 1290.7 kg ha-1 and 511.7 kg ha-1 respectively during 2006/07 planting seasons. Sweet corn intercropped with Red caloona during both planting seasons had higher average grain yield than when intercropped with Pan 311. Although intercropping decreased the partial land equivalent ratio (LER) value of individual component crops, the combined LER values of between 1.1 and 2.3 under intercrop for the different treatment combinations implies that the practice is advantageous. The results of post harvest soil analyses revealed that topsoil has the pH value of 7.11-7.29 indicating neutral soil while subsoil pH value of 6.27-6.91 indicated slightly acidic to neutral soil during both planting seasons. Based on the findings of this study, cowpea variety Pan 311 can be recommended as a better vegetable crop than Red caloona since it has higher leaf and immature pod protein content. It also had higher grain yield than Red caloona when intercropped with sweet corn. Sweet corn had high grain yield when intercropped with Red caloona than when intercropped with Pan 311. Keywords: Cropping systems, protein content, grain yields, leaf pruning and cowpea.

A study was conducted to determine (1) the N contribution of lentil (<i>Lens culinaris</i> Medikus) and its effect on subsequent wheat (<i>Triticum aestivum</i> L.) crops in the Dark Brown and Brown soil zones of Saskatchewan, (2) if synchronization of available N contributes to the rotation benefit, and (3) N fertilizer replacement value of the N effect of lentil on the subsequent wheat crop. Two approaches were used: a landscape-scale study established at Dinsmore in 1994, and a repeated small-plot study established at several locations (Dinsmore, 1993 and 1994; Clavet, Conquest, Eston and Zealandia, 1995). In the landscape-scale study, N2 fixation by lentil ranged from 28 to 46 kg ha-1, with an average of 34 kg ha -1 N and an N balance of -36 kg ha-1. In the small-plot study, N2 fixation ranged from 10 to 112 kg ha -1 with an average of 59 kg ha-1 N and an N balance of -22 kg ha-1. In the landscape-scale study, preseeding available N on the rotation that incorporated lentil was 29 and 61% higher than in the monocropped wheat in the first and second subsequent crops, respectively. The corresponding values for the small-plot study were 59 and 14%, respectively. N availability was well synchronized with the period of maximum N demand by the wheat crop in both rotations. However, both lentil-residue N and wheat-residue N were poorly synchronized with the period of maximum N demand by the wheat. The rotation effect was exhibited in higher grain yield (23% higher in the landscape-scale study, and 21% higher in the small-plot study). Approximately 10 and 70% of the rotation benefit in the landscape-scale and small plot studies, respectively, were attributed to the N effect. Nitrogen fertilizer replacement value ranged from 47 to 89 kg ha-1 N. Therefore, lentil can fix enough N and indirectly contribute to greater available N in subsequent crops than in crops following non-legumes. However, the actual amount of N derived from lentil residue is small. The greater available N is attributed to spared N and enhanced soil N mineralization. Hence, under the conditions of this study, enhancement of available N contributed more to the rotation benefit than synchronization. The high NFRV show that inclusion of lentil in the rotation can enhance available N in the cropping system and potentially reduce fertilizer N application.

A risk analysis of drought and an assessment of irrigation requirements were ascertained for a wheat (Triticum aestivum L.) crop in Parana, Brazil, using 28 years of historical weather data. Two soil moisture models, The Versatile Soil Moisture Budget (VB4) and SWACROP models, were compared using data from six wheat cropping periods. The models showed good performance in predicting soil moisture contents, but SWACROP underpredicted soil evaporation and runoff, and VB4 did not separate evapotranspiration into its components. Therefore, a new soil moisture model was proposed. In the new model, a Darcy type equation was used to calculate fluxes in the soil profile, and inputs of daily rainfall and potential evapotranspiration were partitioned during the day using simple disaggregation methods. Crop growth input parameters, interacting with weather and soil inputs, were used to calculate a detailed output of the water balance components. The validation of the model showed predictions of soil water contents and evapotranspiration in close agreement with field data. / A crop yield model based on the stress day index approach was selected from an evaluation of seven crop-water production functions using wheat field data. This model was combined with the soil moisture model to assess risks of drought during the establishment and development of non-irrigated wheat crops with different planting dates. Irrigation management strategies were simulated to identify net system delivery capacities and application frequencies that promote maximum yield with minimum requirements of water. Yield reductions in non-irrigated wheat due to water stress varied between 16%, for early plantings, to 50%, for late plantings. Maximum yields with minimum applied water was obtained by the use of low intensity (5 to 10 mm) and frequent (3 to 5 days) irrigations. System delivery capacity requirements varied from 1.5 to 3.0 mm/day, according to planting dates.

Transverse cotyledonal cracking (TVC) was characterised at physiological, biochemical and molecular levels in three common bean (Phaseolus vulgaris L.) cultivars: Imbali, Tongaat and Tokai. The incidence of TVC was determined visually on ten-day old seedlings and was expressed as the number of cracks per plant. The effect of Ca++ on TVC incidence was examined by enhancing the calcium content of seed cotyledons using calcium salts in seed priming and coating. EDAX was used to quantify the cotyledonal calcium content. Activities of the pectinolytic enzymes polygalacturonase (PG) and pectin methylesterase (PME) were assayed at dry seed, VC, R4 and R6 phenophases of the bean plant, and zymogram electrophoresis was used to identify the two enzymes. The results showed that cultivars Imbali, Tongaat, and Tokai were susceptible resistant and intermediate, respectively, with respect to TVC incidence. Calcium uptake was higher in Tongaat cultivar (P= 0.05) compared with Imbali and Tokai, irrespective of calcium salt enhancement. Vigour was significantly reduced (P< 0.01) by both coating and priming. TVC significantly lowered yield (P= 0.05) in the susceptible Imbali cultivar. Zymogram analysis identified lytic bands at ~45kDa (PG gel) and ~30kDa (PME gel). The activity profile of PME was similar for all cultivars. However, PG activity of susceptible Imbali was high in dry seeds and at the R4 and R6 stages of plant development, whereas the more resistant cultivars displayed high activity at the VC stage only. It is concluded that high PG activity at R4 stage is a more reliable determinant of green bean propensity to cotyledonal cracking. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2005. / Thesis documentation sheet inserted. Appendix consists of reproductions of 5 published papers and manuscripts, four co-authored with others. Includes bibliographical references. Issued also electronically via World Wide Web in PDF format; online version lacks appendix of papers; map in online version displays in color.