Masters Degrees (Soil, Crop and Climate Sciences)
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Browsing Masters Degrees (Soil, Crop and Climate Sciences) by Author "Allemann, J."
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Item Open Access Evaluation of irrigated cotton cultivars in South Africa(University of the Free State, 2011-09-20) Pretorius, M. M.; Allemann, J.English: Cotton (Gossypium hirsutum) is a globally important fibre crop. The cottonseed has a high oil and protein content and is used for human and animal consumption. Innumerable commodities are made from cotton. Annual cultivar evaluations are essential to compare the yield and quality obtained in different production areas, to obtain experimental data to recommend the most suitable cultivar for a production area. The objective of this study was to evaluate the performance of different cotton cultivars under irrigation in South Africa. The cultivars planted from the 2003/2004 season up to the 2005/2006 season were NuOPAL, DeltaOPAL, DeltaOpal RR, LS9219 and SZ9314. The localities were Loskop (Mpumalanga Province), Makhathini (KwaZulu- Natal), Rustenburg (North-West Province), Vaalharts and Upington (Northern Cape) and Weipe (Limpopo Province). The Additive Main Effects and Multiplicative Interaction (AMMI) statistical model was used to describe the effect of cultivar x environment interaction on the yield of cotton planted under irrigated conditions. It is recommended that cotton producers should plant NuOPAL, since it was selected by the AMMI model as the best performer in respect of seed cotton yield and fibre yield (kg ha-1) in fifteen out of eighteen environments.Item Open Access Factors affecting maize (Zea mays L.) sensitivity to acetochlor(University of the Free State, 2009-12) Mphundi, Patricia Makuzana; Allemann, J.; Ceronio, G. M.English: A number of the commercially available maize cultivars were screened in order to establish their tolerance to acetochlor. These cultivars demonstrated significant differences in their tolerance, with some cultivars being tolerant and others sensitive to the herbicide. The cultivar PAN6Q521R was the most tolerant and DKC 73-76R was the most sensitive, while most other cultivars were intermediate in their sensitivity. This indicates that maize tolerance to acetochlor is genetically controlled. The influence of planting depth on maize tolerance to acetochlor was investigated using these two cultivars. Both cultivars were found to be more sensitive as the planting depth increased to 45 mm. However, seedlings of DKC 73-76R exhibited more phytotoxicity than PANQ6521R at all planting depths. The effect of seed size on acetochlor tolerance could not be determined with any clarity. Cultivar sensitivity to the herbicide as well as seed shape appeared to also play a role. In DKC 73-76R it appeared as though large flat seeds produced plants more tolerant to acetochlor than smaller flat seeds. The effect of soil type on acetochlor phytotoxicity on a tolerant (PANQ6521R) and sensitive (DKC 73-76R) maize cultivar was examined in two trials, one using an average application rate on all soils, and the second utilizing the recommended application rates for each soil. Acetochlor activity was found to be lowest on the clay loam soil (38% Clay) and highest on the sandy soil (8% Clay) in the first case, with severe phytotoxicity occurring on the latter soil. In the second trial bioactivity was similar on all soils, although greater on the sand. This indicated that the recommended application rate on sandy soils might need adjustment. The influence of temperature on maize tolerance to acetochlor was investigated at suboptimal (15/8oC), optimal (25/18oC) and supra-optimal (35/28oC) temperature regimes (day/night temperature respectively). Seedling growth of both cultivars was inhibited significantly by acetochlor at the optimum temperature regime (25/18oC). All results confirmed that DKC 73-76R was more sensitive to acetochlor than PAN6Q521R.Item Open Access Growth and physiological response of amaranth seedlings to temperature and drought stress(University of the Free State, 2013-10) Nuugulu, Leonard Megameno; Pretorius, J. C.; Allemann, J.English: Several environmental factors constantly play a role in crop failures. Of these high temperature and limited water supply are major factors that limit plant productivity and threatens food security. Hence, a search for alternative crops with good tolerance characteristics towards abiotic stress is an ongoing process. Amaranth has been established as an annual vegetable and grain crop and is seen as a prospective alternative crop. Seed germination and seedling development are presumed to be the most critical stages in the life cycle of many seed propagated crops. This served as a rationale for the underlying study on two amaranth species in terms of seed germination, as well as the morphological and physiological response of seedlings to different temperature (25, 30, 35, 40˚C) and water potential (0, -250, -500, -750, -1000, -1250 kPa) regimes. For A. cruentus the optimum temperature was between 25 and 30oC and between 30 and 35oC for A. hybridus in terms of seed germination and early seedling growth. A. hybridus showed a greater level of adaptation to the higher temperature regimes as well as when simultaneously exposed to a rather stringent water potential of -1250 kPa by maintaining root growth better than A. cruentus. Moreover, the imposed temperature/drought stress condition had no significant effect on either of the physiological parameters tested in the former species. These included sugar and total water soluble protein levels as well as photosynthesis and respiratory capacity. Together with the ability of stressed seedlings to maintain growth, the latter strongly suggests that the metabolic events were scarcely affected in A. hybridus, supporting the postulate that it showed a higher degree of tolerance towards abiotic stress conditions. Alternatively, more than half of these events were found to be upgraded in A. cruentus seedlings and interpreted as an attempt by this species to counteract the stress effects, but not successfully, as measured by its inability to maintain seedling growth under these stress conditions.Item Open Access Influence of temperature on yield and quality of carrots (Daucus carota var.sativa)(University of the Free State, 2011-11) Manosa, Nthabiseng Adelaide; Engelbrecht, G. M.; Allemann, J.The influence of temperature on yield and quality of carrots were examined using two pot trials that were conducted in the glasshouse and growth chambers at the Department of Soil, Crop and Climate Sciences, on the Bloemfontein campus of the University of the Free State in 2009 and 2009/10. In the first trial the influence of four temperatures (10, 18, 26 and 32°C) on the growth, yield and quality of two pre-pack carrot cv’s. Nectar and Star 3002 were studied. Carrot seed were sown in 0.34 m x 0.34 m x 0.35 m pots, filled with topsoil of the sandy loam Bainsvlei form. Pots were kept in the glasshouse at 20°C (±1°C) for four weeks to allow the seedlings to establish and reach the first true leaf stage whereupon they were moved to the controlled environment chambers at different temperatures for 20 weeks. Growth parameters such as leaf number, plant height and leaf growth were significantly influenced by temperature and all these parameters performed the best at 10°C at the end of the growth season irrespective of cultivar. Root fresh and dry mass did not differ significantly between the two cultivars but the affect of temperature was significant. The highest root fresh mass for both cultivars was also obtained at 10°C, with “Star 3002” with the highest mass (39.12 g) followed by “Nectar” (34.26 g). Both cultivars exhibited the highest root dry mass at the lower temperature treatment (10°C) with “Star 3002” having a higher root dry mass (4.15 g) than “Nectar” (3.87 g). External quality parameters such as root length and diameter differed significantly between the temperature treatments and only the length of carrot roots did not differ significantly between the cultivars. Both “Nectar” and “Star 3002” exhibited the longest roots at 10°C and the shortest roots at 18°C. Root diameter for both cultivars was significantly greater at 10°C than at 18°C. The only defects observed were green shoulder and misshapen roots. Although not significant, the percentage green shoulders and misshapen roots were higher at 18°C than at 10°C. Carrots were significantly firmer at the low temperature (10°C) than at 18°C. The total soluble solid content of carrots however, grown at 18°C was significantly higher than those grown at 10°C. In the second pot trial the influence of four dual temperatures (15/5, 24/10, 28/20 and 35/25°C) on the growth, yield and quality of two pre-pack carrot cultivars “Nectar” and “CS 1006” was studied. Based on the results of this study, temperature influenced leaf number and plant height of both cultivars, although not always significantly, during the 32 weeks of growth. Leaf number and plant height of carrot plants were greater at 15/5°C treatment. Yield parameters and the external quality parameters such as root length; diameter and absence of defects were also influenced significantly by temperature. Carrot root length and diameter were significantly influenced positively by lower temperatures (15/5°C) and absence of defects such as green shoulder and hairiness were significantly influenced negatively by higher temperatures (28/20°C). Some of the internal quality parameters such as firmness, total soluble solids, carotene, β-pinene and caryophyllene were also significantly affected by temperature. Firmness, total soluble solids and carotene were significantly influenced by lower temperature (15/5°C) whereas β-pinene and caryophyllene were significantly influenced by higher temperatures (28/20°C). Free choice profiling (FCP) was carried out in order to investigate how semi-naïve panelists described and perceived carrot samples cultivated under different temperature conditions. This method allowed participants to use their own attributes to describe and quantify the food product. The FCP procedure generated six descriptors on the attribute taste and one on aftertaste. The two carrot cultivars grown at the higher temperatures (24/10 and 28/20°C) had descriptors like bitter, sour, bland and chemical, with a definite aftertaste while carrot cultivars grown at lower temperatures (15/5°C) had descriptors such as sweet and carrot taste.Item Open Access Response of maize to rainwater harvesting and conservation techniques on the Glen/Oakleaf ecotope(University of the Free State, 2016-11) Chuene, Mardulate Motlalepula; Allemann, J.; Botha, J. J.English: Rainfall in semi-arid areas fluctuates constantly and it is difficult for farmers to increase crop productivity. The rainfall is insufficient, erratic and unreliable, which is associated with poor water availability due to increased water losses such as high evaporation from the soil (Es) due to rising temperatures, runoff (R) and deep drainage (D). These unproductive losses (Es, R & D) contribute to inefficient rainfall, which increases food insecurity and poverty. Crops produced in semi-arid areas under rainfed agriculture by smallholder farmers are usually produced using conventional tillage (CON). This system uses a moldboard plough, which turns and exposes the soil and therefore increases Es and R while organic matter is decreasing. In many semi-arid areas, research was conducted to improve crop production. One of these researches was conducted in South Africa at the Thaba Nchu villages where the Agricultural Research Council (ARC-ISCW) introduced an In-field rainwater harvesting technique (IRWH) to increase efficiency and use of limited water. This system was used to reduce unproductive water losses especially Es and R, to optimize rainwater productivity (RWP). This study was conducted to investigate the ability of different rainwater harvesting and conservation (RWH&C) techniques to produce higher yield in using and storing water efficiently under rainfed conditions of Glen/Oakleaf ecotope. To test the hypothesis, a field experiment was conducted in a semi-arid area under rainfed conditions at the Glen/Oakleaf ecotope in Bloemfontein. The area is characterized by an average long-term (LT) rainfall in the growing period of 262 mm and an evaporation demand of 758 mm. Treatments used were In-field rainwater harvesting with a 2.0 m runoff strip (IRWH-2.0m), In-field rainwater harvesting with a 2.4 m runoff strip (IRWH-2.4m), Mechanised basins (MB), Minimal tillage (MIN), Darling plough (DAL) and Conventional tillage (CON). The experiment was conducted in two consecutive growing seasons (2008/09 & 2009/10) laid out in a complete block design (RCBD), with four replications and six treatments. The study was aimed to identify the most appropriate RWH&C techniques that will increase rainwater availability throughout the growing season to increase crop productivity by maximizing yield per unit of water. The first season had 260 mm of rainfall, and was considered a dry season, the second season was a wetter season with 486 mm. rainfall. During the first growing season rainfall was 8% lower than the LT (262 mm), while in the second season it could be considered wetter as the rainfall was 85% higher than LT. Rainfall during Vp was greater than LT during both seasons with 19% and 49% higher rainfall respectively. During the first dry season rainfall at Rp was 41% lower than LT and 160% higher during the second wet season. A short growing maize cultivar was chosen as a crop indicator, PAN 6Q-521R with a growing period of 120 days from planting to harvest. The ecotope had a fine sandy loam soil with a depth of ± 1200 mm and a clay content of 15% in the A horizon and 30% in the B horizon. Land preparation was done by loosening up the soil to avoid compaction before implementing the different RWH&C techniques and CON treatment. Therefore, CON treatment was tilled with a moldboard plough. Only CON was ploughed during the second season and other treatments were not implemented. Evapotranspiration was calculated by using the soil water balance equation for dryland crop production. Soil water content was measured with a neutron water meter and crop water efficiencies (RSE, WUE, PUE & RWP) were calculated. Maize height, stem diameter, leaf area index and biomass were measured in four growth development stages only during the 2008/09 growing season while grain yield was measured during both seasons. The first objective is explained in chapter 4, which was to evaluate soil water balance and different rainwater efficiency (Rainwater storage efficiency (RSE), Water use efficiency (WUE) and Precipitation use efficiency (PUE)) of various RWH&C techniques against CON tillage for possible adoption by smallholder farmers to increase crop productivity. The Plant available water at planting, tasseling and harvest were higher with RWH&C techniques compared to the CON treatment during both growing seasons. Similarly soil water content during both seasons were higher with RWH&C techniques compared to CON tillage. However, during the first growing season at 13 DAP, the soil water content of all treatments was above the DUL line of 280 mm indicating that D could have occurred. MIN treatment was shown to have the highest runoff percentage followed by CON tillage. The ET of RWH&C techniques during the dry season (2008/09) was higher than that of CON tillage, however more water was lost through Es with RWH&C techniques. During the second season RWH&C techniques excluding MIN tillage had higher ET compared to CON tillage and higher Es. RSE was not included during the first season due to late implementation of treatments. During the second season IRWH-2.0 m and IRWH-2.4 m treatments had the lowest RSE compared to MIN CON, MB and DAL treatments. The results showed that IRWH-2.0m treatment had the lowest WUEET during both seasons. During the dry season (2008/09) WUEEV based on transpiration was highest on the IRWH-2.0m treatment and during the wetter season (2009/10) CON treatment had the highest WUEEV. During the 2009/10 season, RWH&C techniques excluding IRWH-2.0m showed to have greater PUEfg than that of CON treatment. During the dry season the results showed a higher PUEg with RWH&C techniques than that on CON treatment; however during the wet season PUEg was higher with IRWH-2.4m treatment compared to that of CON treatment. For both seasons (2008/09 & 2009/10) IRWH-2.4m, MIN and MB techniques had greater RWP compared to CON tillage. Overall the results showed that RWH&C techniques collected and stored water better during the dry season than in the wet season. The second objective of this study was to determine maize performance under the various RWH&C techniques compared to CON tillage on the Glen/Oakleaf ecotope. This objective is explained in Chapter 5. Plant height, stem diameter and LAI data were collected only during the first season and the study revealed that maize plants exposed to the CON treatment were taller and thicker compared to RWH&C techniques. During the Vp, plants exposed to the CON treatment had lower LAI than those exposed to RWH&C techniques. At 66 DAP there were no differences between the treatments, however, at 90 DAP plants exposed to the CON treatment had higher LAI. During the Vp of the first season at 30 DAP, plants exposed to the IRWH-2.4m treatment had greater biomass than all other treatments, however during the second season plant biomass exposed to the IRWH-2.0m, and MB treatments were greater than those exposed to the CON treatment. During the first season at 45 DAP plants biomass exposed to the MIN and IRWH-2.0m treatments were both greater than that of other treatments and during the second season plants exposed to the CON treatment were higher than those exposed to the RWH&C techniques. During the Rp at 66 DAP, in both seasons plants exposed to the DAL treatment produced less biomass than in all the other treatments. During the 2008/09 season at 90 DAP, plants exposed to the IRWH-2.4m, MIN and CON treatments were higher than DAL. However, in the second season at 90 DAP plants showed no difference in biomass between treatments. Grain yield differed between the two seasons due to differences in rainfall. During the dry season of 2008/09, RWH&C techniques had higher grain yield than that of CON treatment. In the wet season of 2009/10 IRWH-2.4m was the only RWH&C technique with a high yield. It was concluded that RWH&C techniques were most likely to perform better in dry conditions than during wetter conditions. During the wet season only IRWH-2.4m techniques performed better than that of CON treatments.Item Open Access Response of onion (Allium cepa L.) to sowing date and plant population(University of the Free State, 2012-06) Bosekeng, Gagopale; Engelbrecht, G. M.; Allemann, J.Field trials were conducted on the West Campus facility of the Department of Soil, Crop and Climate Sciences of the University of the Free State in Bloemfontein during 2009 and 2010. The first trial during 2009 investigated the response of onion (Allium cepa L.) cultivars to sowing date. Cultivars namely; Charlize, Jaquar, Python and South Wester were used in 2009. Onions were sown on 31 April, 7 May and 21 May during 2009. The second trial was conducted during 2010, where cultivar Ceres Gold was used to replace South Wester as the latter was no-longer available in the market and sowing was done on 11 May, 25 May and 8 June. In both seasons, experiments were laid out as a randomized complete block design with each treatment combination replicated three times. During 2009, plant population of 41 plants m·2 was used, while in 2010 plant population of 61 plants m·2 was used. Plots of 1.8 m2 were used with each plot having five rows. Each row had fifteen plants during 2009 and twenty two plants during 2010. Before planting, soil sampling and analysis were made, thereafter, fertilizers were applied as per soil analysis results. A third field trial was conducted in 2010 to evaluate the three sowing dates (11 May, 25 May and 8 June) with a combination of five plant populations (95, 83, 74, 67 and 61 plants rn") using one onion cultivar ('Jaquar'). The experiment was laid out as a randomized complete bock design, with three replications having 1.8 m2 plots. In each plot there were five rows. A bulb storage trial was also conducted under room (±25°C) and cold room temperatures (±5°C). This was done for all field trial in both seasons. In a trial investigating response of cultivars to sowing date, better plant height, number of leaves, bulb fresh mass, and yield were observed when sowing was done from the end of April to the end of May. Sowing date significantly influenced bulb and neck diameters only during 2009. Bulbs were becoming more firm as sowing date was delayed, and the opposite was observed for bolting. Cultivar South Wester bolted more, followed by cultivar Jaquar while other cultivars did not bolt. The shape of bulbs was not significantly influenced by sowing date but it showed to be cultivar authentic. No split bulbs were observed. In a trial of sowing date and plant population, significantly taller plants were obtained with early sowing date than the two later sowing dates. Leaf production was not significantly influenced by sowing date. Sowing date and plant population affected bulb fresh mass, yield, bulb and neck diameters as well as firmness. Sowing date did not influence bulb shape while plant population did. None of the bulbs bolted from this trial. Mid-intermediate day cultivars ('South Wester' and 'Ceres Gold') recorded the shortest duration (105 days and 63 days respectively), while on average other cultivars were stored for 126 days in 2009 and 105 days in 2010. Storage disease (black mould), sprouting and loss of moisture from the bulbs were the contributing factors for reduction in storage duration. These factors were promoted by both field and storage conditions. Onion producers should have adequate information on the cultivars and the production In a trial of sowing date and plant population, significantly taller plants were obtained with early sowing date than the two later sowing dates. Leaf production was not significantly influenced by sowing date. Sowing date and plant population affected bulb fresh mass, yield, bulb and neck diameters as well as firmness. Sowing date did not influence bulb shape while plant population did. None of the bulbs bolted from this trial. Mid-intermediate day cultivars ('South Wester' and 'Ceres Gold') recorded the shortest duration (105 days and 63 days respectively), while on average other cultivars were stored for 126 days in 2009 and 105 days in 2010. Storage disease (black mould), sprouting and loss of moisture from the bulbs were the contributing factors for reduction in storage duration. These factors were promoted by both field and storage conditions.Item Open Access Response of onion (Allium cepa L.) to sowing date and plant population(University of the Free State, 2014-05-27) Bosekeng, Gagopale; Engelbrecht, G. M.; Allemann, J.Field trials were conducted on the West Campus facility of the Department of Soil, Crop and Climate Sciences of the University of the Free State in Bloemfontein during 2009 and 2010. The first trial during 2009 investigated the response of onion (Allium cepa L.) cultivars to sowing date. Cultivars namely; Charlize, Jaquar, Python and South Wester were used in 2009. Onions were sown on 31 April, 7 May and 21 May during 2009. The second trial was conducted during 2010, where cultivar Ceres Gold was used to replace South Wester as the latter was no-longer available in the market and sowing was done on 11 May, 25 May and 8 June. In both seasons, experiments were laid out as a randomized complete block design with each treatment combination replicated three times. During 2009, plant population of 41 plants m-2 was used, while in 2010 plant population of 61 plants m-2 was used. Plots of 1.8 m2 were used with each plot having five rows. Each row had fifteen plants during 2009 and twenty two plants during 2010. Before planting, soil sampling and analysis were made, thereafter, fertilizers were applied as per soil analysis results. A third field trial was conducted in 2010 to evaluate the three sowing dates (11 May, 25 May and 8 June) with a combination of five plant populations (95, 83, 74, 67 and 61 plants m-2) using one onion cultivar (‘Jaquar’). The experiment was laid out as a randomized complete bock design, with three replications having 1.8 m2 plots. In each plot there were five rows. A bulb storage trial was also conducted under room (±25°C) and cold room temperatures (±5°C). This was done for all field trial in both seasons. In a trial investigating response of cultivars to sowing date, better plant height, number of leaves, bulb fresh mass, and yield were observed when sowing was done from the end of April to the end of May. Sowing date significantly influenced bulb and neck diameters only during 2009. Bulbs were becoming more firm as sowing date was delayed, and the opposite was observed for bolting. Cultivar South Wester bolted more, followed by cultivar Jaquar while other cultivars did not bolt. The shape of bulbs was not significantly influenced by sowing date but it showed to be cultivar authentic. No split bulbs were observed. In a trial of sowing date and plant population, significantly taller plants were obtained with early sowing date than the two later sowing dates. Leaf production was not significantly influenced by sowing date. Sowing date and plant population affected bulb fresh mass, yield, bulb and neck diameters as well as firmness. Sowing date did not influence bulb shape while plant population did. None of the bulbs bolted from this trial. Mid-intermediate day cultivars (‘South Wester’ and ‘Ceres Gold’) recorded the shortest duration (105 days and 63 days respectively), while on average other cultivars were stored for 126 days in 2009 and 105 days in 2010. Storage disease (black mould), sprouting and loss of moisture from the bulbs were the contributing factors for reduction in storage duration. These factors were promoted by both field and storage conditions. Onion producers should have adequate information on the cultivars and the production.