Masters Degrees (Agronomy)
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Browsing Masters Degrees (Agronomy) by browse.metadata.advisor "Agenbag, G. A."
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- ItemAspects of honeybush tea (Cyclopia species) propagation(Stellenbosch : Stellenbosch University, 2008-12) Mbangcolo, Mongezi Morrison; Reinten, E.; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.Honeybush (Cyclopia spp. Fabaceae) is indigenous to the fynbos botanical biome of the Eastern and Western Cape of South Africa. The increase in the international demand for honeybush tea for health benefits, concern over exploitation of wild populations and the lack of published agronomic information necessitated this study to evaluate different aspects of honeybush propagation. The main objectives of this study were to evaluate the effect of species and cutting position on rooting of cuttings of Cyclopia species using different rooting hormones, to evaluate the effect of an organic plant fertilizer and cutting position on growth and establishment of rooted cuttings and to study the influence of different seed pre-treatments on germination of Cyclopia species. Terminal and sub-terminal cuttings of C. intermedia and C. genistoides treated with different rooting hormones were rooted under day/night temperature controlled glasshouse conditions. Intermittent mist was used as means of moisture supply to the cuttings for 45-60 seconds daily every 30 minutes. C. genistoides rooted significantly better compared to C. intermedia as measured by rooting percentage, number of roots per cutting, length of longest root and mean root length during the summer season. The cutting position had a significant effect on rooting of the cuttings in summer compared to winter and spring season. The interactive effect of species, treatment and cutting position resulted into 86% of rooting in summer from the terminal cuttings of C. genistoides, while only 4% was recorded as the highest rooting percentage in both winter and spring seasons. The highest number of roots and the greatest root length per cutting were obtained with 2 and 4 g L-1 IBA from terminal cuttings of C. genistoides and these hormone concentrations were not significantly different to each other. To evaluate the effect of an organic plant fertilizer and cutting position on plant growth and establishment, rooted cuttings of two Cyclopia species (C. intermedia and C. genistoides) from two cutting positions (terminal and sub-terminal) were transferred to pots (576 cm3) and treated with Nitrosol fertilizer at application rates of 3.33 ml.L-1, 1.67 ml.L-1 and 0 ml.L-1 (control). Cyclopia plantlets were uniformly inoculated once with a symbiotic Rhizobium bacteria to improve the formation of nodules. Nitrosol® at 3.33 ml.L-1 significantly affected fresh and dry plant weight, fresh and dry root weight, number of shoots and nodules per plant compared to either 1.67 ml.L-1 or the control. Relative to species, C. genistoides performed better in terms of fresh and dry plant weight, fresh and dry root weight, and number of shoots and nodules per plant compared to C. intermedia. The origin of the cutting position did not significantly affect the above mentioned parameters. Plant mineral analysis revealed that most of the essential elements increased with increasing Nitrosol® application rates, with C. genistoides having higher levels of mineral elements than C. intermedia. This could be an indication of the differences between the two species in terms of nutrient uptake, utilization and distribution within the plant tissues. In the germination studies, seeds obtained from different seed sources of Cyclopia species were subjected to different pre-sowing treatments. Seed treatments were sulphuric acid (95%), hot water (100°C), water with smoke paper disk, and demineralised water (control). The study revealed that all the treatments had a significant effect on germination with the exception of eight year old seeds obtained from C. subternata (seed source two). Although hot water treatment improved germination compared to smoked paper disk and the control, seeds treated with hot water degenerated rapidly. The highest overall germination (77.33%) was found with one year old seeds compared to other seed sources older than one year. Although smoked paper disks generally did not improve germination compared to the control, in one year old seeds from seed source one, this treatment greatly influenced germination, suggesting that seed age might have influenced germination of these seeds. In terms of germination rate, germination generally started after four days in most treatments.
- ItemEffect of mycorrhizal inoculation and phosphorus levels on growth and yield of wheat and maize crops grown on a phosphorus deficient sandy soil(Stellenbosch : University of Stellenbosch, 2010-12) Pharudi, Joseph Albert; Agenbag, G. A.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy.ENGLISH ABSTRACT: See full text for the abstract
- ItemThe effect of Phosphorus on the growth, plant mineral content and essential oil composition of Buchu (Agathosma betulina)(Stellenbosch : University of Stellenbosch, 2007-12) De Villiers, Chris Johan; Agenbag, G. A.; Langenhoven, P.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy.An increase in the demand of buchu (Agathosma betulina) oil has lead to an increase in the commercial cultivation of buchu in fields and also in hydroponic systems. A nutrient solution for hydroponically grown buchu is still required to ensure optimal growth and yield. ASNAPP (Agribusiness in Sustainable Natural African Plant Products) South Africa has done some trials to achieve optimal EC and pH in the nutrient solution. Phosphate concentrations in the nutrient solution might play a significant role due to reports by a variety of researchers on the sensitivity of Protea plants to phosphate. Buchu and Proteas are both part of the Fynbos biome and are found in regions with similar soil (sandy soils with a low pH and mineral contents) and climatic conditions. Two separate experiments were conducted to determine the effect of increasing phosphate concentrations (ranging from 0.00 to 1.40 me L-1) in the nutrient solution on buchu growth. The first experiment was done in a plastic covered structure with a pad and fan and the objective of this trial was to determine the effect of increasing phosphate concentrations in the nutrient solution on the general growth, biomass production, oil composition, mortality rate and chemical composition of the buchu plants. The second experiment was done in a glasshouse with mechanical temperature control and the aim of this trial was to determine the response of buchu to increasing concentrations of P at two different root temperatures. A chemical analysis of the plants was done and the general growth, yield and root mass were recorded to determine the response of buchu plants to the phosphate and temperature treatments. In the greenhouse experiment an optimum growth and yield response of buchu plants was found at a phosphate concentration of 0.7 me L-1 in the nutrient solution. Phosphate concentrations lower or higher than 0.7 me L-1 lead to a decrease in growth and yield. An increase in the phosphate concentration in the nutrient solution lead to a general increase in N, P, K, Ca, Mg and B content in the buchu plants and a decrease in Fe content. The mortality rate of the buchu plants increased with an increase in the phosphate concentration from 0.0 to 1.4 me L-1 in the nutrient solution. The phosphate concentration in the nutrient solution only made a significant difference on one major component of the buchu oil which was Ψ-Diosphenol, but no general trend with Ψ-Diosphenol content and P concentration could be found and the significant difference in Ψ-Diosphenol observed in this trial may only have been due to genetic variation between the plants. The effect of the different root temperatures in the glasshouse experiment was very clear. The buchu plants grown at the high root temperature (20°C) produced a higher yield and better overall growth than the plants grown at lower (10°C) temperatures. The buchu plants grown at 20°C had a significantly higher N, K, Na and B content than plants grown at 10°C. Buchu plants grown at 10°C showed no significant response in terms of growth and yield to the phosphate concentration in the nutrient solution, but plants grown at 20°C exhibited growth and yield peaks at phosphate concentrations of 0.35 and 1.4 me L-1. The peak observed in the plants growth at high phosphate concentrations is unexplainable and can possibly be ascribed to the limitation of the plants per experimental unit and/or amount of replications. The increase in P concentration in the nutrient solution caused a general increase in N, P and K content in the buchu plants. A significant interaction between the phosphate concentration and root temperature was observed for the P, Mn en Zn contents of the plants which meant that the buchu plants respond differently towards phosphate concentrations at different root temperatures.
- ItemEffect of salinity on germination and seedling growth of Canola (Brassica napus L.)(Stellenbosch : University of Stellenbosch, 2007-03) Bahizire, Francois B.; Agenbag, G. A.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy.Soil salinity is a serious constrain to crop production in many countries. In the Western Cape canola production area, large variability in soil properties within the same field is a very common feature. Some of this variability may be ascribed to differences in salinity. These saline patches affected the germination and survival of cereal crops like wheat and may therefore also be a reason for the high variability and generally low canola yields obtained in this area. It will therefore be important to quantify the effect of such saline conditions on the germination and seedling establishment of canola in an effort to improve yields. In this study several experiments were conducted under controlled conditions in either Petri dishes in an incubator or pots in a temperature controlled glasshouse to determine the salinity response of canola. Results of the experiments done in Petri dishes, showed that the germination response of canola (Brassica napus L., cv. Tornado) to increasing levels of salinity is very similar to that of wheat (Triticum aestivum L., cv SST 88). Although canola germinated more rapidly than wheat at a temperature of 20 ºC, the final percentage germination for both crops decreased severely when NaCl induced salinity exceeded levels of an EC of 8 dS m-1, but less severe responses were obtained with NaCl/CaCl2 induced salinity. Under soil conditions an interaction between soil type and salinity level showed that the responses in sandy soil to an increase in salinity from 0 to 8 iv dS m-1 were less severe than in loamy soil and especially when salinity stress was induced by NaCl. Although cultivar Spektrum showed more tolerance to saline conditions during the germination and seedling stages in pot experiments when compared to other cultivars tested, these results will have to be confirmed in field trails where grain yield and quality can be measured.
- ItemThe effect of temperature on phenological responses and growth of canola cultivars(Stellenbosch : Stellenbosch University, 2014-12) Nwogha, Jeremiah Sunday; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ABSTRACT ENGLISH: Canola is increasingly becoming an important economic field crop in South Africa, because it can be used to produce high quality cooking oil and margarine, animal feed, biofuel and in crop rotation systems to break the disease cycle and improve weed management. Effect of temperature on phenological responses with respect to required number of days, growing degree days, photothermal units to specific growth stages, growth rate, as well as vegetative and reproductive growth of canola were studied under controlled conditions. Seven canola cultivars selected from early and mid-maturing groups of canola cultivars, presently planted in the Western Cape canola production area, were grown in 3 litre plastic bags filled with a mixture of sand and compost at ratio of 1:1 and irrigated with fully balanced nutrient solution at EC=2.0 in two glasshouses at night/day temperature regimes of 10/15oC and 15/20oC. Number of days, growing degree days (GDD) and photothermal units (PTU) from planting to seedling emergence, first true leaf appearance, visible flower buds, first flower opening, seed ripening and seed physiological maturity were recorded. Plant heights were measured at 14 day intervals from 28 to 84 days after planting (DAP). Plants were sampled for leaf area (LA) and above ground dry mass (DM) at budding, flowering and seed physiological maturity. Plant growth rates (PGR) from planting to budding, from budding to flowering and from flowering to physiological maturity were calculated. Relative growth rates (RGR) and net assimilation rates (NAR) from budding to flowering and from flowering to physiological maturity were also calculated. Days after planting, GDD and PTU at budding, flowering and physiological maturity were correlated with leaf area, dry mass, number of pods plant-1 and pod dry mass plant-1 at budding, flowering and physiological maturity to determine whether there were relationships between the variables. The study showed that by increasing night/day temperature from 10/15⁰C to 15/20⁰C plant height, number of leaves plant-1 at budding stage, leaf area at budding , plant growth rate (PGR) from planting to budding stage and relative growth rate (RGR) from budding to flowering stage were increased. However, PGR from budding to physiological maturity, RGR from flowering to physiological maturity, net assimilation rate (NAR) from budding to flowering stage, leaf area at flowering and physiological maturity stages , as well as number of flower stems, number of pods plant-1, above ground total dry mass at flowering and physiological maturity stages were decreased. Pod dry mass at physiological maturity decreased by 22.24% to 40.35% for different cultivars which clearly demonstrated the sensitivity of canola cultivars to increasing night/day temperatures. By increasing the mean daily mean temperature from 12.5⁰C (10/15⁰C night/day) to 17.5⁰C (15/20 ⁰C night/day) the duration of the period from planting to seedling emergence as well as the vegetative and reproductive growth stages were decreased. With the exception of the vegetative growth stage, GDD and PTU requirements to reach specific growth stages increased with an increase in temperature. Plant growth parameters such as dry mass, leaf area, number of pods plant-1 and pod dry mass plant-1 at specific growth stages showed a positive correlation with the number of days needed to reach that growth stage, but not with GDD or PTU requirements. Although the responses of cultivars to increasing temperatures did differ for most parameters measured, responses did not always correlate with the maturity grouping of cultivars, suggesting that responses to temperature may to a large extent be determined by the genetic make-up (breeding company) of cultivars. These results indicate that number of days, GDD and PTU requirements to reach physiological maturity may be used to describe the cultivar maturity groupings, but because of the effect of temperature and day length, GDD and PTU should be more accurate.
- ItemThe effect of timing of stripping on hop production under South African conditions(Stellenbosch : Stellenbosch University, 2015-12) Joseph, Beverley-Anne; Agenbag, G. A.; Reinten, E.; Stellenbosch University. Faculty of Agrisciences. Dept. of Agronomy.ENGLISH ABSTRACT: Hops is a small, but important agricultural commodity in South Africa. The hop cones contain secondary metabolites responsible for the flavour, aroma and bitterness in beer. The George and Waboomskraal area are the best suited for growing hops due to climate and geographical location. The optimum latitude for hops growing is 45° - 54° north and south of the equator, while these areas are at 34° S. International hop varieties are not adapted to the South African climate. Winters are too warm and summer days too short, thus all the varieties grown in South Africa have been bred for these specific conditions. The Hop breeding and research program strives to develop internationally competitive varieties with higher yields, desirable brewing characteristics, reducing input costs and increased productivity. To evaluate the current agricultural practices and to determine whether some of these practices negatively affect the plant health and yield, a study was conducted to investigate the effect of the time of stripping. Stripping refers to the practice of removing basal growth of the lower laterals and untrained bines. The study was done in two different microclimates, namely George and Waboomskraal. The aim was to determine the effect of the time of stripping on the vegetative growth, light interception, biomass, soft resins (alpha and beta acids), yield, rootstock weights and carbohydrate concentrations. The effect of stripping was also evaluated on different planting systems and plant maturity, namely Tram lines and conventional planting and 3 years old versus 5 year old plants. The effect of early stripping in terms of dry weight on mature plants is considerably less than the effect on younger plants. Young plants delivered lower dry weights, but accumulated higher carbohydrate reserves in the early stripping treatment. On young plants early stripping showed a significant difference favouring yield on tramlines. There is a general trend across all sites of higher crop efficiencies in the early stripped treatments. Growers could significantly increase yields without negatively affecting the quality (alpha and beta acids) by applying early stripping, especially in the George area. The effect of early stripping becomes more apparent in consecutive years as the time of defoliation affects foliage, carbohydrate concentration, canopy microclimate and light interception resulting in increased yields, especially on tramlines. From this study it can be concluded that early stripping appeared to have an influence on the dry root weight, carbohydrate concentration, light interception, crop efficiencies, yield and biomass. This practice is not only environmentally friendly by using less herbicide, it also delivers an economic gain. The effect of the time of stripping in consecutive years and different varieties deserves further study.
- ItemEstablishment, growth and yield of canola (Brassica napus L.) as affected by seed-drill opener, soil quality and crop residue in the Swartland(Stellenbosch : Stellenbosch University, 2018-03) Le Roux, Pieter Johannes Grobler; Swanepoel, Pieter Andreas; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: Canola (double low varieties of Brassica napus) is an important crop for farmers implementing conservation agriculture (CA). Famers implementing CA seek to minimise soil disturbance before, during and after planting. Many farmers in the grain producing regions (Overberg and Swartland) of the Western Cape have widely adopted CA over the past two decades. Although most farmers rely on tine openers to establish canola, disc openers are becoming more popular. Soil quality in these canola production areas are relatively low. The aim of this study was to compare tine and disc openers and the effects of soil quality and crop residue on canola production, by evaluating establishment, biomass production, leaf area index (LAI), yield, thousand seed mass (TSM) and soil disturbance. The first objective was to determine whether soil quality along with residue level should be considered when choosing between a tine or disc seed-drill opener. The second objective was to compare tine and disc openers to produce canola from soil with contrasting qualities and on fields comparable in size to commercial farms. Trials were conducted in 2016 and 2017 at Langgewens Research Farm in the Swartland area. During the first year of the trial the opener had an effect on canola plant population (p<0.05), while during the second year no differences between treatments were recorded (p>0.05). Tine openers performed better on high quality soil while disc openers performed better on low quality soil. Crop residue can become a problem when establishing canola with both the tine and disc openers, and establishment was the best at low residue levels. The poorer canola establishment with the disc opener during 2016 might be due to fertiliser application as fertiliser was applied with seeding which may have caused chemical injury to the seed. Overall the tine opener resulted in more biomass than the disc opener during the first year of the trial while similar biomass productions were achieved during the second year. The leaf area-index (LAI) was similar except that a higher LAI was recorded with the tine opener on low residue levels on high quality soil at 30 days after emergence during the 2017 season. Treatments had no effect on TSM in 2016 (p>0.05), while in 2017 a higher TSM was obtained on low quality soil with high residue levels than on high quality soil with low residue levels. The treatments had no effect on yield in both 2016 and 2017 (p>0.05). On field scale, similar results were recorded as on small plots with low residue levels, with regards to plant population, biomass production, LAI, yield and TSM. Contrary to what was expected, no difference in disturbance was recorded between tine and disc openers (p>0.05), so if the aim is to minimise soil disturbance, either a tine or disc opener can be used. It is recommended that this study is repeated in the southern Cape as soil and climatic conditions differ substantially from the Swartland. It is also recommended that this study is repeated in different years in the Swartland due to seeding in dry soil in both years of this study due to the drought.
- ItemGermination and competition studies on selected weed species in cereal cropping systems in the Western Cape(Stellenbosch : Stellenbosch University, 2002-12) Manoto, Martha Mmamontsheng; Agenbag, G. A.; Ferreira, M. I.; Stellenbosch University. Faculty of AgriScience. Dept. of Agronomy.ENGLISH ABSTRACT: The high cost of herbicides for weed control in crop fields in the Western Cape is a major cause of reducing farmers' net income. As chemical weed control became more difficult and expensive, it became necessary to focus on the technique of reducing weed impact, which does not only involve herbicide usage. Aspects such as tillage method, sowing date of crops, crop rotation, weed ecology and germination requirements, amongst other, may play a role in reducing weed impact. The first experiment was done to determine whether temperature and light had an effect on the germination of six selected weed species, namely Arctotheca calendula, Avena fatua, Bromus diandrus, Emex australis, Lolium temulentum and Raphanus raphanistrum. Seeds of the aforementioned weeds were collected from Langgewens during 2000 and stored at room temperature before being used in this study. The seeds were germinated in a germination cabinet at three temperature regimes namely 5 "C /15 "C, 10°C / 15°C and 10°C / 20°C. Most seeds showed a positive germination response at the 10°C / 15°C treatment, except for Emex australis and Lolium temulentum, which was believed to germinate throughout the year under favourable conditions. Among the germinated weed species, Avena fatua germinated best with a cumulative value of 90% as compared to Raphanus raphanistrum, which germinated least with a cumulative value of 12%. The second experiment was done to evaluate the effect of three growth regulators, namely gibberellic acid, hydroxylamine (auxin), and kinetin (cytokinin) to break dormancy and enable simultaneous germination of the six weed species mentioned above. Weed seeds were germinated in a germination cabinet at 20 °C using the test solutions of the aforementioned growth regulators. The germination was assessed after 3, 7, 10 and 14 days of incubation and the tetrazolium test for the viability of seeds was done for ungerminated seeds. The result obtained showed that no chemical/concentration proved to be successful in stimulating the germination of all species tested. As for example a high concentration of hydroxylamine increased germination of Emex australis to nearly 100% and inhibited germination of Raphanus raphanistrum to less than 12.5% at all hydroxylamine concentrations. The third experiment was conducted with the aim of determining the competitiveness of the six weed species mentioned above when grown together with wheat in order to decide when weed control will be cost-effective. An additive series experiment was conducted in a glasshouse. The influence of weed species on wheat plant height, tiller number at different growth stages, vegetative dry mass and gram mass was determined by using different varying weed densities. Weed densities, through reduction in number of tillers, reduced wheat grain yield. By increasing the density of wheat this competitive effect could be reduced. Different weed densities caused a significant difference in wheat plant height, tiller number, dry mass and grain mass. The results showed that species had a significant effect (p < 0.05) on wheat plant height during tillering, stem elongation and heading growth stages. Total wheat plant above-ground dry mass was significantly (p < 0.05) reduced by an increase in weed density.
- ItemGrowth, mineral content and essential oil quality of buchu (Agathosma betulina) in response to ph under controlled conditions in comparison with plants from its natural habitat(Stellenbosch : University of Stellenbosch, 2007-12) Ntwana, Babalwa; Langenhoven, P.; Agenbag, G. A.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy.The Cape Floristic Region is a highly distinctive phytogeographical unit which is recognized as a floral Kingdom on its own. Buchu (Agathosma betulina) plants fall under this important Kingdom. Buchu is one of the traditional medicinal plants originating in the Western Cape province of South Africa and the essential oil derived from the leaves is exported in large volumes. Due to high demand, under supply, restrictions of wild harvesting and high prices for Buchu essential oil, growers have started to introduce and commercialize this species as a crop. This commercialization of Buchu necessitated agronomic research to optimize production techniques. The objective of this study was to determine the optimum pH range for the cultivation of high yielding Buchu with acceptable essential oil quality under controlled conditions and compare this with the conditions in the natural habitat. Plant, soil and climatic data were gathered from eleven sites in the natural habitat of Buchu (A. betulina) in the Cederberg Mountains. At all sites most rainfall occurred from May to September, while high temperatures were recorded in summer. Soil analyses indicated low levels of nutrients and low soil pH, ranging from 3.7 to 5.3 at all the sites studied. Low levels of nutrients were also obtained from foliar analysis collected from plants at each of the different sites. Chemical analyses of the essential oil indicated that the plants were from a high quality diosphenol chemotype. In the greenhouse experiment, five different pH levels (pH 33.99, 4-4.99, 5-5.99, 6-6.99 and 7-7.99) were evaluated to determine the effect on growth, yield and quality of A. betulina. Complete nutrient solutions were used to irrigate the plants grown in pots filled with a sand and coco peat mixture. Although the plants subjected to the pH treatment of 4-4.99 tended to have the highest growth rate and yield, this did not differ significantly (P=0.05) from plants subjected to pH values between 3 and 6.99. In contrast, the pH 7-7.99 treatment lead to reduced growth and lower vegetative yields. Levels of nutrients obtained from the leaf mineral analysis differed significantly with different pH treatments. High pH levels resulted in high nitrogen, phosphorus, sodium, manganese and boron contents, but lower contents of copper. Nitrogen, phosphorus, calcium and zinc were higher than those recorded for plants from their natural habitat, but still within the norm reported for most plants. Levels of manganese, sodium, magnesium and copper were found to be more or less similar to the values obtained in plants from the natural habitat. No significant differences were found in essential oil quality in response to the pH treatments. However, high pulegone levels (10.8 to 13.2 %) were obtained from all the treatments in the greenhouse experiment. The high levels of this essential oil constituent could have a negative effect on the marketability of the oil and this aspect may need some attention in future studies.
- ItemIdentification of soil and biological factors in crop rotation systems with significance to wheat crop performance in the Overberg production area of South Africa(Stellenbosch : University of Stellenbosch, 2008-03) Human, Hans Jurie; Agenbag, G. A.; University of Stellenbosch. Faculty of Agrisciences. Dept. of Agronomy.A two year experiment (2004-2005) was conducted at the Tygerhoek Experimental Farm near Riviersonderend in the Western Cape Province of South Africa. The effect of different crop rotation systems on soil properties, disease and insect pests, weed populations, wheat growth, yield and quality in the wheat crop phase, included in these crop rotation systems, was determined. This trial was part of a long term crop rotation experiment started in 2002. This trial was laid out as a block design with four replications. Crop rotation systems included wheat, barley, canola, lupins and pasture phases which consisted of medics and clovers planted collectively. Soil samples were taken at each replication for N-incubations for determination of mineral N (NO3 - -N plus NH4 + -N) at 0-150 mm soil depth. A basic soil chemical analysis was done at 0-150 mm and 150-300 mm soil depths, respectively. Each sub-plot (replication) consisted of a 3 m2 block that was divided into a 1.5 m2 block for harvest and smaller 0.25 m2 blocks for samples that were taken at different growth stages throughout both seasons. Dry mass and nitrogen (N) content of different plant components, leaf area index, disease symptoms and pest damage were recorded from each sample. Trends in basic soil chemical properties mostly differed between crop rotation systems during different seasons while similar trends in soil mineral nitrogen occurred. Highest soil mineral N levels occurred after one or two consecutive years of pasture while levels after a lupin phase were disappointingly low in both seasons. These high soil mineral N levels showed similar trends to wheat grain quality and some wheat yields, while the most influencing factors on wheat grain yield were probably soil physical properties. Soil mineral N after canola was high during plant after which levels were much lower than many other crop rotation systems. This occurrence will probably need a re-evaluation of N fertilizing programs if the same trends are found in similar, but longer trials. Lolium spp. was the most prominent weed that occurred in both seasons at some crop rotation systems seemingly with no direct effect from crop rotation. Highest disease incidence mainly from Septoria spp. and Puccinia spp. occurred, particularly in wheat/wheat rotations, except for Puccinia which showed high ratings of disease symptoms in all crop rotations in the drier 2004 season. Lower ratings occurred in crop rotation systems when wheat was preceded by nonwheat crops. Insect pest damage showed no similar trends indicating no direct effect of crop rotation on these pests and/or effective control from applied pesticides in both seasons. It was concluded that climate was one of the most influencing factors affecting differences and seem to be the main cause for different trends found between these two seasons in similar crop rotation systems. A similar trial with longer duration than this one is thus needed to obtain conclusive trends. This also indicates the importance of integration of crop rotation and management practices that are most optimal during dry and wet seasons, thus limiting risk.
- ItemThe impact of paraffin on germination of selected crop seeds and its possible pest repellent action(Stellenbosch : Stellenbosch University, 2014-12) Kadende, John Sembeba; Pieterse, P. J.; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: Paraffin, also called kerosene is used by small-scale soya bean farmers in some parts of Africa as a pest repellent. The repellent action is claimed to be effective against parasites during seed germination and development of the seedlings. Seeds are immersed in commercial paraffin for a few seconds and sown in the soil immediately. This method raised some questions about possible negative effects on the seed after the imbibition process but also on humans and animals consuming the plants and seeds. Experiments were designed to investigate whether this practice would have negative effects on seed germination and vigour of the resulting seedlings of seven selected crop species. A trial was also carried out to test the effectiveness of paraffin as a pest repellent on canola in a field situation. The collected data were analyzed using STATISTICA, software version 11. Wherever the experiments showed significant interaction or differences within main factors, the means were separated making use of Fischer’s LSD post-hoc analysis at p = 0.05. The first series of experiments was done in the laboratory. It was carried out on seeds of seven crop species: canola (Brassica napus L.), common beans (Phaseolus vulgaris L.), ground nuts (Arachis hypogea L.), maize (Zea mays L.), soya bean (Glycine max L.), sunflower (Helianthus annuus L.) and wheat (Triticum aestivum L.). In the germination trial, seeds were subjected to a 7X5X4 factorial design treatment with factors Crop species (CS) (see above), Paraffin concentration (PC) (0, 25, 50, 75 and 100% of commercial paraffin diluted with distilled water) and Time of immersion (TOI) (1, 5, 10, and 30 minutes). Treatments were repeated four times. After immersion seeds were dried with water absorbent paper and immediately germinated in 90 mm diameter petri dishes containing two filter papers and 5 ml of distilled water. Germination tests included 10 seeds per replicate and were incubated at a constant temperature of 20°C under dark conditions in an incubator. Findings showed that canola, sunflower and soya bean are paraffin tolerant (>70 % germination), wheat and groundnuts are less tolerant (30% – 70% germination) and beans and maize are intolerant (< 30 % germination). The paraffin had a negative influence on the rate of germination but there were no statistically significant differences between the 25% to 100% paraffin concentrations. Measurements of the quantity of water and of paraffin absorbed were done after seeds of the seven crop species were immersed in 0, 25, 50, 75 and 100% paraffin concentrations for 30 minutes. Beans absorbed more water at 100% water and more paraffin at 25% paraffin than the other crop species. The paraffin uptake decreased with the increase of paraffin concentration while water uptake increased with the increase in water percentage. In both cases canola had the lowest uptake. Differential uptake of water and paraffin did not explain the results of the germination test. Seeds of the seven crop species immersed in different paraffin concentrations (0, 25, 50, 75 and 100%) for thirty minutes were dried and then soaked in distilled water for 20 hours. The electrical conductivity (EC) of the liquid was determined by means of an EC meter after 20 hours of soaking. This was done to investigate whether paraffin treatment influenced leaking of electrolytes, which would indicate damage to the cell membranes in the seed. Results showed that sunflower leaked more electrolytes than any other seed, while wheat and maize had lower electrolyte leakage than the other species. This showed that the negative effect of paraffin on the germination of some crop species was unlikely to be due to membrane damage because sunflower seeds that leaked most electrolytes had a high germination percentage while the maize and wheat seeds that leaked little electrolytes, had poor germination after paraffin treatments. The second experiment was conducted in a glasshouse. Seeds of the seven crop species were subjected to the same PC and TOI treatments as described in the germination experiment above but instead of being placed in an incubator to germinate, they were planted in 8cm x 8 cm plastic pots (10 seeds in each) in coarse sand in a glasshouse that was running at approximately 20ºC. The establishment of the seedlings was monitored daily in the glasshouse. The final percentage of establishment was calculated. Three weeks after planting, the seedlings were thinned to one plant per pot. The mean root and stem lengths as well as dry mass of the seedlings was recorded when the seedlings were thinned. The one plant per pot that was retained was harvested six weeks after establishment. Root and stem length and dry mass were determined. Establishment percentage and tolerance indices were calculated. Maize and beans showed the lowest establishment percentages and sunflower scored the highest establishment percentage after treatment with paraffin. The root and stem lengths of the crops were generally unaffected by paraffin treatments. In terms of dry mass paraffin had a significant negative effect on groundnut at three weeks but at six weeks no effect of paraffin on any of the vegetative growth parameters could be observed. The third experiment was run in the microscope laboratory. A test using a confocal and fluorescence microscope was carried out to determine if residues of paraffin could be found in germinating soya bean seeds and seedlings. Specimens collected from the germinating soya bean seed and seedlings were mounted on the fluorescent microscope and stained with a solution of 100 μg.ml-1 Nile Red and observed with LD Plan-Neofluar 60X/0.6. Results showed that paraffin did penetrate the soya bean seed and was translocated within the plant system (endodermis) as the plant grows. The concentrations of paraffin in the tissue were however quite low. The fourth experiment was run on the Langgewens Experimental Farm near Moorreesburg in the Western Cape Province. Forty blocks were spatially grouped into two separate groups. Twenty blocks received the five paraffin treatments replicated four times and the other twenty blocks received the five water treatments also replicated four times. Within each group the treatments were allocated randomly to the plots. The experimental design was a 2X5 Factorial experiment with factors Treatment liquid (distilled water and paraffin) and Time of immersion (0, 1, 5, 10 and 30 minutes) replicated four times. No pesticides were applied to the canola crop. Stand density, leaf area and dry mass were recorded at the first harvest at 12 weeks, and then dry mass was determined at 21weeks. Final yield was determined after 27 weeks when the plots were harvested by means of a combine plot harvester. The stand density, leaf area and dry mass were significantly increased by paraffin treatments at the time of the first harvest. After 21 weeks paraffin treatment had no significant effect on the dry mass production of the canola and the same was true of the final seed yield. . Even though there was no serious attack by pests, the little feeding damage that occurred in the water treated plots and not in the paraffin treated plots, indicate that paraffin may have a repellent effect. Paraffin had no negative effects whatsoever on the growth and yield of canola in this experiment. This study indicates that different crops react differently to seed treatment with paraffin. The results of the fourth experiment indicate that paraffin might be used as pest repellent on certain selected crops but more research is needed on the subject.
- ItemThe influence of different calcium levels, irrigation methods and storage temperatures on the yield, quality and growth potential of G0 mini-tubers(Stellenbosch : University of Stellenbosch, 2007-12) De Villiers, Andre Jaco; De Villiers, R. J.; Agenbag, G. A.Calcium (Ca) is an important plant nutrient with many functions, such as strengthening of cell walls and maintaining membrane stability and cell integrity. A greenhouse experiment was conducted using an aeroponic production system, to evaluate the influence of different Ca: K & Mg ratios (consisting of a control [100% Ca], and three treatments in which the Ca levels were changed to 33%, 66% and 133% of the control, while the K and Mg levels were adjusted to compensate for the change in Ca) and two different irrigation methods (irrigation on roots only, and irrigation on roots and stolons) on tuber yield and mineral concentration. The treatment that received the highest Ca: K & Mg ratio had significantly more larger tubers than the lowest Ca treatment, although there was no significant difference in total tuber number between treatments. The high Ca treatment also had a significantly higher Ca concentration in the skin than the low Ca treatment. The site of irrigation did not have a significant effect on the total tuber number per plant, or on the Ca content of the tubers that were produced. The tubers produced in the first experiment were divided into two weight classes, and stored at three different temperatures. The percentage weight loss during storage was determined by weighing the tubers before, and again after storage. The firmness of the tubers was also measured after storage. Tubers were then stored in a dark room at room temperature to allow sprouts to develop. The sprouts of each tuber were counted and weighed. Weight loss was the lowest for tubers stored at 3oC. Firmness of the tubers increased as the Ca: K & Mg ratio of the nutrient solution used during production was increased. Number of sprouts was the highest for tubers stored at 6oC. Sprout number was also significantly higher for the larger tubers compared to the smaller ones. Total sprout weight was the highest for the tubers stored at 6oC, and was also the highest for the larger tubers. After sprouts started to develop, the tubers were planted again in the greenhouse, in sawdust and irrigated with a complete Steiner nutrient solution at 1.5 mS cm-1. After these plants were harvested, the leaf area and dry weight of the leaves were determined. The first generation tubers were counted and weighed. The only factor that had a significant influence on the growth of the plants, was the size of the seed tubers that were used. The larger seed tubers produced plants that had significantly higher leaf areas, dry weight of leaves, as well as higher yields than that of the plants produced from the smaller seed tubers. From the results of this study, it can be concluded that Ca has a definite positive effect on the quality of seed potatoes as well as the size of the tubers that are produced. This study also supported that seed tubers should be stored at low temperatures, around 3oC, to maintain the highest quality, while larger tubers proved to out-yield smaller ones.
- ItemThe influence of different production systems, planting densities and levels of shading on the yield, quality and growth potential of ‘Chandler’ strawberry plants (Fragaria ananassa) grown in coir(Stellenbosch : Stellenbosch University, 2008-12) De Villiers, Johannes Jacobus; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.The use of hydroponic strawberry production systems is increasing worldwide. Although higher planting densities are possible in vertical production systems, these higher planting densities may have a negative effect on individual plant yield and fruit quality due to lower light levels when compared to conventional (horizontal) production systems. Optimum planting densities will for this reason be affected by light intensities inside the greenhouse and configuration of the vertical production systems. Two experiments were conducted in a plastic cladded greenhouse, fitted with a wetwall and fan cooling system, at the Department of Agronomy, University of Stellenbosch, South Africa during the period of April 2007 to November 2007 (late autumn to early summer). Mean daily maximum temperatures exceeded 26 oC during most of the 14 week harvest period (22 August to 30 November 2007), while photosynthetic active radiation (PAR), measured at 12h00 on cloudless days, inside the greenhouse increased from about 200 μMol m-2 s-1 to about 460 μMol m-2 s-1 during this period. The first experiment compared the effect of two vertical production systems (vertical system and ‘A-shape’ system), subjected to different planting density (16.7, 23.3 and 33.3 plants m-2) and shading (0%, 20%, 50%) treatments, as measured on selected yield, quality and growth factors. The second experiment studied the effect of different planting density (3.3, 5.6 and 10 plants m-2) and shading (0%, 20%, 50%) treatments on the same yield, quality and growth factors in a conventional production system. A comparison with regard to these factors was also made between the highest planting densities of the conventional-, vertical- and ‘A-shape’ system.
- ItemThe influence of nutrient solutions on growth, seed production and seed quality of broccoli (Brassica oleracea L. var. italica Plenck)(Stellenbosch : University of Stellenbosch, 2011-03) Du Randt, Marius Louis; Langenhoven, P.; Agenbag, G. A.; University of Stellenbosch. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: Little is known about the nutrient requirements of broccoli grown for seed production. During 2006 and 2007 broccoli were grown for seed production in sand bags in a net structure, using a drain to waste hydroponic system. The experimental design was a randomized complete block with seven treatments replicated in four blocks. In 2006 seven nutrient solution treatments were tested. The Standard solution based on Steiner’s universal solution was compared with different levels of N, S, K and Ca with regard to the effect on total biomass, nutrient concentration, nutrient assimilation, seed yield and quality. No significant differences in total biomass produced were found. Total dry mass increased by 225% from the mature head stage until harvest of seed. Nutrient concentration in plant samples were not influenced by treatments except where low levels of K and S in nutrient solutions led to significantly lower levels of K and S concentrations. The total assimilation of elements were calculated to determine the effect of the much longer growth period needed for seed production in comparison to normal head production on nutrient requirements. Major elements assimilated ha-1 was: N 173.0 kg, P 35.5 kg, K 348.4 kg, Ca 114.7 kg, Mg 30.5 kg, S 42.2 kg. The seven treatments used during 2007 included three of the treatments which were used in 2006 as well as treatments with foliar sprays containing Ammonium Nitrate and Calcium Metalosate. The standard solution treatment was also used in 2007 to compare results with 2006. Plant analysis done on plants from the standard solution (2006 & 2007) showed similar trends. As the plants developed towards maturity there was a relative increase in concentration in the top plant parts (pods, flowers and stems) for Ca, Mg and S. Contrary, N and P concentration declined. The minor elements, Fe, Mn and B also increased in concentration in the top plant parts at harvest indicating a strong relative flow of these elements to the top plant parts towards maturation. Concentration values of major elements in plant samples were generally different when the two years were compared. Element concentrations in the seed pods were in general higher than in the rest of the plant indicating the pods as a strong sink on the plants. During both years the two best nutrient solutions for yield were the same, namely the Standard solution and Standard - K which contain low levels of K. During 2006 no significant differences in seed quality were found. During 2007 no significant differences were found for seed quality measurements, except for size (of the cotyledons). The results indicate that no special adjustments need to be made to the Standard solution in order to produce good broccoli seed yield of good quality. As substantial differences in nutrient solution composition did not significantly affect the quality of broccoli seed produced. Seed yield was however significantly affected by nutrient solution composition. Key words: Brassica seed, broccoli seed, seed production, broccoli nutrition, hydroponic production, broccoli production, nutrient assimilation.
- ItemMorphological and physiological responses of cowpea (Vigna unguiculata (L) Walp.) cultivars to induced water stress and phosphorus nutrition(Stellenbosch : Stellenbosch University, 2003-12) Chiulele, Rogerio Marcos; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: Cowpeas are produced under low and irregular rainfall in most of arid and semi-arid areas of sub-Saharan Africa. Growth and yield are therefore reduced due to the occurrence of water stress during the growing season. Knowledge of the responses and adaptive mechanisms of cowpeas to water stress may help to improve the management practices for these areas. Therefore, three glasshouse experiments were conducted at Welgevallen Experimental Farm of the University of Stellenbosch to test the responses of two cowpea cultivars to water stress. In the first experiment, physiological responses were used to identify those physiological parameters, which can be used to distinguish between drought tolerant and susceptible cowpea cultivars. In the second experiment, some of the identified physiological parameters together with some morphological growth responses, yield and grain protein content of the same two cowpea cultivars were used to identify which is the more tolerant cultivar. Tn the third experiment, the hypothesis that increased phosphorus supply may improve the tolerance of cowpea plants to water stress and their ability of recover from the stress was tested. The results showed that water stress affected water relations, morphological growth parameters, yield and grain protein content, but increasing P supply reduced the effect of water stress and promoted more rapid recovery after re-watering. Water relations were affected by water stress because it reduced relative water content, which resulted in reduced water potential and increased leaf diffusive resistance and proline accumulation. Morphological growth responses and yields were affected because water stress reduced the leaf area, which resulted in reduced biomass production and seed yield. Lower leaf area under water stress was the result of the reduced number of leaves and leaf expansion rate, but the number of leaves was the most important parameter. Reduced seed yield was due to reduced number of pods. The responses of the two cultivars tested were different. AB Wit, which performed better under well-watered conditions was more affected by water stress due to its larger leaf area that resulted in excessive water loss by transpiration. ACH14 was more drought tolerant than AB Wit due to a combination of a more rapid stomatal closure and proline accumulation, which induced osmotic adjustment, and which in tum helped to maintain higher water potentials. The increased P supply reduced the effect of the water stress. High-P level plants showed higher root growth, which resulted in more water uptake and larger leaf area during the water stress period, and after re-watering these plants recovered more rapidly. The more rapid recovery from stress was the result of enhanced root growth and leaf expansion rate and most probably due to increased water uptake. High-P level plants also showed more rapid leaf appearance and plant growth at earlier stages compared to the low-P level plants.
- ItemRate and timing of nitrogen fertilisation for canola production in the Western Cape of South Africa(Stellenbosch : Stellenbosch University, 2017-03) Coetzee, Albert; Swanepoel, Pieter Andreas; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: Canola (Brassica napus) is increasing in popularity as a cereal crop in the Western Cape. Nitrogen (N) is generally the most limiting nutrient to canola production. Nitrogen fertiliser guidelines for canola are currently adopted from international literature or adopted from guidelines for wheat, and should be refined for the local environmental conditions. The aim of this study is to determine the optimal rate of N fertilisation, and the distribution thereof in the Western Cape. Field experiments were conducted in 2015 at Langgewens and Altona (Swartland) and Roodebloem (southern Cape). The trial was laid out as a factorial arranged in a randomised block design, with six N rates (0, 20, 60, 90, 120 and 150 kg N ha-1), of which each rate was applied in either one, two or three increments after planting, replicated in four blocks. Twenty kg N ha-1 was applied at planting. The rest was divided in equal increments either 30 days after planting (DAP), 30 and 60 DAP or 30, 60 and 90 DAP. Soil mineral N, leaf area index (LAI) and biomass was determined at 30, 60 and 90 DAP. Grain yield and thousand kernel mass (TKM) was recorded. Using these values obtained, agronomic N use efficiency (ANUE), water use efficiency (WUE) and profitability was determined by means of a sensitivity analysis. Treatments had no effect (P>0.05) on total soil mineral N content at any locality at any physiological stage with the exception of 90 DAP at Langgewens. Neither LAI nor biomass was affected by treatments (P>0.05) at any locality, at any physiological stage. Yield at Roodebloem was affected (P<0.05) by N fertilisation and treatments which had the highest yield were those who received 20 kg ha-1 at planting, and 70 or 100 kg ha-1 at 30 DAP respectively. These treatments did not differ (P>0.05) from treatments which received more than 60 kg N ha-1, regardless of the distribution. At Langgewens and Altona, N fertilisation had no effect (P>0.05) on yield, while TKM was not affected by treatments at any locality. No differences (P>0.05) were observed for ANUE at Altona and Langgewens, while treatments had a significant effect on ANUE at Roodebloem. The treatment that received 20 kg N ha-1 at planting and 100 kg N ha-1 at 30 days after planting and no N later, had the highest WUE, but did not differ (P>0.05) from a number of treatments that received more than 90 kg N ha-1 at various time intervals. The WUE at Altona and Langgewens was not affected by treatments (P>0.05). At both Altona and Langgewens the highest gross income was obtained by treatment that received no N at all, while at Roodebloem the highest gross income was obtained by applying 90 kg N ha-1 for the entire duration of the growing season. Preliminary results indicate optimum N fertiliser rate of 90 to 120 kg N ha-1, applied as 20 kg N ha-1 at planting and the remainder at 30 DAP at Roodebloem. No significant response to N applications was recorded in the Swartland. These results could be ascribed to drought conditions during 2015, which may have prohibited efficient uptake of N in the Swartland localities of Altona and Langgewens during critical periods. The differences between treatments at Roodebloem in the southern Cape might be due to a combination of sufficient rainfall over the growing season, lower temperatures and sufficient N being available during early, rapid vegetative growth. This in turn enabled a higher LAI which allowed for higher biomass accumulation, and consequently higher translocation to seeds. It is recommend that this study be repeated before results could be used to develop fertiliser guidelines for canola production in South Africa.
- ItemReducing height and lodging in canola (Brassica napus L.) using plant growth regulators(Stellenbosch : Stellenbosch University, 2014-12) Eksteen, Lambertus Lochner; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: In South Africa, canola (Brassica napus L.) is produced under short day conditions during winter months. These conditions, together with high fertiliser application levels required to maximize grain yields, often result in tall growing bulky crops which are prone to lodging. This will especially be true if canola production is expanded to irrigated areas. Plant growth regulators (PGRs) have successfully been used to reduce canola plant height and lodging under experimental conditions in Australia and are worldwide commercially used to reduce plant height and lodging in winter cereals such as wheat and barley. The primary objective of this study was to determine the effect of anti-lodging PGRs on the agronomic and quality characteristics of commercial canola cultivars under South African conditions. This study was conducted under field conditions at three research farms, as well as controlled glasshouse conditions at Welgevallen Research Farm, situated in the Western Cape Province of South Africa. Foliar treatments consisted of a control (untreated) and four PGRs; CeCeCe® 750 (chlormequat chloride), Moddus® 250 EC (trinexapac-ethyl), Primo MAXX® (trinexapac-ethyl), and Kelpak®, applied either individually or in combination with wetting agent at budding stage (growth stage 3.1) of canola. Whilst glasshouse trials were conducted with spring canola cultivars “Hyola 555TT” and “43C80”, field trials were done with Hyola 555TT only. Monitoring and measuring various plant parameters during different growth stages of canola, the morphological and physiological impact of PGR-treatments on growth and development were determined. Though Primo MAXX® tends to reduce plant height in all trials; reductions were only significant during one of the glasshouse trials. Fortunately, compared to the control, none of the PGRs significantly reduced the leaf area, number of flowers or number of pods plant-1 during this study, while Primo MAXX® and Moddus® 250 EC tend to increase the grain yield under field conditions. This study indicates that PGRs can possibly be used to improve lodging resistance and yield of canola. Identifying the most effective PGRs on specific cultivars, the results of the study will contribute to the knowledge of using PGRs in canola to reduce lodging and improve grain yields in South Africa.
- ItemResponse of wheat (Triticum aestivum L.) and barley (Hordeun vulgare L.) to salinity stress(Stellenbosch : Stellenbosch University, 2015-12) Bagwasi, Gaesejwe; Agenbag, G. A.; Stellenbosch University. Faculty of Agrisciences. Dept. of Agronomy.ENGLISH ABSTRACT: Good quality water for agricultural use is rapidly becoming a luxury due to competition for this water among the municipal, industrial and agricultural sectors. This has often forced growers to use poor quality water for irrigation. Salinity is one of the main sources of poor water quality and high electrical conductivities (EC’s) due to salinity may become a problem. The aim of this study was to compare the response of South African spring wheat and South African spring barley at germination, seedling growth, vegetative growth, reproductive growth and maturity stage to salinity stress caused by irrigation with saline water. This study was conducted in the laboratory and under controlled glasshouse conditions at the University of Stellenbosch in the Western Cape Province of South Africa. Treatments in trial 1 (incubation trial) were made up of three wheat cultivars (SST 027, SST 056 and SST 087) and three barley cultivars (Nemesia, Erica and Hessekwa) exposed to five EC levels of NaCl solutions (4, 8, 12, 16 and 20 dS m-1) and a control (0 dS m-1) of distilled water, during the germination phase. In trial 2 (pot trial), wheat cultivar SST 027 and barley cultivar SVG 13 were also subjected to the above solutions, but plants were grown till the tillering stage. In trial 3 (pot trial) cultivars used in trial 2 were subjected to five nutrient solutions with EC levels of 1.6, 3, 6, 9 and 12 dS m-1 and allowed to grow till maturity (harvesting stage). Fully balanced nutrient solution with EC = 1.6 dS m-1 was used as a control and NaCl was added to the solutions to obtain the needed EC. In trial 1, final germination percentage (FGP), salt tolerance (ST) and germination rate (GR) were measured at 7 days after incubation. The study showed that when the EC level was increased, FGP, ST and GR of all wheat and barley cultivars tested were decreased. However, significant reduction was only observed at high EC levels with regard to FGP and ST. Wheat cultivars recorded faster GR compared to barley cultivars and tended to be less sensitive to salinity in the germination stage. Cultivars from the same species did not show significant differences. In trial 2, shoot length (SL), root length (RL), shoot fresh weight (SFW), root fresh weight (RFW), shoot dry weight (SDW) and root dry weight (RDW) were measured at 35 days after planting (DAP). In general, the study showed that salinity had a significant (P0.05) effect on seedling growth of all measured parameters of both wheat and barley. Mean values for most growth parameters were higher for barley cultivar SVG 13 as compared to wheat cultivar SST 027. However, little evidence was found to show that barley is more salt tolerant than wheat at the seedling stage. In trial 3, selected growth parameters were measured at tillering (28 DAP), booting (54 DAP), flowering (71 DAP) and maturity stage (150 DAP). The study showed that salinity had a significant (P0.05) effect on the vegetative growth, reproductive growth and grain yield of both wheat and barley. Although barley generally produced higher dry weights especially at the early growth stages no clear evidence was found that South African spring barley is more salt tolerant than South African spring wheat.
- ItemResponse of wheat (Triticum eastivum L.), canola (Brassica napus) and medic (Medicago) to a once-off mouldboard and deep tine tillage in the Swartland sub-region of the Western Cape(Stellenbosch : Stelllenbosch University, 2017-03) Van Zyl, Johannes Geldenhuys; Labuschagne, Johan; Agenbag, G. A.; Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy.ENGLISH ABSTRACT: The study was done (2014 = year 1 and 2015 = year 2) at the Langgewens Research Farm of the Western Cape Department of Agriculture near Moorreesburg (33o17’00” S, 18o42’00” E; 191 m). The aim of this study was to evaluate the effect of a once-off strategic tillage operation with a mouldboard plough or tine implement within different crop rotation systems on mineral-N levels of soils, soil moisture content, biomass production, chlorophyll content of leaves, stomatal conductance, light interception, initial and final root mass, reproductive components, seedling survival, weed seed bank, grain yield and grain quality of spring wheat (Triticum aestivum L) and canola (Brassica napus). Medic (Medicago) biomass and root mass was recorded during year 2. The experimental design was a split-plot employed as a randomised complete block design. Three cropping sequences namely: medic/clover-wheat-medic/clover-wheat (McWMcW), wheat-lupin-wheat-canola (WLWC) and lupin-wheat-canola-wheat (LWCW) were allocated to main plots and replicated four times in year 1. The same plots were used during year 2 but due to crop rotation the cropping sequences were WMcWMc, WCWC and LWCW. The last letter in the sequence represents the crop on the field at the time of data collection. Tillage treatments were allocated to subplots namely: (a) continuous no-till (NT), soil left undisturbed until planting, (b) non-inversion tillage, with a tine (DT) to a depth of 400 mm and (c) inversion tillage with a mouldboard plough (MP) to a depth of 250 mm. The seed were planted with a tined no-till planter with knife openers. Plant and soil samples were collected every 30 days from a day before planting until harvesting and the relevant parameters determined. The study area was managed as a no-till system under the cropping systems mentioned above since 2000 and no stubble were removed from the research area since 2007. Soil water content (SWC) and soil mineral nitrogen content (NH4+-N + NO3- -N) were determined one day before planting and every 30 days thereafter until harvesting. Soil water content in McWMcW was not influenced by tillage at all sampling dates during year 1. Significant differences were however recorded in LWCW with MP and DT that resulted in an increase in SWC during June and July of year 1. During year 2, NT resulted in higher (P=0.05) SWC 90 days after planting in LWCW compared to MP and DT. Soil water content was not influenced by tillage in either WMcWMc or WLWC for both years 1 and 2, 90 days after planting. Soil mineral nitrogen was not influenced by tillage in McWMcW and LWCW during year 1. There were however significant differences recorded during year 2 with MP and DT increasing mineral nitrogen content 60 and 120 days after planting in LWCW. Tillage did not influence mineral nitrogen content during year 1 in WLWC, however, in year 2 mineral nitrogen content was significantly increased. Tillage treatments did not resulted in significant differences in mineral nitrogen content during year 2 in WMcWMc. Tillage treatments resulted in a higher amount of mineral nitrogen in McWMcW compared to the other sequences during year 1. Glomalin content is an indicator of mycorrhizal growth. During year 1 DT significantly increased the glomalin content. It is concluded that a disruptive effect of DT and MP did not have a negative effect on SWC, mineral nitrogen or glomalin content. During year 1 no significant differences (P=0.05) were recorded for the effect of tillage on light interception (LI), chlorophyll content (CC), stomatal conductance (SC) and initial root mass (IRM) in LWCW and McWMcW. Final root mass (FRM) in LWCW was significantly higher in NT in the 200 – 300 mm depth compared to MP. Tillage did not influence LI, SC or FRD in WLWC during year 1. There were however significant differences in CC between tillage practices in WLWC rotation. Deep tine resulted in significantly lower flag leaf CC compared to MP. Biomass production (BMP) was significantly higher in MP compared to NT for WLWC. IRM was significantly higher in DT compared to MP and NT for WLWC. During year 2 no significant differences were recorded for the effect of tillage on LI, CC, BMP and FRM in LWCW. DT however resulted in a significantly higher IRM compared to MP in LWCW. Tillage did not influence FRM in WLWC during year 2. MP and NT however resulted in significantly higher LI compared to DT in the beginning of the season. Leaf CC was significantly higher in MP, 60 and 120 days after planting compared to NT and DT in WLWC. MP also significantly increased BMP in WLWC compared to NT. The IRM for WLWC increased significantly with DT compared to NT. During year 2 no significant differences were recorded for the effect of tillage on BMP in McWMcW. NT had a significantly higher IRM compared to MP for WMcWMc. The final root mass also showed significant differences in the 100 - 200 mm range. DT significantly increased FRM in this range compared to MP. During year 1 no significant differences between tillage practices were recorded for seedling emergence and survival rates, ear-bearing tillers per square metre (ear-bearing tillers per m2), spikelets per ear, kernels per ear, thousand kernel mass (TKM), grain yield, grain protein and hectolitre mass (hl). Significant differences were recorded between crop rotations as grain protein content of wheat was higher in McWMcW compared to LWCW. Canola seedling emergence and survival, number of pods, seeds per pod, seed yield and TKM was not influenced by tillage in year 1. No-till (NT) however resulted in significantly higher seed oil content than MP. During year 2 wheat spikelets per ear and kernels per ear were not influenced by tillage. No-till however, resulted in significantly higher wheat seedling emergence and survival rates, ear-bearing tillers per m2, grain yield, grain mass, TKM and Hl compared to MP. In comparison with DT, NT significantly increased the amount of ear-bearing tillers per m2 and grain yield. Mouldboard plough and DT however showed a significant increase in protein content compared to NT. There were no significant differences for the effect of tillage on canola seedling emergence and survival, seeds per pod, seed yield, TKM and percentage oil for year 2. DT and MP however had a significantly higher number of pods per plant compared to NT. Medic biomass production was not influenced by tillage during year 2. Strategic tillage resulted in positive and negative effects regarding reproductive components. Soil samples taken before tillage treatments were applied showed that there were no significant differences in the number of weeds (Lolium multiflorum, Polygonum aviculare and Vicia spp) that germinated between subplots. Data recorded in the field during year 1 showed a significant reduction in the number of Lolium multiflorum with a strategic MP tillage compared to NT. During year 2 the number of seeds that germinated under shade net showed that MP tillage the previous year significantly reduced the number of Lolium multiflorum seedlings. These results were also recorded in the field study which showed a reduction in the number of seeds that germinated the second year after tillage. During year 2, shade net trials showed that MP significantly reduced the number of Polygonum aviculare compared to DT and NT. Tillage had no significant effect on the number of Vicia spp and on the number of broadleaf weed species recorded during year 1 and year 2. MP however, reduced the number of unidentifiable weed species during year 1 and year 2. Crop rotation with canola and medic reduced the number of weed plants recorded throughout this study. The conclusion is that a strategic tillage operation can have positive effects on crop production, but the tillage operation has to be economically viable and improve yield without damaging the environment.