Thesis (MScAgric)--Stellenbosch University, 2014. / 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. / AFRIKAANSE OPSOMMING: Canola se waarde as ekonomies belangrike akkerbou-gewas in Suid-Afrika het die afgelope aantal jare skerp toegeneem, omdat dit gebruik kan word om hoë kwaliteit kook-olie en margariene asook bio-brandstowwe en dierevoere, te vervaardig. In wisselboustelsels kan dit gebruik word om die siekte-ketting te breek en onkruidbeheer te vergemaklik. In hierdie studie is die invloed van temperatuur op die fenologiese reaksies van canola in terme van die aantal dae, gewasgroeidae en fototermiese eenhede, benodig om spesifieke groeistadiums te bereik, asook die invloed op groeitempo, vegetatiewe- en reproduktiewe groei onder gekontroleerde toestande nagevors. Sewe canola cultivars vanuit die kort en mid-groeiseisoen volwassenheidsgroepe wat tans in die Weskaap verbou word is geplant in 3-liter plastiek houers gevul met „n 1:1 sand: kompos mengsel as groeimedium en besproei met „n volledig gebalanseerde voedingsoplossing met EC=2.0. Twee glashuise met nag/dag temperature van onderskeidelik 10/15oC en 15/20oC is vir hierdie doel gebruik. Die aantal dae, gewasgroeidae (GGD) en fototermiese eenhede (FTE) wat vanaf plant tot saailingverskyning; eerste volwasse blaarverskyning; eerste blomknop verskyning; eerste blom; saad verkleuring en fisiologies volwasse stadiums vereis word, is bepaal. Plant lengte is gemeet met 14-daagse tussenposes vanaf 28 tot 84 dae na plant. Plante is gemonster is tydens die eerste blomknopverskyning asook blom- en fisiologies volwasse stadiums om blaaroppervlakte (BO) en droëmassa (DM) te bepaal. Plant groeitempos (PGT) vanaf plant tot blomknopverskyning; blomknopverskyning tot blom en vanaf blom tot fisiologiese volwasse stadium is bereken. Relatiewe groeitempos (RGT) en netto-assimilasietempos (NAT), is bereken vanaf blomknopverskyning tot blom en vanaf blom tot fisiologiese volwasse stadium. Die aantal dae vanaf plant, asook GGD en FTE benodig om blomknopstadium, blomverskyning en fisiologies volwasse stadiums te bereik, is gekorreleer met BO en DM plant-1 asook die aantal peule en peulmassa plant-1 tydens genoemde groeistadia om moontlike verwantskappe te bepaal. Die studie het getoon dat deur die nag/dag temperatuur te verhoog vanaf 10/15⁰C tot 15/20⁰C, plant lengte, aantal blare en BO plant-1 tydens blomknopverskyning, asook PGT vanaf plant tot blomknopverskyning en RGT van blomknopverskyning tot blomstadium, toeneem. Daarteenoor het PGT van blomknopverskyning tot fisiologies volwassenheid, RGT van blom tot fisiologies volwassenheid, asook NAT van blomknopverskyning tot blomstadium en BO tydens blom en fisiologies volwasse stadium, afgeneem. Reproduktiewe ontwikkeling soos gemeet aan die aantal bloeistele, peule plant-1 en peulmassa plant-1 is ook benadeel deur genoemde verhoging in temperatuur. Die afname in peulmassa het gewissel tussen 22.24% en 40.35% vir verskilende cultivars en is „n duidelike aanduiding van die verskillende canola cultivars se gevoeligheid teenoor toenemende nag/dag temperature. Die toename in gemiddelde nag/dag temperatuur vanaf 12.5⁰C (10/15⁰C) tot 17.5⁰C (15/20 ⁰C) het die aantal dae vanaf plant tot saailing verskyning asook die vegetatiewe en reproduktiewe groei fases verkort. Met die uitsondering van die vegetatiewe groei fase, het die GGD and FTE vereistes om spesifieke groeistadiums te bereik toegeneem met „n toename in temperatuur. Plant komponente soos DM, BO, aantal peule plant-1 en peulmassa plant-1 tydens spesifieke groeistadia het „n positiewe verwantskap getoon met die aantal dae wat benodig is om spesifieke groeistadiums te bereik, maar sodanige verwantskap is nie bevestig met GGD en FTE vereistes. Hoewel die reaksie van verskillende cultivars teenoor „n toename in temperatuur vir die meeste gemete plantkomponente verskil het, het die reaksie nie altyd verband gehou met die volwassenheidsgroepering van die cultivars. Dit wil dus voorkom asof die reaksie teenoor temperatuur tot „n groot mate ook verband hou met die genetiese samestelling van die cultivar soos bepaal deur die telingsmaatskappy. Hierdie resultate toon dat die aantal dae, GGD en FTE wat vereis word om fisiologiese volwassenheid te bereik gebruik kan word om die cultivar se volwassenheidsgroepering te beskryf maar dat GDD en FTE waarskynlik meer akuraat sal wees weens effek van temperatuur en daglengte op die ontwikkkeling van cultivars.

Thesis (PhD(Agric))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: There is an increasing demand for canola (Brassica napus L.), an emerging oilseed crop in South Africa. Canola thrives in the Western Cape. However, yet low yields are still obtained within the production areas with poor and or variable responses to nitrogen applications. Crop nutrition and specifically the contribution of sulphur (S) to nitrogen (N) use and selection of nutrient efficient genotypes can be strategies of considerable significance in increasing yields. This study investigated growth, yield and quality responses of canola to different N (0, 30, 60, 90 and 120 kg N ha-1) and S (0, 15 and 30 kg S ha-1) fertilisation rates in field trials at different localities, during the 2009-2011 period. Responses to N and S under optimum growing conditions and responses of different cultivars were investigated in unison in glasshouse trials at the Department of Agronomy of the University of Stellenbosch. Locality and growing season (year) significantly affected nutrient content in plants at flowering (90 days after planting), dry mass production as well as yield and quality of canola in field trials at five different localities during the 2009-2011 period. Growth and yield were also affected by N application rate in both field and glasshouse trials. Sulphur applications did not have an effect on vegetative growth, but rather stimulated flower and pod production in glasshouse trials and resulted in higher grain yields in field trials. Response depends largely on rainfall and S content of the soil. Highest yields were, on average, obtained with application rates of 120 kg N and 30 kg S ha-1, while glasshouse trials showed that even higher rates may be considered under optimum growing conditions. High application rates of N and S also improved water use efficiency from approximately 4-5 kg grain yield to about 8-9 kg grain yield mm-1 of rain during the growing season. Agronomic efficiencies of applied N decreases with increasing N rates and values of about 8 kg grain yield increase per kg of N applied at N rates of 120 kg N ha-1 indicated that high N rates may improve profit margins of canola as long as the cost of N is not more than eight times the producers price of canola. Agronomic efficiencies of N applications are improved if 15 kg S ha-1 is applied complimented with high rainfall, but not with applications of 30 kg S ha-1. Improved agronomic efficiencies of S applications shown at higher N rates, confirmed the dependency of S responses to sufficient availability of nitrogen. Sulphur applications, in contrast to N, resulted in an increase in oil content of the grain in field trials. Yield responses of different cultivars to nitrogen fertilisation under glasshouse conditions differed, with better responses obtained within short and medium season cultivars, than with a late maturing (long season cultivar), in spite of a better vegetative (dry mass) response of the later maturing cultivar. These results may indicate differences in the growth habit of different cultivars, but more research in this regard is needed. / AFRIKAANSE OPSOMMING: Canola (Brassica napus L.), ‘n relatief nuwe oilsaadgewas wat goed aangepas is, word in ‘n toenemende mate in die produksiegebiede van die Weskaap verbou. Lae opbrengste en wisselvallige reaksies teenoor stikstofbemesting word egter verkry ten spyte van die gewas se hoë stikstofbehoefte en dit mag moontlik aan swaweltekorte toegeskryf word. In hierdie ondersoek is die groei-, opbrengs- en kwaliteitsreaksie van canola teenoor verskillende N (0, 30, 60, 90 en 120 kg N ha-1) en S (0, 15 en 30 kg S ha-1) bemestingspeile in droëland proewe op verskillende lokaliteite bestudeer gedurende die 2009-2011 groeiseisoene. Reaksies teenoor N en S onder optimale groeitoestande en vir verskillende cultivars is in glashuisproewe van die Departement Agronomie van die Universiteit van Stellenbosch, uitgevoer. Die chemiese samestelling van die plante tydens blomstadium (90 dae na plant), asook droëmateriaal produksie, graanopbrengs en kwaliteit het betekenisvol verskil tussen die lokaliteite, maar lokaliteitsverskille is ook deur die seisoene beïnvloed. Die ontwikkeling, groei en graanopbrengs van die canola is ook beïnvloed deur die stikstofbemestingspeile in beide die veld en glashuisproewe. Swawelbemesting het nie die vegetatiewe groei van canola beïnvloed nie, maar het blom en peulproduksie in glashuisproewe en graanopbrengste in veldproewe verhoog. Die reaksie van canola teenoor die swawelbemesting is grootliks bepaal deur die swawelinhoud van die grond asook klimaatsfaktore soos reënval. In die algemeen is die hoogste canola opbrengste in veldproewe met toedienings van 120 kg N en 30 kg S ha-1 verkry, maar glashuisproewe het getoon dat hoër toedieningspeile nodig mag wees onder optimale groeitoestande soos in besproeiingsgebiede. Hoë toedieningspeile van N en S het veroorsaak dat die waterverbruiksdoeltreffendheid toegeneem het van 4-5 kg graanopbrengs per mm reën tot sowat 8-9 kg graan opbrengs per mm reën. Agronomiese doeltreffendheid van toegediende stikstofbemesting het afgeneem met toenemende N peile, maar waardes van ongeveer 8 kg opbrengsverhoging per kilogram N toegedien met stikstofpeile van 120 kg ha-1, toon dat hoë N toedieningspeile mag steeds winsgrense verhoog mits die prys van een kilogram N nie meer is as agt maal die produsente prys van canola is nie. Agronomiese doeltreffendheid van stikstofbemesting is verhoog deur ook 15 kg S per hektaar toe te dien, maar nie deur die toediening van 30 kg S ha-1 nie. Die agronomiese doeltreffendheid van S toedienings het slegs by die gelyktydige toediening van hoë stikstoftoedienings toegeneem, wat die wisselwerking tussen N en S ten opsigte van graanopbrengs bevestig. In teenstelling met stikstof het swawel toedienings die olie-inhoud van canola in die veldproewe verhoog. In glashuisproewe is gevind dat kort en medium groeiseisoen cultivars, ten spyte van ‘n groter vegetatiewe reaksie van die lang groeiseisoen cultivars, groter opbrengsreaksies teenoor stikstof- en swawelbemesting toon. Meer navorsing word egter in hierdie verband benodig.

Thesis (MScAgric)--Stellenbosch University, 2014. / 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. / AFRIKAANSE OPSOMMING: In Suid-Afrika word canola (Brassica napus L) gedurende die wintermaande onder kort-dagtoestande verbou. Hierdie verbouingstoestande, tesame met verhoogde toediening van bemesting vir maksimum opbrengs, lei dikwels tot welige, hooggroeiende plantegroei, wat „n geneigdheid toon om om te val (lodge). Hierdie probleem vererger indien canola onder besproeiingstoestande gekweek sou word. Plantgroeireguleerders (PGRs) is reeds met sukses onder eksperimentele toestande in Australië gebruik om die planthoogte en dus omval (lodging) van canola te beperk. Plantgroeireguleerders word reeds kommersieel gebruik om planthoogte en omval van wintergraangewasse, soos koring en gars te verminder. Die hoofdoel van hierdie studie was om die effek van omval-teenwerkende PGRs op die agronomiese en kwaliteitseienskappe van kommersiële canola-kultivars onder Suid-Afrikaanse groeitoestande te bepaal. Hierdie studie is uitgevoer d.m.v. veldproewe op drie navorsingsplase, sowel as gekontrolleerde glashuisproewe te Welgevallen Navorsingsplaas, geleë in die Wes-Kaapprovinsie van Suid-Afrika. Blaartoedienings het bestaan uit „n kontrole (onbehandeld) en vier PGRs: CeCeCe® 750 (chlormequat chloride), Moddus® 250 EC (trinexapac-ethyl), Primo MAXX® (trinexapac-ethyl) en Kelpak®, wat afsonderlik of in kombinasie met benattingsmiddels toegedien is tydens die blomknopverskyningstadium (groeistadium 3.1) van canola. Die glashuisproewe is uitgevoer met lente-canolakultivars, nl. “Hyola 555TT” en “43C80”, terwyl veldproewe slegs uitgevoer is met Hyola 555TT. Verskeie plantparameters is gemonitor en gemeet gedurende die verskillende groeistadia van canola, waartydens en die morfologiese en fisiologiese impak van PGR-toedienings op die groei- en ontwikkeling van canola bepaal is. Alhoewel Primo MAXX® neig om die planthoogte in al die proewe te verkort, het dit planthoogte slegs beduidend verkort in een van die glashuisproewe. Geen van die PGRs het in vergelyking met die kontrole, die blaar-oppervlakte, aantal blomme of aantal peule plant-1 beduidend verminder gedurende die studie. Primo MAXX® en Moddus® 250 EC het inteendeel daartoe geneig om die saadopbrengs onder veldtoestande te verhoog. Hierdie studie toon dus dat PGRs moontlik gebruik kan word om omval te verminder en die opbrengs van canola te verhoog. Deur die mees doeltreffendste PGRs op spesifieke kultivars te identifiseer, kan die resultate van hierdie studie bydra tot die kennis van die gebruik van PGRs op canola, om omval te voorkom en saadopbrengs in Suid-Afrika te verhoog.

Thesis (M. Sc. Agriculture (Soil Science)) -- University of Limpopo, 2016. / Canola (Brassica napus) is an important oil crop which is not well grown in Limpopo Province. Planting date is identified as a critical management decision in canola production for enhanced biological and economic returns as it has direct influence on the growing condition at which the crop is exposed to. The objective of the study was to determine the impact of planting date on growth, grain yield, oil content and economic returns on canola production as a winter crop option in the province. The study was conducted at two climatically diverse locations; the University of Limpopo experimental farm at Syferkuil and an Ofcolaco farmers’ field in 2013 and 2014. Canola was planted at four different dates (April, May, June and July) and (March, April, May) during 2013 and 2014 growing seasons, respectively, in a randomised complete block design (RCBD) under four replications, using AG-Muster cultivar. Weather parameters were obtained from Agricultural Research Council and University of Limpopo experimental farm. Plant parameters measured were days to seedling emergence, flowering and physiological maturity, plant height, number of main and sub branches, dry matter at onset of flowering and crop residues after threshing, number of pods per plant, number of seeds per pod, unshelled and shelled weight, and grain yield. The results revealed that, days to seedling emergence responded significantly (P≤0.01) and (P≤0.05) to planting date at both locations and years except in 2014 at Syferkuil. Plant height was significantly influenced by planting date in 2013 at both locations but in 2014, the effect was significant at maturity and flowering at Syferkuil and Ofcolaco respectively. At Ofcolaco, planting date influenced days to 50% flowering, physiological maturity and plant height in both growing seasons. The influence of planting date on days to flowering and physiological maturity was significant (P≤0.01) at both locations and seasons. Canola dry matter accumulation at flowering responded significantly (P≤ 0.01) to planting date only at Syferkuil in 2013 across seasons and locations whereas residue after seed threshing responded significantly at both locations and seasons. Grain yield was significantly (P≤0.01) influenced by planting dates at all locations and seasons ranging from 292 to 2983 kg ha-1. At Syferkuil, planting canola not later than April resulted in higher grain yield whereas at Ofcolaco, planting between April and May produced the highest grain yield. The number of pods per 2 plant influenced grain yield more than the other yield components studied and regarding weather variables, minimum temperature was found to be most important in influencing growth and grain yield of canola. Oil yield ranged from 155 to 539 kg ha-1 at Syferkuil, in 2013 whilst in 2014, the range was 252 to 614 kg ha-1. At Ofcolaco, significant response of oil yield to planting dates was observed in both seasons. Economic returns at Syferkuil ranged from -R6213.00 to +R2130.00 whereas at Ofcolaco the range was +R793.00 to +R6555.00. The study revealed that Ofcolaco appeared to be better suited for canola production compared to Syferkuil due to higher grain yield and positive economic returns at the former. Keywords: canola; grain yield; oil yield; plant density, planting dates, weather parameters. / The National Research Foundation (NRF) through the Risk and Vulnerability Science Centre (RVSC). VLIR-IUC Programme.

Thesis (MScAgric (Agronomy)--University of Stellenbosch, 2007. / 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.