Thesis (MScAgric)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Southern highbush (SHB) blueberries are relatively new to the blueberry industry and are adapted to grow in areas with low winter chilling and therefore can be grown in the Mediterranean-type climate of South Africa. The blueberry industry in South Africa is still relatively young, but it is quickly expanding and therefore appropriate cultivation practises are becoming more important. This study mainly focuses on the appropriate fertilization practises for SHB cultivars Snowchaser and Emerald grown in an ever-greening system. Plants were cultivated in plant containers in a netted tunnel in the Paarl district of South Africa. All plants received continuous fertigation with a standard commercial nutrient solution containing nitrogen, phosphorus, potassium, magnesium, calcium and all micro-elements. Carbohydrate patterns were determined on newly established tissue culture plants at two-weekly intervals from April 2013 to June 2014 and macro nutrient patterns were determined at four-weekly intervals from May 2013 to June 2014. The phenology of these plants was also visually assessed during the sampling period. Macro nutrient content was determined for two-year old „Snowchaser‟ and „Emerald‟ plants at five phenological stages during the 2013/2014 season and nutrient losses due to harvest and pruning was recorded. The phenology of evergreen „Snowchaser‟ and „Emerald‟ SHB blueberries were very different from deciduous blueberries, to such an extent that fruit could be harvested at the end of winter to early spring. Carbohydrate patterns differed between the first and the second season. Reserve carbohydrates were accumulated in the first season, but not in the second season possibly due to the difference in photosynthate production between the seasons. Plants were significantly bigger, with higher total leaf area, in the second season and it could be that carbohydrates from current photosynthesis were enough to supply new growth, thus making reserves less important. Carbohydrates could also have been used to increase flower bud development instead of being stored as reserves in the second season. Nutrient patterns also differed between the two seasons, but nutrient accumulation was apparent in the second season and not in the first. Nutrient uptake was highest when plants were growing rapidly, emphasizing the importance of fertilizer during periods of rapid growth. Huge fluctuations in the nutrient concentration patterns in the root, shoot and leaf tissues were observed over the sampling period and could have been a result of irregular fertigation and therefore it is uncertain whether flushes in nutrient uptake was a result of higher nutrient demand by the plant. Nutrients are lost due to harvest and pruning and need to be replaced by applying the right amount of fertilizer. Nutrient uptake differs throughout the season as the demand for nutrients fluctuates and therefore fertilizers should be applied at different rates during the season. In the two-year old plants, the most nutrients were accumulated after summer pruning and before growth cessation and therefore most of the fertilization would occur during this stage. Recommendations for correcting nutrient losses due to harvest and pruning are made, together with recommendations for rate and timing of fertilizer application throughout the season. / AFRIKAANSE OPSOMMING: „Southern highbush‟ (SHB) bloubessies is ‟n relatiewe nuwe ontwikkeling in die bloubessie-industrie en is aangepas om in minder koue areas aangeplant te word en daarom kan hulle in die Meditereënse-tipe klimaat van Suid-Afrika aangeplant word. Die bloubessie-industrie in Suid-Afrika is nog relatief jonk, maar dit is vinnig besig om uit te brei en daarom raak geskikte verbouingspraktyke al hoe belangriker. Hierdie studie fokus hoofsaaklik op die geskikte bemestingspraktyke vir SHB kultivars Snowchaser en Emerald wat in ‟n immergroen sisteem verbou word. Plante is in houers in ‟n tonnel, wat met net bedek is, in die Paarl distrik van Suid-Afrika, aangeplant. Alle plante het dieselfde standaard kommersiële verreikte wateroplossing, teen ‟n konstante vloei, ontvang. Die oplossing het stikstof, fosfor, kalium, magnesium, kalsium en al die mikro-elemente bevat. Koolhidraatpatrone is in twee-weeklikse intervalle, vanaf April 2013 tot Junie 2014, vir nuut gevestigde weefselkultuurplante bepaal en makro-element patrone is in vier-weeklikse intervalle, vanaf Mei 2013 tot Junie 2014, bepaal. Die fenologie van dié plante is visueel waargeneem tydens die monsternemingsperiode. Makro-elementinhoud is vir tweejarige „Snowchaser‟ en „Emerald‟ plante by vyf fenologiese stadiums tydens die 2013/2014 seisoen bepaal en die voedingstofverliese as gevolg van oes en snoei is bepaal. Die fenologie van immergroen „Snowchaser‟ en „Emerald‟ SHB bloubessies het opmerklik verskil van bladwisselende bloubessies, tot so ‟n mate dat vrugte al teen einde winter na vroeë lente geoes kon word. Koolhidraatpatrone van die eerste en tweede seisoen het verskil deurdat reserwe koolhidrate in die eerste seisoen opgebou het, maar nie in die tweede seisoen nie, moontlik as gevolg van die verskil in fotosintaatproduksie tussen die twee seisoene. Plante was opmerklik groter, met groter blaaroppervlak, in die tweede seisoen en dit kon wees dat koolhidrate van huidige fotosintese genoeg was om die groei te onderhou en sodoende die afhanklikheid van reserwes te verminder. Koolhidrate kon ook vir verhoogde blomknopontwikkeling gebruik geword het, in plaas van om as reserwes vir die tweede seisoen gestoor te word. Voedingstofpatrone het ook tussen seisoene verskil, maar voedingstofakkumulasie was duidelik in die tweede seisoen en nie in die eerste nie. Voedingstofopname was die hoogste wanneer plante vinnig gegroei het en daarom is bemesting tydens periodes van vinnige groei uiters belangrik. Groot wisselinge in die voedingstofkonsentrasiepatrone van die wortels, lote en blare is tydens die monsternemingsperiode waargeneem en onreëlmatige verrykte watertoediening kon dit veroorsaak het. Daarom is dit onseker of fluktuasies in voedingstofopname ‟n gevolg was van hoër voedingstofaanvraag deur die plant. Voedingstowwe gaan verlore deur oes en snoei en moet deur die toediening van korrekte bemesting vervang word. Voedingstofopname verskil oor die verloop van die seisoen soos die aanvraag vir voedingstowwe deur die plant verander en daarom moet bemestingstowwe teen verskillende hoeveelhede deur die seisoen toegedien word. In die tweejarige plante is meeste van die voedingstowwe ná somersnoei en voor groeistaking opgeneem en daarom moet meeste van die bemesting tydens hierdie stadium toegedien word. Aanbevelings vir die korrigering van voedingstofverliese as gevolg van oes en snoei, tesame met aanbevelings vir die hoeveelheid en tyd van bemestingstoediening deur die seisoen, word gemaak.

Thesis (M.Sc. (Agronomy)) -- University of Limpopo, 2021 / Soybean (Glycine max L.) is one of the valuable leguminous crops with grain used for human consumption, livestock feeding, bio-fuel (bio-diesel) production, vegetable oil and is a protein resource. The crop also fixes atmospheric nitrogen. The study aimed to evaluate the performance of two soybean varieties to a combination of inoculation and seaweed extract. The research trial was conducted at Syferkuil farm during 2017/2018 summer season in which two soybean varieties (TGx 1937-1F promiscuous) and (PAN 1583R specific-nodulating) were evaluated for their growth, nodulation and yield responses to rhizobium inoculation and seaweed extract (0 % rate (0ml/12L), 50 % rate (30ml/12L) and 100 % (60ml/12L). The research trial was laid out as a split-split plot arrangement fitted in RCBD with four replications. Inoculation significantly influenced grain yield at P≤0.05, seed nutrient content and total above-ground biomass, except for seed potassium. No inoculation significantly achieved higher primary branches per plant at P≤0.05, pod number per plant, stem diameter (P≤0.05), grain yield (P≤0.05), harvest index and total above-ground biomass at P≤0.001. The variety TGx 1937-1F had significantly (P≤0.001) higher nodule number per plant, effective nodules per plant, nodule dry weight, dried shoot biomass, leaf number per plant, pod number per plant, primary branches per plant, stem diameter, plant height, leaf chlorophyll content, total above-ground biomass, grain yield and seed iron (Fe) content. Application of full rate seaweed extract significantly (P≤0.001) increased primary branches per plant, stem diameter, leaf number per plant, plant height, shelling percentage, total above-ground biomass, grain yield, and seed content of calcium (Ca), potassium, magnesium (Mg), manganese (Mn) and sodium (Na) all at P≤0.05. Seaweed extract rate at 0 % obtained the highest harvest index (P≤0.001). Inoculation and variety TGx 1937-1F interaction exhibited a significant increase on leaf number per plant at P≤0.001, primary branches per plant at P≤0.001 and plant height at P≤0.001. Variety TGx 1937-1F, without inoculation, obtained significantly higher pod number per plant (P≤0.001), stem diameter at P≤0.001, grain yield at P≤0.05 and total above-ground biomass at P≤0.001. Variety PAN 1583R, without inoculation, obtained significantly higher harvest index and shelling percentage at P≤0.001. Interaction of vi inoculation and seaweed extract showed that no inoculation × 100 % rate of seaweed extract significantly (P≤0.001) increased primary branches per plant, leaf number per plant, stem diameter, pod number per plant and plant height. Interaction of inoculation × 100 % rate of seaweed extract increased grain yield (P≤0.001) and total above-ground biomass at P≤0.001. Inoculation × 50 % rate of seaweed extract interaction increased shelling percentage at P≤0.001. No inoculation × 0 % rate of seaweed extract interaction obtained significantly higher harvest index (P≤0.001). Interaction of variety and seaweed extract showed that variety TGx 1937-1F × 100 % rate of seaweed extract significantly increased primary branches per plant (P≤0.001), pod number per plant at P≤0.001, grain yield at P≤0.001 and total above-ground biomass at P≤0.001. The variety TGx 1937-1F × 50 % rate of seaweed extract significantly raised the size of stem diameter (P≤0.01) and plant height (P≤0.001). Three-way interactive effects of inoculation × variety TGx 1937-1F × 100 % rate of seaweed extract obtained significantly higher number of shelling percentage at P≤0.001, leaf number per plant at P≤0.05 and primary branches per plant at P≤0.001. Interaction of no inoculation × variety TGx 1937-1F × 100 % rate of seaweed extract obtained significantly high pod number per plant at P≤0.001, grain yield at P≤0.05, total above-ground biomass at P≤0.001 and plant height at P≤0.001. No inoculation × PAN 1583R × 100 % rate of seaweed extract interaction had a higher harvest index at P≤0.001. The study showed that inoculation, seaweed extract, or their combination generally enhanced seed nutrient content, especially in variety TGx 1937-1F. The study further showed that promiscuous soybean (TGx 1937-1F) had higher grain yield, under stressful growing conditions as compared to PAN 1583R variety. This implies that soybean variety TGx 1937-1F, with 50 % or 100 % application rate of seaweed extract could be recommended to smallholder farmers. Key words: Soybean, inoculation, seaweed extract, phenological development, growth, nodulation, grain yield and seed nutrient content. / National Research Foundation (NRF)

In dieser Arbeit wurden die Veränderungen der agrarklimatologischen Bedingungen im Zuge des Klimawandels für ausgesuchte Sauerkirschanbauregionen in Europa und Nordamerika untersucht. Es wird auf veränderte Risiken (Spätfrost, Hitzewellen, Wassermangel) hingewiesen, die durch nachhaltige, praxisorientierte und ökonomisch vertretbare Anpassungsmaßnahmen (Überdachung, Frostschutz, Bewässerung, Anbausystem, Wahl der Sorte und Unterlage, etc.) begrenzt werden können. Der Klimawandel kann neben Risiken aber auch Chancen für den Sauerkirschanbau eröffnen. Höhere Temperaturen und eine längere Vegetationsperiode können regional differenziert zu günstigeren Anbaubedingungen führen. Ein besonderer Schwerpunkt wurde auf die Entwicklung phänologischer Modelle gelegt, mit denen Veränderungen im Entwicklungsrhythmus der Sauerkirschgehölze analysiert werden konnten. Dafür wurden acht Modelle zur Vorhersage des Blühbeginns und Blühendes entwickelt. Weitere phänologische Stadien konnten mit dem Modell von Zavalloni et al. (2006) berechnet werden. Die Untersuchungen haben ergeben, dass sich der Blühbeginn unter geänderten Klimabedingungen verfrüht, aber nur geringe Verkürzungen der Zeiträume zwischen den phänologischen Stadien zu erwarten sind. Zu den gefürchteten Witterungsschäden im Obstbau gehört Spätfrost, der zu hohen Ertragsverlusten führen kann. Im Zuge des Klimawandels können sich die Häufigkeit und Stärke der Fröste ändern. Die Frostwahrscheinlichkeit während der untersuchten Entwicklungsphasen von Sauerkischgehölzen könnte in diesem Jahrhundert in Rheinland-Pfalz und Eau Claire abnehmen, während sich die Verhältnisse in den anderen Anbaugebieten nur geringfügig ändern. In einem zweiten Schritt wurden die Ertragsverluste durch Frost bestimmt. Hierbei hat sich ergeben, dass die Frostschäden in den untersuchten Anbauregionen wahrscheinlich geringer werden. Allerdings differieren die Ergebnisse zwischen den Berechnungen mit beobachteten und modellierten Temperaturen oft stark. / This thesis investigates the changes in agro-climatic conditions for selected growing region in Europe and North America under current and future climate conditions. The overall aim of the study was to identify possible risks (spring frosts, heat waves, water shortages), which can be limited by sustainable, practically oriented and economically viable adaptation measures (hail- and frost-protection, irrigation, cultivation system, choice of variety and rootstock). Besides risks, climate change can provide new opportunities. Higher temperature levels and extended growing season lengths could regionally differentiated improve the growing conditions. Particular focus was given to developing phenological models, used to investigate shifts in spring phenology of sour cherry trees due to climate change. Therefore, eight models to predict the beginning and end of blossom were optimized and validated. Further phenological stages were calculated with the model by Zavalloni et al. (2006). The results show an earlier onset in the beginning of sour cherry blossom under future climate conditions, while the length of the period between the phenological stages only shortens slightly. Spring frosts are feared weather hazards in orchards which can cause substantial yield losses. The changing climate conditions could influence the frequency and strength of spring frosts. In the course of this century the spring frost probability is likely to decrease in Rhineland-Palatinate and Eau Claire, while only slight changes are expected in the other growing regions. In the second step, yield losses caused by spring frost were calculated. The frost damages on sour cherries in the investigated growing regions will probably decrease. However, the yield losses calculated with observed and modeled temperatures often differ strongly.