Kritzinger, Hannelize (2014-12)
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.
Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/96069
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