Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Soil is a fundamental, non-renewable resource in any ecosystem. To uphold food production for increasing global human populations, it is imperative to develop ways in which to sustain healthy biological productivity and sustainability of agricultural soils. Nematodes are one of the most abundant groups of Metazoa occurring in all soils, and form an integral part of the soil food web at several trophic levels. They respond rapidly to changes within their environments, and can easily be extracted from soil, identified and characterised into functional guilds. Nematodes thus have the potential to impart insight into the condition of the soil food web. This study aims to establish whether nematodes will be suitable bio-indicators of soil health for the deciduous fruit industry in the Western Cape. Three different objectives have been set to determine the practical use of nematode community structures as a tool for the measurement of soil health. The objectives include describing the nematode community structure, biodiversity and functionality within Fynbos soils; the characterization of organic and conventional orchards; and the differences in nematode soil communities in differently managed soils in an apple orchard. The number of nematodes in each soil sample was quantified and identified to family level. The nematode biodiversity and functionality for each site was determined by evaluating the nematode food webs for trophic group distribution, as enumerated by the Maturity Index (MI), the Enrichment Index (EI), the Structure Index (SI), the Basal Index (BI) and the Channel Index (CI), based on the weighted abundance of coloniser-persister guilds. The functional guild analysis of Fynbos samples indicated that the enrichment and the structure of any given sample were not bound to a certain area, but it was representative of each of the four quadrats within the faunal analysis. Different geographic areas were found to differ in nematode diversity and functionality, which was mainly associated with dominant plant families and species (such as strong associations between Fynbos families Fabaceae, Solanaceae and Celestraceae with the nematode family Pratylenchidae). The most abundant nematode families present in the Fynbos were Tylenchidae, which are plant-feeding nematodes, and Cephalobidae which are bacterial-feeding nematodes. Despite Tylenchidae and Cephalobidae both having coloniser-persister values (cp-values) of two, they are split up into different feeding types. Cp-2 nematodes are tolerant to disturbances, and occur in all environments. Only one omnivorous family, the Dorylaimida, was identified in Fynbos samples. The average MI value for Fynbos was found to be very low, with a mean value of 1.26. The value obtained indicated the presence of taxa with tolerance to disturbance, which, in turn, indicated the presence of a disturbed soil, in general. The number of plant-parasitic nematodes within the Fynbos soils was low, which was supported by the low plant-parasitic index (PPI) of 0.85. The diversity, richness and evenness values were low, indicating low nematode diversity, but a distribution of abundances amongst the families. The average Hill’s N0 index value was 8.0, indicating that, in general, eight nematode families would have been present in a Fynbos soil sample. A study was done to determine the biodiversity and the functionality of the nematodes associated with deciduous fruit orchards that were conventionally, or organically, managed. Herbivores were dominant in all the orchards. The organic apple orchard had the lowest numbers of herbivores and fungivores, with the highest number of carnivores. When comparing organic and conventional apricot orchards, higher numbers of plant-parasitic nematodes were found in the organic orchard. Criconematidae occurred in higher numbers in conventional apricot orchard soil. When comparing organic apricots and apples, higher numbers of Criconematidae occurred within the organic apple soil. Overall, higher levels of plant-parasitic nematodes occurred in the organic apricot orchard. The MI indicated that all orchard soils had values below 1.5, indicating disturbance. Conventionally managed apricot orchard soil had the highest MI value of 1.48. The PPI value was highest in organically managed apricot orchards. All orchard soils were located within Quadrat B of the faunal analysis, indicating enrichment and structure. Regarding the diversity, richness and evenness of the distribution, conventional apricot soil had the highest species richness, while organic apple soil had the most even family distribution. Different management practices did not show marked differences in community composition and structure. The species richness of Fynbos soils was comparable to those of deciduous fruit orchards. Soil samples from eight different soil surface treatments were collected from an apple orchard in the Grabouw area. Treatments were combined according to the soil surface treatments received (chemical control of cover crops and weeds, mulch and mulch + effective micro-organism spray). Bacterivores were dominant in all soil treatments, with the least number being present in the chemical control (of cover crops and weeds) treatment. Sites which received chemical control of cover crops and weeds had higher levels of fungivores, compared to the levels at the other sites. High numbers of Rhabditidae occurred within mulch and mulch + effective micro-organism (EM) treatment sites, while high numbers of Aphelenchidae occurred in chemical control sites. The carnivorous family Ironidae only occurred in mulch + EM sites. Strong associations were found between soil surface applications and nematode families present within the soil. Chemical control (of cover crops and weeds) applications had the highest MI value, while values were equal for the other soil applications. The faunal analysis indicated that the mulch and the chemical control fell within Quadrat A, indicating enriched, but unstructured, soil, while the mulch + EM treatment fell within Quadrat B, indicating enrichment and structure, as well as good overall soil conditions. All the systems were dominated by bacterial decomposition pathways. Controversially, sites that received chemical control of the cover crops and weeds had the highest species richness of all three applications, as well as the highest level of diversity, according to the Simpson Index. As only the cover crops and the weeds were chemically controlled, the soil can be regarded as undisturbed, which explains the results obtained in this study. Clear differences in nematode community structure and composition were observed between the different soil applications in the apple orchard. / AFRIKAANSE OPSOMMING: Grond is 'n fundamentele, nie-hernubare hulpbron binne enige ekosisteem. Ten einde voedselproduksie vir die toenemende globale menslike bevolking te handhaaf, is dit noodsaaklik om maniere te ontwikkel om gesonde biologiese produktiwiteit en volhoubaarheid van landbougrond in stand te hou. Nematodes is een van die volopste Metazoa in alle gronde en vorm 'n integrale deel van die grond voedsel-web op verskeie trofiese vlakke. Hulle reageer vinnig op veranderinge binne hul omgewings, kan maklik ekstraheer en identifiseer word; en ook maklik in funksionele gildes ingedeel word. Nematodes het ook die potensiaal om insig oor te dra ten opsigte van die toestand van die grond voedsel-web. Hierdie studie het ten doel om vas te stel of nematodes geskikte bio-indikatore van grond gesondheid kan wees spesifiek vir die sagtevrugte bedryf in die Wes-Kaap. Drie verskillende doelwitte is gestel om die praktiese gebruik van nematode populasie samestelling as 'n instrument vir die meting van grond gesondheid te gebruik. Die doelwitte sluit in die nematode populasie samestelling, biodiversiteit en funksionaliteit binne natuurlike Fynbos; organies verboude versus konvensionele boorde; en die verskil in nematode populasie samestelling tussen verskillend behandelde en bestuurde grondpersele binne ʼn appel boord. Die nematode biodiversiteit en funksionaliteit vir elke perseel was bepaal deur die evaluering van die nematode voedselweb vir trofiese groep verspreiding en enumerering deur die Maturity Index (MI) en die Enrichment Index (EI), Strukturele Indeks (SI), Basale Indeks (BI) en Channel Index (CI) wat gebaseer is op die geweegde oorvloed van koloniseerder-persister gildes. Die funksionele gilde vir Fynbos monsters het aangedui dat die verryking en struktuur van enige gegewe perseel nie gebonde is aan ʼn bepaalde gebied nie, aangesien dit verteenwoordig was in elk van die vier kwadrante van die Fauna Analiseerder. Daar is gevind dat verskillende areas verskil in nematode diversiteit en funksionaliteit, wat hoofsaaklik geassosieer was met die dominante plant families en spesies in die omgewing. Die volopste nematode familie wat teenwoordig was in die Fynbos was Tylenchidae, wat plant-voedende nematodes is, en Cephalobidae, wat bakterie-voedend is. Tylenchidae en Cephalobidae het beide ʼn cp-waarde van twee, maar is verdeel in verskillende VIII tipes voedingsgroepe. Die cp-2 nematodes is verdraagsaam vir versteurings en kom in alle omgewings voor. Slegs een omnivoor familie is geïdentifiseer in Fynbos monsters, nl. die Dorylaimidae. Die gemiddelde MI waarde vir Fynbos was laag, met 'n gemiddelde waarde van 1.26. Hierdie waarde is ʼn aanduiding van die teenwoordigheid van taxa met verdraagsaamheid tot versteuring, wat op sy beurt 'n versteurde grond in die algemeen aangedui het. Die aantal plant-parasitiese nematodes binne die Fynbos-gronde was laag, wat ondersteun word deur die lae PPI-waarde van 0.85. Die waardes vir die diversiteit, spesie-rykheid en egaligheid was laag, wat dui op 'n lae nematode diversiteit, maar 'n egalige verspreidings onder families. Die Hill’s N0 indeks waarde was gelyk aan 'n gemiddelde van 8.0 en dui daarop dat in die algemeen agt nematode families teenwoordig sal wees in 'n Fynbos grondmonster. 'n Studie is gedoen om die biodiversiteit en funksionaliteit van nematodes wat verband hou met vrugteboorde wat organies en konvensioneel bestuur is te bepaal. Herbivore was dominant in alle boorde. Organiese appels het die laagste aantal herbivore en fungivore gehad en die hoogste aantal karnivore. Wanneer organiese en konvensionele appelkoosboorde met mekaar vergelyk is, was hoër getalle van plant-parasitiese nematodes gevind in die organiese boord. Criconematidae was teen ʼn groter aantal in die grond van die konvensionele appelkoosboord gevind. Met die vergelyking van organiese appelkose en appels word, is ʼn hoër aantal Criconematidae binne die organiese appelgrond aangetref. In die algemeen was hoër vlakke van plant-parasitiese nematodes gevind in die organiese appelkoosboord. Die MI het getoon dat alle boord waardes laer as 1.5 gehad het, wat daarop dui dat die gronde versteurd is. Die konvensioneel bestuurde appelkoosboord het die hoogste MI waarde gehad met ʼn vlak van 1.48. Die waarde vir die PPI was die hoogste in organies bestuurde appelkoosboorde. Alle boord gronde is geleë binne kwadrant B van die Fauna Analiseerder, wat dui op verryking met struktuur. Met betrekking tot die diversiteit, spesie-rykheid en egaligheid van die verspreiding van families, het konvensionele appelkoos grond die hoogste spesierykheid, terwyl die gronde van die organiese appelboord die mees egalige familie verspreiding vertoon het. Verskillende bestuurspraktyke nie toon nie merkbare verskille in die gemeenskap samestelling en struktuur nie. Die spesie-rykheid van Fynbos gronde is vergelykbaar met dié van sagtevrugte-boorde. Monsters is geneem van agt verskillende grondeoppervlak-behandelings in ‘n appelboord in die Grabouw area. Die behandelings is gekombineer volgens die grond toediening wat dit ontvang het (chemiese beheer van dekgewasse en onkruid, deklaag en ‘n deklaag + effektiewe mikro- IX organismes). Bakterievoedende nematodes was dominant in elke grondoppervlak-behandeling, met die minste teenwoordig in die behandelings wat chemiese beheer van die dekgewasse en onkruid ontvang het. Behandelings wat chemiese beheer van die dekgewasse en onkruid ontvang het, het ook hoër vlakke van fungivore in vergelyking met die ander behandelings. ʼn Hoë aantal Rhabditidae het voorgekom in grondmonsters van die deklaag en die deklaag + EM (effektiewe mikro-organismes) behandeling persele, terwyl ʼn groot aantal Aphelenchidae voorgekom het in chemiese beheer persele. Die predatoriese familie, Ironidae, het slegs voorgekom in persele wat die deklaag + EM behandeling ontvang het. Sterk assosiasies bestaan tussen grond behandeling en nematode families wat in die grond teenwoordig was. Die chemiese beheer behandeling het die hoogste MI waarde getoon, terwyl waardes vir die ander behandelings laer en gelyk was. Die fauna analise het daarop gedui dat die deklaag en chemiese beheer binne kwadrant A is en dus verryk, maar ook ongestruktureerd is. Die deklaag + EM behandeling het binne kwadrant B geval wat aandui op toestande van verryking en struktuur wat 'n goeie algehele grondtoestand tot gevolg gehad het. Al die stelsels is oorbruggingsweë wat oorheers was deur bakteriële ontbinding. Kontroversieel, het persele wat chemiese beheer van die dekgewasse en onkruid ontvang het, die hoogste spesierykheid van al drie behandelings getoon asook die hoogste vlak van diversiteit volgens die Simpson-indeks. Slegs die dekgewasse en onkruid is chemies behandel, nie die grond nie, en dus kan die grond as onversteurd beskou word en die resultate wat verkry is in die studie verklaar. Duidelike verskille in die nematode gemeenskap struktuur en samestelling is waargeneem tussen die verskillende grond behandelings in appel boorde.

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Biochar is a carbon-rich solid material produced during pyrolysis, which is the thermal degradation of biomass under oxygen limited conditions. Biochar can be used as a soil amendment to increase the agronomic productivity of low potential soils. The aim of this study was to investigate the effect of applying locally-produced biochar on the fertility of low-nutrient holding, sandy soil from the Western Cape, and to determine the optimum biochar application level. Furthermore, this study investigates the effect of biochar on the leaching of an inorganic nitrogen fertilizer and a multi-element fertilizer from the sandy soil. The biochar used in this study was produced from pinewood sawmill waste using slow pyrolysis (450 °C). The soil used was a leached, acidic, sandy soil from Brackenfell, Western Cape. In the first study, the sandy soil mixed with five different levels of biochar (0, 0.05, 0.5, 0.5 and 10.0 % w/w) was chemically characterised. Total carbon and nitrogen, pH, CEC and plant-available nutrients and toxins were determined. The application of biochar resulted in a significant increase in soil pH, exchangeable basic cations, phosphorus and water holding capacity. A wheat pot trial using the biochar-amended soil was carried out for 12 weeks and to maturity (reached at 22 weeks). The trial was conducted with and without the addition of a water-soluble broad spectrum fertilizer. Results showed that biochar improved wheat biomass production when added at low levels. The optimum biochar application level in the wheat pot trial was 0.5 % (approximately 10 t ha-1 to a depth of 15 cm) for the fertilized treatments (21 % biomass increase), and 2.5 % (approximately 50 t ha-1 to a depth of 15 cm) for unfertilized treatments (29 % biomass increase). Since most biochars are alkaline and have a high C:N ratio, caution should be taken when applying it on poorly buffered sandy soil or without the addition of sufficient nitrogen to prevent nutrient deficiencies. In the second study, leaching columns packed with sandy soil and biochar (0, 0.5, 2.5 and 10.0 % w/w) were set up to determine the effect of biochar on inorganic nitrogen fertilizer leaching over a period of 6 weeks. It was found that biochar (0.5, 2.5, and 10.0 % w/w) significantly reduced the leaching of ammonium (12, 50 and 86 % respectively) and nitrate (26, 42 and 95 % respectively) fertilizer from the sandy soil. Moreover, biochar (0.5 %) significantly reduced the leaching of basic cations, phosphorus and certain micronutrients. This study demonstrated the potential of biochar as an amendment of acidic, sandy soils. Our findings suggest that an application rate of 10 t ha-1 should not be exceeded when applying biochar on these soils. Furthermore, biochar application can significantly reduce nutrient leaching in sandy agricultural soils. / AFRIKAANSE OPSOMMING: Biochar is ʼn koolstof-ryke, soliede materiaal geproduseer gedurende pirolise, wat die termiese degradasie van biomassa onder suurstof-beperkte omstandighede behels. Biochar kan gebruik word as ʼn grondverbeterings middel om die agronomiese produktiwiteit van grond te verhoog. Die doel van hierdie studie was om die effek van plaaslike vervaardigde biochar op die vrugbaarheid van die sanderige grond van die Wes-Kaap te ondersoek, en om die optimale biochar toedieningsvlak te bepaal. Verder, het hierdie studie die effek van biochar op die loging van anorganiese stikstof kunsmis en ‘n multi-elementkunsmis op sanderige grond ondersoek. Die biochar wat in hierdie studie gebruik is, is van dennehout saagmeul afval vervaardig d.m.v. stadige pirolise (450 °C). Die grond wat in hierdie studie gebruik is, is ‘n geloogde, suur, sanderige grond van Brackenfell, Wes-Kaap. In die eerste studie, is ‘n chemiesie ondersoek van die sanderige grond wat vermeng met is met vyf verskillende vlakke van biochar (0, 0.05, 0.5 en 10.0 % w/w) uitgevoer. Totale koolstof en stikstof, pH, KUK, en plant-beskikbare voedingstowwe en toksiene is in die grondmengsels bepaal. Die toediening van biochar het ‘n veroorsaak dat die grond pH, uitruilbare basiese katione, fosfor en waterhouvermoë beduidend toegeneem het. ‘n Koringpotproef was uitgevoer vir 12 weke en ook tot volwassenheid (wat op 22 weke bereik was) om die effek van die biochar op die sanderige grond teen die vyf verskillende toedieningsvlakke te bepaal. Daar was behandelings met en sonder die bykomstige toediening van ‘n wateroplosbare breë-spektrumkunsmis. Resultate toon dat die toediening van biochar teen lae vlakke koringbiomassa produksie verbeter. Die optimale biochar toedieningsvlak in die koringpotproef is 0.5 % (omtrent 10 t ha-1 tot ‘n diepte van 15 cm) vir die bemeste behandeling (21 % biomassa toename), en 2.5 % (omtrent 50 t ha-1 na ‘n diepte van 15 cm) vir onbemeste behandelings (29 % biomassa toename). Aangesien die meeste biochars alkalies is en ‘n hoë C:N verhouding besit, moet sorg gedra word wanneer dit op swak-gebufferde of lae N-houdende sanderige gronde toegedien word. Die resultate het aangedui dat die biochar versigtig aangewend moet word om grond oorbekalking te voorkom. In die tweede studie, was kolomme gepak met 2.0 kg van die sanderige grond gemeng met biochar (0, 0.05, 0.5, 2.5 en 10.0 % w/w) om die effek van biochar op die loging die anorganiese stikstof kunsmis oor ‘n tydperk van 6 weke om vas te stel. Daar is gevind dat biochar (0.5, 2.5 en 10.0 % w/w) die loging van ammonium (12, 50 en 86 % onderskeidelik) en nitraat (26, 42 en 95 % onderskeidelik) op sanderige grond aansienliek verminder. Verder, het biochar (0.5 %) die loging van basiese katione, fosfor en mikrovoedingstowwe aansienlik verminder. Hierdie studie het die potensiaal van biochar as verbeteringmiddel van suur, sanderige grond gedemonstreer. Ons bevindinge dui daarop aan dat ‘n toepassing vlak van 10 t ha-1 moet nie oorskry word nie wanneer biochar op hierdie gronde toegedien word. Die toediening van biochar op sanderige grond kan die loging van voedingstowwe aansienlik verlaag.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Apple replant disease (ARD) is one of the major impediments to the establishment of an economically viable apple orchard on sites previously planted to apple. In spite of extensive research on ARD, the etiology remains to be fully elucidated. A possible biological origin of ARD etiology in South Africa was investigated by the dilution of replant field soil with sterilised soil. Commercial orchards with ARD were selected for use in pot trials and disease severity evaluated after three months, by measuring shoot length, dry mass of plants as well as root discolouration. Although diluting replant soil to 25 and 50% (v/v) significantly reduced the effects of ARD, symptoms were only absent in 0% replant soil. It was clear that seedlings planted in any mixture containing replant soil, even only 25% replant soil, consistently exhibited symptoms of stunted growth and root discolouration similar to those seedlings grown in 100% replant soil. This indicates that ARD in South Africa is primarily of a biological nature. As an initial step in formulating sustainable disease control alternatives to replace methyl bromide, pot trials were conducted to assess the impact of compost treatments as well as biological control products on ARD. Compost as well as sterilised and unsterilised compost teas (compost extract) significantly increased seedling growth even under optimum nutrient conditions when compared to the control, suggesting that they negate the effects of ARD. Results also indicated that applying high concentrations of compost does not necessarily provide additional growth benefits compared to lower concentrations. Results with biocontrol formulations were less favourable. Only one of the biocontrol formulations, a combination of Bacillus spp. (Biostart®) improved growth significantly compared to the control. There was, however, some inconsistency with results for the different trials conducted using this product. Fungal as well as nematode populations associated with ARD soils were characterised to the generic level to get a clearer understanding of the etiology of ARD in South Africa. Pythium and Cylindrocarpon spp. were consistently isolated from all six replant soils in all trials that formed part of this study, indicating that these fungi may have a role in ARD etiology in South Africa. Nematodes implicated in ARD development were inconsistently associated with ARD soils used in these studies. This suggests that nematodes do not have a primary causal role in ARD etiology in South Africa. Field trials were conducted in commercial orchards to assess the impact of organic amendments and promising biological control products, as indicated by the pot trials, on ARO severity under field conditions. These biological soil amendments were also compared with the standard chemical control methods for ARO, methyl bromide and chloropicrin. In all three trials established, compost and mulch as well as manure and mulch, consistently increased growth to the same extent as the standard chemical treatments and by combining these chemical treatments with organic amendments a significant, additional growth increase could be attained. Biocontrol formulations evaluated in field studies gave variable results. Biostart® improved growth when applied on its own, but not in combination with the chemical Herbifume (metham-sodium). Inoculating soil with effective microorganisms (EM), consisting primarily of photosynthetic bacteria, had no significant effect on growth. Results from this study indicate that application of organic amendments could possibly substitute for soil fumigation in replanted apple orchards. However, compost quality standards need to be implemented and because few types of compost are universally effective, different types of composts should be compared in specific soil environments before recommendations can be made. Oue to variable results with biocontrol products, ARO management with these biological soil amendments cannot be guaranteed at this stage and further studies are recommended. / AFRIKAANSE OPSOMMING: EVALUERING VAN DIE SPESIFIEKE APPELHERVESTIGING-PROBLEEM IN BOORDE IN DIE WES-KAAP Appelhervestiging-siekte (AHS) skep 'n groot probleem in die vestiging van jong appelbome op grond waar daar reeds voorheen appels verbou is. Ten spyte van omvangryke navorsing is die oorsaak van die probleem nog hoofsaaklik onbekend. 'n Moontlike biologiese oorsaakleer is in Suid-Afrika ondersoek deur die hervestigings-effek te probeer verminder deur die vermenging van hervestigingsgrond met gesteriliseerde grond. Kommersiële boorde met 'n appelhervestigingsprobleem is geselekteer en gebruik in potproewe. Die ernstigheidsgraad van die siekte is na drie maande se groei geevalueer deur lootlengte, droë massa en wortelverkleuring te meet. Alhoewel verdunning van die hervestigingsgrond tot 50 en 25% (vlv) die effek van AHS op groei betekenisvol verminder het, kon die skadelike effek van die veroorsakende faktor slegs uitgeskakel word deur saailinge in 100% gesteriliseerde grond te plant. Dit was duidelik dat saailinge wat in enige grondmengsel geplant is waarin hervestigingsgrond voorgekom het, selfs al was dit net 25%, konsekwent simptome van vertraagde groei en wortelverkleuring getoon het. Dit is 'n aanduiding dat AHS in Suid-Afrika hoofsaaklik biologies van aard is. Potproewe is uitgevoer as 'n eerste stap in die formulering van volhoubare siektebeheer-strategieë, om die impak van kompos-behandelings en biologiese beheer produkte op AHS te ondersoek. Kompos sowel as gesteriliseerde en ongesteriliseerde kompos-tee (kompos-water) het, selfs onder optimale voedingsomstandighede, die groei van saailinge betekenisvol verbeter. Dit dui aan dat hierdie behandelings die effek van AHS kan teenwerk. Resultate het ook daarop gedui dat hoër kompos konsentrasies nie noodwendig enige addisionele voordele vir groei inhou in vergelyking met laer konsentrasies nie. Resultate met biologiese beheer produkte was minder gunstig. Slegs een van die produkte wat geëvalueer is, 'n kombinasie van Bacillus spp. (Biostart®), het groei betekenisvol verbeter in vergelyking met die kontrole. Resultate was egter inkonsekwent vir die verskillende proewe waarin hierdie produk gebruik is. Swampopulasies sowel as aalwurmpopulasies wat met hervestigingsgrond geassosieer word, is geïdentifiseer tot op generiese vlak om vas te stel waardeur AHS in Suid-Afrika veroorsaak word. Pythium en Cylindrocarpon spp. is konsekwent van al ses hervestigingsgronde geïsoleer wat daarop dui dat hierdie twee swamgenera 'n beduidende rol in AHS ontwikkeling in Suid-Afrika mag hê. Aalwurms wat aangedui is in die literatuur om 'n moontlike rol in AHS te hê, was slegs in enkele gevalle geassosieer met hervestigingsgronde waarvan in hierdie studie gebruik gemaak is. Die gevolg-trekking is dus gemaak dat aalwurms nie 'n betekenisvolle rol speel as hoof-veroorsakende organisme onder Suid-Afrikaanse toestande nie. Veldproewe is uitgevoer in kommersiële appelboorde om vas te stel wat die effek van organiese materiaal, asook belowende biologiese beheermiddels, soos aangedui deur potproewe, op AHS onder veldtoestande is. Die biologiese grondtoedienings is ook vergelyk met die standaard chemiese beheermiddels (metielbromied en chloorpikrien). In al drie proewe wat gevestig is, het kompos met 'n deklaag, sowel as kraalmis met 'n deklaag, groei betekenisvol verbeter tot dieselfde mate as chemiese middels. Daar kon ook 'n beduidende, addisionele groeitoename gemeet word in gevalle waar chemiese middels met organiese materiaal gekombineer is. Resultate met biologiese beheer formulasies wat onder veldtoestande geëvalueer is, het gevarieer. Biostart® het groei verbeter wanneer dit alleen toegedien is, maar in kombinasie met die chemiese middel Herbifume (metham-sodium) het dit geen effek gehad nie. Die inokulering van grond met 'n oplossing van effektiewe mikroorganismes (EM) wat hoofsaaklik uit fotosinterende baterieë bestaan, het ook geen betekenisvolle effek op groei gehad nie. Die gevolgtrekking is gemaak dat toediening van organiese materiaal moonlik as plaasvervanger vir metielbromied-beroking kan dien in die beheer van AHS. Die nodige komposkwaliteit-standaarde moet egter eers geïmplimenteer word. Omdat feitlik geen kompos universeel effektief kan wees nie, is dit ook nodig dat verskillende tipes kompos met mekaar vergelyk moet word in spesifieke grondtoestande voordat verdere aanbevelings gemaak kan word. As gevolg van variërende resultate met biologiese beheer produkte kan AHS beheer met hierdie middels nie gewaarborg word op hierdie stadium nie en verdere studies word aanbeveel.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2005. / This thesis forms part of a research program that is investigated by ARC Infruitec- Nietvoorbij and the University of Stellenbosch. The aim of this program is to quantify the effect of soil and climate on wine quality and character as a basis for scientific demarcation of production regions. Natural factors are first quantified and characterised so that relative homogeneous natural terroir units (NTU) can be identified. Thereafter wines made from these different localities are assessed for similarities which permit grouping of localities into viticultural terroirs. The present study involved seven research plots in the Robertson district, making use of initial measurements by ARC Infruitec-Nietvoorbij in the 2000/01 and 2001/02 seasons together with more intensive measurements in the 2002/03 and 2003/04. The seven plots are located in two wards, Le Chasseur and Vinkrivier. Sauvignon blanc plots were marked at two localities, each with two sub-plots occurring in one block. Three Cabernet Sauvignon plots were marked out. Two plots occurred in one block in Le Chasseur and one plot in Vinkrivier. Plots within the same block were located on different soil types so that the effect of soil type on wine quality and character could be monitored. Morphological examination of soil profiles at each plot was carried out together with physical and chemical analysis of samples taken at 30cm depth intervals. Soil water content was measured at regular intervals to assess soil water tension. Vineyard performance was assessed in terms of phenology, root system studies, leafwaterpotential measurements, canopy quality assessment, leaf analysis, shoot growth, and data relating to ripening, harvest and pruning. Wines were made from each plot by ARC Infruitec- Nietvoorbij and evaluated by a tasting panel after six months and then again after eighteen months. Meteorological data were collected in each ward.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Little scientific information regarding the effect of different geological parent materials on grapevine performance is currently available in South Africa. This aspect is of special significance for the Helderberg area, where parent material may change from granite to shale over a short distance. This results in shale- as well as granite-derived soils often occurring within the same vineyard. The objectives of this study were to (i) quantify the nutritional status and other soil properties of different parent materials (shale and granite) and overlying soils (ii) investigate the impact of geological differences in the soil on the vine nutritional status and certain vine parameters. This study was done over two seasons (2006/2007 and 2007/2008). Two Sauvignon blanc and two Cabernet Sauvignon vineyard blocks were selected at two different localities for each cultivar in the Helderberg area, South Africa. Shale- and granitederived soils were identified within each block. Kaolinite was the dominant mineral, whereas quartz and feldspar were sub-dominant. Traces of mica were also present in some shale- and granite-derived soils. Granite- contained significantly higher contents of coarse sand than shale-derived soils, whilst the opposite occurred in terms of fine sand. These differences affected the water holding capacity, in general making it higher in shale- than granite-derived soils. Shale-derived soils had higher concentrations of total K but granite-derived soils had a higher ability to release K as they contained higher concentrations of soluble K. The Q/I parameters, potential buffering capacity of K (PBCK) and equilibrium activity ratio of K (ARK) showed no consistent responses to geological differences. Potassium concentrations were higher in the leaf blades (obtained before harvest in 2007) from Sauvignon blanc grapevines on granite- than on shale-derived soils. Potassium concentrations in the Cabernet Sauvignon juice (obtained in 2007) tended higher in juice from granite- than from shale-derived soils. In 2008, K concentrations tended higher in juice from shale- than from granite-derived soils for both cultivars. The pH of the Sauvignon blanc juice (obtained in 2008) tended higher in juice from shale-than from granite-derived soils, thus corresponding with the K concentrations in the juice in this season. Nitrogen concentrations were higher in Cabernet Sauvignon juice (obtained in 2007) and Sauvignon blanc juice (obtained in 2008) from shalethan from granite-derived soils. In terms of vine water status, vines on granite-derived soils appeared more stressed than those on shale-derived soils in both seasons at one of the vineyards. In these Sauvignon blanc and Cabernet Sauvignon vineyards, the K nutritional status was not affected by geology in a consistent manner but there were some noticeable tendencies for a specific cultivar during certain seasons. On account of vines being planted on shale- and granite-derived soils within the same block, soil preparation was done similarly for both soils, and they were exposed to similar irrigation schedules, canopy management strategies and climatic conditions. Therefore, there is a high probability that all these practices may have negated the effect of geology on the K status of soils and especially on juice K concentration at the time of harvest. It was clear that seasonal differences and fertilisation affected the nutritional status of the vines more than geology. / AFRIKAANSE OPSOMMING: In Suid-Afrika is daar tans min wetenskaplike inligting oor die effek van verskillende geologiese moedermateriale op die prestasie van wingerd beskikbaar. Hierdie aspek is veral van belang in die Helderberg-area, waar moedermateriaal oor ‘n baie kort afstand van graniet na skalie kan wissel. Dit lei daartoe dat skalie-, sowel as granietgronde, dikwels binne dieselfde wingerd voorkom. Die doelwitte van die studie was om: (i) die voedingstatus en ander grondkundige eienskappe van die verskillende moedermateriale (skalie en graniet) en oorliggende gronde te kwantifiseer (ii) die impak van geologiese verskille in die grond op wingerd se voedingstatus en sekere wingerdkundige parameters, te ondersoek. Hierdie studie is oor twee seisoene (2006/2007 en 2007/2008) gedoen. Twee Sauvignon blanc en twee Cabernet Sauvignon wingerdblokke is geselekteer by twee verskillende lokaliteite vir elke kultivar in die Helderbergarea, Suid-Afrika. Beide skalie- en granietgrond is binne elke blok geïdentifiseer. Kaoliniet was die dominante mineraal, met kwarts en veldspaat sub-dominant, terwyl spore van mika ook in beide skalie- en granietgronde gevind is. Granietgronde het betekenisvol hoër hoeveelhede growwe sand bevat, terwyl skaliegronde meer fyn sand bevat het. Hierdie verskille het ‘n effek op waterhouvermoë gehad en daartoe gelei dat waterinhoude oor die algemeen hoër was vir skaliegronde. Skaliegronde het groter hoeveelhede totale K bevat, maar granietgronde se vermoë om K vry te stel was hoër, omdat hulle ‘n hoër konsentrasie oplosbare K bevat het. Die Q/I parameters, potensiële buffervermoë vir K (PBCK) en ewewig aktiwiteitsverhouding vir K (ARK), is nie op ‘n konsekwente wyse deur geologiese verskille beïnvloed nie. Vir die Sauvignon blanc wingerde was kalium konsentrasies in blaarskywe (gemonster voor oes in 2007) hoër vir graniet- as vir skaliegronde. Kalium konsentrasies in die sap vanaf Cabernet Sauvignon (gemonster in 2007) het hoër geneig vir granietgronde. In 2008 het die kalium konsentrasies, vir beide kultivars, hoër geneig in sap vanaf skaliegronde. Gedurende dié seisoen het die pH van sap ook hoër geneig vir Sauvignon blanc vanaf skaliegronde, wat dus ooreenstem met die K inhoud van die sap. Stikstof konsentrasies was hoër in sap vanaf skaliegronde vir Cabernet Sauvignon (2007) en vir Sauvignon blanc (2008). In terme van die wingerde se waterstatus, het stokke op die granietgrond, by een van die lokaliteite, geneig om gedurende beide seisoene onder groter stremming te wees op graniet as op skaliegrond. In hierdie Sauvignon blanc en Cabernet Sauvignon wingerde, is K voedingstatus nie op ‘n konsekwente wyse deur geologie geaffekteer nie, maar gedurende sommige seisoene was daar wel duidelike tendense vir ‘n spesifieke kultivar. Omdat die stokke binne dieselfde blok op skalie- en graniet gronde geplant is, was grondvoorbereiding eenders vir die twee grondtipes terwyl besproeiingskedule, lowerbestuur en klimaatstoestande ook identies was. Daar is dus ‘n hoë waarskynlikheid dat al hierdie faktore daartoe kon bygedra het dat die effek van geologie op die K status van van gronde versluier is, veral die effek op die K inhoud van sap teen oestyd. Dit was duidelik dat seisoenale klimaatsverskile en bemestingspraktyke ’n groter effek as geologie op die voedingstatus van die wingerd gehad het.