Role of soil carbon in crop yields and quality in crop rotational system

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dc.contributor.advisorHardie-Pieters, Ailsa G.en_ZA
dc.contributor.advisorStrauss, J. A.en_ZA
dc.contributor.authorDaiber, Roccoen_ZA
dc.contributor.otherStellenbosch University. Faculty of Agrisciences. Dept. of Soil Science.en_ZA
dc.date.accessioned2023-02-22T07:33:11Z
dc.date.accessioned2023-05-18T07:00:38Z
dc.date.available2023-02-22T07:33:11Z
dc.date.available2023-05-18T07:00:38Z
dc.date.issued2023-03
dc.descriptionThesis (MScAgric)--Stellenbosch University, 2023. en_ZA
dc.description.abstractENGLISH ABSTRACT: Conservation agriculture (CA), which includes no-till (NT) and crop rotation, can be implemented for a positive effect on soil organic matter (SOM) accumulation and carbon sequestration. This can lead to greater soil health and resilience, with subsequently increased yields. Previous research has shown soil organic carbon (SOC) accumulation is site-specific, with the climate, crops, and the soil properties to be considered. Studies about the role that SOC plays in wheat yield are lacking in the Western Cape. In this study, soil (0-15 cm) and yield data from long- term field trials under CA conducted at Langgewens Research Farm (24ᵗʰ year) and Tygerhoek Experimental Farm (20ᵗʰ year) in the Western Cape were analyzed. The rotational systems implemented during the trials included wheat monoculture, 100% crop, 50% crop/50% pasture, and 33% crop/67% pasture. The objectives of this research project were i) to look at the long-term effect of the no-till crop rotations systems on SOC and wheat yield, ii) explore the relationship between the SOC content and the yield and protein content of wheat, and iii) obtaining optimum values and sufficiency ranges for the factors affecting wheat yield, protein content, and SOC content using boundary Line Analysis (BLA). Over the entire trial period, a significant increase in SOC content was only found at Langgewens (0.4%) attributed to it its substantially lower starting SOC (0.91%). The average SOC content being higher at Tygerhoek (1.68%) compared to Langgewens (1.17%) attributed to differences in soil properties and climate. It was observed that the SOC had likely reached a ‘saturation point’ at both sites. At both sites, the wheat monoculture had a significantly lower yield, and the incorporation of natural vegetation (pastures and saltbush) had a benefit on the SOC content, wheat yield, and protein content. The rainfall showed a significant linear correlation with wheat yields. While soil pH, lime, gypsum, N fertilizer, soil nutrients, and the clay:C ratio did not show a significant correlation. No linear correlation was found between wheat yield and the SOC content, while some seasons showed a significant partial correlation. A panel regression showed significant correlations of some variables to wheat yield. Wheat monoculture and 100% crops had a significantly lower protein content at Langgewens and Tygerhoek respectively. The BLA for wheat yield showed that above and below a certain SOC point wheat yield will decrease at each site. Protein content decreased above 20 mg kg⁻¹ soil Sulphur. The BLA showed a decreased protein content above and below a certain SOC point. A significant negative correlation between average minimum temperatures and SOC content was found. The focus of this study was the long-term dynamics of SOC and yields, and their relationship. There was SOC accumulation with the implementation of CA but is dependent on the soil and climate, along with a ‘saturation point’. The SOC did not directly correlate with yield as it is likely not directly addressing the main yield limiting factors in this production area, which are mainly climate and soil related.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Bewaringslandbou (BL), wat geenbewerking (GB) en wisselbou insluit, kan geïmplementeer word vir 'n positiewe effek op grondorganiese materiaal (GOM) akkumulasie en koolstofsekwestrasie. Dit kan lei tot groter grondgesondheid en veerkragtigheid, met gevolglik verhoogde opbrengste. Vorige navorsing het getoon dat grond-organiese koolstof (GOK) akkumulasie terrain spesifiek is, met die klimaat, gewasse en die grondeienskappe wat in ag geneem moet word. Studies oor die rol wat GOK in koringopbrengs speel, ontbreek in die Wes-Kaap. In hierdie studie is grond (0-15 cm) en opbrengsdata van langtermyn veldproewe onder BL wat by Langgewens Navorsingsplaas (24ste jaar) en Tygerhoek Proefplaas (20ste jaar) in die Wes-Kaap uitgevoer is, ontleed. Die wisselboustelsels wat tydens die proewe geïmplementeer is, het koringmonokultuur, 100% gewas, 50% gewas/50% weiding en 33% gewas/67% weiding ingesluit. Die doelwitte van hierdie navorsingsprojek was i) om te kyk na die langtermyn effek van die GB wisselboustelsels op GOK en opbrengs, ii) die verband tussen die GOK-inhoud en die opbrengs en proteïeninhoud van koring te ondersoek, en iii) die verkryging van optimum waardes en voldoende reekse vir die faktore wat koringopbrengs, proteïeninhoud en GOK-inhoud beïnvloed deur grenslynanalise (GLA) te gebruik. Oor die hele proeftydperk is 'n beduidende toename in GOK-inhoud slegs by Langgewens gevind (0.4%), aangesien die begin GOK (0.91%) aansienlik laer was. Die gemiddelde GOK-inhoud is hoër by Tygerhoek (1.68%) in vergelyking met Langgewens (1.17%) wat toegeskryf word aan verskille in grondeienskappe en klimaat. Daar is waargeneem dat die GOK waarskynlik 'n 'versadigingspunt' by beide terreine bereik het. By beide terreine het die koringmonokultuur 'n aansienlik laer opbrengs gehad, en die inkorporering van natuurlike plantegroei ( weidings en soutbos) het 'n voordeel op die GOK-inhoud, koringopbrengs en proteïeninhoud gehad. Die reënval het 'n beduidende lineêre korrelasie met koringopbrengste getoon. Terwyl grond pH, kalk, gips, N kunsmis, grondvoedingstowwe en die klei:K verhouding nie 'n beduidende korrelasie getoon het nie. Geen lineêre korrelasie is gevind tussen koringopbrengs en die GOK-inhoud nie, terwyl sommige seisoene 'n beduidende gedeeltelike korrelasie getoon het. 'n Paneelregressie het beduidende korrelasies van sommige veranderlikes tot koringopbrengs getoon. Koringmonokultuur en 100% gewasse het 'n aansienlik laer proteïeninhoud by onderskeidelik Langgewens en Tygerhoek gehad. Die GLA vir koringopbrengs het getoon dat bo en onder 'n sekere GOK-inhoud koringopbrengs by elke proef sal afneem. Proteïeninhoud het tot bo 20 mg kg⁻¹ grond Swael afgeneem. Die GLA het 'n verlaagde proteïeninhoud bo en onder 'n sekere GOK-punt getoon. 'n Beduidende negatiewe korrelasie tussen gemiddelde minimum temperature en GOK-inhoud is gevind. Die fokus van hierdie studie was die langtermyndinamika van GOK en opbrengste, en hul verhouding. Daar was GOK-akkumulasie met die implementering van BL, maar was afhanklik van die grond en klimaat, tesame met 'n 'versadigingspunt'. Die GOK het nie direk met opbrengs gekorreleer nie, aangesien dit waarskynlik nie die belangrikste opbrengsbeperkende faktore in hierdie produksiegebied direk aanspreek het nie, wat eerder die klimaat en grond was.af_ZA
dc.description.versionMastersen_ZA
dc.format.extent196 pages : illustrations (some color), mapsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/127024
dc.language.isoen_ZAen_ZA
dc.rights.holderStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshConservation agricultureen_ZA
dc.subject.lcshSoils -- Carbon content -- South Africa en_ZA
dc.subject.lcshSoil organic carbonen_ZA
dc.subject.lcshCrop rotation -- South Africa -- Western Cape -- Data processingen_ZA
dc.subject.lcshSoil fertility -- South Africa -- Western Capeen_ZA
dc.subject.lcshNo-tillageen_ZA
dc.subject.lcshTillageen_ZA
dc.subject.lcshCrop yields -- Qualityen_ZA
dc.subject.nameUCTDen_ZA
dc.titleRole of soil carbon in crop yields and quality in crop rotational systemen_ZA
dc.typeThesisen_ZA
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