Evaluating the short-term effects of conservation agriculture on soil health and crop production

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dc.contributor.advisorSwanepoel, Pieter Andreas en_ZA
dc.contributor.advisorRoets, Francoisen_ZA
dc.contributor.advisorCrous, Casperen_ZA
dc.contributor.authorAndrews, Jadeen_ZA
dc.contributor.otherStellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.en_ZA
dc.date.accessioned2023-03-03T07:00:42Z
dc.date.accessioned2023-05-18T07:11:17Z
dc.date.available2023-03-03T07:00:42Z
dc.date.available2023-05-18T07:11:17Z
dc.date.issued2023-03
dc.descriptionThesis (MScConsEcol)--Stellenbosch University, 2023. en_ZA
dc.description.abstractENGLISH ABSTRACT: Conservation agriculture (CA) – broadly defined as the implementation of three management principles – permanent soil cover, diverse crop rotations, and reduced soil disturbance – has increased steadily over the years and now accounts for 12.5% of global croplands. The implementation of these principles has improved soil health and crop yields, reduced production costs, and increased the profitability of agricultural systems. However, the application of CA in vegetable production systems is limited. As vegetable production is constrained by its high nutrient and water requirements, and crops are plagued by pests and diseases, the implementation of sustainable farming practices in these intensive systems is essential for sustained food production. This study aimed to evaluate the short-term effects of CA adoption in an irrigated vegetable production system located in Lutzville, South Africa. This area is known for wine and table grape production; vegetable production is also a major contributor towards the agricultural economy in the region. The effects of three treatments – control (“business-as-usual”), mulch (wheat straw mulch), and cover crop (a mixture of two cereals and a legume) – was determined on (i) soil fertility and biological activity; and (ii) crop yield (cauliflower seed, watermelon, tomato, and sweet melon). Soil fertility indicators included pHKCl, electrical resistance, organic C, and macronutrients, while biological activity indicators, such as enzyme activity, active C, and microbial activity, were measured. These treatments were applied to three crop rotation systems: (1) cauliflower- watermelon-soil cover; (2) soil cover-tomato-cauliflower; and (3) soil cover-sweet melon-soil cover. Clear site and crop effects were observed on soil biochemical properties. While soil biological indicators did not differ between treatments, the effects of treatments on soil fertility varied between crop rotations. Sodium content and pHKCl were higher on mulch plots, resistance lower on control plots, and P lowest on cover crop plots on rotation 2, while no treatment differences were found on rotation 1. However, soil potassium content was higher on mulch plots and phosphorus was lowest on cover crop treatments on crop rotation 3. Treatment effects on summer crop yield were varied between crops species. Mulch treatments increased cauliflower seed yield, but not watermelon yield on rotation 1. This increase in cauliflower yield was likely due to the higher application rate of compost on mulch plots (30 m³ ha⁻¹) in comparison to control and cover crop plots (15 m³ ha⁻¹), rather than soil cover treatment as it was only applied towards the end of the study period. While tomato yield was highest on control plots, no treatment effects were observed for sweet melon yield. The findings of this study suggest that the effects of treatments on both soil biochemical properties and crop yield may differ with rotation systems. Although this was a short-term study – and differences are usually only seen after at least 2 years of CA adoption – these results are promising for CA adoption and provides a good starting point for further studies in irrigated vegetable production systems in semi-arid regions.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: (BL) – in die algemeen gedefinieer as die implementering van drie bestuursbeginsels – permanente gronddekking, gewasrotasies, en verminderde grondversteurings – het stadig maar seker oor die jare vermeerder en beloop tans op 12.5% van die globale gewasproduksiearea. Die implementering van hierdie beginsels het verbeterde grond- en gewasgesondheid, verminderde produksie-onkoste en ʼn toename in die winsgewendheid van bewaringstelsels tot gevolg. Die toepassing van BL in groenteproduksiestelsels is egter beperk. Omdat groente produksie ʼn hoe voeding- en watervereiste het, en gewasse deur plae en siektes geteister word, is die implementering van volhoubare boerderypraktyke in hierdie intensiewe stelsels uiters belangrik vir volhoubare voedselproduksie. Hierdie studie beoog om die korttermyngevolge van BL in ʼn besproeide groenteproduksie stelsel, gesetel in Lutzville, te bestudeer. Die gevolge van drie tipes behandelings – kontrole (die gewone praktyk), ʼn deklaag (koringstrooi deklaag), en ʼn dekgewas (ʼn mengsel van twee graangewasse en ʼn peulgewas) was toegepas om (i) grond vrugbaarheid en biologiese aktiwiteit; en (ii) oesopbrengs (kopkool saad, waatlemoen, tamatie en spanspek) te bepaal. Grondvrugbaarheidaanwysers het pHKCl, elektriese weerstand, organiese C en makronutriënte ingesluit, terwyl biologiese aktiwiteit aanwysers ensiemaktiwiteit, aktiewe C en mikrobiese aktiwiteit gemeet het. Hierdie behandelings was toegepas op drie gewas rotasie sisteme (1) kopkool-waatlemoen-grondbedekking; (2) grondbedekking- tamatie-kopkool; en (3) grondbedekking-spanspek-grondbedekking. Duidelike lokaliteit en gewasgevolge was waargeneem op grondbiochemiese eienskappe. Terwyl grond biologiese aanwysers nie tussen behandelings verskil het nie, het die gevolge van behandelings op grondvrugbaarheid tussen gewasrotasies verskil. Natriuminhoud en pHKCl was hoër op deklaag erwe, weerstand laer op kontrole persele, en fosfor die laagste op dekgewas persele op rotasie 2, terwyl geen behandelingsverskille op rotasie 1 gevind is nie. Grond kalium was hoër op deklaag persele en fosfor was die laagste op dekgewas behandelings. Someroes opbrengs (waatlemoen, tamatie en spanspek) het verskil tussen lokaliteite. Lokaliteitverskille was gekoppel aan verskille in biochemiese eienskappe. Behandelings het ook verskil tussen gewasse. Deklaag behandeling het ʼn toename in kopkoolsaadopbrengs tot gevolg gehad, maar nie waatlemoen opbrengs in rotasie 1 nie. Hierdie toename in kopkoolopbrengs was waarskynlik as gevolg van ʼn hoër toepasingstoediening van kompos op deklaagpersele (30 m³ ha⁻¹) in vergelyking met kontrole en dekgewas erwe (15 m³ ha⁻¹), eerder as gronddekkings behandelings omdat dit slegs toegedien was teen die einde van die studie periode. Tamatieopbrengs was die hoogste op die kontrole erwe, geen behandelings gevolge was op die spanspek opbrengs waargeneem nie. Die bevinding van hierdie studie suggereer dat die effekte van behandelings op beide grond biochemiese eienskappe en gewas opbrengs mag verskil met rotasies (gewasspesies) en lokaliteite. Alhoewel dit ʼn korttermyn studie was – en verskille word eintlik eers waargeneem na 2 jaar vanaf die aanvangs van BL, is hierdie resultate belowend vir BL toepassing en voorsien dit ʼn goeie aanvangspunt vir verdere studies in besproeiings groenteproduksie stelsels in halfdroë streke.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxii, 88 pages : illustrationsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/127236
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshConservation agriculture -- Environmental aspects -- South Africaen_ZA
dc.subject.lcshAgricultural conservation -- Evaluationen_ZA
dc.subject.lcshSoil healthen_ZA
dc.subject.lcshSoil productivityen_ZA
dc.subject.lcshSoil fertility -- South Africaen_ZA
dc.subject.lcshCrop yieldsen_ZA
dc.subject.lcshVegetables -- Water requirementsen_ZA
dc.subject.lcshIrrigation -- South Africa -- Managementen_ZA
dc.subject.nameUCTDen_ZA
dc.titleEvaluating the short-term effects of conservation agriculture on soil health and crop productionen_ZA
dc.typeThesisen_ZA
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Masters Degrees (Conservation Ecology and Entomology)