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The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape
Thesis (MScAgric)--Stellenbosch University, 2022.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2022
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| _version_ | 1867614065775345664 |
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| access_status_str | Open Access |
| author | Van der Merwe, Annemarie |
| author2 | Hardie-Pieters, Ailsa G. |
| author_browse | Hardie-Pieters, Ailsa G. Van der Merwe, Annemarie |
| author_facet | Hardie-Pieters, Ailsa G. Van der Merwe, Annemarie |
| author_sort | Van der Merwe, Annemarie |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MScAgric)--Stellenbosch University, 2022. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/124615 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:46:07.073Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2022 |
| publishDateRange | 2022 |
| publishDateSort | 2022 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/124615 The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape Van der Merwe, Annemarie Hardie-Pieters, Ailsa G. Labuschagne, J. Stellenbosch University. Faculty of AgriSciences. Dept. of Soil Science. Soil chemistry Conservation agriculture -- South-Western Cape Soil fertility Soil tillage Crops and nitrogen Tillage -- South Africa Western Cape Crop rotation -- South Africa UCTD Thesis (MScAgric)--Stellenbosch University, 2022. ENGLISH ABSTRACT: The Western Cape is one of the most successful provinces in South Africa in converting to Conservation Agriculture (CA), with an adoption rate of around 80%. CA is a production system that promotes minimal soil disturbance, maintaining crop residues on the soil surface combined, with crop rotation with different species, including legumes. The absence of soil mixing in CA systems can lead to the stratification of immobile nutrients at the surface of the soil profile. Rapid drying of top soil layers may prevent roots from absorbing nutrients from these layers. Up until now, little was known regarding the extent of nutrient stratification in CA systems in the Western Cape. The first objective of this study was to determine the vertical distribution of plant-available nutrients under different tillage practices and rotation sequences at Tygerhoek (34 ̊29’32” S, 19 ̊54’30”E) and Langgewens (33 ̊16’34” S, 18 ̊45’51” E) Research Farms. Soil samples were collected at 0-5, 5-10, 10-15, 15-20 and 20-30 cm depth intervals in zero-till (ZT), no- tillage (NT), minimum tillage (MT) and conventional tillage (CT) treatments combined with 4 crop rotation sequences - wheat monoculture (WWWW), wheat and medics rotation (WMWM and MWMW) and canola/wheat/lupine/wheat (CWLW). Crop rotation and its interaction with tillage and soil depth did not influence (p < 0.05) the distribution of nutrients in the soil at Tygerhoek, but the distribution of K and S in the soil at Langgewens was influenced. Tillage significantly influenced nutrient stratification at both sites. The amount of extractable Ca, Mg, P, K and C were significantly higher in the surface 0-5 cm of the soil under ZT and NT compared to CT. The higher soil organic carbon (SOC) in the topsoil under CA (ZT, NT and MT), may be due to reduced soil disturbance and retention of crop residues. The organic C in the 0-5 cm layer decreased as degree of soil disturbance was increased (ZT2.6%>NT 2.23%> MT 2.15% > CT 1.96%). The percentage difference in soil exchangeable K at Langgewens between 0-5 cm (308 mg kg-1) and 5- 10 cm (172 mg kg-1) layers were the most at 79% for ZT. The second objective was to evaluate the extent of soil nutrient stratification in a wide range of CA systems on commercial farms. Stratification was observed in both the natural veld and the cultivated soil. The cultivation and addition of ameliorates (fertiliser and lime) in the cultivated soil have accentuated the stratification compared to the natural veld. The use of incremental soil sampling identified layers with levels of deficiency for K, S, Zn as well as the occurrence of subsoil acidity. On farms where CA was practiced for more than 25 years, C was built up and the highest values of Ca, K, P and S were present. The third objective was to determine the adoption rate of CA principles and awareness of soil nutrient stratification through a questionnaire. Most of the respondents (63%) indicated that they used CA as farming system. Minimum soil disturbance (47%) was indicated as the most important CA principle, followed by crop rotation (37%) and stubble retention (10%). More than half of the respondents (54%) indicated that the carbon content in the soil were higher than 1.5 %. This could be influenced by the fact that 82% of the respondents were from the southern Cape. More attention to sampling depth is required in conservation agriculture when sampling for lime and fertiliser recommendations to reflect the nutrient status of the soil. In the shallow soil of the Western Cape, soil increments of 0-10 cm and 10-30 cm are recommended for a better reflection of the nutrient status of the soil. AFRIKAANSE OPSOMMING: Ongeveer 80% van die produsente in die Wes-Kaap maak gebruik van bewaringlandbou. Bewaringslandbou behels die gebruik van minimum grondversteuring, bewaring van oesreste op die grondoppervlak en wisselbou met verskillende spesies, insluitende peulgewasse. Die afwesigheid van grondvermenging in die bewaringslandboustelsel kan lei tot die stratifikasie van immobiele nutrient in die grond. Wanneer die grond droog word, kan dit die opname van nutrient deur die wortels verhoed. Daar bestaan beperkte kennis van die stratifikasie van nutrient in bewaringslandboustelsels in die Wes-Kaap. Die eerste doelwit van die studie was om die vertikale verspreiding van plantbeskikbare nutiente te bepaal by verskillende bewerkingspraktyke en wisselboustelsels by Tygerhoek (34 ̊29’32” S, 19 ̊54’30”O) en Langgewens (33 ̊16’34” S, 18 ̊45’51” O) Proefplase. Grondmonsters is geneem by diepte intervalle van 0-5, 5-10, 10-15, 15-20 en 20-30 cm in nulbewerking (ZT), geenbewerking (NT), minimumbewerking (MT) en konvensionele bewerking (CT). Hierdie is gekombineer met vier wisselboustelsels van koringmonokultuur (WWWW), medics-koring (WMWM en MWMW) en canola/koring/lupine/koring (CWLW). Wisselbou en die interaksie daarvan met bewerking en grondiepte het geen betekenisvolle effek (P<0.05) op die verspreiding van nutrient in die grond by Tygerhoek gehad nie. Op Langgewens is die verspreiding van K en S wel deur wisselbou beïnvloed. By biede die proefplase het bewerking ‘n betekenisvolle invloed op die stratifikasie van nutrient gehad. Die hoeveelheid uitruilbare Ca, Mg, P, K en C was betekenisvol hoër in vergelyking met CT. Die hoër konsentrasie van C by bewaringslandbou (ZT, NT en MT) in die bogrond kan toegeskryf word aan die verminderde grondversteuring en bewaring van stoppel op die grondoppervlakte. Die organiese C in die 0-5 cm laag neem af met ‘n toename in grondversteuring (ZT 2.6% > NT 2.23% > MT 2.15% > CT 1.96%). Die persentasie verskil tussen die uitruilbare K by Langgewens tussen die 0-5 cm (308 mg kg- 1) en die 5-10 cm laag (172 mg kg-1) was die meeste by nulbewerking (79%). Die tweede doelwit van die studie was die evaluasie van die stratifikasie van nutrient in die grond van ‘n wye reeks bewaringsboerdery op kommersiële plase. Stratifikasie is gevind op beide die natuurlike veld en bewerkte grond. Die toevoeging van grondverbeteraars (kunsmis en kalk) in die bewerkte grond het die stratifikasie meer geklemtoon in vergelyking met natuurlike veld. Die neem van grondmonsters op verskillende dieptes het tekorte van K, S, Zn en ondergrondversuring getoon. Op die plase waar bewaringslandbou vir meer as 25 jaar toegepas word, is die C opgebou en die hoogste waardes van Ca, K, P en S is gevind. Die derde doelwit is om die toepassing van die beginsels van bewaringslandbou te bepaal en die bewustheid van stratifikasie te toets deur middel van ‘n vraelys. Die meeste deelnemers (63%) het aangedui dat hulle boer volgens bewaringslanbou metodes. Minimum grondversteuring (47%) is aangedui as die belangrikste beginsel, gevolg deur wisselbou (37%) en stoppelbewaring (10%). Meer as die helfde van die deelnemers (54%) het aangedui dat die C persentasie in die grond meer as 1.5 % is. Hierdie resultaat kan gedeeltelik verklaar word omdat 82% van die deelnemers van die Suid-Kaap afkomstig is. Die klimaat is meer gematig en die opbou van koolstof in die grond bevorder in vergelyking met die warm en droë somers van die Swartland waartydens die koolstof in die grond afgebreek word. In bewaringslandbou behoort meer aandag gegee te word aan die diepte van monsternemings wanneer grondmonsters vir kalk- en kunsmisaanbevelings geneem word sodat dit die voedingstofstatus van die grond meer akkuraat weerspieël. In die vlak grond van die Wes-Kaap word grondmonster op die dieptes van 0-10 cm en 10-30 cm aanbeveel. Masters 2022-02-11T11:16:55Z 2022-04-29T09:22:29Z 2022-02-11T11:16:55Z 2022-04-29T09:22:29Z 2022-04 Thesis http://hdl.handle.net/10019.1/124615 en_ZA Stellenbosch University xvii, 30, 103 pages : maps (some color) application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Soil chemistry Conservation agriculture -- South-Western Cape Soil fertility Soil tillage Crops and nitrogen Tillage -- South Africa Western Cape Crop rotation -- South Africa UCTD Van der Merwe, Annemarie The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape |
| title | The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape |
| title_full | The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape |
| title_fullStr | The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape |
| title_full_unstemmed | The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape |
| title_short | The effects of long-term tillage and crop rotation practices on nutrient stratification in the Western Cape |
| title_sort | effects of long term tillage and crop rotation practices on nutrient stratification in the western cape |
| topic | Soil chemistry Conservation agriculture -- South-Western Cape Soil fertility Soil tillage Crops and nitrogen Tillage -- South Africa Western Cape Crop rotation -- South Africa UCTD |
| url | http://hdl.handle.net/10019.1/124615 |
| work_keys_str_mv | AT vandermerweannemarie theeffectsoflongtermtillageandcroprotationpracticesonnutrientstratificationinthewesterncape AT vandermerweannemarie effectsoflongtermtillageandcroprotationpracticesonnutrientstratificationinthewesterncape |