Developing nitrogen fertiliser management strategies for canola (Brassica napus L.) under conservation agriculture practices in the Western Cape
| dc.contributor.advisor | Labuschagne, Johan | en_ZA |
| dc.contributor.advisor | Swanepoel, Pieter Andreas | en_ZA |
| dc.contributor.author | Du Toit, Etienne | en_ZA |
| dc.contributor.other | Stellenbosch University. Faculty of AgriSciences. Dept. of Agronomy. | en_ZA |
| dc.date.accessioned | 2018-11-26T17:59:43Z | |
| dc.date.accessioned | 2018-12-07T06:46:07Z | |
| dc.date.available | 2018-11-26T17:59:43Z | |
| dc.date.available | 2018-12-07T06:46:07Z | |
| dc.date.issued | 2018-12 | |
| dc.description | Thesis (MA)--Stellenbosch University, 2018. | en_ZA |
| dc.description.abstract | ENGLISH ABSTRACT: Nitrogen (N) is one of the most important nutrients in canola production systems. Improper N supply due to lack of knowledge regarding canola N management and inappropriate fertiliser guidelines, frequently results in low canola yield and profitability in the Western Cape. Current N guidelines are based on international literature or adapted from wheat guidelines. Conservation agriculture practices have also changed soil N dynamics. More N is mineralised from soil organic matter than conventional systems, which were historically practised. Canola N guidelines should therefore be refined to account for the abovementioned changes. The aim of this study was to determine the effect of different topdress N rates, foliar N application at stem elongation and N source on plant parameters, canola seed yield, oil content and N use efficiency, whilst monitoring the effect of different topdress N rates on the soil mineral N concentration at plant, pre-topdress, post topdress and at harvest. This study was conducted at five canola producing areas in the Western Cape during 2016 and 2017. The trial was laid out as a randomised block design consisting of seven different topdress N rates (0, 25, 50, 75, 105, 135 and 165 kg N ha-1) applied at the rosette stage. For all the above mentioned treatments, 25 kg N ha-1 was applied at planting. A control treatment was included that received no N. A foliar N application that consisted of 20 kg N ha-1 (urea ammonium nitrate) was applied at stem elongation. Five N sources were evaluated, applied as topdressing at rosette stage. Increasing topdress N rate increased (p<0.05) soil mineral N concentration. Plant population at harvest and biomass production did not respond (p<0.05) to topdress N rates, a result not expected but could be ascribed to the relative dry seasons experienced in 2016 and 2017. Canola yield responded (p<0.05) to topdress N rate. Maximum yield response was recorded at lower topdress N rates than expected. The N use efficiency (NUE) decreased (p<0.05) as topdressed N rate was increased, with a drastic reduction in NUE when total N application was increased above 25 kg N ha-1. Foliar N application at stem elongation did not (p>0.05) influence yield or oil content at most sites. Nitrogen source did not influence (p>0.05) plant population, biomass production or yield, except at one site (Langgewens) in the Swartland in 2017 where the urea + inhibitor outperformed LAN. No differences (p>0.05) were recorded in oil content between different N sources in 2016. Generally, in 2017, oil content was lower compared to 2016 and inconsistent results were recorded between N sources. This was possibly due to the dry conditions during 2017, which may have influenced oil production. It is apparent that N fertiliser recommendations have to be adjusted for certain areas. Current N recommendations may result in over-fertilisation and reduced profitability at sites in the southern Cape. Current N recommendation at the Swartland sites has a low NUE and further increase in topdress N rates would likely result in pollution of the environment. Nitrogen source did not affect canola productivity. Selection of N source should be based on cost. In general, CA practices tended to decrease fertiliser N requirement for canola production. Refined N fertiliser guidelines may result in more consistent canola yield and ensure profitability. Guidelines will only be finalised on completion of the research project after at least four years of data capturing. | en_ZA |
| dc.description.abstract | AFRIKAANSE OPSOMMING: Stikstof (N) is een van die belangrikste voedingstowwe in kanolaproduksiesisteme. Onvoldoende N-bemesting a.g.v. onsekerheid t.o.v. kanola N-bestuur lei dikwels tot beperking van kanola-opbrengs en -winsgewendheid in die Wes-Kaap. Tans is kanola N-bemestingsriglyne in die Wes-Kaap gebaseer op internasionale literatuur of aangepas vanaf koring N-bemestingsriglyne. Bewaringslandbou het ook grondstikstofdinamika oor die langtermyn verander. Kanola N-bemestingsriglyne moet dus aangepas word in lyn met die veranderinge om N-bestuurseffektiwiteit te verhoog. Die doel van die studie was om die effek van verskillende N-bemestingspeile, addisionele N-blaarbespuitings by stamverlenging en verskillende N-bronne op plantparameters, kanolasaadopbrengs, olie-inhoud van saad en stikstofverbruiksdoeltreffendheid (NUE) te bepaal, terwyl die effek van verskillende N-bemestingspeile op grond N-inhoud gedurende die groeieseisoen gemonitor is. Die studie is uitgevoer by vyf verskillende kanolaproduksie-areas regoor die Wes-Kaap gedurende 2016 en 2017. Eksperiment een is uitgelê as ʼn ewekansige blokontwerp van sewe verskille N-peile (0, 25, 50, 75, 105, 135 and 165 kg N ha-1) wat toegedien is by rosetstadium. Al die bogenoemde N-peile het 25 kg N ha-1 met planttyd ontvang. Daar was ook ʼn kontrolebehandeling wat geen N gekry het nie. Alle behandelings is vier keer herhaal. Eksperiment twee was ʼn addisionele N-blaarbespuiting by stamverlenging teen 20 kg N ha-1 UAN. In eksperiment drie is vyf verskillende N-bronne geëvalueer wat ook toegedien is by rosetstadium. Al die behandelings het ook 25 kg N ha-1 met planttyd gekry. Verhoging van N-peil het gelei tot ʼn verhoging (p<0.05) in grond N-inhoud. Verskillende N-peile het geen effek (p>0.05) gehad op plantpopulasie en biomassaproduksie by oestyd nie. Die resultaat was onverwags en kan toegeskryf word aan die relatiewe droë jare wat tydens 2016 en 2017 ondervind is. Kanolaopbrengs het verhoog (p<0.05) soos N-peil verhoog het. Maksimum opbrengsreaksie was alreeds bereik op ʼn laer N-peil as wat verwag is. Stikstofverbruiksdoeltreffendheid het afgeneem (p<0.05) soos N-peil verhoog het, met ʼn drastiese afname wanneer totale N-bemesting bo 25 kg N ha-1verhoog is. ʼn Addisionele N-blaarbespuiting by stamverlenging het geen effek (p>0.05) gehad op kanolaopbrengs en –olie-inhoud nie. Stikstofbron het geen effek (p>0.05) op plantpopulasie, biomassaproduksie en kanolaopbrengs gehad nie, behalwe by Langgewens in 2017. Urea + inhibeerder het hoër (p<0.05) opbrengs gelewer as KAN by Langgewens in 2017. Geen verskil (p>0.05) is waargeneem in olie-inhoud tussen verskillende N-bronne tydens 2016 nie. In 2017 was olie-inhoud oor die algemeen laer as in 2016 en wisselvallige olie-inhoudwaardes is waargeneem. Dit kan wees weens die verskriklike droogte tydens die groeiseisoen in 2017 wat olieproduksie negatief kon beïnvloed het. Vanuit die resultate is dit duidelik dat kanola N-bemestingsriglyne in sekere areas gewysig moet word. Huidige N-riglyne kan lei tot oorbemesting in die Suid-Kaap. In die Swartland met die lae NUE is daar ʼn groot kans vir omgewingsbesoedeling. Verskillende N-bronne het geen effek op produktiwiteit gehad nie en keuse moet gebaseer word op koste. Bewaringslandboupraktyke is geneig om die N-bemestingsbehoefte te verlaag in vergelyking met konvensionele praktyke. Verbeterde kanola N-bemestingsriglyne wat die bostaande resultate in ag neem, kan lei tot meer konstante opbrengste wat winsgewendheid sal verbeter. Stikstof N-riglyne sal egter eers gefinaliseer word na vier jaar van data-insameling. | af_ZA |
| dc.format.extent | xix, 128 pages : illustrations | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/10019.1/104804 | |
| dc.language.iso | en_ZA | en_ZA |
| dc.publisher | Stellenbosch : Stellenbosch University | en_ZA |
| dc.rights.holder | Stellenbosch University | en_ZA |
| dc.subject | Canola -- Fertilizers -- Western Cape (South Africa) | en_ZA |
| dc.subject | Crops and nitrogen -- Western Cape (South Africa) | en_ZA |
| dc.subject | Nitrogen fertilizers -- Environmental aspects -- Management -- Western Cape (South Africa) | en_ZA |
| dc.subject | UCTD | |
| dc.title | Developing nitrogen fertiliser management strategies for canola (Brassica napus L.) under conservation agriculture practices in the Western Cape | en_ZA |
| dc.type | Thesis | en_ZA |