Establishment, growth and yield of canola (Brassica napus L.) as affected by seed-drill opener, soil quality and crop residue in the Swartland

Le Roux, Pieter Johannes Grobler (2018-03)

Thesis (MScAgric)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Canola (double low varieties of Brassica napus) is an important crop for farmers implementing conservation agriculture (CA). Famers implementing CA seek to minimise soil disturbance before, during and after planting. Many farmers in the grain producing regions (Overberg and Swartland) of the Western Cape have widely adopted CA over the past two decades. Although most farmers rely on tine openers to establish canola, disc openers are becoming more popular. Soil quality in these canola production areas are relatively low. The aim of this study was to compare tine and disc openers and the effects of soil quality and crop residue on canola production, by evaluating establishment, biomass production, leaf area index (LAI), yield, thousand seed mass (TSM) and soil disturbance. The first objective was to determine whether soil quality along with residue level should be considered when choosing between a tine or disc seed-drill opener. The second objective was to compare tine and disc openers to produce canola from soil with contrasting qualities and on fields comparable in size to commercial farms. Trials were conducted in 2016 and 2017 at Langgewens Research Farm in the Swartland area. During the first year of the trial the opener had an effect on canola plant population (p<0.05), while during the second year no differences between treatments were recorded (p>0.05). Tine openers performed better on high quality soil while disc openers performed better on low quality soil. Crop residue can become a problem when establishing canola with both the tine and disc openers, and establishment was the best at low residue levels. The poorer canola establishment with the disc opener during 2016 might be due to fertiliser application as fertiliser was applied with seeding which may have caused chemical injury to the seed. Overall the tine opener resulted in more biomass than the disc opener during the first year of the trial while similar biomass productions were achieved during the second year. The leaf area-index (LAI) was similar except that a higher LAI was recorded with the tine opener on low residue levels on high quality soil at 30 days after emergence during the 2017 season. Treatments had no effect on TSM in 2016 (p>0.05), while in 2017 a higher TSM was obtained on low quality soil with high residue levels than on high quality soil with low residue levels. The treatments had no effect on yield in both 2016 and 2017 (p>0.05). On field scale, similar results were recorded as on small plots with low residue levels, with regards to plant population, biomass production, LAI, yield and TSM. Contrary to what was expected, no difference in disturbance was recorded between tine and disc openers (p>0.05), so if the aim is to minimise soil disturbance, either a tine or disc opener can be used. It is recommended that this study is repeated in the southern Cape as soil and climatic conditions differ substantially from the Swartland. It is also recommended that this study is repeated in different years in the Swartland due to seeding in dry soil in both years of this study due to the drought.

AFRIKAANSE OPSOMMING: Kanola (dubbel-lae variteite van Brassica napus) is ’n belangrike gewas vir boere wat bewaringslandbou toepas. Bewaringslandbouboere mik vir minimum grondversteuring voor, gedurende en na plant. Baie boere in die graan produserende areas (Overberg en Swartland) van die Wes-Kaap het bewaringsboerderybeginsels oor die afgelope twee dekades aangeneem. Alhoewel meeste boere op tandoopmakers staatmaak om kanola te vestig, neem gewildheid van skyfoopmakers toe. Grondkwaliteit in hierdie kanolaproduksieareas is redelik laag. Die doel van hierdie studie was om tand- en skyfoopmakers met mekaar te vergelyk en die effek wat grondkwaliteit en oesreste op kanolaproduksie het, deur versteuring, vestiging, biomasssaproduksie, blaaroppervlak-indeks (BOI), duisendkorrelmassa (DKM) en opbrengs, te evalueer. Die eerste doelwit was om te bepaal of grondkwaliteit en oesresvlakke in ag geneem moet word wanneer daar tussen ’n tand- en skyfoopmaker gekies word. Die tweede doelwit was om tand-en skyfoopmakers te vergelyk op grond wat verskil in kwaliteit op groot persele wat vergelyk kan word met ’n kommersiële plaas. Die proewe was in 2016 en 2017 uitgevoer op die Langgewens Navorsingsplaas in die Swartland area. Gedurende die eerste jaar van die proef het die oopmaker ’n effek op plantpopulasie gehad (p<0.05), terwyl gedurende die tweede jaar geen verskille tussen behandelings waargeneem is nie (p>0.05). Tandoopmakers het beter presteer op hoë kwaliteit grond terwyl skyfoopmakers beter presteer het op lae kwaliteit grond. Oesreste kan ’n probleem word wanneer kanola met beide ’n tand- of skyfoopmaker gevestig word en vestiging was die beste by lae oesrestevlakke. Die swakker kanolavestiging met die skyfoopmaker gedurende 2016 kan wees as gevolg van kunsmistoedienning tydens plant wat chemiese skade aan die sade kon veroorsaak het. Oor die algemeen het die gebruik van die tandoopmaker meer biomassa tot gevolg gehad as die gebruik van die skyfoopmaker gedurende die eerste jaar van die proef terwyl soortgelyke biomassaproduksie gedurende die tweede jaar behaal is. Die BOI was soortgelyk behalwe dat ’n hoër BOI aangeteken is vir die tandoopmaker op lae oesreste op hoë kwaliteit grond teen 30 dae na opkoms gedurende die 2017-seisoen. Behandelings het geen effek op DKM in 2016 gehad nie (p>0.05), terwyl ’n hoër BOI in 2017 behaal is op lae grondkwaliteit met hoë oesreste as op hoë grondkwaliteit met lae oesresvlakke. Behandelings het geen effek op opbrengs in beide 2016 en 2017 gehad nie (p>0.05). Op plaasvlak is soortgelyke resultate behaal as op klein persele met lae oesvlakke, met betrekking tot plant populasie, biomassa produksie, BOI, opbrengs en DKM. Anders as wat verwag is daar geen verskille in grond versteuring tussen tand- en skyfoopmakers waargeneem nie (p>0.05). So as die doel is om grondversteuring te verminder kan beide ’n tand- of skyfoopmaker gebruik word. Dit word voorgestel dat die studie in die Suid-Kaap herhaal word omdat grond- en klimaatstoestande verskil van die Swartland. Dit word ook aanbeveel dat die studie oor verskeie jare in die Swartland herhaal word omdat in beide 2016 en 2017 in droë grond geplant is as gevolg van die laat voorkoms van voldoende herfsreën.

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