Wheat and canola establishment in the Western Cape : openers, nitrogen placement and planting depth

Thesis (MScAgric)--Stellenbosch University, 2019.

ENGLISH ABSTRACT: Wheat, the main cereal crop and canola, the main oilseed crop are the two most prominent crops established in the Western Cape under dryland conditions. Tine openers are most commonly used to establish these crops, but disc – and double chute openers are emerging as viable alternatives. The suitable planting depth for each opener has not yet been evaluated in the Western Cape. These openers place nitrogen (N) fertiliser at different depth in soil. Tine openers place N below the seed and disc openers mix N with seed and place it at the same depth. The double chute places N fertilser in between two twin rows of seed. The aim of the study was to determine the efficiency of establishment of wheat and canola using a tine, disc, and double chute openers, with different fertiliser placement.This study was divided into three trials, each with a specific objective: i) The first trial was conducted in a growth room to determine the effect of N rate on wheat and canola sown at different depths (1, 2, 4, and 8 cm) and in different soil types. ii) The second trial was conducted in the field to evaluate the effectiveness of a tine or disc opener to establish canola and wheat at different depths. iii) The third was another field trial to evaluate the efficiency of tine, disc, and double chute openers on wheat and canola establishment. There was no clear effect of N rate in almost all soil types for wheat and canola, but planting depth had an effect (Objective i). Most established well when sown at depths of 1 or 2 cm. Though overall canola seed establishment was poor in most soils, it is possible that the canola seeds or seedlings were damaged by coming into contact with the N fertiliser since it was previously observed that canola seeds are sensitive to N fertiliser. The tine opener planted the seed acurate at a deeper depth (Objective ii), while the disc opener planted the seed well at a shallower depth, particularly for wheat. In contrast, for canola, planting depth was not successfully controlled by either tine or disc opener. Wheat and canola seeds were affected by the N fertiliser placement (Objective iii). When the double chute and tine openers were used in placing N fertiliser, the differences were significant in comparison to when N was broadcasted or placed using the disc opener. Plant population and biomass production was determined after 30, 60, 90 and 120 days of plant emergence, while the leaf area index (LAI) was only determinedafter 30, 60 and 90 days of plant emergence. Yield was also quantified. In most cases there were no differences between broadcasted N (control) and the disc opener for plant population, biomass production and LAI; yet, there were noticeable differences to double chute and tine opener with regard to plant population, biomass production and LAI. No yield differences were observed between the various openers.

AFRIKAANSE OPSOMMING: Koring, die hoof graangewas, en canola, die hoof oliesaadgewas, is die twee meer prominente gewasse wat onder droëlandtoestande in die Wes-Kaap gevestig word. Tandoopmakers word algemeen gebruik om die gewasse te vestig, maar skyf- en dubbelsaadskut-oopmakers word toenemend beskikbaar as alternatiewe opsies. Die optimale plantdiepte vir elke oopmaker is nog nie in die Wes-Kaap evalueer nie. Die oopmakers plaas stikstof-(N)-bemesting op verskillende dieptes in die grond. Tandoopmakers plaas N onder die saad, terwyl skyfoopmakers N op die selfde diepte as saad plaas. Die dubbelsaadskut plaas N tussen twee treinspoorrytjies saad in die middel van die ry. Die doel van die studie was op die effektiwiteit van vestiging van koring en canola te bepaal, deur van tand, skyf en dubbelsaadskut-oopmakers gebruik te maak, met verskillende plasing van N. Die studie was in drie gedeeltes verdeel, elk met sy eie objektief: i) Die eerste proef was in ‘n groeikamer uitgevoer om die effek van N-peil op koring en canola wat op verskillende dieptes (1, 2, 4, en 8 cm) en in verskillende gronde gevestig is, te bepaal. ii) Die tweede proef was uigevoer onder veldtoestande om die effektiwiteit van tand en skyfoopmakers om koring en canola te vestig op verskillende dieptes te bepaal. iii) Die derde proef was ook ‘n veldproef om die effektiwiteit van tand, skyf en dubbelsaadskut oopmakers op koring en canola te bepaal, met ‘n fokus op N. Daar was geen defnitiewe effek van N-peil in byna alle grondtipes vir koring en canola nie, maar plantdiepte het wel ‘n effek gehad (objektief 1). Die meeste saad het gevestig teen dieptes van 1 of 2 cm. Alhoewel canola-vestiging oor die algemeen swak was, was dit moontlik dat canolasaailinge deur kontak met N-bemesting beskadig was. Die tandoopmaker het saad op ‘n akkurate diepte geplaas, terwyl die skyfoopmaker saad vlakker geplaas het, veral koring. Teenstaande, vir canola was plantdiepte nie suksesvol deur die tand of skyfoopmaker beheer nie. Koring en canola was wel deur N-plasing beinvloed (objektief iii).Wanneer dubbelsaadskut- en tandoopmakers gebruik was om N te plaas, was daar betekenisvolle verskille vergeleke met wanneer N breedwerpig toegedien of met ‘n skyf geplaas was. Oor die algemeen was daar geen verskille tussen N wat breedwerpig toegedien was en die skyfoopmaker i.t.v. planpopulasie, biomassaproduksie en BOI nie, alhoewel daar wel verskille tussen die dubbelsaadskut en tandoopmaker was. Geen opbrengsverskille was waargeneem nie.