The Teagasc cost and returns 2015 estimates the breakeven yield of oilseed rape is 3.9t/ha (1.6t/ac), with an overall variable cost of €1,214/ha. Plough, till and sow establishment costs are estimated at €170/ha (€68/ac). As winter oilseed rape is established in mid-late August, coinciding with the cereal harvest, many growers struggle to find the time to plant the crop. Growers have been testing various methods over the past number of years to increase the speed of establishment and reduce costs. Alternative methods used include minimum tillage (min till) and subsoil type machines (wide row spacings of 600mm). Machine examples include HEVA, Sumo, etc. There is a potential to reduce establishment costs by 40-50% and increase the speed of planting (by up to 50%). However growers have questioned the reliability of establishment in different years, the ideal plant number for wide rows spacings and whether oilseed rape planted in wide rows spacings should be managed differently to conventionally established oilseed rape.

Trials in Oak Park (2008-2010) have shown no yield differences between plough-based and min-till systems. However, elsewhere min-till has proven to be unreliable in wet conditions – particularly on heavy ground. Further trials are being carried out to determine if subsoil type machines can reliably reduce costs while maintaining yield and the ideal management strategies for oilseed rape growing in wider row spacings.

Trials in Oak Park are comparing plough-based systems (plough/till and sow), to min-till and direct subsoiling using wide row spacing. In a number of experiments, a range of row spacings (125-750mm), seed rates (10-60 seeds/m2), nitrogen rates (0-320kg/ha N) and response to plant growth regulators are being tested.

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Preliminary results from the first year’s work give some pointers as to future practice. However, it’s too early to give definite answers. Establishment rates of the subsoil system were slightly lower (64%) compared with plough-based systems (75%). This is not surprising as the subsoil system scatters the seed on top of the subsoil cultivated strip, whereas the plough based system places the seed at 15mm in the soil.

An overall pre-emerge herbicide was used to control weed control in both systems with no damage observed to emerging plants. Ideally, oilseed rape seed should be covered by 15mm of soil when using metazachlor (Butisan, Katamaran, etc) herbicide.

There was no difference in yield (average 4.2t/ha) between plough, min-till and subsoil-based systems in 2014. Yield responses to 160-240kg/ha N in the plough-based and subsoil (600mm) systems were similar, with the lower nitrogen rate (160kg/ha) out-yielding the higher rate (240kg/ha) suggesting the site was not overly responsive to nitrogen in 2014.

The work in Oak Park is preliminary (one year of data), but supports recent research from the UK which suggests increasing row widths can be achieved without yield reduction.

Planting oilseed rape in wide row spacings has the potential to reduce establishment costs and can increase planting speed compared with conventional establishment. The results over the coming years from Oak Park will give increased precision as to the management of these systems.

Disease Control

Disease control in oilseed rape is a significant cost, estimated at €90/ha (€36/ac). The target diseases are Phoma, Light Leaf Spot (LLS) and Sclerotinia. Both phoma and LLS infect the plant early in its development. Phoma can cause up to 25% yield loss, with LLS potentially reducing yield by 40%. LLS was especially problematic in 2014, with early infection on the main growing point (main raceme) stunting its growth. Across Ireland and the UK, LLS is more problematic than in the past. New information emerging from trials may change how the disease is controlled in the future.

Growers should choose varieties with high resistance against LLS and Phoma. For disease control, apply a fungicide in November to control autumn infections. Another fungicide may be needed in early to mid-February to control LLS. Depending on crop growth, a PGR fungicide may be needed at green bud stage. And depending on crop rotation/surrounding crops, a final fungicide for sclerotinia should be applied at the start of petal fall.