Winter oilseed rape is one of the few crops that lends itself to decreased costs when grown in a controlled manner.
Technical husbandry has advanced for the winter crop.
Use of autumn applied animal manure can supply most or all the P and K requirements and can take
the spring applied nitrogen requirement down from the allowed maximum of 225kgN/ha to below 160kg. This saving in nitrogen can then be used to support other crops.
Potential yield from the winter crop tends to lie between 1.5 and 2.0t/ac at the dry 9% moisture level.
The potential for margin is influenced by both seed yield and price but, in latter years, straw sale can add €40 to €70 on the income side. As new varieties and improved soil management come on stream, it should be possible to push the yield of winter rape up towards 2.5t/ac.
Rape supplies two main market slots --- oil crushing market and high-energy feed market. Values can vary for each market, depending on the price of oil but the changes being brought about in the energy market and the way the biofuels obligation scheme is being implemented will make life very difficult for the crushing sector.
Prices have been satisfactory for 2010 with growers receiving €280 to €300 from the point of planting. Prices have firmed since and with the MATIF at €375/t growers have received up to €350/t.
It is the relative margin that people look at and with €300 for winter rape and €150 for feed wheat a two tonne winter rape crop is equivalent to a four tonne winter wheat crop.
If rape goes to €350/t dry, then two tonnes of rape is equivalent to four tonnes of wheat at €175/t green. Some growers have already locked into €350 for the coming season.
pH: Above 6.2 and preferably above 6.5.
N, P & K: The Teagasc advice for application of the main nutrients to winter oilseed rape are included in Table 1. These are the maximum rates allowed and advised of available forms of the nutrients. Note the high requirement for phosphate, even at index 2 and 3 fertility.
Sulphur: Oilseed rape also responds well to sulphur especially on lighter land where no animal manures are used regularly. Recommendations vary as to the amount needed but 35kg to 40kgS/ha should be regarded as minimum. Growers on medium to light land tend to use 50kg to 60kgS/ha.
Magnesium: Mg is important for all crops and signs of deficiency should be treated with either soil or foliar applied nutrient.
Boron: Boron needs to be routinely applied to oilseed rape. This can be done through soil or foliar application. Even mild deficiencies result in poor seed set and a reduction in seed numbers per pod. Summer drought can exacerbate these problems. On light worn soils, foliar boron might be considered post emergence in autumn, at the start of spring growth and at flowering.
Slurry: Winter rape is an ideal crop for manure application. Planting date is within the allowed application timing and the nitrogen applied can act to drive canopy development through to spring time.
Where enough manure is applied, it can supply the P and K needs of a crop and most of the nitrogen needed to produce the desired GAI 3.5 canopy. Where manure plus soil N produce the desired canopy, only 90kgN/ha is needed to produce a 2.0 t/ac yield. So, slurries can decrease production
cost by €70 to €90/ac and also result in higher yield.
Sowing date: The winter crop should be sown before the start of September for consistently high yield potential. Planting might begin from 21 August. In general, less fertile sites and heavier land should be sown earliest. Also, sites further north should be sown earlier.
Seeding rate: Canopy size is important for yield production in oilseed rape. Crops that are too thick result in less efficient sunlight utilisation and less yield because there can be too many pods at the top of the crop shading the leaves beneath. Lower seed rates result in more branching, with less of the total pods at the top of the canopy. Seeding rate is generally defined by seed number with 70 to 80 seeds per square metre appropriate for conventional varieties and 35 to 50 seeds adequate for hybrid varieties. Hybrid varieties show more early season vigour and, so, can branch more in lower populations.
Cultivation: Oilseed rape seedbeds need very little cultivation but they do need soils with an easy path to deep rooting. For this reason, seedbeds must be free of compaction. Planting systems are in the market from He-Va, Sumo and Spaldings which plant behind a sub-soiler to ensure deep and straight taproots on the plants. In compaction-free fields, the crop can be planted using either min-till or plough based systems.
Varieties: Our variety base has been broadly similar for the past number of years but change is happening. Old favourites like Castille and Excalibur (hybrid) are still to the fore but other conventional varieties include Catana, DK-Cabernet, Epure, NK Bravour and Osprey and new hybrids include DK ExPower and Flash.
Rotation is important with oilseed rape to preserve high yield potential. A maximum of one year in five is recommended.
Yields reduce with tighter rotations for, as yet, unexplained reasons. Rotation is also important to prevent common diseases like clubroot.
The main diseases are phoma (Stem Canker), Light Leaf Spot and Sclerotinia but alternaria can also be a problem. Disease prevention is important.
On winter rape, the main pest problem tends to be slugs post planting and they are also a problem for the following crop.
Sensible stubble cultivation, allowing the soil to dry out post loosening, will reduce or prevent the problem in both instances. Virus diseases spread by aphids are being identified.
The winter crop needs to be killed off in some fashion for harvesting. This tends to be done either by desiccation using Roundup or by swathing. Both work well when done correctly.
Both systems carry a degree of risk of losses post treatment. However, the risk of widespread pod shatter (shedding) is not so high in uniform crops that are well protected from disease attack.
Value in rotation
Winter rape is a very good break crop with the potential to add significantly to following cereal crop yields.
Early harvest enables early planting of a following first wheat.
Traditionally, second wheat crops after rape were very prone to take-all and so they were not advised.
However, for whatever reasons, the yield penalty on second wheats after rape is not as great as it used to be but the overall yield levels may still not be sufficient for profitability.
Rape adds value to the rotation by providing increased yield in the following crop and by providing an opportunity to tackle grass weeds using different chemistry.