19 June 1999


Some growers swear by swathing, others reckon direct combining is best. Tom Allen-Stevens weighs up the harvesting options.

ITS a perennial quandary: how best to get oilseed rape through the combine. And it is not an argument that can be resolved on financial terms alone – so much rides on the weather, the state of the crop and how exposed the field is.

But some, like Martin Kinch, have no doubts. He has tried direct combining and desiccating, but reckons swathing on his 110ha (270 acres) of rape in Oxfordshire is best: "Im looking for a uniform sample that can be dried easily with my batch drier. You are unlikely to get this when the crop is direct combined."

Swathing also helps to dry out the stems, which means less mess inside the combine. Another advantage is that, after the combine has been through, there is no need to return to the field to cut the stubble. "The swather aims for an 18in stubble and the combine will reduce this down to six inches," he says.

He also likes the ease with which he can combine: "The crop lies evenly and in one direction. This means we can romp along with little danger of bunging up the combine. There are also far fewer header losses since the pods enter the combine first." In very dry years that combining swathed crops can continue throughout the night because good visibility is not as crucial as direct combining.

At £28.50/ha, the contractors charge is quite high, but Mr Kinch believes it is worth it.

He accepts that there is a risk associated with swathing however. The crop can be swathed in most conditions, even rain, but this sets a definite date of about a week to 10 days until it must be harvested. "A thunderstorm near harvest can have a devastating effect on yield, and I quite regularly have more than 100 acres on the floor in this critical period," Mr Kinch warns. It is also important that is swatthed well: "An even swath with no lumps can be achieved with the right machine and a good contractor."

Direct tactics

Robert Pask, who farms 375ha (920 acres) near Grantham in Lincolnshire, has tried them all. He used to run his own swather, then switched to desiccating and now combines direct. His main reason is cost: "If you get a contractor in to swath or desiccate your crop, you have instantly hiked up your costs before it is even off the field."

He also believes direct combining has benefits for the combine itself: "Desiccating or swathing the crop makes it much more brittle. This means it will be smashed up in the concave and there will be little bits of straw that will get stuck in the sieve and affect performance and forward speed. With direct combining the crop stays intact better through the combine. This leads to less debris and a cleaner sample."

Mr Pask has found that a dressing of Folicur (tebuconazole) reduces canopy height which means the crop bunches up less on the header. He also uses a Massey combine with a Power-Flo table which helps present the crop pod end first. A side knife gives a clean cut on one side. He has converted one or two local farmers to his approach and now does a lot of contract combining.


The time to consider desiccation is when the crop has ripened unevenly or if it is badly infested with weeds. It may not be necessary to spray the whole field if, for example, only the headland is behind the rest of the crop. The advantage over swathing is that it allows the crop to continue to fill as the desiccant slowly senesces the crop.

Reglone (diquat) can be used for fast desiccation and should be applied 7-10 days before harvest. Although fast-acting it can leave the crop brittle and prone to wind damage and pod shatter.

Roundup (glyphosate) or Touchdown (glyphosate trimesium) preserves the suppleness of the pod and should therefore minimise this risk. However, it acts more slowly – about 14-21 days. Timing is therefore critical; glyphosate should be applied when the seeds in the pods in the middle third of the stem have just turned from completely green to half green/half brown.

It does, however, have the drawback that it carries an additional cost (including usually being a contractors operation), and the standing crop still has to be combined directly, which can mean extra capital costs in equipping the combine with the necessary kit. The chemical would typically cost around £15/ha and the contractors charge would be a further £8.50/ha for the spraying operation itself.

See more