What effect does stubble length have?
What effect does standing stubble length have on different direct-drilled crops assuming the drill can cope?
That is the main problem, can the drill cope!
Long stubble can be tolerated from time to time. In the long term we should always try to keep stubble length short.
Direct drill oilseed rape is an obvious contender for leaving the stubble long as this can help reduce pigeon damage.
The only problem is where you are just starting a lo-till system the stubble can still be there when you harvest the rape, which then becomes a problem for the following crop.
The sort of problems you get are blocking of cultivators and drills and, for cereal crops, disease transfer.
Long stubbles can keep the soil cool, which is important if looking to direct drill spring crops. But on light land the wick action of the stubble can dry out the soils in the autumn (in a dry spell of weather).
I believe it is best to keep stubbles short four inches is ideal and use long stubble as a now and again management tool once you are into the system. Dont use it as something to start with due to the problems mentioned above.
The only crop where stubble length has had any influence has been oil seed rape. Long stubbles have made the crop look a bit leggy for a short time.
Usually the stubble becomes brittle and is either destroyed by the drill or is broken down by the elements before it has had any influence on the following crop.
Deciding on how long or short to leave the stubble is a bit of a lottery. The general rule is: as short as possible if you intend to bale or incorporate chopped straw and as long as possible if you intend to direct drill into chopped straw, thus reducing the amount of material to be chopped and spread.
We have found that it is very difficult to get a decent establishment, especially with oilseed rape, without some form of straw/chaff spreading operation.
Without wishing to blow my own trumpet, Ive found the Bullock Lo-Till Harrow does a good job. It not only spreads the residue but it reduces the influence the stubble has on the following crop.
We have been direct drilling for 4 years and the harrow is the piece of equipment that has made it possible.
This year our best crops of winter wheat, winter beans, spring barley and spring beans were all direct drilled (after one or two passes of our harrow).They had fewer weeds and better soil moisture retention.
Where we cultivated we had a serious weed problem, especially with spring crops, and we have lost soil moisture.
Our best crop of wheat (Hereward) yielded 3.25 t/acre (8t/ha) established after rape with a pass of the harrow directly after the combine and a second pass 24 hours in-front of the drill (4 October).
Our best crops of winter and spring beans were both direct drilled into untouched stubbles.
The highest yielding spring barley crop was direct drilled into winter wheat stubble then harrowed to cover the seed in the open slots.