Archive Article: 1997/09/06
WINTER linseed is something of a conundrum. A total loss is quite feasible in certain conditions yet the most unhealthy plants can recover in the spring despite seemingly losing the main shoot.
ADAS research for MAFF is still at the stage of attaining a basic understanding of the crop but some pointers are already coming through to help growers this year.
At the end of the three year study in 1998, co-ordinator Dr Jenny Smith of ADAS Boxworth hopes to be able to pinpoint ideal sowing dates for the different climatic regions in the UK.
With the second year of trials from Hampshire and Yorkshire just harvested, it is already clear that winter linseed plants need to reach a critical size to be able to survive the frosts of winter.
Not that there wont be variation. One reason more northerly crops survived this year while those on southern chalks struggled was because snow cover – absent in the south – protected northern crops from biting winds.
It appears that winter linseed plants need to reach a critical size before they can survive severe frosts. This critical mass is about 0.035 grammes dry matter per plant, about the time basal branches are just visible. This needs to be confirmed in continuing research.
A range of drilling dates from early September through to February is being used by ADAS to monitor the number of day degrees needed by plants to reach their critical mass.
Less than this critical size the plant is unlikely to survive severe frost. At ADAS High Mowthorpe in Yorkshire, plants drilled on 6 September maintained populations through the winter but as sowings went into October the survival rate drops off.
However, planting too early can also cause problems in some years. Early September sowing can result in the crop putting on too much growth only to be knocked back during subsequent cold conditions.
At High Mowthorpe in 1995, plants from the highest yielding sowing dates had already formed two to four basal branches before frost damage occurred.
Increasing seed rate might help when a late crop will be borderline in reaching the critical size, but isnt necessarily to be recommended.
In 1996/97, Dr Smith suggests that cases of complete crop loss occurred either from planting too late, drilling into a dry seedbed, or herbicide damage making the plants more susceptible to frost.
"The key things are that you need a good seedbed, and that you need to look after winter linseed well. It is not a crop you can plant and hope for the best."
Despite the losses, ADAS has seen evidence of winter linseeds ability to re-tiller even when the main shoot has been destroyed by cold. The effect of this on yield is the subject of a new study sponsored by Semundo.
A detailed measurement of crop development, leaf area and components of yield is being made at ADAS Terrington to help assess the yield potential of crops.
From that, it is hoped to learn how best to maximise the yield of the crop, possibly including the use of nitrogen.
French growers advocate the application of around 150-160kgN/ha (119-127 units/acre), in conjunction with growth regulators to maximise yield, but Dr Smith points out this can produce badly lodged crops and may not be suitable for the UK.