Following the driest autumn in years, NIAB seed experts have been receiving an increasing number of queries regarding emergence problems in this year’s winter crops.

NIAB's Dr Neil Glynn says, "Some crops have been exposed to periods of light rain, followed by warm dry periods and seedlings have emerged, but then died. Where noticeable cereal germination has occurred, followed by the seedlings dying off, there is no alternative but to re-drill."

However, where seeds have not yet emerged, what is actually going on may be quite complex. Where there has been no moisture available, an enforced or pseudo-dormancy may occur.

"This is a situation equivalent to the seed sitting in a store. If the conditions then become right, the seed will germinate as normal. However, where moisture availability has fluctuated, enhanced deterioration of the seed may occur and emergence may be poor" added Dr Glynn.

"These conditions will also favour infection by any seedborne pathogens present, as anything which slows the germination process usually aids disease. Within a field, the effect on individual seeds is unlikely to be uniform, so crop emergence will be varied," he warns.

Seed quality

In most cases, where good quality seed has been used, the best advice is simply to wait for the rain to come.  Seed of poor initial quality is likely to be more severely affected, and without testing, there is no way to be certain whether non-emerged seed is suffering from enforced dormancy or has been killed by disease.

Some wheat growers may simply decide to bite the bullet and re-drill. Others may wish to check the physiological state of their seed to help make an informed decision.

"NIAB Labtest may be able to help here," says Dr Glynn. "We would advise growers to have a germination test done on seeds taken from the soil. By comparing this result to the original germination result for the seed lot, we'd be able to indicate how badly the seed has been affected."

"Whilst this may be possible for wheat, finding rapeseed would be much more of a challenge. The most useful thing growers can do is to mark a small point in the field, apply water and wait to see if anything emerges. The result will indicate if seed is dead or is likely to germinate normally," he continued.

Oilseed rape

Simon Kightley, NIAB’s oilseed and pulse variety specialist, adds, “Things are very grim for winter rape this year.  There are reports of very poor emergence from the Humber down to the Thames and as far west as Herefordshire. We just have no idea how much of the crop has simply died.  Re-drilling is out of the question now of course."

"Limited experience tells us that winter rape emerging this late will be low yielding.  Rotationally, a switch to an alternative crop such as wheat or beans will be undesirable in many cases and may be precluded by herbicides already applied."

"The best thing now is to sit tight and see what happens and think about re-drilling with spring rape in March.  Even then, you need to be sure that the winter rape is not going to come through as a late flush with the spring crop.  Perhaps the best strategy for oilseed rape is to wait until early March and, if you haven’t got a viable crop by then, cultivate lightly to stimulate any further germination, then spray-off in late March to give a sterile seed bed for spring rape."