A new agronomy guide from BASF is confirming the heightened risk of take-all in winter barley crops, if they follow a first wheat.
This is an issue addressed by ADAS agronomist, Jonathan Blake, courtesy of his contribution to the publication.
Take-all infects cereal crops the first year they are grown, but is generally at non-yield damaging levels. The disease generally effects yield where susceptible crops are grown for two or more years in a row.
Winter barley crops grown in Ireland and the UK tend to be grown in the second ‘slot’, often after first wheats.
According to the ADAS agronomist, this second cereal situation tends to be where take-all pressure is highest. Barley is often sown in this rotational position, as it is more tolerant of take-all than wheat.
Spring barley can also be affected by take-all levels when sown after a susceptible crop.
Although levels will decline between the first cereal and the second because there is a bigger gap between the harvest of one and the sowing of the next, this is counterbalanced by spring barley rooting less extensively.
So, although take-all is at lower levels than in a winter crop, it can have a similarly significant effect.
Plants affected by take-all show black roots and black lesions on stem bases. The disease can occur in patches and leads to stunted plant growth, uneven ripening, and white heads.
In affected barley crops, yield losses can amount to 0.5 t/ha.
The degree of yield loss due to take-all is severely impacted by weather factors. Rainfall is the key parameter.
A wet and mild winter, followed by a dry late spring and summer, is where the biggest effects of the disease are seen.
Wet winters, will limit root growth and allow the take-all pathogen to spread. A dry, late spring will potentially have a dire effect on barley, as the restricted rooting will prevent adequate water and nutrient uptake.
Extending the rotation
Blake points out that varietal tolerance and chemical options for take-all are limited, so, reducing the severity and impact is largely dependent on cultural control approaches.
Extending the rotation is the most effective way to manage take-all.
The longer the period prior to planting of barley, where a non take-all host crop has been grown, the less take-all you will have in that first barley crop.
According to the ADAS agronomist, growing barley in first cereal situations can be a win-win situation.
This will reduce take-all and lead to higher yields. In crops grown for malting, this can be significant as higher yields will dilute grain nitrogen (N), a key parameter for this crop.
Take-all is affected by soil type and risk can vary within a soil series. Light soils, either because they are better suited to the pathogen, or that they are more likely to suffer from drought effects that take-all can cause, tend to be most affected by the disease.
Growers should, therefore, ensure soil pH is appropriate to the barley crop so that it can grow effectively.
N should be applied earlier to crops in a take-all risk situation than to crops sown in ‘first slots’.
Applying N early encourages early growth so plant roots can explore the soil more effectively, which will reduce the impact of take-all as will ensuring indices of phosphorus and potash are conducive to good early growth.
Also, greater soil fertility tends to reduce the impact of the disease.