Knowledge Hub Article

Black-grass - What is it?

What is it?

Biology/agroecology and implications for integrated weed management

Black-grass is a medium to large annual grass-weed which is increasingly common on arable land. It is  propagated solely by seeds and, if uncontrolled, weed populations can increase by >10 fold/year.

For successful long-term control, seed return must be minimised. The following five key characteristics underpin successful non-chemical management strategies:

Black-grass characteristic

Quantification of characteristic

Practical consequence

Plant emergence pattern

80% of weed emergence occurs in early autumn

Later autumn or especially spring sowing will reduce infestations substantially

Depth of emergence

Plants can only emerge successfully from seeds within 5 cm of the soil surface

Cultivations will have a large effect on determining infestation level

Seed longevity in soil

Approx. 75% decline/year - about 3% of seeds will still be viable after 3 years burial

If seed return can be prevented, infestations will decline fairly rapidly

Population dynamics

>95% control needed to prevent weed increasing

Difficult to achieve with herbicides alone  – impossible at high resistance levels

A competitive weed

12 plants/m2 give a 5% wheat yield loss on average – but much higher losses possible

Aim for <5 surviving plants/m2 to minimise yield loss and seed return