Black-grass Cultural Control
Relying solely on herbicides for control of black-grass is not sustainable in the long-term, due to increasing resistance. Non-chemical methods have considerable potential, although each individual method tends to give mediocre control. Integrating the use of several non-chemical methods, in combination with herbicides, should improve overall control
Plan to employ at least two methods of non-chemical control:
Balance your rotation with spring cropping:
The prevalence of autumn sown crops is the main reason why black-grass is an increasing problem in the UK. About 80% of black-grass emergence occurs in autumn, so spring sown crops tend to be much less affected and have given a consistently good reduction in weed infestation in field trials. Remember that establishing crops in spring can be difficult, however, especially on heavy soils; and herbicide choice is more limited.
Consider fallowing/grass ley breaks:
Fallowing or a grass ley break of 2 – 3 years is helpful in preventing seed return, but note that a 1 year fallow or grass ley is not long enough to reduce high black-grass infestations to acceptable levels. Ensure sufficient time has elapsed between cultivating and sowing the next crop to allow the destruction of black-grass seedlings emerging from residual seeds.
Grow competitive crops to out-compete weeds:
Higher winter wheat populations (e.g. >300 plant/m2) are much more competitive than low populations (e.g. 100 plants/m2), but excessively high seed rates increase the risk of lodging.
HYVIDO® hybrid barley is an extremely competitive crop with a vigorous growth habit and unique crop architecture; a large root mass to compete with black-grass for water and nutrients; and a large canopy (with flag leaves up to three times larger than conventional barley) which restricts the sunlight available to weeds.
Early season vigour from HYVIDO reduces black-grass tillering
Surviving black-grass plants have less seeds per head in HYVIDO plots
In a recent trial, HYVIDO gave a massive 70% reduction in black-grass head numbers compared with winter wheat, with a reduction in black-grass seed return by 85%.
Source: Calculated NIAB (Wragby) Hyvido Bazooka @ 250 seeds compared to Two Row Conventional Winter Barley and Gallant both sown at 350 seeds/m2
Bury black-grass seeds by ploughing:
Ploughing reduces the risk by burying freshly shed seeds to a depth of five centimetres or more, from which seedlings are unlikely to emerge. Black-grass seeds are relatively nonpersistent in the seed bank, so usually fewer old, buried seeds are brought back up to the surface, especially if ploughing is done on a rotational basis, once every 3 – 6 years. Additionally, older, less selected seeds may be brought back to the soil surface thus increasing the proportion of susceptible plants in the weed population. The benefits of rotational ploughing are totally dependent on achieving a good level of soil inversion. Plan your cultivation strategy on an individual field level.
Create stale seedbeds to prevent seed return and spread of resistent seeds:
Spraying off patches of black-grass in winter wheat with glyphosate in the first week of June will prevent viable seed return. Consider spraying the same areas for 2 – 3 years to maximise reductions. Cutting, or spraying in May or later in June, is likely to be less effective. Minimise spread of seeds and plants in combine harvesters, balers, cultivation equipment, straw or manure.
Delayed drilling of autumn cereals has two benefits:
1. It allows more weed seedlings to emerge and be controlled (e.g. with cultivations or glyphosate) before sowing.
2. Residual pre-emergence herbicides can be more effective when applied in later drilled crops, because soil conditions are more favourable for good activity.
Adequate soil moisture is vital to maximize the value of both benefits which can be achieved by drilling in mid-October (or later if feasible), rather than September. Delaying drilling carries obvious risks – these can be minimised by having adequate drilling capacity or by using drills that are capable of working in sub-optimal soil conditions.