Pre-Emergence Herbicide Use Rises as Tillage Farmers Double Down on Precision Drilling

A notable increase in pre-emergence herbicide use across winter wheat and winter barley marks this season's tillage campaign, according to agronomists who report generally excellent establishment in crops drilled from the end of September through to mid-October.

The rise in pre-em applications follows an excellent spell of autumn weather that allowed most winter cereals to go into ideal seedbeds. Agronomists say the trend also reflects growing awareness of the threat posed by grass weeds in these crops, particularly brome species and annual meadow grass.

Late October and early November is the ideal window to walk crops and assess both establishment rates and weed control performance. For growers, that assessment now closes the loop on a drilling operation that has become markedly more precise.

How has drilling changed?

Tillage farmers continue to lead arable sectors in precision technology adoption, particularly around drilling. The result, according to the report, is highly accurate bout widths and perfectly straight tramlines across the country.

Drill calibration has also become simpler. Seed companies now print the thousand grain weight on seed bags, which allows farmers to fine-tune seeding rates with greater accuracy than bag weights alone ever permitted.

The final piece of the jigsaw is measuring how many plants actually established. An establishment rate of 85% is often assumed as the rule of thumb, but actual rates vary significantly between fields and seasons. Calculating the real figure lets farmers adjust future drilling rates with confidence rather than guesswork.

How should farmers count plants?

Experienced farmers and agronomists can make a good visual assessment, but actual counts deliver more precise information on plant populations. That data feeds future seed rate decisions and serves as a management tool later in the crop's development.

Three simple methods work in the field:

• Quadrat: count plants in a 0.1 m² quadrat and multiply by 10 to get plants per square metre.
• Pipe ring: a circular pipe with a circumference of 158cm encloses an area of 0.2 m²; multiply the count by five.
• Row count: count plants along 1m of row using a stick or tape, count how many rows fit into 1m across the drill width, then multiply the two figures together.

What about weed control?

Good weather at drilling facilitated the increase in pre-emergence herbicide use in both winter wheat and winter barley this year. In some fields, slight phytotoxic effects are visible, typically as leaf whitening or bleaching.

This is normal, and crops usually recover within a few days. Symptoms show most clearly on overlaps and headlands, where application rates stack up.

For crops yet to receive a herbicide, the advice is to target pre- or early post-emergence applications as soon as possible. Early control of weeds, especially grass weeds, is far more effective when weeds are small. Delaying control until spring has caused increasing challenges in recent years, particularly with brome species and annual meadow grass.

Growers who have not yet completed plant counts or checked untreated fields for bleaching symptoms should do so in the coming weeks, before crops close and counting becomes unreliable. Those figures will set next autumn's seed rates.