Measuring grass for grazing

Most graziers start by walking a field with a sward stick or a plate meter. The reading comes out in centimetres. A grazing plan works in kilograms of dry matter per hectare (kg DM/ha), so each height has to become a grass cover first. The numbers below come from AHDB, Farming Connect and GOV.UK, as their pages read on 19 October 2026.

A stick and a plate measure different heights

A sward stick measures sward surface height. Farming Connect's 2017 factsheet says to run your thumb down the stick until it touches the top of the grass leaf.

A rising plate meter is a disc on a shaft. The plate rests on top of the grass and records the compressed height. Each tool has its own conversion. AHDB's sward stick carries its conversion factor on the stick, and plate readings go through an equation.

From centimetres to kilograms

AHDB gives a typical plate meter equation. Cover in kg DM/ha is the compressed height in centimetres times 140, plus 500. Farming Connect uses the same equation. The 140 reflects a dry matter content of about 14%. The 500 allows for grass at the base of the sward that the plate does not measure.

In AHDB's worked example, an average compressed height of 15 cm gives 2,600 kg DM/ha. AHDB calls the answer an estimate. It says species, clover content, soil moisture and the time of day can all move it. Farming Connect suggests checking the equation against oven-dried grass samples from your own fields.

The season changes the answer

AHDB's guide to wintering at grass has a table that converts compressed height to feed available, season by season. At 3 cm it gives 1,140 kg DM/ha in winter and 1,340 in spring. Late spring is 1,400, summer is 1,450 and autumn is 1,290. AHDB calls these reference values. They vary with weather, location, grass variety and the age of the pasture.

Grazing a herbal ley

AHDB describes multi-species swards, also known as herbal leys, as a range of clovers, herbs and grasses. It treats them as distinct from species-rich grassland, because they hold sown productive species in temporary grassland.

AHDB recommends rotational grazing, with stock typically moved every 3 to 7 days. Its typical rest periods are 21 to 30 days in summer and 30 to 40 days in spring and autumn. In winter it suggests 60 days or more, or a complete rest. The sward should regrow to over 15 cm before the next grazing. Typical post-grazing heights are 10 cm in spring and late autumn, and 6 to 8 cm in summer.

The herbal ley action in England

In England, the Sustainable Farming Incentive 2026 (SFI26) has a herbal ley action called CSAM3. Its seed mix must include at least 1 grass, 2 legume and 2 herb or wildflower species. GOV.UK last updated the action's page on 17 June 2026.

The same page suggests resting the ley for at least 5 weeks in a row between early May and late July. That lets the flowers open and feed insects with pollen and nectar. It says the roots can take up to 4 years to improve soil structure and fertility.

Clover and the animals

Clover-rich swards bring some risks for stock. AHDB says swards with a high share of legumes, particularly clovers, are more prone to causing bloat, especially in wet, humid conditions. If bloat occurs, AHDB's first steps are to move the animals off that pasture at once and to contact your vet.

Some red and white clover varieties contain phytoestrogens. AHDB says these can disrupt breeding in female livestock, and that sheep are more sensitive than cattle. It advises keeping breeding ewes off high red clover for six weeks before and after tupping. For any question about your own animals, your vet is the person to ask.

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