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Monitor your grass growth
Grass growth starts when soil at a depth of 10 cm reaches 5°C for five consecutive days. White clover and other legumes begin to grow at 8°C. Grass in compacted and wet soils will start growing later because the high moisture content makes the soil colder. To monitor your fields, measure soil temperature using a soil thermometer for a quick, easy and cheap method of identifying when the plant is actively growing so that nitrogen fertiliser can be applied to promote growth. Typical monthly grass growth in March is 10 kg DM/ha per day, with some sites achieving up to 20 kg DM/ha per day. At peak growth, all three leaves can be replaced within two to three weeks, but in midwinter, when grass growth is at its slowest, it can take 30 days to produce one new leaf.
The best time for grazing is when the plant is at the 2.5–3 leaf stage. Grazing too low, i.e. below the two-leaf stage, can reduce grass growth by up to 85%. There are many ways to measure the amount of grass available, including sward height in centimetres and weight per hectare in kilograms of dry matter, also known as pasture cover. Target swards heights at turnout are:
- Cows and calves in rotational grazing: 10–14 cm, set stocked 5–6 cm
- Growing cattle in rotational grazing: 10–12 cm, set stocked 5–6 cm
- Ewes and lambs in rotational grazing: 8–10 cm, set stocked 4 cm
For more information, see Grazing strategies for Better Returns. To measure your grass growth, order your free sward stick by contacting brp@ahdb.org.uk. For guidance on how to use our sward stick, watch our sward stick demonstration video.