Sward Assessment

Healthy soils are the foundations for healthy grassland. To know what is going on in your soil you need to go out into your fields, dig a hole and examine it. The key features of healthy soil and the ways to assess it are explained in more detail on the Swarm Hub. Click on the links below to explore:

• Soil structure
• Soil testing
• Soil health
• Soil pH and liming
• Soil biology
• Field drainage

You need to know how much grass is growing so you can make informed decisions about grazing and so you can minimise grass waste.

Grass growth is determined by a range of factors including soil health and temperature, light, water, nutrient availability and variety of species within the sward. Most grasses have evolved to withstand grazing by having growing points near ground level which will quickly regrow after defoliation. When grass growth is at its highest, a new leaf is produced every 4-5 days, in winter it can take up to 30 days to grow a new leaf. There are two stages to grass growth:

1. Vegetative growth – leaf production, best for grazing
2. Reproductive growth – production of flowers and seed heads, less productive grazing

The only way to really know how well your grass is growing is to measure it. You can either measure sward height (in cm) or kg of dry matter/hectare (KgDM/ha). Sward height is usually measured in centimetres and using a sward stick, but you can use general items such as your welly boot or a bit of pipe. It doesn’t matter as long as you are consistent. (Click here to order a FREE sward stick from EBLEX).

To measure KgDM/ha use a sward stick that shows this unit or a rising plate meter (a guide to using plate meters can be found here).

A guide to livestock grass demands is shown in the table below (adapted from DAERA guide and AHDB’s sward stick AHDB’s sward stick )

• Speed of re-growth after cutting
• Can the sward still support the same numbers of livestock it has done in the past?
• Are patchy or poached areas developing?

If your grass is achieving an annual yield of 12 tonnes of DM/ha, or more then it is doing really well. If it is falling between 5 – 8 tonnes of DM/ha/year then you should be thinking about rejuvenating the existing sward.

Weeds reduce sward yields and quality and are often an indication that something is amiss. Weeds can be a sign of:

• Low pH, P or K index
• Acidic soils
• Over or under grazing
• Soil compaction
• Open swards – so choose varieties carefully

Common weeds include chickweed, thistles, docks, buttercups, nettles and ragwort.

Assess a 50 x 50 cm square at a number of places. If more than 10% of the squares are populated by weeds, then production is being compromised.

There are various ways to tackle weed problems by using cultural control practices, such as:

• ploughing and other cultivations
• mechanical weeding
• cutting and pulling
• grazing management in grassland
• crop rotation

Changing your cultural practices can provide an effective method of weed control in itself and prove particularly effective when combined with an appropriate herbicide strategy. Cultivations are also an integral part of many programmes to deal with herbicide resistance.

If you wish to use herbicides you should take advice from a BASIS-registered agronomist, who will be able to guide you on the most effective form of weed control.

(source: EBLEX: Improving pasture for better returns)