With the wet/cold weather hopefully behind us now, attention needs to focus on repairing damaged swards caused by grazing stock in less than ideal conditions. Damaged swards can produce >20% less dry matter (DM), in a year compared to a sward in good health. A healthy sward should produce 12 tonnes per hectare of DM per annum, so a 20% drop in production equates to 2.4 tonnes of DM per hectare less. This will need to be replaced by other feeds. With concentrates on the increase the cost per tonne DM of a standard 16%HDF is around £278. A poor performing sward will cost you an extra £668 per hectare in concentrates over a season.
Repairing may require a full reseed, but often over seeding or direct drilling can be just as effective. The machine in picture one is ideal for overseeding.
The type of action required depends on the level of damage. If poaching is only a couple of inches deep this will fix itself after the next couple of grazings or with a pass of a grass aerator, not a roller. I say not a roller as this will just squash down what is already potentially a compacted topsoil and reduce oxygen levels in the soil, reducing soil microbe and earth worm activity, (these two are key to nutrient release in soil). Remember there are more soil microbes in a spoon full of soil than humans on the earth. That’s a lot of microbes and thus a lot of oxygen needed.
The type of aerator will depend on soil type. Heavy clay soils benefit from the type in picture two, whilst light soils only need a lighter weight machine, see picture three.
Deeper poaching may require a more aggressive approach, but before you jump for the plough consider other options. Ploughing is great for burying trash/weeds and removing topsoil compaction. The problem with ploughing is it can also bring up new weed seeds and heavy/infertile subsoil, burying the good quality topsoil and organic matter out of reach of the plant. In some cases, ploughing is the only option, but there is often an opportunity to either minimal tillage the field or direct drill after spraying off.
A number of our clients have moved away from the plough now and use a sward lifter and heavy duty cultivator, see pictures four and five, to make a rough seedbed and then either direct drill or use a seed box on grass harrows to sow the grass seed. This is followed by a roll to gain good seed to soil contact. This option is around two thirds of the cost of ploughing, does not bring up fresh weed seeds and does not bury the good quality topsoil and organic matter away from the new plants.
Pictures Four and Five.
Before making any decision on cultivations it is essential to dig some holes and look at the levels of compaction in the soils. Are there any obvious signs of compacted layers? Is there any mottling indicating water logging? What is earthworm activity like?
If you would like some help planning a reseeding program or how best to regenerate worn grass leys, contact Phil Cooper on 07798 673665 or e-mail firstname.lastname@example.org
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