Compaction

Compaction........

Winter is a time when the ground gets very wet and when horses on our land can cause the most damage Compacted ground is caused by either horses or the weight of water or both combined. It is also caused by a lack of soil fertility. Compacted soil will not allow water through and grass will not grow due to the restriction of the movement of air around grass roots. In Autumn or Spring it can be difficult to overseed compacted ground as the seed just sits on top and fragile root systems find it hard to penetrate through the surface and anchor themselves. If the ground is too hard for the seed to germinate, it can just be taken by wind and hungry birds .

Compaction tends to be the result of repeated or continuous grazing, especially strip grazing which is murder for the soil and grass or the use of heavy machinery, as well as overgrazing on wet or clay ground.

Tackling compaction is a year around process of careful management and prevention.

The best thing we can do is aerate the soil.

This lets more water and oxygen through into the lower layers of soil. Aerification can be best done in late summer. There are many types of aerifiers. One that I like is a machine which removes plugs of soil, leaving holes about a half-inch in diameter and up to 3 inches deep. The cores of soil are left on the soil surface to gradually break down and filter back into the grass. I use a plug tine Harrow for this in late summer once the horses have been rotated off and throw a thinly spread mixture of compost and grass seed down over the top. I tend to use a garden tractor, rather than a big or compact tractor so as not to compact the soil further by the weight of the machinery. Rotating them off is important as there is a correlation between grass sickness and soil disturbance.

Other types of machinery can allow air into the surface and also pull up moss and shallow rooted weeds. This is best done late spring when the ground is not too dry yet not too wet. In the U.K., we usually get a small window of perfect opportunity early April. These are spring tine harrows, spiked harrows, fixed tine harrows or chain harrows. Their effectiveness depends on the type of soil you have, moisture levels, weight of machine and ballast used to weigh it down further and the speed at which your tractor goes. They typically work at a depth of 5 to 10 cms. Some schools of thought are that the disc or spiked harrows actually can further compaction by moving the earth closer together, between the spaces, but I would assume that the oxygen and moisture into the soil causes that to be temporary and remedied by the breakdown of the now growing root structure.

If severe compaction is observed, tillage (such as plowing or disking) may be needed. This isn't for the faint hearted. They work at quite a depth. My sub soiler can lift a piece of ground the size of a sofa when pulled up. See what I mean? More effective and expensive grassland subsoilers are available which can leave minimal mess but here you will be working at a depth of up to 50 cms and will be using heavy machinery. Typically, they are ridiculously expensive.

Very compacted grounds are impossible to de-compact naturally unless we use weeds. Eh? What did she say? Yes ...... Weeds! ....... those with deep, thick tap-roots can only grow in hard, compacted soils, so before they seed cut them down, safe in the knowledge that the roots in the ground also die and break down, allowing air and moisture in and adding organic matter high in minerals and other nutrients to the soil. Once the soil biology and minerals are restored, weeds are ‘out-competed’ by grasses, because the weeds cannot grow in nutrient-dense soil. Yes folks, time to start smiling, rather than scowling at your weeds ( apart from raggy, of course, no one needs that critter, apart from a rare type of striped caterpillar)!

Remember that unless you change your practices (like giving the pasture rest), keeping horses off when it's wet, reducing heavy machinery use, compaction will continue to occur. Once you have aerated the soil, it is very susceptible to recompaction, unless you move the horses off to allow the roots and organic matter to grow and become stabilised. De-compacting the soil can take years and unless we go for a complete pasture refurbishment using ploughing and reseeding, expect to wait for results. Oh ..... and keep adding that compost, mulch and manure to add to your top soil !

Edit... beginning of feb 2020 ...... Do not Harrow too early in the year! Land conditions will not be right, you will spread moss spores and repeated bouts of wet weather will encourage more moss to grow. I know we are all desperate to get on to it, but we are a good way from this yet. If you must, try plug tine Harrow only if ground is dry.