Early turnout, will your soils take it?

Published 27 February 15

To grow grass, manage that growth and to utilise it, it needs to be grazed. This is where the potential for soil damage starts, according to Piers Badnell, DairyCo technical extension officer.

“To see how good soil structure looks, you can best dig a hole in a place where stock and tractors do not go, a wood or under a hedge for example. It is during ‘catchy’ conditions, when most soil damage is done, that the potential for better grass utilisation often lies. Key is to find the balance between early turnout and soil damage.”

A three-year DairyCo-funded trial, on grassland compaction at SRUC in Dumfriesshire, shows that compaction caused by trampling reduced grass DM yield by 14% see Picture 1.

Soil compaction 1

Simulated poaching  

“There is an impact on yield from compaction but if you don’t get out and graze you are losing potential anyway, which is probably far more than from the compaction itself. The key then, is in reducing soil compaction, while still grazing.

“The first way to reduce soil compaction is via infrastructure, using tracks and multiple entrances to paddocks. A gateway in, and a separate one out vastly reduces problems. Picture 2 below shows a gateway from 2012, when this farm had 165cm (65 inches) rain. They milked 500 cows, on heavy clay, and the cows did not come in at all over the season.

Soil compaction 2

Gateway with measures to prevent poaching

“Although the gateway in picture 2 is not perfect, it is not a bog. This was achieved by putting up a length of electric wire to funnel cows through the dry part of the gateway. Another way, is by dropping the gate wire an hour before milking start and let the cows find their own way out. Cows will pick the dry part of the gateway, as opposed to being driven through when they have no choice and create a quagmire.

“Damage happens when a paddock is grazed for a second time in wet conditions, so with care and using on/off grazing this can be minimised. Picture 3 shows the same farm, again in 2012. It was taken in the spring, after 25mm of rain fell over night onto saturated soil. Note the wet conditions, but also the good grass residual and how little damage has actually been done to the soil structure.

Soil compaction 3

Wet conditions

“Picture 4, taken in August of the same year, shows how careful management, and getting the cows off as soon as they have filled themselves, and before they can wander around doing damage, can have a huge effect. 

Soil compaction 4

Field recovery after wet conditions.

“The example in the picture is an extreme. Although, I’m not advocating to graze all fields as in picture 3, it shows what can be done, and that you can manage turnout on wet conditions.

“If conditions are really bad, try to avoid grazing, or graze a drier field. Use a low stocking rate, which at this time of year is easier because the covers will be lower, making residuals easier to hit. back fencing, allowing access only to graze and then keep cows off. While on/off grazing, in two blocks of three hours, supplies a cow with 90 to95% of her requirements.  This time allocation means she only has time to eat rather than wander about and cause damage to the field.

“Remedying soil damage issues is also important. With compaction down to 10cm, slit aeration will alleviate the problem, when it’s deeper you need to use a sward lifter. Slit aeration is probably best done in the autumn, so you do not chop up any new grass roots. The use of aeration varies depending on the severity of compaction: depth of problem, soil type, weather conditions after aerating and sward quality. Assess the problem, act, and assess the results.

“I once saw an example of the use of a sward slitter being used in a way which may not have increased yield, but did allow for earlier access, and more grazing. So possibly, an increase in grass yields.

“With one of my discussion groups we visited a members farm in early February 2013, and walked a paddock at the back of the buildings, where there was very little cover. The surface of the paddock was water logged and difficult to walk across. When digging a small hole, to see soil type and structure, it turned out not to be as heavy as we expected, but in fact quite light, and what is known in the South West as ‘shillit’. So, it was a surprise as to why it had not drained. Further digging, showed a very compacted layer just below the surface and below this it was dry. The group concluded the host should slit the field, which he did later that year. We revisited in late February 2014, after it had rained in excess of 25mm the night before. The paddock had grass cover and cows were out grazing. The slitting allowed water drainage, and enabled cows to graze.

“So walk your fields and see how you can improve your paddocks. Put a plan in place to get out earlier and to get control of grass - in the next two months growth goes from very little to very rapid and we need to be on top of it. Graze, but be aware of the potential for soil damage and put a plan in place to minimise and alleviate any problems.”

Check list:

  • Infrastructure
  • Plan which paddocks can take a bit more and which cant
  • Monitor yield so are any paddocks suffering – is it compaction
  • Dig holes to see where a potential problem is
  • Alleviate compaction
  • Lengthen grazing period – reducing conserved and bought feeds and reduce housing costs
  • Take control of grazing and don’t let it “get away” and so utilise the quality as well as the quantity.