50% reduction in grass yield seen in compacted soilsWednesday 24 July 2013
First off, grassland specialist Charlie Morgan demonstrated where and how to dig a sample hole to assess compaction at this uplands demo event organised by Cumbria Farmer Network and held at at Low Beckside Farm, Mungrisdale.
He looked at the level of compaction on the sample, the effect of sheep, cattle and machinery on the structure. Root length was poor and there were few worms. An oxide russet effect could be seen indicating anaerobic conditions due the soil standing in water with no oxygen. This sample was compacted at about 10 inches below the surface. Charlie advised that a compacted soil could result in a reduction of yield by 50%.
This particular field suffered from a poor summer last year, wet conditions and compaction due to machinery. John, the farm manager, was keen to improve this field by leaving this field out of this year’s current silaging plans. This would result in the farm having to buy in silage bales at some point.
Soil sample showing the russet colour, poor root development and sheer compaction.
Sub-soiler in operation
Sub-soilers should only be used once every three years
Another hole was dug where the sub-soiler had just passed. It showed the channels under the soil where the fins had passed which would improve drainage. There was some improvement in the soil however this process should be carried out in dry conditions to avoid smearing. Charlie advised sub-soilers should only be used once every three years.
The aerator has no impact on this soil as the compaction was too great. Using an aerator would actual make this field worse leading to water logging.
Charlie emphasised that we need to be investing in our dated drainage system or at the very least clear out field ditches to the side. This field would benefit from using a sub-soiler or even ploughing to 6” and then use a sub-soiler.
Six tonnes of worms per hectare!
The next field had a better soil sample. It had a good colour, was relatively crumbly, good root development and an abundance of worms. Charlie shocked the farmers by informing them that there should be six tonnes of worms per hectare.
25% visual soil needed for a good reseeding
This field would benefit from some re-seeding. We watched the grass harrows in operation. This showed that conditions were not currently right, needing 25% visual soil for a good re-seeding.
Charlie advised using Italian ryegrass and introducing clover into the mix would help the nitrogen cycle. He has seen a farm at 1,200ft benefit from re-seeding, even hill farms can achieve good grassland.
Rushes need to be cut back at least four times a year to have any effect
We moved down to Top Meadow where rushes are preventing grass growth. The soil was very rich and crumbly which just showed the potential of the field. The rushes had been topped in February this year but had great re-growth. Rushes need to be cut back at least 4 times a year to have any effect. Rushes can only be topped at certain times of year due to nesting birds, field and weather conditions.
They can be sprayed back with Roundup, using a weed wiper, the Logic ATV towed machine can be used and is effective with just one pass.
Charlie made the suggestion that this field could be sprayed off and ploughed to a depth to prevent re-growth. This would have to be planned in when the weather conditions suited the soil and field.