Sand is only one option available for bedding dairy cubicles, posing its own challenges and benefits. Laura Bowyer visited Richard Chewter at a quarry in Hampshire.
At a 49-hectare (120-acre) site in Fawley, Hampshire, natural materials mining firm Mid Hants is digging for sand, destined for dairy cattle bedding.
One of the firm’s 10 sites across the UK, the Fawley quarry is excavated in phases, and then restored to its original farmland state.
Now in it’s fourth working year, the quarry is a joint venture with the land owner, who is paid a royalty, and the company expects to work it for a further 20 years yet.
The site is headed up by operations manager Richard Chewter, an ex-dairy farmer who is clearly passionate about the quarry and its relationship with the dairy industry.
Mr Chewter says: “Ultimately the farmer wants cheap sand, but in the long-term, it is not always the most cost-effective option.”
But it is not just the type of sand which can have an effect on quality in the cubicle he explains, but also the way it is handled, stored and managed.
Mr Chewter explains the firm’s sand quarrying process.
He says: “Firstly the topsoil is stripped off the area, followed by the sub-soil, and trenches are dug round the edge. Sand from the trench is removed and the trench is filled with the site’s sub-soil and topsoil to create a bund.”
This process leaves three to eight metres of flint gravel in the quarry which is subsequently washed and sold. Beneath this flint lies 10m of sand, he says.
This sand was deposited some 37-40 million years ago as beaches and shoals in a shoreline environment. Sands are of different colour and character, with the deposit at Fawley being unusually pale in colour and free from silts.
“The sand varies slightly in colour,” says Mr. Chewter. “But following excavation and screening they become whiter, being exposed to the sun and oxygen, but the grade stays the same”.
The sand is dug by 50-tonne excavators and moved by 30t dumpers, which are able to quarry up to 5,000t per day. The excavation is dewatered by pumping to ensure the sand is dry enough to be screened. The screeners use 0.8mm piano wires at 3mm intervals to produce an evenly-graded product. The water at the quarry is clean and fresh and tested every three months for e.coli and salmonella, which Mr Chewter says would not be done by a quarry not dealing specifically with bedding sand. The quarry also produces a range of construction aggregates.
Aggregates are being imported from the sea, to extend the life of the quarry.
Once the company has finished digging in the quarry, most of the site will be filled in, the subsoil and topsoil replaced, and it will go back to its previous use as farmland, with some areas left as lakes and wetland to encourage biodiversity.
Mr Chewter says bedding sand is not treated in anyway at the site, but dehydrated lime can be used to increase its pH level, as an environment with a pH over 6.5 will kill bacteria. Bacteria cannot grow in sand alone because it is inert, and thus chemically inactive.
But managing slurry from a sand system can pose problems on some farms.
Mr Chewter says: “If you use sea sand the slurry will have a high pH, causing minerals in the ground to lock-up, which is almost impossible to counteract. Many farmers in Devon and Cornwall are moving away from using sea sand because their soil pH is getting too high.
“But, on the flipside, spreading sand could lighten your soils.”
Recycled sand could be contaminated with anything he says, including oil, selenium and arsenic. If this is to be used, Mr Chewter advises a full chemical analysis of the sand, along with the water it was washed in.
He says: “Do not be fooled by cheap sand which looks good, because it could be heavily contaminated waste material which your cows will lie on and then spread on your ground.
“If recycling sand, it needs to be washed in clean water, otherwise you are putting dirt into the beds.”
When it comes to grain size, it all comes down to personal preference says Mr Chewter, but be aware finer sands will hold moisture longer than coarser sands. Sand destined for bedding is from 60-120 microns.
He says: “Finer sands will fall off the cow, coarser sands will drain better. I would not use fine sand in cubicles closer to the doorways as it retains water and coarser sand copes better with being stored outside.”
Dispensers may not run properly if moisture levels in sand are too high.
• On delivery put the sand in a cone and cover with a sheet
• The bigger the heap the better, as there will be less wet sand
• If it looks wet when you come to use it, go to the front of the heap with the bucket, rather than forcing it into the wet bottom which will cause problems in the dispenser
• Avoid pot holes when moving sand in a bucket or in the dispenser as the bouncing motion will encourage compaction
• Use a lining in the bucket
• Take out obstructions in the dispenser – the slides can be taken out once the lining is in
• Speed your tractor up as sand will dispense quickly. Line the hopper and use v-belts on your discharge belt, as it will grip sand and throw it
Not everyone can use sand because of their slurry routes
Mr Chewter says many farmers are struggling with pumping slurry containing sand, but these difficulties can be avoided if they installed, or rented, construction pumps. Most pumps used are only designed for moving grey water, he says:
• Line pumps and stainless steel impellers and use an imbilical injection system
• Do not allow sand in the slurry lagoon. It needs to rest and let water run off it, leaving sand, silt and muck
• Disposing of solids will prevent a lot of sand going in the lagoon
• If the lagoon floor is concreted, suck the water out, leaving the solids behind and then retrieve them
• Lagoons should be stirred and sucked together to stop sand settling. Finer sands will take a while to settle
• Create a sand lane
• Sand must be put into the beds dry, at six to eight inches deep, on top of a chalk base
• Use a light rake, either aluminium or wood, to make the work easier
• Check cubicles daily, scrape the alley and rake daily and then rebed as required
• Make sure sand is deep enough to allow the cow to get comfortable
• Dehydrated lime should, preferably, be mixed with sand prior to spreading, though it can be applied once sand is in the cubicle
• Test for salmonella and e.coli on a monthly basis. This stops any problems and allows fresh sand to be put on top of the beds safely
• Take any dirty sand off the top so the udder is sat on fresh sand and bacteria cannot make their way up as they have nothing to feed on