The benefits of sand bedding for dairy cows are many. However, sand is not always the easiest material to incorporate into manure management systems.
From the cows you milk to the crops you grow, bedding with sand impacts every aspect of your dairy farm. Use these suggestions to reap the benefits of sand while honing manure system management skills and equipment to keep sand in its place.
Cow comfort
First, focus on why sand bedding was selected in the first place.
Clean, dry, deep sand-bedded stalls are more comfortable for cows, and more comfortable beds lead to longer bouts of lying time. Generally speaking, the more time cows spend lying down, the more milk they produce.
On average, cows spend about 10 to 12 hours lying in freestall barns. Research shows stall surface can influence lying time, with sand a preferred option for cows.
Also, herds with deep-bedded stalls have a significantly lower prevalence of lameness compared to herds with mattress stalls.
Lastly, because sand is inorganic, it is not a haven for mastitis-causing bacteria. As a result, properly maintained sand-bedded stalls can benefit milk quality and cow health.
The goal is to keep sand working for cows where it does the most good.
Moving and separating
Sand-laden manure is abrasive and known to be tough on equipment. Plus, it is heavier than manure alone.
Manure weighs about 60 pounds per cubic foot, while sand has a density of 120 pounds per cubic foot. Sand-laden manure will have an approximate density of 72 pounds per cubic foot if 20% of the manure is sand.
Since sand is heavier, it does not remain in suspension indefinitely, eventually settling out from manure. Therefore, it is best if sand and manure solids are stored separately from effluent whenever possible.
This principle is also a good reason to incorporate sand separation into manure management systems. Doing so avoids costly storage facility cleanouts while allowing dairies to capture, recycle and reuse sand.
With the right sand and a properly designed and managed sand separation system, most farms achieve more than 90% sand recovery rates. These solutions allow you to repeatedly reuse sand bedding, saving purchase costs.
Heavy-duty equipment specifically engineered for on-farm conditions will help to harvest sand and extend the life of manure system components, reduce downtime and lower maintenance costs.
Anaerobic digesters
The impact of sand is heightened as more dairies turn to anaerobic digester technology.
Without separation beforehand, sand-laden manure is largely incompatible with anaerobic digester systems. These systems are engineered to handle organic material, so when inorganic sand replaces desired materials, it impedes digester operation.
With sand separation, it is not uncommon to achieve greater than 90% sand recovery and capture an additional 5% of fines.
Keep in mind that it may take several steps, including mechanical sand separation, a hydrocyclone, a sand lane or other tools to remove the maximum amount of sand from manure before digestion. Work with your manure management partners to ensure you are properly equipped to meet the standards needed for successful digester function.
Effluent solids content (organic) is another important consideration and part of a larger discussion about adopting digester technology. The total solids content for effluent intended for an anaerobic digester depends on the type of digester – different types of digesters operate at different total solids ranges.
Engage with your digester partners to learn more and determine which digestion system will work best under your specific conditions.
Field effects
Every soil is unique, so precise effects from land application of sand-laden manure will vary by location and original soil texture. However, sand has been shown to influence several important soil characteristics following repeated application. The effects are slow but cumulative.
Research shows that over time, applying sand-laden manure can change the composition of soils.
Let’s do the math. The recommended 50 pounds of sand per stall per day, multiplied by 365 days in a year, equals 18,250 pounds per stall per year or about two-thirds of a dump truck per year per cow stall. That’s a significant amount of sand to purchase each year.
Many dairies have a land base of 2 to 5 acres per cow. At that rate, if equally spread, a farm will add between 4,550 pounds and 9,125 pounds of sand per acre per year. Depending on tillage, application levels, soil type and other factors, in 25 to 50 years the soil sand percentage will increase by 20%.
Perhaps more important is that repeated sand application to fields changes soil texture and decreases its infiltration capacity. This means water is not as easily absorbed by the soil. The reduction potentially leads to increased field runoff, taking valuable water and nutrients with it.
Also, note the quality per volume of manure is also diminished when sand is added. As sand is added to the manure, the percentage of nitrogen, phosphorus, potassium and sulfur is diminished.
Removing sand prior to field application of manure will help dairies, and their crops, gain more benefit from this organic fertilizer.
Wrap-up
To sum it up, sand is a valuable asset for dairies and should be managed as such. You and your cows benefit from sand remaining in the places on your farm where it provides the most advantage – under cows and not in storage facilities, anaerobic digesters or fields.
Success begins and ends with capitalizing on physics, good partnerships and engineering know-how.
References omitted but are available upon request by sending an email to the editor.
