Fundamentals of compost dairy barn management

Wayne Schoper

We have been working with the concept of the compost dairy barn for a few years now, and it seems we learn something new just about every day. That might be an exaggeration, but we have learned a few things that seem to be cornerstones of well-bedded pack management.

We have been able to establish that good-quality, dry sawdust still works best for a bedding material. Many producers have tried alternative materials such as corn stalks and various types of straw. The corn stalks hold water up to a certain point and then the cell walls release the water and create a real mess. Some producers have tried sawdust from cedar trees which did not work at all because of the material in the wood that inhibits the growth of bacteria. Research is being conducted to look at other possibilities such as soybean residue in the mix to reduce the expense of using pure sawdust.

So what are the fundamentals we know at this point? What are some of the things we know to work consistently in all barns? The following are some observations.

Particle size and type of material
Dry, fine wood shavings or sawdust seem to do the best job. Wood products have significant amounts of lignin which resists microbial breakdown and lasts longer. The fine material has more surface area and is conducive to good tilling. Wood chips or material with large chunks of wood do not work well at all. We have to be careful about non-biodegradable material in the sawdust such as plastic and metal fragments. These do not break down and can cause problems at cleanout. Small particle size also breaks down easier and is ready to be field-applied and serve as an excellent source of nutrients for growing crops.

We know good tilling of the pack is important for a variety of reasons. First of all, tilling incorporates oxygen into the pack and enhances microbial activity. Most experienced producers do not till for the first few days after a new load of sawdust. Once tilling does start, a twice-per-day program seems to work best. Going to once-a-day incorporation or even less leads to dirty cows and less microbial activity in the pack.

Tilling also reduces compaction and provides a comfortable resting area for cows. We recommend stirring to a depth of 10 to 12 inches for best results.

Barn ventilation and location
In warm months, adequate ventilation is needed to remove cow heat and moisture as well as the heat and moisture generated by the biologically active pack. Sufficient air exchange in cold weather is needed to remove moisture from the pack and extend time between bedding addition.

If your compost barn is naturally ventilated, location becomes very important. Build the barn in an open area where summer winds can blow through the structure. Current recommendations show a 16-foot sidewall is needed to allow for a 4-foot concrete wall to hold the composted area. The open area above the wall allows for good aeration and space for cleaning and incorporation.

Compost dairy barns are an excellent choice for housing dairy cows because of the excellent cow comfort afforded by these facilities. Sawdust prices have climbed in recent years and currently stand at around $900 for a semi-load. However, a recent analysis shows that amounts to around $0.55 per cow per day. Even with $10 milk, this amounts to about 5 pounds of milk to pay for the bedding and the kind of cow comfort we do not get in other facilities. PD

References omitted but are available upon request.

—From University of Minnesota Compost Dairy Barn Newsletter, November 2006