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There are only a few different materials used by dairy producers in freestall beds. The most commonly found ones are sosnd and compost. We looked at ammonia emissions from sand, compst, and pine shaving bedding types to evaluate the beding type with the lowest ammonia emission rate.
The Problem
In Colorado, and most dairies in the nation, the most common type of bedding used in freestalls is sand. This is because it has been relativly cheap, readily available, inert (low bacterial count), has not been shown to increase cases of clinical mastitis, and is easy on cows hocks and knees (less rubbing and slipping). However, sand is very hard on manure removal equipment, plugs up solid seperation facilities, and takes a lot of effort to clean and recycle back to stalls. An alternative bedding is compost. Compost is relativly free if made on site with existing equipment, doesn't harm manure removal or solid seperation equipment, doesn't need to be seperated from the waste stream, is easy on cows hocks and knees, and can be removed from stalls and directly applied to fields. The drawbacks to compost bedding are that, if not processed properly, compost may have a higher bacterial count; however, this has not been shown in studies to case an increase in clinical mastitis. Compost production also requires a capital investment if not already a practiced technology on farm, and some technical experience to process. However, the on-farm production of compost at dairy operations is a fairly common practice these days and is an economical way to process manure. Another alternative to sand bedding is pine shavings. While this type of bedding is not comonly used in dairy barns in CO, it has similar manure handling benifits to compost and has been shown to have low ammonia emissions (22, 39). Additionally, it is an added C source in the waste stream for manure solids composting. However, dispite these alternative bedding types, there is still some speculation as to whether compost, pine shavings, or sand is the better bedding matterial for freestalls.
Background
The use of bedding in freestall dairy barns has been evaluated by Misselbrook and Powell (22) who cxonducted laboratory trials of six different bedding types typically used in dairy barns (chopped straw, sand, pine shavings, chopped newspaper, chopped cornstalks, and recycled manure solids) and their impact on ammonia emissions. They found that physical structure and relative absorbance capacity were the two most important characteristics influencing ammonia emissions from bedding. The recycled manure was the most absorbent, retaining 15 times more urine than sand, which was the least absorptive. Recycled manure also had one of the highest rates of ammonia volatilization. They hypothesize this to be because the urine stayed on the top of the manure surface where it was more susceptible to volatilization. With sand bedding, the urine percolated to the bottom of the pile, reducing the urine-air interface and decreasing ammonia emissions. Additionally, pine bedding had the second lowest ammonia emissions, likely due to its high percolation rate and low pH (4.5), even though this was not concluded in their study. Other studies have found that pine shaving had 20% lower ammonia emissions than manure solids, but gave no specific reasoning for the difference (39).
Experimental Method
Method. For this BMP, we had three different trials. Trial I and II looked at two different bedding treatments: sand verses compost bedding in freestall pens; while Trial III looked at sand, compost, and pine shavings in freestall barns. Sand has been shown to be the most popular bedding in freestall dairy barns because it is clean, inexpensive, and has been shown to have the lowest ammonia emission when compared against other bedding types in a controlled laboratory study (22). However, it has its limitations and is a major problem in waste processing. Since compost is usually produced on farm (no additional input cost), causes no problems in the waste management stream, and if properly managed has been shown to have average ammonia emissions, we wanted to compare its ammonia emissions and cost efficiency to sand bedding. Additionally, pine shavings have been shown to have low ammonia emissions, and while they are not as widely used as the other two bedding types, they have similar benifits in the waste stream to compost bedding.
To compare sand and compost in Trials I and II, we installed fresh Class II dairy compost and conventional sand bedding in freestalls in dairy barns at two facilities. For the two treatments, 12 freestall beds were tested; 6 with sand, and 6 with compost bedding. The beds were all located in the same row of the same barn to eliminate placement bias. Sample beds were grouped in pairs (two sand next to two compost) with three non-treatment beds between each pair. The spacing between treatment sample pairs decreases the spatial bias within the barn. Trial III had the same set up with 6 sand, 6 Class II dairy compost, and 6 pine shaving beds.
Treatments were installed on day 0, and each bed was measured once daily, in sequence, for 10 minutes from approximately 0800 to 1200 using our surface ammonia sampler (Figure 1). Beds were measured at approximately the same time each measurement day to eliminate time of day bias. Beds were measured on day 0, 1, 2, 4, 11, and 18. Samples of the three bedding types were collected (Figure 2) each sampling day and analyzed for a variety of things including, but not limited to: moisture, OM, pH, total N, organic N, ammonia N, C:N ratio, and ammonia-N/nitrate-N ratio. After taking ammonia measurements and bedding samples, both sand, compost, and pine beds were restocked on a weekly basis to follow regular bed management practices of the facility.
Results and Cost Analysis
Results. Coming Fall 2008....
Cost Analysis. Coming Fall 2008....
The Solution
Coming Fall 2008....
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