It's horse poop season. Now is the time to check around for used horse bedding, borrow or rent a truck and go shovel some up. Horse bedding and its embedded poop is far easier to come by than cow manure, for social reasons rather than sheer volume. We have some 83,000 dairy cows in Whatcom County. Their manure is either a resource or a problem, depending on how you look at it. (Gene Lodgon's comment about dealing with the manure from large dairy operations was that it consisted of making a solution into the two problems of waste disposal and soil fertility.) In any case, our commercial operations generate a managed waste stream and good luck to the gardener trying getting their hands on some. Horse poop is another matter. We are also fortunate to have a considerable hobby horse population. Hobby horse owners just love having someone show up and make the manure pile vanish.
Horses digest differently from cows, so the weed seeds are not completely killed passing through the horse. Many gardening books will exhort readers to shun horse manure. Between the home grown dock and dandelions and the weed seeds that came with my topsoil, I'm not convinced that it makes much difference.
The age of the used bedding does make a difference. Animals are bedded in the abundant wood shavings from the mills, not in expensive straw from the grain growing regions in Eastern Washington. The bedding is best if it sits around six months and breaks down. Make a pile of fresh bedding someplace convenient and cover it. In the fall, spread it on your beds and plant a cover crop. I am partial to mixed oats and favas. The oats are a nurse crop for the favas. Usually, the oats winter kill and by now the favas are up and going strong. I have one bed of fall planted oats and favas looking very green and fluffy and another where the oats died and the favas are struggling. It seems to depend on microclimates and the timing of your plantings.
The rising popularity of home gardening has created a market for previously composted horse bedding. You may have to pay something for the aged stuff.
A rough and ready hot bed can be made just by digging through fresh horse bedding (with a shovel, eh?) and extracting lumps of poop. Some of the wood shavings will come along; no problem. You want at least 5-10 gallons of fresh poop, enough to fill a small raised bed, perhaps 4 - 10 feet square, at least a couple of inches deep, better 6'. Drawers, abundantly available from the ReStore, with holes drilled in the bottom for drainage, work splendidly. Cover with 2" - 3" inches of dirt and plant your lettuce and spinach in there, or use it to shelter starts. The classical interpretation involves a used window propped at an incline to provide more heat. The minimal effort version: repurposed drawer, 5 gallons fresh horse poop, 2" soil, works just fine. Repeat in the fall to have lettuce and spinach until it really freezes. Set your drawer someplace warm and sunny with a little windbreak. The reflected warmth of the south side of a building is a good place.