Cow manure packs an intense odor that causes most gardeners to wrinkle their noses--particularly those not raised in rural areas. Despite its ripe scent, cow manure makes an excellent addition to any garden, adding valuable plant nutrients to your soil. Make sure you understand the facts about this prime fertilizer to maximize the benefits it brings to your garden.
According to Oregon State University Cooperative Extension, one year's worth of manure from one lactating dairy cow contains 300 pounds of nitrogen, 45 pounds of phosphorus and 165 pounds of potassium. Cow manure has lower nutrient levels than other types of manure, such as poultry waste. However, these low nutrient values make it a more mild fertilizer, typically less likely to harm your sensitive plants than synthetic fertilizers and most other animal manures.
Many small farms have cow manure mixed with urine and bedding material, such as straw, sawdust or shredded newspaper, which creates a blend of carbon and nitrogen waste ready for composting. Most large dairy farms dispose of manure in a liquid form, which mixes the manure with urine and waste water; this mixing often results in lower nutrient values in cow manure. If you purchase manure directly from a farmer, make sure you get a lab analysis to verify the nutrient content, especially if you're planning on using the manure to provide the bulk of your garden fertilizer.
Cow manure provides your garden with fertilizer, mulch and compost. Spread it directly on your garden soil as a fertilizer right after you harvest your fruits and vegetables in the fall. Use a 2- to 3-inch layer of cow manure and let it sit on the surface of the soil until springtime. Till it into the top several inches of soil before planting time to give your plants a boost of valuable nutrients to promote early growth.
The ammonia present in fresh cow manure can burn young plants and seedlings, according to Marian Owen, co-author of "Chicken Soup for the Gardener's Soul." Fresh cow manure also needs to break down before its nutrients become completely available to your plants. During this period of organic breakdown, the nutrients already present in the soil become unavailable to your plants. Consider composting the cow manure ahead of time so that you can add the aged cow manure directly to your plant soil.
According to Washington State University Cooperative Extension, fresh cow manure may contain bacteria, such as E. coli, which could infect humans. Minimize your chances of possible infection by waiting at least 120 days after a manure application before you harvest root and leaf crops. Compost your cow manure before adding it to your garden to further protect from possible problems. Commercial bagged cow manure is already composted and aged, so you don't need to worry about pathogens in it.