With the warm weather spell we’ve recently had, I’ve been getting quite a few calls from clients looking to gear up for their vegetable gardens for spring. Of those calls, a large number of folks asked me about using animal manure in their vegetable gardens. Animal manures can be a great addition to the home vegetable garden; however, there precautions you should take when using it.
First, when I refer to animal manure, I am talking primarily about the waste products of farm animals. Never use the manure from dogs and cats in the vegetable garden. Parasites from pets are more likely to survive in garden soil and infect people than those in other types of manures.
Animal wastes, such as chicken manure and litter may also harbor pathogens, such as E. coli, Salmonella, Cryptosporidium and others. To reduce risk to humans and pets, proper handling and precautions are necessary. Stockpiled manure should be kept in a protected area where children, pets and livestock do not have access.
Additionally, prior to applying manure or litter to the garden, it should be composted or aged.
Proper composting will generate temperatures of 140 F to 160 F, which is enough to kill most human and animal pathogens, such as E. coli and Salmonella. An important factor to keep in mind is that pathogens are not actively killed by aging, rather they are inhibited from reproducing, which results in a slow decline of the population.
Again, aging the manure and litter only reduces populations of disease-causing microbes by providing unfavorable growing conditions that cause them to die off gradually due to changes in moisture content, temperature and nutrient availability. So, safe handling and incorporation into the garden is essential when using animal waste productions.
Having said that, we have some general rules of thumbs for how composted or aged manure should be applied into a garden. For best management practices, manure should be applied to a garden no later than 90 days prior to harvest of non-ground-contact crops such as trellised tomatoes, cucumbers and peppers; and no later than 120 days prior to harvest of ground-contact crops such as lettuce, strawberries and carrots. Following these guidelines will greatly reduce the probability of food-borne illness.
Additionally, fresh manure should not be applied to growing plants. Fresh manure will be going through what we call a “heat” and is therefore quite potent and can easily burn seeds, seedlings, and delicate plants. If you have a source for fresh manure either you can either compost it or apply it early enough to break down in the soil. It is important that you never use raw manure to sidedress growing plants in the garden.
So how much manure should you apply? Well, a general rule of thumb that many organic gardens use is to apply a 2-3 inch layer of well-rotted or composted manure over the garden and then till it into the soil. Specialists at the University of Georgia recommend a rate of 150 pounds of cattle manure or up to 200 pounds of horse manure or 50 pounds of poultry manure per 1000 square feet of garden soil.
If vegetable plants need additional fertilizer during the growing season sidedress with commercial fertilizer or some other non-manure source of nutrients. As you gain experience using manure in the garden you will be able to fine tune your application rate. Regardless of whether you are an organic gardener or you are just looking to build up soil organic matter, manure can be a good addition to your soil. Just be sure to use it correctly!
Interested in learning more about using organic fertilizers and soil amendments? Check out our UGA Extension Bulletin 1011: Growing Vegetables Organically for more details. This publication can be found free online or we can print one out for you at our office.