Question: We would like to make our vegetable garden entirely organic this year, but are confused about what to use for fertilizer and how much to apply?

Answer: Organic fertilizers come from materials that were at one time living or byproducts of living things. Old leaves, bone meal and animal manures are just a few examples of organic fertilizers. There are advantages and disadvantages of to using organic fertilizers. One advantage of organic materials is that they provide beneficial organic materials that can improve both the water and nutrient holding capacity of the soil. This organic matter also creates an environment that encourages beneficial soil organisms such as earthworms. Another advantage is that organic materials take longer to break down and release nutrients. This creates a slow-release situation that provides nutrients over a longer period of time and can also help in reducing the loss of nutrients to leaching. A third advantage to organic materials is that they are often far less expensive. Many livestock producers and industries that produce organic wastes are required to properly dispose of them and are more than happy to have you take some of the material off their hands.

One of the disadvantages of using organic fertilizers is that they are more difficult to apply. Organic fertilizers are usually lower in nutrient content, therefore requiring more material to be applied to acquire the same amount of nutrient from an inorganic source. Most organic materials can only be applied by hand unless you have access to some kind of specialized equipment. In addition, the slow release property of the nutrients, which can be a benefit, can also be a detriment. If not applied properly and in a timely manner, the nutrients can be tied up in the organic matter and not be available to the plant. That is why it’s advisable to apply these materials well in advance of the need for nutrients so there will be enough time for the material to break down. Finally, the nutrient content of organic fertilizers materials can be highly variable – making it difficult to determine the proper amount to apply.

Question: Our neighbor told us we should not use livestock manure in our garden because of E. coli. Is this true?

Answer: Pathogens (microorganisms which cause disease) can be transferred from animal manures to humans. The pathogens salmonella, listeria and E. coli, as well as parasites, such as roundworms and tapeworms, have been linked to applications of manure to gardens. Publicity about illnesses due to E. coli, has made people more aware of the potential risk of food borne illness from manure contamination. As a result, many are now asking whether it is safe to use manure in their gardens.

In home gardens, it’s recommended that all manure be well composted before being added to soil where vegetables or fruit will be growing. The compost should heat to 140 degrees F. for five days or more to be effective. Never apply fresh manure after the garden is growing. Never use cat, dog or pig manure in vegetable gardens or compost piles. Parasites that may be in these types of manure are more likely to survive and infect people than those in other types of manure. It is also important to keep your pets out of your vegetable garden. For some gardeners, the best time to apply raw manure to the garden may be in the fall after harvest. Composted manure added to the garden in the spring should be thoroughly tilled into the soil prior to planting. Packaged manure products should be safe to use as most have been steam treated which kills harmful bacteria. It’s always a good idea to thoroughly wash all produce especially root crops such as carrots, beets, radishes, and onions prior to eating.

Question: How will we know the nutrient content of an organic fertilizer?

Answer: The most accurate way would be to have the product tested for its nutrient content. This will tell you how much of the essential nutrients are available to the plant and how much material to apply. This will allow you to receive the fullest benefit of your fertilizer by applying it in proper amounts. Keep in mind however, that you may not be able to apply all of the nutrients in the proper amounts. The nutrient rations don’t come out in nice even numbers like 5-10-5 or 10-10-10, so you may have to supplement organic materials with some inorganic fertilizers to get the proper amounts of all nutrients.

Fertilizer labels on organic products have been standardized so that the concentration of nitrogen, phosphate, and potash always appear in the same order on the front of the package. Many organic fertilizers also contain other nutrients like sulfur, iron and zinc; however, concentrations of these are usually not given on the label because levels are either too low or too variable to be specified.

EDITOR’S NOTE: For answers to local gardening questions go to www.pnwmg.org or call 360-249-4125, the WSU Extension office in Elma, or call Rachel Gana at 642-8723 or e-mail her at acornwp@yahoo.com.