   Using Manure in the Home Garden - November 20, 2013 Jeff Schalau, Agent, Agriculture & Natural Resources University of Arizona Cooperative Extension, Yavapai County Many vegetable gardeners apply manure to supply plant nutrients and organic matter to the soil. The organic matter in this manure helps build and maintain soil structure, which is important for drainage, root and water penetration, and water storage. Nutrients in manure can supply plants with part or all of their nutritional needs. Animal manures are excellent sources of nitrogen and phosphorus, and are used to replace manufactured fertilizers in organic agricultural production. They can also contain pathogens (such as E. coli O157:H7, Salmonilla, and Listeria) which must be considered and appropriately managed to mitigate risk factors. The nutrient composition of animal manure is variable, depending on animal species, quality of feed consumed, moisture content, and methods of handling and storage. Generally, manure costs less than commercial fertilizers for comparable amounts of nutrients. Drier manure tends to have greater nutrient concentrations whereas wet manure will have lower nutrient concentrations. During storage manure can lose from 15 to 60% nitrogen, however nutrient losses can be minimized by covering manure during storage. Roughly half of the nitrogen in manure will be available to plants in the first year after application and the other half will be released slowly over time as more complex compounds are decomposed. Salts from feeds, concentrates and water given to the animal are also quite variable and can, if not properly managed, accumulate in soil and damage plants. In general, dairy and beef manures have the highest salt contents, whereas sheep and hog manures have lower salt contents and present the least risk of causing salt damage. Salt level is a function of animal diet as well as species. These salts can be leached below the plant root zone by irrigating the soil with enough water to flow through the soil and carry salts downward. Ideally, uncomposted manure should be applied several weeks before planting, incorporated in the crop rooting zone (usually 6 to 10 inches deep), and the soil well watered. Incorporation well in advance of planting and watering are not required, although this practice is helpful for leaching salts, reducing odor and pathogens, and helping manure to decompose, allowing nutrients contained in the manure to be released. Irrigation following manure application also will encourage weed seed to germinate, after which weed seedlings can be destroyed by tillage or other techniques. Recent USDA food safety guidelines also recommend that fresh manures be incorporated into soil 120 days prior to harvest to minimize risks associated with pathogens. If manure has been properly composted prior to application, viable weed seeds should be considerably reduced compared to fresh manure. When manure is composted, several additional changes occur. The mass of the manure is reduced as sugars, starches, and cellulose are converted to carbon dioxide and lost to the atmosphere. Depending on the composting conditions, considerable nitrogen and potassium also can be lost from the manure. This reduces the likelihood of damaged plants from manure application. If properly composted, the number of pathogenic and other microorganisms in the manure will also be substantially reduced. The optimum amount of uncomposted manure to be applied varies depending on its composition. Manure application often is calculated on the basis of its nitrogen content such that enough manure is added to provide the nitrogen for growing plants. Tables are available that list approximate nitrogen content of various animal manures (one is included in a publication linked below). To provide some general guidelines, you should apply no more than the following amounts of fresh manure to each square foot of garden space per year: cattle - 1 lb; horse - 1 ¼ lb; chicken - 1/3 lb; and sheep/goat/llama/alpaca - 2/3 lb. Do not use dog or cat manures in gardens or compost – they can contain additional pathogens which do not readily decompose or neutralize. Animal manures supply plant nutrients and can supplement or replace manufactured fertilizers. Manure also adds organic matter to the soil. Even in desert soils, where organic matter decomposes quickly, addition of manure helps to build and maintain soil structure, improving soil drainage, root and water penetration, and water storage. As stated above, I would recommend using composted over uncomposted manure. And lastly, composting manure or applying manure directly to soil is a responsible, efficient way of disposing of animal wastes. I’d also like to acknowledge my colleague, Jim Walworth, Extension Soil Specialist for providing much of the information for this column. Follow the Backyard Gardener on Twitter – use the link on the BYG website. If you have other gardening questions, call the Master Gardener help line in the Camp Verde office at 928-554-8999 Ext. 3 or e-mail us at cottonwoodmg@yahoo.com and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. Additional Resources Manure in the Home Garden, University of Arizona Cooperative Extension This publication includes tables with nitrogen content and fresh manure application guidelines. http://cals.arizona.edu/pubs/garden/az1590.pdf Preventing E. coli From Garden to Plate, Colorado State University Extension http://www.ext.colostate.edu/pubs/foodnut/09369.pdf  |