Using Manure and Compost as Nutrient Sources
Manure is a valuable fertilizer for any farming operation and has been used for centuries to supply needed nutrients for crop growth. The use of manure has generally declined on many farms over the past 50 years due to:
- Farm specialization with increasing separation of crop and livestock production;
- Cost of transporting manure, which is a bulky, relatively low analysis nutrient source; and
- Increased availability of high analysis synthetic fertilizers that usually provide a cheaper source per unit of nutrient than manure.
Despite these limitations, manure (and other organic nutrient sources) produced on or near a vegetable farm provides many benefits and should be beneficially utilized whenever possible.
Manure and compost not only supply many nutrients for crop production, including micronutrients, but they are also valuable sources of organic matter. Increasing soil organic matter improves soil structure or tilth, increases the water-holding capacity of coarse-textured sandy soils, improves drainage in fine-textured clay soils, provides a source of slow release nutrients, reduces wind and water erosion and promotes growth of earthworms and other beneficial soil organisms. Most vegetable crops return small amounts of crop residue to the soil, so manure, compost and other organic amendments help maintain soil organic matter levels.
Proper use of manure and compost is essential from both a production and environmental standpoint. Applying rates that are too low can lead to nutrient deficiency and low yields. On the other hand, rates that are too high can lead to nitrate leaching, phosphorus runoff, accelerated eutrophication of lakes and excessive vegetative growth of some crops. Thus, understanding how to manage manure is important for any farming operation with livestock that relies on manure as a major source of nutrients, as well as for vegetable producers who have access to an economical supply of manure, compost or other organic nutrient sources.
Fresh, non-composted manure will generally have a higher nitrogen (N) content than composted manure. However, the use of composted manure will contribute more to the organic matter content of the soil. Fresh manure is high in soluble forms of N, which can lead to salt build-up and leaching losses if over applied. Fresh manure may contain high amounts of viable weed seeds, which can lead to weed problems. In addition, various pathogens such as E. coli may be present in fresh manure and can cause illness to individuals eating fresh produce unless proper precautions are taken. Apply and incorporate raw manure in fields where crops are intended for human consumption at least three months before the crop will be harvested. Allow four months between application and harvest of root and leaf crops that come in contact with the soil. Do not surface apply raw manure under orchard trees where fallen fruit will be harvested.
Heat generated during the composting process will kill most weed seeds and pathogens, provided temperatures are maintained at or above 131°F for 15 days or more (and the compost is turned so that all material is exposed to this temperature for a minimum of 3 days). The microbially mediated composting process will lower the amount of soluble N forms by stabilizing the N in larger organic, humus-like compounds. A disadvantage of composting is that some of the ammonia-N will be lost as a gas. Also, compost alone may not be able to supply adequate available nutrients, particularly N, during rapid growth phases of crops with high nutrient demands. Composted manure is usually more expensive than fresh or partially aged manure.
Manures from concentrated animal feeding operations are usually high in salt content. Most dairy and feedlot manures contain 5 to 10% salt (50,000 to 100,000 ppm). Frequent and/or large (20 tons per acre) applications of manure to cropland increases the risk of salt injury to plants. Salt-sensitive plants such as lettuce, tree fruits and nuts are especially susceptible. The following management practices are recommended for applying animal manures to cropland:
- Use well-aged manures rather than fresh manures taken directly from feedlots;
- Apply up to 5 tons per acre of dry matter per year or 10 tons per acre every other year;
- Use supplemental nitrogen fertilizers only as required based on tissue tests, plant performance and previous experience;
- Plow or rototill manure into the soil, irrigate and wait at least 30 days before planting;
- Do not apply manure where water penetration is poor; and
- Monitor soil salinity and sodium levels by periodic soil tests.
Liquid Chisel® is great for managing the soluble salts that affect plant performance by helping keep the net movement of salts dispersed downward away from the soil surrounding the rooting zone.
- Enhanced soil microbial activity
- Increased soil pore space allows more room for microbial life to flourish
- The polymer component of the formulation is an excellent microbial food source
- Increased seed germination
- Better timing for short residual herbicides
- Better stand establishment
- Keeps bicarbonates from attaching to irrigation system
- Increasing the solubility of calcium and magnesium salts allows them to move through the soil profile
- Changing these salts into ionic forms, Ca++ & Mg++, can displace sodium (Na+) on clay particles allowing the Na to be leached out with the irrigation water
For more information on using manure and compost as nutrient sources, contact your local Helena representative.
- David Gehrts, Product Manager