Organic Fertilizers - Overview
Organic (Natural) vs Chemical (Inorganic)
Man-made chemical fertilizers always have a high total NPK, from 20 to 60 percent or more. The total NPK for organic fertilizer will always be low. Even though the laboratory analysis for chemical fertilizers are high, the total 'usable' nutrients are far less. Much of the nutirents are bound up chemically and unusable by the plants, and much of the excess Nitrogen and Phophorus will leach out into the ground water and streams before the plants can us it..
The majority of the ingredients in the chemical fertilizers (a 10-10-10 has 30% NPK and 70% other stuff), is usually made up of inert filler or possibly 'bad' chemicals. The part of organic fertilizer that is not the NPK is still necessary soil nutrients. The fact that the material is organic - once-living plant, animal or a combination - indicates that it is important to life. In the best organic fertilizers, everything usable by the plants - no filler, no runoff, no waste.
In addition to the NPK, chemical fertilizers may contain major, minor and trace elements, but it takes more than these chemicals to maintain the healthy soil.
Healthy soil makes healthy plants.
For example, there is very little, if any, carbon in a bag of chemical fertilizer. When a plant or animal body is analyzed, one of the most abundant elements in it is carbon, in the form of energy, mainly carbohydrates.
Plants absorb nutrients much better when the microbial life in the soil pre-processes compounds and elements into substances that the plants can better process. The microbes need energy to do this, and they get it from decaying plant or animal matter (carbon/carbohydrates) in the soil.
Organic fertilizer supplies this carbon/energy for the soil microbes, whereas, chemical fertilizer does not. If organic matter is not already present in the soil, the chemicals can quickly become stressful, even toxic, to the plants. This causes plants to be susceptible to disease and insect problems.
Although organic fertilizers are generally slower acting than the chemical fertilizers, their lower NPK analysis allows them to be used in higher volume without the danger of burning plants. Some organic fertilizers, however, are fast acting, such as bat guano or fish meal. These can show results as quickly as the chemical fertilizers do. But you then have to be careful not to burn the plants.
Chemical fertilizers, unless they are processed to keep them from quickly dissolving, must be used very cautiously, since they can burn plant roots and quickly leach beyond the reach of the roots. They generally end up polluting a water supply because they dissolve and quickly move out of the soil. This is less of a problem in heavy clay soils or soil with a high organic and humus content.
Chemical fertilizers, blended for a given soil and used in the correct season and correct amounts can do nothing more than grow a plant. They do not build or sustain a healthy soil. Organic fertilizers contain the energy and many other nutirents that build soil fertility, crumb structure, increased water holding capacity, provides food for the beneficial microbes, condition the soil and contribute to the many things that cause a plants to grow healthy.
Worm Castings vs Other Organic Fertilizers
Worm castings provide basically the same nutrients as 'normal' compost. However, worm castings have several benefits over basic compost. The nutrients in worm castings have exceptionally high availability for the plants, so that while the analysis values of N-P-K may appear low, worm castings provide a nutrient rich diet for plants.
Worm castings improve the soil structure for better air and water infiltration. They also retain water to reduce irrigation requirements.
Worm castings contain a chitinaze-enzyme, an enzyme that destroys insects' exo-skeleton. This means worm castings acts as an insect repellent/pesticide, and actually triggers chitinaze production in the plants.Worm castings have live beneficial bacterial populations that help control 'bad' bacteria and fungi.
By legal definition, the term fertilizer refers to a soil amendment that guarantees the minimum percentages of nutrients (at least the minimum percentage of nitrogen, phosphate, and potash).
An organic fertilizer refers to a soil amendment derived from natural sources that guarantees, at least, the minimum percentages of nitrogen, phosphate, and potash. Examples include plant and animal by-products, rock powders, seaweed, inoculants, and conditioners. These are often available at garden centers and through horticultural supply companies.
These should not be confused with substances approved for use with the USDA National Organic Program (NOP). The USDA NOP, with its “USDA Organic” label, allows for the use of only certain substances. The Organic Materials Review Institute (OMRI www.omri.org) approves brand name products made with ingredients from the “National List” for use with the NOP (see www.ams.usda.gov/nop and click “NOP Regulations” and then “National List Information”). Many of the organic fertilizers listed here will meet NOP standards (based on the National List). Growers participating in the NOP should consult with their certifier to ensure compliance for organic certification.
The terms soil amendment refers to any material mixed into a soil. Mulch refers to a material placed on the soil surface. By legal definition, soil amendments make no legal claims about nutrient content or other helpful (or harmful) affects it will have on the soil and plant growth. In most states, the term compost is also unregulated, and could refer to any soil amendment regardless of active microorganism activity.
Many gardeners apply organic soil amendments, such as compost or manure, which most often do not meet the legal requirements as a “fertilizer” but do add small amounts of nutrients.
Worm Castings as Organic Fertilizer And Soil Conditioner
In addition to a time-released supply of the primary nutrients (Nitrogen, Phosphorus, Potassium - NPK), they provide many of the necessary trace elements and micro-nutrients, beneficial bacteria, other organisms, and natural chemicals and enzymes. These natural, biological controls of disease and insects makes use of additional fungicides and pesticides unnecessary. The live, beneficial organisms in worm castings actively pull nutrients from the air (Nitrogen, Carbon, Sulphur) and make these available to the plants.
Additionally, worm castings improves the soil by balancing the pH, retaining moisture, and improving soil structure for better drainage and aeration. This reduces watering requirements and improved the drought tolerance of plants.
Other Organic Fertilizers
Sewage-Based Fertilizers (labeled as Biosolids, Biowaste) - arsenic, toxic heavy metals, PCB's, Viagra, estrogen, hormones, Rx drugs, biological pathogens (e-coli, salmanila, etc.). There are new doubts on the 30+ year old policy of encouraging farmers and landscapers to spread millions of tons of sewage sludge as a safe, nutrient-rich alternative to commercial fertilizers. The contaminants being introduced by all the new medications on the market are posing a new and unknown factor.
Fish Emulsion - processed with heat and acids - lose much of the proteins, enzymes, vitamins and micronutrients. SMELL.
Cotton Gin trash - may not be fully composted and may contain unwanted contaminates. The last thing they do to cotton before picking is defoliate the plants with a salt spray (herbicide). During the growing season, it's sprayed regularly with synthetic pesticides. High in salts.
Mushroom Compost, also known as Spent Mushroom Substrate or SMS, is a waste product of farms that use SMS as the growing medium for mushrooms. SMS is made from agricultural materials, such as hay, straw, and straw horse bedding. In some SMS, there is poultry litter, cottonseed meal, cocoa shells, gypsum, and sphagnum peat moss.
After mushrooms are harvested, the mushroom compost is pasteurized or steam treated to eliminate any pest, pathogens and weed seeds. SMS is a popular organic soil amendment for the establishment and maintenance of lawns, sports fields and, of course, gardens.
Not recommended for several reasons such as its low nutrient level, high salt content, possible chemical contamination, and high cost. Unamended Mushroom Compost is nutritionally exhausted compost that was used to grow mushroom.
Cow Manure - highly variable. If not well composted, may contain weed seeds and deplete the soil nitrogen as it ages.
Chicken Manure (poultry manure) - highly variable physical and nutrient characteristics of the product. variation is introduced by differences in species, housing systems, and bird age, the feed rations, the use of bedding, and the manure handling system.
Farm/Yard/Manure - highly variable
Other manure sources include feedlots (steer), egg production (hen), and race horses. Manure nutrient content will vary depending on type of animal, moisture content, percentages and type of litter or bedding, age of manure, storage conditions, and how it is spread and incorporated into the soil. Though manure can be applied to cropland in the fall as a source of nutrients for crop production the following growing season, high soluble salts (electrical conductivity readings) for all except horses can cause salt burn on sensitive crops if applied at heavy rates.
Other problems associated with livestock manures include odor and fly problems, weed seeds, high moisture content, and poor particle size and weight uniformity.
Composting livestock manures has a number of advantages over applying them directly to land. The relatively low moisture content of the finished compost, more uniform particle size (screened), and lighter weight make it easier to handle. Thermophilic composting techniques will also kill most annual weed seed and pathogens.
The process of composting biosolids as well as steer manures tends to increase both pH and the soluble salts (electrical conductivity). Composting straight steer manure tends to increase pH and soluble salts more than when it is combined with a feedstock like cotton gin trash. These higher soluble salts could limit the amount of these composts that should be applied per acre.