Source: https://en.wikipedia.org/wiki/Organic_fertilizer
Organic fertilizers are fertilizers that are naturally produced and contain carbon (C). Fertilizers are materials that can be added to soil or plants, in order to provide nutrients and sustain growth. Typical organic fertilizers include mineral sources, all animal waste including meat processing, manure, slurry, and guano, plant based fertilizers, such as compost, and biosolids. There are also other abiotic non-chemical, fertilizer methods that meet the Principles of Organic Agriculture, which determines whether a fertilizer can be used for commercial organic agriculture.
The main organic fertilizers are, peat, animal wastes, plant wastes from agriculture, and treated sewage sludge.
Minerals
Minerals are chemical compositions and can be found in rocks. These minerals can be mined or extracted at surface in order to produce fertilizers. Other mined minerals are fossil products of animal activity, such as greensand (anaerobic marine deposits), some limestones (fossil shell deposits), and some rock phosphates (fossil guano). Adding limestone or “liming” a soil is a way to raise pH. By raising the pH of a soil, microbial growth can be stimulated, which in turn increases biological processes, enabling nutrients to flow more freely through the soil. When nutrients flow freely they are more accessible to plants and therefore can increase plant health and mass. If the soil is already pH balanced, liming the soil, would be ineffective.
Peat
Peat, or turf, is plant material that is only partially decomposed due to the acidic and wet conditions it is found in. It can be added to soil in order to add organic matter. Soil with higher levels of organic matter are less likely to compact, improves the soil aeration and water drainage, as well as assists in supporting soil microbial health. It is sometimes credited as being the most widely use organic fertilizer and by volume is the top organic amendment.
Animal Sources
Animal sourced materials include both animal manures and residues from the slaughter of animals. Manures are derived from milk-producing dairy animals, egg-producing poultry, and animals raised for meat and hide production. Manure is an abundant resource with estimations for cattle manure in the US alone reaching two billion tons annually, and one hen has the potential to produce a cubic foot of manure every six months. By adding manure to crops it adds nitrogen, potassium, phosphorus, sulfur, magnesium and calcium. While also increasing soil stability by increasing organic material, increasing water infiltration, it can add bacteria diversity, and over time reduce the impacts of soil erosion. However, there is organic manure and non-organic manure. In order for manure to be considered organic it must come from organic livestock or certified organic growers. If organic manure is not available, they are permitted to use non-organic manure as long as the animals have room to roam, are not kept in the dark, and growers abstain from using genetically modified feeds. Fresh manure, right from the stall, can cause issues because it can be too high in ammonia, or contain bacteria from the animal’s gut. This can have an adverse effect on plants as the ammonia can burn the roots and microbes from the animal’s gut can harm the microorganisms in the soil, killing them, or contaminate produce, such as E. coli and salmonella. There is also a risk of introducing weeds, as seeds can pass through the gut of an animal relatively unharmed, or there can be seeds in the bedding of the livestock, which is often mixed in with the manure. Therefore, manure is required to be composted which will ideally kill any seeds or pathogens and reduce the ammonia content.
Chicken litter, which consists of chicken manure and bedding, is an organic fertilizer that has been proposed to be superior for conditioning soil for harvest than synthetic fertilizers. It contains similar minerals to other manures, while also having trace amounts of copper, zinc, magnesium, boron, and chloride. Depending on the type of chicken litter obtained, it may contain bird remains. This type of chicken litter should not be spread on crops, and can pose a risk to grazing livestock due to botulism, a disease caused by bacteria within decaying birds.
Urine, from humans as well as animals, is a fertilizer. Urea in urine is a nitrogen compound, and urine is also rich in phosphorus and potassium. The amount of potassium in urine is variable, and depends on the amount of potassium in the person’s diet. Urine is not currently allowed to be used in any commercial agricultural operations. However, there are ongoing studies that have shown that aging urine in concealed containers for 12-16 months eliminates 99% of harmful bacteria, due to increasing urea content and therefore pH.
When any animal is butchered, only about 40% to 60% of the live animal is converted to market product, with the remaining 40% to 60% classed as by-products. These by-products of animal slaughter, mostly inedible—blood, bone, feathers, hides, hoofs, horns, — can be refined into agricultural fertilizers including blood meal, bone meal, fish meal, and feather meal.
Plant
Processed organic fertilizers include compost, humic acid, grain meal, amino acids, and seaweed extracts. Other examples are natural enzyme-digested proteins. Decomposing crop residue (green manure) from prior years is another source of fertility.
Compost provides little in the means of nutrients to plants, but it does provide soil stability through increasing organic matter.
Grain meals can be made of corn gluten, alfalfa, cottonseed, or soybean. Most supply nitrogen and potassium, but soybean meal provides nitrogen and phosphorus. When initially spread they can cause an increase in ammonia within the soil and burn seeds, it is recommended to use these after plants have developed, to ensure crop success.
Other ARS studies have found that algae used to capture nitrogen and phosphorus runoff from agricultural fields can not only prevent water contamination of these nutrients, but also can be used as an organic fertilizer. ARS scientists originally developed the “algal turf scrubber” to reduce nutrient runoff and increase quality of water flowing into streams, rivers, and lakes. They found that this nutrient-rich algae, once dried, can be applied to cucumber and corn seedlings and result in growth comparable to that seen using synthetic fertilizers.
Treated Sewage Sludge
Sewage sludge, also known as biosolids, is effluent that has been treated, blended, composted, and sometimes dried until deemed biologically safe. As a fertilizer it is most commonly used on non-agricultural crops such as in silviculture or in soil remediation. Use of biosolids in agricultural production is less common, and the National Organic Program of the USDA (NOP) has ruled that biosolids are not permitted in organic food production in the U.S.; while biologic in origin (vs mineral), sludge is unacceptable due to toxic metal accumulation, pharmaceuticals, hormones, and other factors.
With concerns about human borne pathogens coupled with a growing preference for flush toilets and centralized sewage treatment, biosolids have been replacing night soil (from human excreta), a traditional organic fertilizer that is minimally processed.Decomposing animal manure is an organic fertilizer source
Others
- Alfalfa
- Ash
- Blood meal
- Bone meal
- Compost
- Cover crops
- Fish emulsion
- Fish meal
- Manure
- Rock phosphate
- Raw Langbeinite
- Rockdust
- Unprocessed natural potassium sulfate
- Wood chips/sawdust
- PROM
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Source: https://www.planetnatural.com/big-stink/
Here’s a list of some organic fertilizers you may encounter and their benefits
Manure for the garden comes from cow, sheep, poultry and horses. Pretty self-explanatory. Manure is known as a “complete” fertilizer; it has a lot of organic matter, but is low in nutrients. Manures are most valuable as organic soil amendments and mulches. Note: Beware of using fresh manure as a fertilizer because it can burn plants.
Blood meal is dried, powdered blood collected from cattle slaughterhouses. It’s such a rich source of nitrogen that gardeners have to be careful not to over-apply and burn the roots of their plants. Apply blood meal just before planting to stimulate green leafy growth.
Bone meal is finely ground bone. A by-product from animal slaughterhouses, it is a great source of calcium and contains up to 15% phosphate. Bone meal promotes strong root systems and flowering. It is often used when growing flowers, bulbs and fruit trees.
Bat guano is protected by caves from leaching, so nutrients are conserved. It is rich in soluble nitrogen, phosphorous and trace elements. Usually powdery, bat guano may be used any time of year as a top dressing or diluted in a tea and used as a foliar spray.
Shellfish fertilizer or shell meal is made from crushed bones or shells from crab or other shellfish. It is a great source of calcium in addition to phosphorus and many trace minerals. One benefit of shellfish fertilizer: it contains chitin which encourages the growth of organisms that inhibit harmful pest nematodes.
Rock phosphate is a calcium or lime-based phosphate rock that is usually ground to the consistency of small crumbs. This rock powder contains over 30% phosphate and a large number of trace elements. Rock phosphate does not leach out of the soil, remaining unchanged until taken up by the roots.
Greensand is an iron potassium silicate that gives the minerals in which it occurs a green tint. Mined from an ancient New Jersey sea bed deposit of shells, Greensand is rich in iron, potassium and numerous micronutrients.
Fish emulsion is a partially decomposed blend of finely pulverized fish. It can smell, although some deodorized versions have been developed. Like blood meal, it should be used sparingly in order not to burn plant roots.
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The benefits of organic fertilisers over inorganic (synthetic) fertilisers
There are advantages and disadvantages to organic and inorganic fertilizers. The major benefit of organic fertilizers is that they work slowly. They need to be broken down by soil organisms in order for their nutrients to be released and that takes time. Because they work slowly, nothing is wasted. They are consumed as they are released, unlike chemical fertilizers, which are released immediately into the soil.
Organic fertilizers carry some other perks. Because they contain organic material, they improve the soil’s structure or its “workability”. Soil that’s been fertilized with organic matter is easier to work and allows more air to get to plant roots. The organic material also permits soil to hold water longer. Finally, the addition of organic substances used in fertilizer increases the bacterial and fungal activity in the soil. Overall, organic garden fertilizer not only helps your plants, it improves your soil.
Organic fertilizers’ biggest strengths are also their weakness. Because organic fertilizer’s nutrients are slowly released into the soil, they are not immediately available to plants. If there is an immediate need for nutrients, you may want to consider liquid fertilizers or foliar applications.
Inorganic fertilizers work fast, which can be a boon or a bane depending on your garden’s needs. Another disadvantage of inorganic fertilizer is that over watering or rain can push the chemicals beneath roots where they won’t do any good. Inorganic fertilizers, because they are so rich, can easily “burn” roots or create a toxic concentration of salts if over-applied.
Although organic fertilizers do carry many benefits, especially over time, plants often do not know the difference. Your zucchini plant doesn’t care if the nitrogen it’s feeding on came from a compost pile or a test tube.
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Videos
Other
https://www.pennington.com/all-products/fertilizer/resources/what-is-organic-fertilizer
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/organic-fertilizer
https://www.agrigem.co.uk/fertiliser
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Organic pestides
“Pesticide use in organic farming | Organic UK” https://goorganicuk.com/blog/articles/pesticide-use-in-organic-farming