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Organic fertilizer

From Wikipedia, the free encyclopedia

Organic fertilizers are fertilizers derived from living or formerly living materials. They usually come from animal wastes, plant wastes from agriculture, compost, and treated sewage sludge. Beyond animal wastes from meat processing, peat, manure, slurry, and guano, naturally occurring organic fertilizers can also be derived from animal product which include blood meal, bone meal, feather meal, hides, hoofs, and horns from the slaughter of animals.

A cement reservoir containing cow manure mixed with water. This is common in rural Hainan Province, China. Note the bucket on a stick that the farmer uses to apply the mixture.

In contrast, the majority of fertilizers used in commercial farming are extracted from minerals (e.g., phosphate rock) or produced industrially (e.g., ammonia). Organic agriculture, a system of farming, allows for certain fertilizers and amendments and disallows others; that is also distinct from this topic. Most of organic fertilizers contain less concentrated nutrients, and the nutrients are not as easily quantified. They can offer soil-building advantages as well as be appealing to those who are trying to farm more “naturally”.

Purpose

Organic fertilizers are used to augment the concentrations of plant nutrients and organic substances. Despite the fact organic fertilizers do not yield large concentration of essential nutrients for plants and soil at once, it supplies the long term nutrients for the microbial populations in the soil as well as the soil itself. It is known to work double duty since its effects branch into both restoring the soil fertility and enhancing the crop yield and quality. It effects take a longer period of time to detect, yet efficient approaches are promising - improve farming production and maintain a sustainable environment in the long term.

Biology In Plants

Overall biosynthesis in plants, with input of nutrients as reactants for essential biological processes.

Similar to synthesized fertilizers, the major nutrients in organic fertilizers are phosphorus, nitrogen and potassium. Organic fertilizer blends provide balanced amounts of the macronutrients, but individual soil needs and the desired effects can require specific amendments. Plant development also can suffer negative effects without adequate levels of micronutrients, such as calcium, magnesium, sulfur, copper and zinc, which organic fertilizers restore indirectly to the plants. Plants tend to take in sufficient amount of nutrients into the root for (1) biosynthesis processes producing essential molecules for the development and health of plants, (2) for the uptake of water into the plants, maintaining the adequate amount of water inside the plants.

Nitrogen

Nitrogen is a vital component of amino acid, the building block of proteins. As nitrogen is uptaken from the soil up into the root, it is used as a reactant in amino acid synthesis.

The condensation of two amino acids to form a protein chain through a peptide bond

Nitrogen fixation occurs in soil thanks to microorganisms. Its product is used in protein synthesis in plants

Nitrogen in its gaseous form (N2) can’t be used by most living things, yet once it undergoes nitrogen fixation, its derived molecules can be used as one of the reactants in some biosynthesis. Nitrogen diffuses into the soil from the atmosphere, and species of bacteria convert this nitrogen to ammonium ions (NH4+) used by plants - which explains the cruciality of the abundance as well as the diversity of soil microbiome, as well as enhances the need to improve soil quality. Biological nitrogen fixation (BNF) occurs when atmospheric nitrogen is converted to ammonia by an enzyme called a nitrogenase, and takes place at a metal cluster called FeMoco, an abbreviation for the iron-molybdenum cofactor. A series of protonation and reduction steps are carried out wherein the FeMoco active site hydrogenates the N2 substrate. The overall reaction for BNF is: N2 + 4ATP + 8e- + 8H+ -> 2NH3 + H2 + 4ADP + 4Pi

Once inside the plant, NO3- is reduced to an NH2 form and is assimilated to produce more complex compounds. Because plants require very large quantities of nitrogen, an extensive root system is essential to allowing unrestricted uptake, and nitrate moves freely toward plant roots as they absorb water (bulk flow). Therefore, the high rate of water movement into the root is essential for the intake of nitrate - which depends largely on the fertility of soil (discussed in Water Movement)

Increased nitrogen inputs (into the soil) have led to lots more food being produced to feed more people – known as ‘the green revolution’. Nitrogen-contained compounds diffuse into the roots, and used in different biological processes. One of important processes are amino acid synthesis, which also leads to protein synthesis. Amino acid is an organic compound with an amine group, (-NH2), a carboxyl (-COOH) and a side group specific to each amino acid. In plants, nitrogen is first assimilated into organic compounds in the form of glutamate, formed from alpha-ketoglutarate and ammonia in the mitochondrion. For other amino acids, plants use transaminases to move the amino group from glutamate to another alpha-keto acids. For example, aspartate aminotransferase converts glutamate and oxaloacetate to alpha-ketoglutarate and aspartate

The condensation of two amino acids to form a protein chain through a peptide bond Amino acids are monomers that undergo condensation polymerization to make protein after the transcription (in the nucleus) and translation (in cytoplasm) in protein synthesis. The removal of a hydrogen from one monomer and the removal of a hydroxyl group from the other monomer allows the monomers to share electrons and form a covalent bond. Thus, the monomers that are joined together are being dehydrated to allow for synthesis of a larger molecule. As the process goes on, the next amino acid is added to the chain with peptide bond, and water is formed as side product.

Protein produced in plants participate in every biological process in plants: from DNA replication, expression of certain gene in the cell to the presence of certain protein such as pigments in chlorophylls responsible for absorbing light in photosynthesis, to the protein assisting in Calvin Cycle that makes G3P (early form of sugar in plants).

Besides proteins, other molecules that contain nitrogen are nucleic acid, ATP, enzymes,...

Phosphorus

Phosphorus plays a role in photosynthesis, respiration, energy storage and transfer, cell division, cell enlargement and several other processes in plants. A plant must have phosphorus to complete its normal production cycle. Plants absorb phosphorus from the soil as primary and secondary orthophosphates (H2PO4- and HPO42-).

Phosphorus involved in ATP, energy unit of organism

Phosphorus is a vital component of DNA, as it is included in the phosphate groups, which participates to build the genetic storage unit in the cell nucleus of the organism. Besides, it participates in the building of mRNA, the messenger molecule that delivers the genetic information from the protected DNA inside the nucleus to ribosome, where protein is synthesized based on that information provided. Phosphorus involved in ATP, energy unit of organism Phosphorus is an essential component of ATP, the main energy unit of the organism. Most of the available energy in an organic molecule exists in C-C and C=O bonds as electrons are shared equally between two atoms, such as those in a carbon-to-hydrogen bond, possess a high level of energy because their position in the covalent bond is generally far away from either atomic nucleus. At the end of cellular respiration, these high energy bonds are broken, and the chemical energy in C-C and C=O bonds is transferred to ATP, making it a energy molecule for the organism.

Unlike animals, plants do not have nervous system regulating biological processes in the systems, but rather based on the activity of hormones and enzymes. The most common signal cascade that induces biological activities in plants is phosphorylation signal cascade - putting a phosphate group onto a compound. A number of enzymes, hormones, and cell-signaling molecules depend on phosphorylation for their activation.

In plants, besides ATP used as primary energy, another form of energy is proton gradient that acts as the source of energy for secondary active transport which is responsible for the movement of solute in organism (sugar, ions, molecules,...). Photon pump activity creates the proton gradient that provides energy for solute transportation, and the photon pump activation is regulated by phosphorylation signal cascade.

Potassium

Potassium enhances many enzyme actions aiding in photosynthesis and food formation. It builds cellulose and helps translocate sugars and starches. Potassium is vital to producing grains rich in starch.

Potassium plays an essential role in photosynthesis. Although it is not involved in neither light reaction or Calvin cycle, the presence of potassium in guard cells help increases the pressure potential in guard cells, which makes the cell turgid and opens up the stoma, allowing gas exchange and CO2 to diffuse into the leaf air space. Once CO2 is in the leaf air space, it gradually diffuses into chloroplast where photosynthesis takes place and sugar is produced. The amount of potassium ions in the guard cell increases the amount of solute inside the guard cells, which causes more water to flow into the guard cell and makes the cell turgid enough for the pore to be seen. Without potassium ions, the opening of stomata is really small, which affects the photosynthesis rate and cause plant starvation as the worst scenario.

The presence of potassium in the root cells causes the same effect: causing more water to flow into the root cells, affecting the uptake of water into the plants for photosynthesis and other biological processes.

Magnesium

Magnesium is the element at the center of porphyrin ring of plant pigments, or chlorophylls, where the energy is input to initiate photosynthesis that produce food for plants and the organisms consuming plants. Magnesium in chlorophyll allows chlorophyll molecule, or the pigment in general, to absorb light energy and convert it into chemical energy that launches photosynthesis. Once the energy from photon is absorbed, it excites chlorophyll molecules, which then releases resonance energy to neighbor pigment.

Chlorophyll a with Mg atom in the center.

When chlorophyll absorbs energy from sunlight, electron in chlorophyll molecule is excited from the ground state to the excited state. The excited electron is transferred from one pigment to another, via a chain of redox reactions, as the second chlorophyll molecule accepts a new electron from another. This pattern is observed again on the electron transport chain.

As a metal complex, chlorophyll molecules also absorb some of wavelength in visible spectrum, and some of it are not absorbed. Despite the fact the most chlorophyll molecules contain magnesium atom in the center of porphyrin ring, the differences in outside ligands affect the ability to absorb photon energy, which causes differences in wavelength absorbed. Chlorophyll a is the pigment that plays the crucial role in absorbing light energy, and this metal complex can absorb light wavelength in all color but green. As green wavelength is not absorbed, it get transmitted or reflected, allowing us to see plants in green. Without magnesium, chlorophylls in plants can not absorb light energy as the input for photosynthesis, which leads to no chemical energy produced at the end of this biological process, and causing plant starvation.

In the fall, leaves turn to different colors, such as red, yellow, brown and orange. This results from other pigments besides chlorophyll a, such as carotenoids (orange), anthocyanins (red). These are called accessory pigments that becomes dominant when trees stop producing chlorophyll a in the fall, as it begins to go dormant in anticipation of winter.

Water Movement

Besides playing major roles in many biological processes in plants as well as in building different types of molecules to provide nutrients and structure for plants, the amount of these nutrients in soil is essential to plants as it affect the ability to take up water in plants. Water movement in plants is determined by the water potential (Ψ_w) gradient; in other words, water tends to move from the area of high water potential to the area of low water potential. This driving fore, water potential Ψ_w, is mainly determined by solute potential Ψs and pressure potential Ψp: Ψ_{w =} Ψs + Ψp.

For water movement from the soil into the root, in most cases, it is controlled by solute potential. In the root with adequate amount of solutes, the solute potential decreases, which leads to the decrease in water potential overall. The decrease in water potential in the soil causes the gap in water potential between the soil and the root increases, a.k.a the water potential gradient increases. At this point, more water will diffuse into the root of the plant, and then move up the xylem (water channel in the plant, transporting the water from the root all the way to the tip of the plant). Therefore, it is necessary to have a decent amount of nutrients inside the root. With little amount of water, the root cell secretes ABA hormones that regulate the stomata at the leaves to close up, which leads to plant starvation which results from low photosynthesis rate due to the lack of gas exchange (CO2) into the leaves.

The nutrients are transported actively (the transportation of nutrients from the soil into the root requires energy) into the root with the assistance of proton pump on the root cell membrane. As the soil is less fertile, the proton pump activity increases, meaning more and more energy is invested in the proton pump. The process of transporting nutrients is expensive in energy, and the cellular respiration rate increases. Once the cellular respiration rate outweighs photosynthesis rate, the plants will be starved of food, which leads to several severe problems: lack of food for plants, insufficient reactants for biosynthesis,... Therefore, there is a great need to have large amount of nutrients in the soil to provide sufficient rate of water intake.

Effects on Soil Microbiome

The results are considered and calculated based on three main factors: count of soil microbes, metabolic activity of microbiome population and disease index. After the organic fertilizers are applied for at least three years, the disease index decreases significantly by 30%. At the same time, the population of microbiome as well as their metabolic rate increases markedly.

The research working on the effects of organic fertilizers on soil microbiome focuses on the soil nematodes, globally one of the most abundant and diverse invertebrate taxa, to indicate the function and biodiversity of soil ecosystems. At the food demand increases, the need of effective fertilizers rises in the past decade. However, at the same time, many studies show that fertilization can alter the function and diversity of microbiome where the fertilizers are in use. Particularly, the application of organic fertilizers over a long period of time "significantly increases total nematode abundance and diversity", while the short-term organic amendment application has a impacts greatly on the metabolic footprint.

Organic fertilizer provides not only minerals for plants, but also nutrients for microorganism. The biological relationship between plants and microbiome is mutualism - while the bacteria, fungus,... can get "food" from starch stored in root hairs, they need to carry out several activities (N fixation, P solubilization,...). The nutrients organic fertilizers provide for microorganism focus on the enzymes needed for these processes, such as protease assisting in breaking down sucrose,...

History

Compost bin for small-scale production of organic fertilizer

As people realize the importance of soil health and the preservation of our environment, organic fertilizers have entered the public view as means to enhance the soil quality and increase crop production. But organic fertilizer is not a recent innovation; rather, its history can be traced back to thousands of years ago. In the ancient China, animal wastes were main sources of organic fertilizers. In the ancient Egypt, the river of Nile, which was enriched in mineral ingredients, was the main source of organic fertilizers. People lived in the Roman Empire Columella had a variety of sources of organic fertilizers and summarized their applications in details. From the eleventh to thirteenth centuries, farmers in the western Europe relied on manure for plant nutrients. Although artificial fertilizers provide convenient and cheap choices for farmers to manage their lands in recent decades, organic fertilizers still play an important role in agriculture and crop production.

Statistics

By the data published by the United States Department of Agriculture (USDA), the consumption of organic fertilizers has increased since 1986 due to the growing demand of food for increasing world population and people's environmental consciousness. In the table below, the amount of consumption of several natural organic materials from 1986 to 2014 was listed in short tons. In 2014, 118,068 short tons of compost, 193,179 short tons of dried manure, 214,638 short tons of sewage sludge, and 234,701 short tons of other organic materials were consumed. Across the world, the trade market of organic fertilizers also has dramatically increased. In 2014, the world import value of selected organic fertilizers had reached $743.659 million and the export value was $876.794 million according to the data published by the Food and Agriculture Organization of the United Nations.

U.S. consumption of selected natural organic materials in material short tons

Year	Compost	Dried manure	Sewage sludge	Other organic materials
1986	8,968	88,976	42,647	52,676
1987	9,149	111,397	55,081	22,375
1988	17,610	124,066	39,802	18,432
1989	24,169	150,139	47,589	37,032
1990	30,713	146,420	58,672	57,762
1991	43,860	137,486	51,135	221,718
1992	29,628	149,225	112,771	206,433
1993	18,210	116,718	110,345	189,514
1994	23,793	115,950	74,590	172,241
1995	46,782	164,564	91,641	205,286
1996	61,889	114,822	99,502	251,474
1997	77,976	132,045	56,838	275,952
1998	74,873	125,443	82,961	263,643
1999	78,756	157,881	82,828	283,731
2000	88,124	160,680	152,740	234,227
2001	67,563	155,974	232,965	156,715
2002	86,146	156,870	92,814	200,942
2003	67,799	125,754	106,018	191,209
2004	80,149	154,455	58,450	213,922
2005	96,220	144,157	117,134	281,254
2006	104,166	168,805	84,824	217,988
2007	74,860	146,050	96,066	376,451
2008	133,126	188,751	87,425	256,680
2009	77,143	190,435	173,635	213,202
2010	43,327	140,137	96,556	211,617
2011	94,159	204,104	73,086	236,116
2012	170,071	175,738	110,876	228,391
2013	171,785	132,704	230,134	298,492
2014	118,068	193,179	214,638	234,701

Examples and sources

The main organic fertilizers are, peat, animal wastes (often from slaughter houses), plant wastes from agriculture, and treated sewage sludge.

Mineral

By many definitions, minerals are separate from organic materials. However, certain organic fertilizers and amendments are mined, specifically guano and peat. 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).

A large commercial compost operation

Peat, a precursor to coal, offers no nutritional value to the plants, but improves the soil by aeration and absorbing water. It is sometimes credited as being the most widely use organic soil amendment and by volume is the top organic amendment. Coir, (derived from coconut husks), bark, and sawdust when added to soil all act similarly (but not identically) to peat and are also considered organic soil amendments because of their limited nutritive inputs. Some organic additives can have a reverse effect on nutrients — fresh sawdust can consume soil nutrients as it breaks down, and may lower soil pH — but these same organic amendments may increase the availability of nutrients through improved cation exchange, or through increased growth of microorganisms that in turn increase availability of certain plant nutrients.

Rockdust is added to soil to improve fertility and has been tested since 1993 at the Sustainable Ecological Earth Regeneration Centre (SEER Centre) in Straloch, near Pitlochry, in Perth and Kinross, Scotland. SEER's research claims that adding rockdust to soil could increase moisture-holding properties in the soil, improve cation exchange capacity and better soil structure and drainage. It also provides calcium, iron, magnesium, phosphorus and potassium, plus trace elements and micronutrients. By replacing these leached minerals it is claimed that soil health is increased and that this produces healthier plants.

Phosphate rock is a non-detrital sedimentary rock which contains high amounts of phosphate minerals. Its concentration of phosphorus pentoxide (P₂O₅) is about 30%, of calcium carbonate is about 5%, and of combined iron and aluminium oxides is less than 4%. As of 2006, the US is the world's leading producer and exporter of phosphate fertilizers, accounting for about 37% of world P₂O₅ exports.

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. They may contain biological and chemical contaminations and are greatly impacted by the diet of the livestocks. Consequently, they need to be processed carefully and properly.

Most animal manure consists of feces. Common forms of animal manure include farmyard manure (FYM) or farm slurry (liquid manure). FYM also contains plant material (often straw), which has been used as bedding for animals and has absorbed the feces and urine. Agricultural manure in liquid form, known as slurry, is produced by more intensive livestock rearing systems where concrete or slats are used, instead of straw bedding.

Manure from different animals has different qualities and requires different application rates when used as fertilizer. For example horses, cattle, pigs, sheep, chickens, turkeys, rabbits, and guano from seabirds and bats all have different properties.^[1] For instance, sheep manure is high in nitrogen and potash, while pig manure is relatively low in both. Horses mainly eat grass and a few weeds so horse manure can contain grass and weed seeds, as horses do not digest seeds the way that cattle do. Cattle manure is a good source of nitrogen as well as organic carbon.Chicken litter, which consists of chicken manure mixed with sawdust, is an organic fertilizer that has been proposed to be superior for conditioning soil for harvest than synthetic fertilizers. It is highly concentrated in nitrogen and phosphate. Guano, the excrement of seabirds and bats, has a high concentration in nitrogen and phosphorus. However, the demand for guano may lead to the damage of bird habitats and cause histoplasmosis.

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^[1] fish meal, and feather meal.

Plant

Processed organic fertilizers include compost, humic acid, 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. There are two types of agricultural crop residues. Field residues are materials left in an agricultural field after the crop has been harvested, such as stalks and stubble (stems), leaves, and seed pods. They can increase efficiency of irrigation and control of erosion. Process residues are materials left after the crop is processed into a usable resource, such as husks, seeds, bagasse, molasses and roots. They can be used as animal fodder and soil amendment, fertilizers and in manufacturing.

There is some residual benefit of fertilizers as the crops take up a small amount of the nutrients two and three years later. Fertilizer placement can significantly affect the efficiency of crop uptake. The impact of residue placement (buried by tillage or left on the surface in zero tillage) on nutrient cycling and efficiency is under study.

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

Main article: Biosolids

Peat is the most widely used organic amendment.

Treated 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. It may not be acceptable components of organic farming and gardening, because of factors ranging from residual contaminants to public perception. 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, an organic fertilizer source

Animal manure is often a mixture of animal feces and bedding straw, as in this example from a stable

Biofertilizer

Biofertilizers and microbial inoculants are microorganisms applied to the seed, root, or soil of the plant to promote its health and growth. Three major groups of microbial inoculants are: arbuscular mycorrhiza fungi (AMF), plant growth-promoting rhizobacteria (PGPR), and nitrogen-fixing rhizobia. These microorganisms aid nitrogen-fixation, phosphorous solubilization, and synthesize substances that stimulate plant growth. The use of PGPR is shown to increase germination rate, root growth, product yield, and can be used to increase the uptake of nutrients from other fertilizers .

Others

• Alfalfa
• Ash
• Blood meal
• Bone meal
• Cover crops
• Fish emulsion
• Fish meal
• Raw Langbeinite
• Unprocessed natural potassium sulfate
• Wood chips/sawdust
• PROM
• Worm casting

Organic Fertilizer vs. Chemical Fertilizer

Organic fertilizers can be collected from animals and plants, which have undergone a natural process of decomposition. Due to the activity of beneficial bacteria and insects, organic fertilizers contain essential plant nutrients as well as abundant amounts of micronutrients.Organic fertilizer significantly increases the microbial population and soil enzyme activity compared to chemical fertilizer. It generates a higher crop yielding rate in the long term.

Chemical fertilizers are targeted to supply the essential elements plants need most, including the N-P-K on fertilizer labels (nitrogen, phosphorus and potassium). However, they can be used more flexibly than the organic fertilizers: as they are formulated, the fertilizers can focus on the ingredients as well as the nutrients that plants need. The application of chemical fertilizers, on the other hand, could eventually leads to the destruction of soil structure and surrounding environment and higher susceptibility of plants to diseases and pest.

Because organic fertilizer usually has a lower concentration of plant nutrients compared to chemical fertilizer, however, a larger amount of fertilizers needs to be applied and hence increases the cost of crop production. In order to minimize the damage caused by chemical fertilizers and maximize the benefits brought by organic fertilizers, an optimum approach is to apply a combination of both fertilizers. It is proven that such combination indeed would improve the soil quality.

Issues

Livestocks antibiotics

Organic fertilizers made from animal manures might potentially transfer livestocks antibiotics to vegetables. Human are directly exposed to antibiotic-resistant bacteria from the soil with the intake of raw vegetables, such as tomato, pepper, carrot, lettuce, and cucumber. From 1996 to 2010, there has been over 100 contaminated fresh produce outbreaks in the United States. Animal manures may be adulterated or contaminated with other animal products, such as wool (shoddy and other hair), feathers, blood, and bone. Livestock feed can be mixed with the manure due to spillage. For example, chickens are often fed meat and bone meal, an animal product, which can end up becoming mixed with chicken litter.

In order to avoid such contamination, high hygiene standards must be maintained by disinfecting the manure properly. For example, compost from animal manure must be applied for a certain period of time before harvesting the produce.

Environmental impact

The use of organic fertilizers to maintain the integrated nutrient management systems in soil helps with sustainable agricultural productivity but can also have negative effects on the complex system of biogeochemical cycle, run-off nutritions and eutrophication due to the low efficiency of use of external fertilizers by plants and long-term application. It is not only the chemical fertilizer that will be harmful, but also organic fertilizers, such as manures and composts, with N-rich materials and high extractable nutritions will affect nutrition level in soil in the long term.

Like most fertilizers, organic fertilizers introduce nutrients such as nitrogen, phosphorus, and potassium into the soil. The loss of nutrients from the soil causes environmental pollution. The leaching of nitrogen in the form of nitrous oxide and ammonia gas that causes ozone layer depletion, and acidification of neighboring soil and bodies of water. The run-off of nutrients to nearby bodies of water causes eutrophication, making the water unsuitable for supporting aquatic life. The application of manure and compost was observed to emit significantly more greenhouse gases (primarily methane) than chemical fertilizer counterpart over the same area.

The impact of fertilization on surrounding environment could be mitigated by controlling the frequency and amounts used. Multiple flooding and drainage of field can reduce methane emission in the use of manure. Using soil with better water-holding capacity and estimating the appropriate application rate of fertilizer can reduce runoff of nutrients that would pollute nearby bodies of water.

See also

• Biofertilizer
• Organic hydroponic solutions
• Reuse of excreta