The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmospheric, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmospheric nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.
Nitrification is the biological oxidation of ammonia to nitrite followed by the oxidation of the nitrite to nitrate occurring through separate organisms or direct ammonia oxidation to nitrate in comammox bacteria. The transformation of ammonia to nitrite is usually the rate limiting step of nitrification. Nitrification is an important step in the nitrogen cycle in soil. Nitrification is an aerobic process performed by small groups of autotrophic bacteria and archaea.
A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. Constructed wetlands are engineered systems that use the natural functions of vegetation, soil, and organisms to provide secondary treatment to wastewater. The design of the constructed wetland has to be adjusted according to the type of wastewater to be treated. Constructed wetlands have been used in both centralized and decentralized wastewater systems. Primary treatment is recommended when there is a large amount of suspended solids or soluble organic matter.
Ficus religiosa or sacred fig is a species of fig native to the Indian subcontinent and Indochina that belongs to Moraceae, the fig or mulberry family. It is also known as the bodhi tree, pippala tree, peepul tree, peepal tree, pipal tree,, ashvattha tree, or Asathu (ඇසතු) in Sinhala The sacred fig is considered to have a religious significance in three major religions that originated on the Indian subcontinent, Hinduism, Buddhism and Jainism. Hindu and Jain ascetics consider the species to be sacred and often meditate under it. This is the tree species under which Gautama Buddha is believed to have attained enlightenment. The sacred fig is the state tree of the Indian states of Odisha, Bihar and Haryana.
Nitrosomonas is a genus of Gram-negative bacteria, belonging to the Betaproteobacteria. It is one of the five genera of ammonia-oxidizing bacteria and, as an obligate chemolithoautotroph, uses ammonia as an energy source and carbon dioxide as a carbon source in presence of oxygen. Nitrosomonas are important in the global biogeochemical nitrogen cycle, since they increase the bioavailability of nitrogen to plants and in the denitrification, which is important for the release of nitrous oxide, a powerful greenhouse gas. This microbe is photophobic, and usually generate a biofilm matrix, or form clumps with other microbes, to avoid light. Nitrosomonas can be divided into six lineages: the first one includes the species Nitrosomonas europea, Nitrosomonas eutropha, Nitrosomonas halophila, and Nitrosomonas mobilis. The second lineage presents the species Nitrosomonas communis, N. sp. I and N. sp. II, meanwhile the third lineage includes only Nitrosomonas nitrosa. The fourth lineage includes the species Nitrosomonas ureae and Nitrosomonas oligotropha and the fifth and sixth lineages include the species Nitrosomonas marina, N. sp. III, Nitrosomonas estuarii and Nitrosomonas cryotolerans.
Nitrobacter is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria. The name Nitrobacter derives from the Latin neuter gender noun nitrum, nitri, alkalis; the Ancient Greek noun βακτηρία, βακτηρίᾱς, rod. They are non-motile and reproduce via budding or binary fission. Nitrobacter cells are obligate aerobes and have a doubling time of about 13 hours.
Neem cake organic manure is the by-product obtained in the process of cold pressing of neem tree fruits and kernels, and the solvent extraction process for neem oil cake. It is a potential source of organic manure under the Bureau of Indian Standards, Specification No. 8558. Neem has demonstrated considerable potential as a fertilizer. For this purpose, neem cake and neem leaves are especially promising. Puri (1999), in his book on neem, has given details about neem seed cake as manure and nitrification inhibitor. The author has described that, after processing, neem cake can be used for partial replacement of poultry and cattle feed.
In oceanic biogeochemistry, the f-ratio is the fraction of total primary production fuelled by nitrate. The ratio was originally defined by Richard Eppley and Bruce Peterson in one of the first papers estimating global oceanic production. This fraction was originally believed significant because it appeared to directly relate to the sinking (export) flux of organic marine snow from the surface ocean by the biological pump. However, this interpretation relied on the assumption of a strong depth-partitioning of a parallel process, nitrification, that more recent measurements has questioned.
Soil biology is the study of microbial and faunal activity and ecology in soil. Soil life, soil biota, soil fauna, or edaphon is a collective term that encompasses all organisms that spend a significant portion of their life cycle within a soil profile, or at the soil-litter interface. These organisms include earthworms, nematodes, protozoa, fungi, bacteria, different arthropods, as well as some reptiles, and species of burrowing mammals like gophers, moles and prairie dogs. Soil biology plays a vital role in determining many soil characteristics. The decomposition of organic matter by soil organisms has an immense influence on soil fertility, plant growth, soil structure, and carbon storage. As a relatively new science, much remains unknown about soil biology and its effect on soil ecosystems.
Aerenchyma or aeriferous parenchyma or lacunae, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, which allows exchange of gases between the shoot and the root. The channels of air-filled cavities provide a low-resistance internal pathway for the exchange of gases such as oxygen, carbondioxide and ethylene between the plant above the water and the submerged tissues. Aerenchyma is also widespread in aquatic and wetland plants which must grow in hypoxic soils.
Millettia pinnata is a species of tree in the pea family, Fabaceae, native to eastern and tropical Asia, Australia, and Pacific islands. It is often known by the synonym Pongamia pinnata. Its common names include Indian beech and Pongame oiltree.
Nitrifying bacteria are chemolithotrophic organisms that include species of genera such as Nitrosomonas, Nitrosococcus, Nitrobacter, Nitrospina, Nitrospira and Nitrococcus. These bacteria get their energy from the oxidation of inorganic nitrogen compounds. Types include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification: ammonia monooxygenase, hydroxylamine oxidoreductase, and nitrite oxidoreductase.
Mineralization in soil science is the decomposition of the chemical compounds in organic matter, by which the nutrients in those compounds are released in soluble inorganic forms that may be available to plants. Mineralization is the opposite of immobilization.
Dicamba is a broad-spectrum herbicide first registered in 1967. Brand names for formulations of this herbicide include Dianat, Banvel, Diablo, Oracle and Vanquish. This chemical compound is a chlorinated derivative of o-anisic acid.
Human impact on the nitrogen cycle is diverse. Agricultural and industrial nitrogen (N) inputs to the environment currently exceed inputs from natural N fixation. As a consequence of anthropogenic inputs, the global nitrogen cycle (Fig. 1) has been significantly altered over the past century. Global atmospheric nitrous oxide (N2O) mole fractions have increased from a pre-industrial value of ~270 nmol/mol to ~319 nmol/mol in 2005. Human activities account for over one-third of N2O emissions, most of which are due to the agricultural sector. This article is intended to give a brief review of the history of anthropogenic N inputs, and reported impacts of nitrogen inputs on selected terrestrial and aquatic ecosystems.
Chrysocephalum semipapposum, commonly known as clustered everlasting is a perennial shrub native to Australia. Clustered everlasting belongs to the family Asteraceae. C. semipapposum produces terminal flowers heads in clusters, mainly between spring and early summer with silver-grey appearing stems and branches. It grows up to 40cm high and 60 cm high, although there have been some varieties which can grow up to 1 m. C. semipapposum is often confused with Chrysocephalum apiculatum or 'yellow buttons', due to their similar appearances. C. semipapposum has 4 different subspecies, however they lack distinctive qualities and are often hard to identify. C. semipapposum is endemic to Australia and can be found in multiple states, most notably within Victoria. The plant is found in a variety of habitats including dry rocky regions. Clustered everlasting often grows sparsely and is rarely found in abundance and can be mistaken for a weed. Clustered everlasting has many uses, including as a source of nectar for butterflies, cut flowers or as an addition to a garden.
Nitrapyrin is an organic compound with the formula ClC5H3NCCl3, and is described as a white crystalline solid with a sweet odor.It is used as a nitrification inhibitor and bactericide, which is applied to soils for the growing of agricultural crops since 1974. Nitrapyrin was put up for review by the EPA and deemed safe for use in 2005. Nitrapyrin is an effective nitrification inhibitor to the bacteria Nitrosomonas and has been shown to drastically the reduce the amount of N2O emissions from the soil.
Nitrogen-15 (15N) tracing is a technique to study the nitrogen cycle using the heavier, stable nitrogen isotope 15N. Despite the different weights, 15N is involved in the same chemical reactions as the more abundant 14N and is therefore used to trace and quantify conversions of one nitrogen compound to another. 15N tracing is applied in biogeochemistry, soil science, environmental science, environmental microbiology and small molecule activation research.
Urine patches in cattle pastures generate large concentrations of the greenhouse gas nitrous oxide through nitrification and denitrification processes in urine-contaminated soils. Over the past few decades, the cattle population has increased more rapidly than the human population. Between the years 2000 and 2050, the cattle population is expected to increase from 1.5 billion to 2.6 billion. When large populations of cattle are packed into pastures, excessive amounts of urine soak into soils. This increases the rate at which nitrification and denitrification occur and produce nitrous oxide. Currently, nitrous oxide is one of the single most important ozone-depleting emissions and is expected to remain the largest throughout the 21st century.
Potassium thiosulfate, commonly abbreviated KTS, is an inorganic compound with the formula K2S2O3. This salt can form multiple hydrates, such as the monohydrate, dihydrate, and the pentahydrate, all of which are white or colorless solids. It is used as a fertilizer.
