Fertilizer lexicon

Agriculture has its own nomenclature, commonly spoken by agronomists. Sometimes the exact meaning of a technical term cannot be found easily. Our Fertilizer Lexicon helps finding the definitions of the most common keywords in connection with fertilization.
  • A
  • B
  • C
  • F
  • G
  • H
  • L
  • M
  • N
  • O
  • P
  • S
  • T
  • V
  • W
    A
  • ADR

    The Agreement concerning the International Carriage of Dangerous Goods by Road (ADR) was signed at Geneva on 30 September 1957 under the auspices of the United Nations Economic Commission for Europe. The agreement is about the packaging, labelling of dangerous goods and also provides information about the minimum requirements for vehicles transporting dangerous goods.

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  • Antagonism

    An excess of a particular plant nutrient can cause deficiency of another. This can happen when two elements have similar size and charge. For example can an excess of iron block manganese, magnesium can block calcium (or the reverse). 

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  • B
  • Bulk blend

    Bulk blend is a physical mixture of different fertilizer granules containing different nutrients. The size, shape and weight of the different nutrient granules differ from each other, which can cause segregation during transport, storage and spreading. Spreading pattern of bulk blends is worse than that of a COMPLEX fertilizers and distribution of nutrients is not as homogenous.


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  • Biuret content

    Biuret is produced by pyrolysis of urea and its content in fertilizers is limited.

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  • Base fertilizer

    The basic or basal fertilization provides enough nutrients for a good start of the vegetation. It is commonly applied as COMLEX NPK fertilizer before planting of the crop. 

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  • Base saturation (BS)

    The BS is related to CEC and expresses the percentage of CEC occupied by cations. The availability of cations (bases, Ca2+, Mg2+, K+ ) increases with increasing BS.

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  • Biological nitrogen fixation (BNF)

    Bacteria, often in relationship with legumes, carry out nitrogen fixation. This is the reason why legumes do not need much nitrogen fertilization but instead are a favourable environment for the formation of root nodules. 

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  • C
  • Crush strength

    Crush strength indicates how much pressure is needed to break a granule. This is a predictor for degradation due to transport, storage and spreading. Low crush strength can cause granules to break and therefore dust content will increase in the bags. If crush strength is low, then granules will break in the bottom of the big bags especially in the case of multi-level storage. The normal crush strength of fertilizer granules is between 18-27N. 

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  • Compacted fertilizers

    The compaction technology uses high pressure without chemical reactions to produce complex granules. After crushing, grinding and homogenization of the various ingredients, they are pressed to 2-7 mm particles. The particles receive a surface treatment, which prevents them from sticking together during storage. All granules have the same chemical composition and physical properties. Therefore, they have a more uniform spreading pattern than bulk blends.


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  • Cation exchange capacity (CEC)

    CEC shows the soil’s ability to hold and supply nutrients. Negative charges on clay and humus are responsible for holding and exchanging positively charged cations like Ca2+, Mg2+, K+, and NH4+. The higher the CEC the more cations can be held in the soil. 

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  • F
  • Foliar fertilizer

    Foliar fertilizers are applied on the crop’s leaves. This facilitates a quick uptake and correction or prevention of deficiencies during the crop development. 

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  • Fixation

    Some nutrients (in particular phosphate) can be fixed to other soil minerals forming in-soluble compounds. For instance, phosphorus is fixed to calcium phosphates at high soil pH and to iron (Fe) and aluminum (Al) compounds at low soil pH. 


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  • G
  • Granulometry

    Granulomentry describes the particle size distribution. It is expressed as a number that quantifies how much variance exists between particles in a given sample. The lower the number, the more uniform the sample. The granulomteric spread index is calculated with the following form:


    ((d84-d16) / (2Xd50) ) X 100

    Where d84 and d16 means the diameter of mass fraction at the 84% and 16% percentile level and d50 is the median diameter of the sample.


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  • H
  • Hydrolysis

    The hydrolysis of urea is an enzymatic reaction where urea and H2O are hydrolysed to CO2 and NH4 (NH3). 

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  • Haber-Bosch process

    Ammonia, which is the starting molecule for all nitrogen fertilizers, is synthesized using the Haber-Bosch process. The process converts atmospheric nitrogen (N2) into ammonia (NH3) through a reaction with hydrogen (H2). The main hydrogen source is methane (CH4) from natural gas. 

    The synthesis of ammonia had an enormous impact on mankind and is often hailed as the most important invention of the 20th century. Both inventors Fritz Haber and Carl Bosch received the Nobel prize.

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  • L
  • Leaching

    Leaching is the transport of nutrients with rainwater into deeper soil profiles and finally into groundwater. Anions (NO3-, SO32-) are particularly susceptible to leaching but also cations (Ca2+, K+) can be lost due to leaching. 

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  • Liming

    Means the application of calcium- and magnesium-rich materials such as limestone powder. This is done to increase the soil pH (reverse acidification) and to supply Ca and Mg.

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  • M
  • Microelements

    Nutrients which are essential for plant growth in only very small quantities are called microelements. The elements are boron, chlorine, copper, iron, manganese, molybdenum and zinc. Avoiding deficiency of a microelement is equally important as avoiding a macro element deficiency. 


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  • Mixing of fertilizers

    Some chemical reactions need to be considered when mixing fertilizers. For instance insoluble compounds can be formed when calcium cations are mixed with phosphate or sulphate anions.

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  • Mineralization

    Plants take up nutrients in mineral form. In plant tissue, the nutrients (elements) are integrated in organic molecules. In order to become plant available these organic compounds need to be mineralized. Mineralization is an aerobic or anaerobic degradation process (decomposition). 


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  • N
  • Nitrogen forms

    The nitrogen in fertilizers is commonly described as:


    a. Nitrate (NO3-): Mainly nitrate is present in aerated arable land, this is available for direct plant uptake.

    b. Ammonium (NH4+): Causes soil acidification but is also available for direct plant uptake. 

    c. Urea (CH4N2O): Needs to be converted to NH4+ and/or NO3- to become plant available for uptake. This process is called hydrolysis. 

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  • Nitrogen immobilization

    Plant residuals such as straw can accumulate in the soil without decomposition. If there is too much plant residual with a low nitrogen content left in the soil, the carbon-to-nitrogen ratio increases. As microbes and plants compete for the nitrogen, a C:N ratio higher than 25 causes N immobilization in microbial biomass. Nitrate fertilization corrects the C:N ratio and avoids nitrogen deficiency in crops

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  • Nitrogen use efficiency (NUE)

    This important indicator describes the efficiency of applied nitrogen. It can be expressed as percentage of fertilized nitrogen taken up by the crop or as units of grain harvested per unit of N fertilized.


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  • O
  • Odda process

    The Odda process is named after a municipality in Norway and is also called the nitrophosphate process. In this process phosphate rock (Ca5(PO4)2OH) is acidified with nitric acid (HNO3). The products are phosphoric acid (H3PO4) and calcium nitrate (Ca(NO3)2). These are base materials for the production of fertilizers. Compound fertilizers (COMPLEX, NPK) are produced by adding potassium chloride (MOP, KCl) or potassium sulphate (SOP, K2SO4).

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  • P
  • Plant available P content

    Most of the phosphorus in our NPK fertilizers is water soluble and a smaller fraction is soluble in neutral ammonium citrate. Both fractions are availbale for the plants. The water soluble proportion is immediately available, while the neutral ammonium citrate soluble proportion becomes plant available in an acidic environment such as rhizosphere (near the plant roots). This proportion is less susceptible for P-fixation and still available for the crops.  


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  • Particle shape

    Fertilizers can have different granule formats, from perfectly round to amorphous shapes. It is an important factor for product handling. A round shape is always better to store and transport because amorphous granules with jagged-edges can break more easily forming dust in the bags. Premium fertilizers have round shaped granules.

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  • Prilled fertilizer

    Prilled fertilizers have smaller granules and are not as homogenous as granulated ones. Prills are not round shaped, have pointed edges and therefore this fertilizer format is prone to dust formation. Prilled fertilizers have better heat tolerance then granulated ones.

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  • Passive and active nutrient uptake

    There are two types of mineral absorptions based on the involvement of metabolic energy. Wheras passive absorption does not require metabolic energy, active mineral absorption does require metabolic energy. Active absorption works along and against the concentration gradient. 

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  • S
  • Spreading pattern

    Uniform distribution depends on even fertilizer output from the disc and overlapping between two passes (out and back) of the broadcasted fertilizer granules.

    To test the regularity of fertilizer spreading, the actual dose of fertilizer spread over the projecting distance is measured and the curve of the spreading profile is plotted. Spreading regularity is expressed in coefficient of variation (CV), which quantifies the average deviation of doses applied in relation to the mean dose and is stated as a percentage. CV, as defined in European Standard 13739, is the ratio between the standard deviation and the mean total distribution.

    The lower the CV, the better the distribution. The quality of fertilizer distribution is expressed as follows:

    * A CV between 0% and 10% is good

    * A CV between 10% and 15% is medium

    * A CV above 15% is poor Is this chart correct, UK works on the following ratings; <10% is excellent, 10-15% is good, 15-10% is poor and >20% is unacceptable.

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  • Surface area and volume

    An important ratio is the surface area compared to the volume of a fertilizer. If granules have a bigger surface, contact with the soil is increased which gives a faster delivery of active ingredients. Smaller granule sized materials have a bigger total surface and have a higher surface area: volume ratio.


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  • S content

    Sulphur trioxide (SO3) is the oxide form and S the elemental form of sulphur. The content of S is multiplied by the factor 2.5 to convert to SO3. 


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  • Salinity index

    Fertilizers consist of salts and in soil solution they have a different salinity or salt index. Different fertilizers are compared to the salinity of sodium nitrate (NaNO3) which has an index of 100. 

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  • Soil erosion

    Erosion is a process of losing soil by wind-, or water-transport. 

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  • T
  • Theory of minimum

    The German botanist Philipp Carl Sprengel (1787-1859) formulated the “Theory of Minimum” in agricultural chemistry. This means that the growth of plants is limited by the element that is relatively at scarcest supply. The scarcest resource is also termed minimum factor. Therefore, it is essential that all nutrients must be supplied in appropriate amounts.


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  • V
  • Volatilization

    Voltatilization is the conversion of a chemical into gaseous form. Ammonia (NH3) volatilization is one of the main nitrogen loss mechanisms. Surface application and a high soil pH foster the ammonia volatilization. The hydrolysis of urea causes a temporarily increase in soil pH and therefore urea is particularly susceptible to volatilization losses.

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  • W
  • Warm granulated fertilizers

    This is the modern technology of producing fertilizers. Each and every granule contains all nutrients of the fertilizer type. Each granule of our COMPLEX fertilizers contains nitrogen, phosphorus and potassium. The benefit of this format is the equal spreading and homogeneous distribution of nutrients in the field. Some nutrients, for example phosphorus, are not mobile in the soil. Only complex fertilizers facilitate a dense distribution of phosphorus which is particularly important for the early crop development.

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