|
item |
description |
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actual yield |
Yields reduced by the presence of weeds, pests and diseases for a least part of the growing season. Reducing factors may be counteracted by yield protecting measures, like weeding, and (biological or chemical) pest control. |
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assimilation |
Assimilation refers to transformation of carbon dioxide (CO2) and water (H2O) into CH2O (i.e. assimilates) as precursor for structural dry matter. This process requires energy from sunlight and O2 is produced as a by-product. Distinction is made between gross and net assimilation, the latter accounting for respiratory losses. |
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ATP |
adenosine tri-phosphate: energy rich compound, generated during the photo-chemical reaction within the assimilation process |
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bio-chemical reaction, dark reaction |
Last stage of the assimilation process during which energy-rich compounds, NADPH and ATP, from the preceeding photo-chemical process reduce CO2 into CH2O-components. |
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C3-crop |
Crop with C3-assimilation pathway, in which the enzyme rubisco acts as primary CO2-acceptor, forming a C3-component |
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C4-crop |
Crop with C4-assimilation pathway, in which the enzyme PEP-carboxylase acts as primary CO2-acceptor, forming a C4-component |
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CVF |
conversion factor (from assimilates to structural dry matter) |
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development |
Process which regulates dry matter partitioning among plant organs, as characterized by different developmental stages (a.o. emergence, flowering, fruitset, ripening). This process may be triggered a.o. by day length and temperature sums. Ambient temperature will affect the developmental rate. |
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FC |
field capacity (pF ~ 2) |
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Gha |
1 Gha (gigahectare) corresponds with the surface area of Canada. The earth surface measures 51 Gha, of which 29,2% (≈ 14,9 Gha) is covered by land. |
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GJ, gigajoules |
1 GJ = 109 J 6 GJ is about the amount of potential chemical energy in a barrel of oil when combusted. |
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growth |
Accumulation of dry matter within a plant, assuming favourable light and temperature conditions and light intercepting green leaves. |
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hectare, ha |
1 ha = 10 000 m2, which is an area corresponding to 1,5 soccer fields (=6 000 m2 according to Olympic standards). |
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HI, harvest index |
Expresses the part of total dry matter allocated to the main economic product. Presently, so-called crop residues also represent an economic value as an energy source, implying that the concept of harvest index becomes less clear. |
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Joule, J |
1 kJ = 240 cal, 1 kcal = 4,2 kJ. 1 Joule is the amount of energy released by a small apple falling 1 meter from a tree. The daily caloric requirements of an average person amounts to 2000 kcal = 8400 kJ. A dry slice of wholemeal bread generates 200 kJ. An average summer day in the Netherlands generates 200 kg of dry matter or 3,2 GJ per hectare, implying that the daily caloric requirement of one person is covered by just over 25 m2 (area of a small classroom or garden) |
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kWh |
1 kWh (kilowatt hour)= 3,6 MJ per hour, and as such refers to the amount of energy generated/consumed per unit of time. Commonly used to express electric power (e.g. engines, power generators). A 60 watt light bulb consumes 60 kWh of electricity over 1000 hours (i.e. in nearly 17 hours, a 60 watt light bulb consumes 1 kWh) |
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LAI |
Leaf area index (m2 leaf/m2 soil) |
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limited yield |
Yield limited by water and/or nutrient availability for a least part of the growing season within an environment free of weeds, pests and diseases. Limiting factors may be alleviated by introducing yield increasing measures such as irrigation and applying fertilizers. |
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LUE |
Light use efficiency: the amount of dry matter produced per unit PAR (g DM MJ-1 PAR) |
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MC |
Maintenance coefficient, depending on tissue composition to assess its maintenance respiration requirement |
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Mha |
1 Mha (megahectare) is roughly the surface area of Lebanon. The Netherlands measures roughly 4 Mha. (For other countries check wikipedia) |
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NADP(H) |
Nicotinamide adenine dinucleotide phosphate: energy rich compound with reducing power, generated during the photo-chemical reaction within the assimilation process |
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NIR |
Near infrared radiation (>800 nm) |
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NUE |
Nutrient use efficiency (expressed in different units, e.g. kg DM kg-1 Nutrient taken up) |
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PAR |
Photosynthetically active radiation (J m-2 s-1 400-800 nm) |
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photo-chemical reaction, light reaction |
Part of the assimilation process during which 4 H and O2 are formed from splitting H2O under the influence of light (i.e. photolysis). The energy-rich compounds NADPH and ATP are formed. |
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photoperiodism |
Crop characteristic which determines a.o. the onset of flowering, based on preceeding day length regime. Day-neutral plants are insensitive to daylength, whereas flowering of ‘long-day plants’ is induced by occurence of preceeding days, with light exceeding 12 hours. Likewise, flowering of ‘short-day’ plants is triggered by a period with short day light. |
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photorespiration |
The energy required to regenerate the enzyme rubsico to its initial form by removing O2. O2 competes with CO2 for attaching to rubisco. Less energy is left for assimilation. |
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photosynthesis |
Bio-chemical process in the chloroplasts of green leaves, by which water (H2O) and carbon dioxide (CO2) molecules are synthesized into carbohydrates (CH2O) and oxygen (O2), using light energy from the sun. Physical energy is chemically fixed in biomass as ‘bio-energy’. |
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potential yield |
Yield defined by ambient radiation and temperature, CO2-concentration in the air and the crop’s genetics. Supply of water and nutrients during the entire growing season is ample and in an environment free of weeds, pests and diseases.
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production situation |
Situation characterized by factors that influence crop production, resulting in potential, limited or actual yield levels. |
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PWP |
Permanent wilting point (pF ~ 3.5 – 4.2) |
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relation diagram |
Visual representation of a model with constituting elements and their relations used in system analyses and simulation of processes. |
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respiration |
The process in which energy is released by breaking down CH2O compounds, using energy, into CO2 and H2O. The energy is used in the maintenance of (living) phyto-mass or converting assimilates into more complex compounds like proteins and fats, to be incorporated into structural dry matter (a.o. leaves, stems, roots or storage organs) |
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SMC |
Soil moisture content (cm3/cm3) |
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SWP |
Ssoil water potential (hPa) |
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TAR |
Transpiration assimilation ratio |
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TC |
Temperature coefficient (as modifying factor to quantify respiration rate) |
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temperature sum, thermal unit |
The accumulative value of daily temperatures above a base temperature that triggers crop development (˚C) Crop characteristic which determines a.o. the onset of germination, leafing out or flowering, based on preceeding temperature regime. Crops may require a certain number of days below or beyond a threshold temperature to force a next development stage to occur. |
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transpiration |
The process by which water is lost as vapour when stomata are open, to enable exchange of CO2 inflow and O2 outflow during assimilation. As gas exchange generally occurs during the day time, transpiration rates increase with radiation load and temperatures, next to vapour pressure deficit. The positive side effect of this water loss is the cooling down of leaves, keeping enzyme-driven processes within acceptable temperature ranges. |
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VPD |
Vapour pressure deficit (kPa) |
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WUE |
Water use efficiency (expressed in different units, e.g. kg DM mm-1) |
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yield gap |
Yield difference between potential yield or rainfed water limited yield and actually realized yields, given ambient yield defining factors. |