Isobutylidene Diurea 
An inorganic, controlled release fertiliser, supplying 38% nitrogen. It is a fertiliser created from the combination of urea and isobutraldehyde. It is slow release, typically being over a period of 3-months. Like many of these types of fertiliser, it creates a neutral reaction on a turf surface and overuse encourages annual meadow grass, weeds and earthworm activity. It might also be spelt with a space, i.e. Isobutylidenediurea, and is usually just referred to by its acronym of IBDU.
Law of Limiting Factor
A law proposed by Frederick F. Blackman in 1905 (‘Optima and Limiting Factors’, Annals of Botany, Vol.19, Issue 2, April 1905, pp281-296) which stated that a plant’s physiological process, in particular photosynthesis, respiration or growth, is dependent on several factors which limit its efficiency and effectiveness, with the factor with the least influencing value determining the rate of the physiological process. Light, temperature, water, nutrients, and air are all significant external factors which influence and limit plant growth. Internal plant factors might be chlorophyll content or ce
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Law of the Minimum
Often called Liebig’s law of the minimum, which states that plant growth (focusing on agricultural yield) is limited by the least available resource, which might be nutrients, water, light, temperature, etc. There might be an abundance of a range of plant nutrients, however, if one essential plant nutrient is lacking, for achieving high yield, then this will reduce (i.e. limit) the growth potential of the plant. A sufficiency of a resource will aid achieving maximum or optimum yields, whilst an inadequate amount of availability will reduce and limit yield, although this is frequently assessed
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Law of Tolerance
A law developed by Shelford (1911) which states that the success of an organism is dependent on a range of environmental conditions, having minimum, optimum and maximum values, which can be tolerated for successful development to take place. Optimum values for environmental conditions allow for good, strong plant growth and reproduction to take place, however, as conditions move towards minimum and maximum values then this increases stress placed on plants reducing their abundance and durability. Conditions with values outside of the maximum and minimum range, result in an intolerable environment in which the plants will be eliminated.
Liebig’s Law
Also called Liebig’s law of the minimum; see Law of the Minimum.
Ligand
An ion or molecule that binds a centralised metal atom into a structure called a coordination complex. Where several bonds exist with the central atom this will be called a chelate complex. Different chelates can be used for the binding of metallic atoms.
Liquid Fertiliser
A fertiliser which is supplied in concentrated form as a liquid. Liquid feeds are applied at heavier rates than foliar feeds and are absorbed through the grass roots. It is diluted with water and applied at an appropriate rate. It can also mean that a soluble solid fertiliser has been dissolved in water and then applied as a liquid feed. This is also referred to as a Liquid Feed.
Luxury Consumption
The uptake of a nutrient by a plant in greater amounts than it appears to need. Potassium is one such mineral nutrient where this appears to be the case. This could negatively influence plant growth by interfering with the availability of other nutrients.
Macronutrient
An element which is vital for plant growth in relatively large quantities. There are nine plant macronutrients. The first three are Carbon, Oxygen and Hydrogen, and these are easily obtained from air and water; whilst the other six macronutrients are Calcium, Magnesium, Nitrogen, Phosphorus, Potassium and Sulphur; these are obtained from the soil solution. These are also sometimes referred to as Major Nutrients.
Magnesium
A major plant nutrient, which is represented by the chemical symbol Mg. It typically forms the fifth highest percentage of any plant nutrient (excluding carbon, hydrogen and oxygen) within a turfgrass leaf, with a typical dry matter mid-range concentration being around 0.2%.
It is involved with photosynthesis, forming part of the chlorophyll molecule and therefore is essential for producing a green turf. It is an essential contributor to the synthesis of ATP, improves the efficiency of enzyme reactions and regulation, as well as cell pH regulation and helps maintains a suitable balance betw
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