Order

A taxonomic category that is used to group organisms. An Order is a grouping of similar families. Similar Orders are in turn grouped into a Class.

  Organic Matter [1]

The remains or waste product of living material. On the surface this may mean grass clippings or dying leaf sheaths; whilst in a soil this might be thatch, digested material within earthworm casts, or any decaying and decayed organic remains of plants and soil fauna. Increasing organic matter content within a soil increases the retention and release of nutrients (improved Cation Exchange Capacity), making for a more fertile soil.

  Osmosis

The movement of water from a region of a low concentration of dissolved salts (a source) to a region of a high concentration of dissolved salts (a sink). The movement is through a semi-permeable membrane (also called partially permeable) and aims to help dilute the higher concentrated solution so as to be in equilibrium with the source.

  Other IPM

Integrated Pesticide Management, which is the discriminate use of pesticides, which should focus on specific targeting of pests. However, instead of being an integral part of an acknowledged Integrated Pest Management process, pesticides are often used as short cut to control the present problem and this " perpetuates a "quick-fix mentality" that targets symptoms and fails to address the root causes of pest problems." (Source: Ehler, L. E., (2006), "Perspectives. Integrated pest management (IPM): definition, historical development and implementation, and the other IPM", Pest Management Science, 62(9):787-9)

  Overlap

The extent of how much a mower overlaps on each cut to reduce the chance of missing a strip of grass. This is the same meaning as Overlapping.

  Pale Grass

Usually a sign that the grass has limited nutrition, or water availability for healthy growth. This might also be a sign that the grass will soon attempt to set seed, in which case the leaves will turn yellow and die.

  Parasite

An organism that lives on or inside another organism (the host) which result in harm being caused to the host organism. One example is the parasitic Root Knot Nematode (Meloidogyne species) which feeds internally on a host organism, such as a leatherjacket grub.

  Parenchyma

One of the three main ground tissues (the others being Collenchyma and Sclerenchyma). These cells generally provide packing within a plant, forming tissues such as the pith and cortex. The cells can function as storage places for products of photosynthesis as well as for water. Some specialised parenchyma cells are formed within a leaf, the mesophyll layer, being called Chlorenchyma and include chloroplasts for photosynthesis. Other parenchyma cells within this layer are called the spongy mesophyll and function as a place for the exchange of plant and atmospheric gases.

  Parts Per Million

This is often used to indicate the concentration of elements within a plant or nutrients needed by a plant for adequate growth, for example, 30ppm of x-nutrient; or as a quantity of active ingredient within a pesticide above which there is considered an unacceptable risk, for example 80ppm of x. It is often referred to as PPM or ppm.

  Pathogen

An organism which causes a disease or disorder. Fungi are typical pathogens of turf. Pathogens might be specific a certain plant, or may only infect certain parts of a plant, root, leave or stem.