An understanding of the physical, chemical and biological characteristics of a growing media can improve plant growth and the bottom line. This article looks at the characteristics of growing media and how these qualities can affect crops.
pH and Electrical Conductivity meters are extremely useful pieces of equipment used to measure and monitor basic chemical characteristics of water and growing media. Regular and correct calibration of this equipment is necessary to ensure the results are as accurate as possible. The following video describes the basic procedures for calibrating pH and EC meters.
Coir, coir fibre pith or coconut fibre is a one hundred percent natural, sustainable and renewable product. Coir is a ‘peat like’ byproduct produced from the processing of coconut husks, and is composed of the fibrous material found between the hard, internal shell and the outer coat of a coconut. Coir is lightweight, retains moisture and is an affordable growing media substrate or component for adding to growing media blends, producing stronger, healthier and more fibrous root systems.
Plant roots require air as well as water to remain healthy. The amount of air held within a growing media is referred to as Air filled porosity or AFP . Testing procedures for AFP aren't difficult and can be done at minimal cost with simple equipment built from readily available materials and a little bit of time. This video shows a process for carrying out a practical on-site air filled porosity test on growing media.
Knowing the amount of water held within a growing media, referred to as Water Holding Capacity (WHC) of your growing media can help you manage irrigation scheduling more effectively and ensure plants have adequate moisture.
Knowing the pH and Electrical Conductivity or EC of your growing media can help you to grow better and more consistent crops. Testing procedures aren't difficult and can be done at minimal cost. This video shows a process for carrying out a practical on-site pH and electrical conductivity
The ability of a growing media to take up water effectively once it has dried out is critical to the growth of plants and the ability of the media to become wet again. This is known as wettability. Testing for wettability isn't difficult and can be done at minimal cost with some basic equipment
The Water Holding Capacity (WHC) of a growing media measures the amount of water that a growing media can hold without causing plant stress. The WHC is largely determined by the amount and type of pore spaces available in the growing media, however the height and shape of the growing container also influences the growing media’s WHC (see Container Media Management; K. Bodman & Dr. K.V. Sharman which can be purchased from NGIQ). EcoHort guidelines recommend a WHC of greater than 40% (see EcoHort Guidelines from NGIQ).
Water retention efficiency (WRE) is a measure of the ability of a growing media to hold water applied from irrigation and this influences how long the irrigation must be run to wet up the media. An Australia wide survey
has shown that the WRE of commercially available growing media varies considerably, and suggests that the choice of growing media can influence water consumption and the quantity of nutrient runoff produced from a sprinkler or drip irrigation system.
Air filled porosity (AFP), water holding capacity (WHC), bulk density, shrinkage, wettability and water retention efficiency (WRE) are all physical properties of growing media that influence plant growth and ultimately plant health.
The pH measures the hydrogen ions in the growing media, while EC (electrical conductivity) measures the soluble salts in the mix. For optimal plant health, the pH and EC of the growing media should be in accordance with the plant’s requirements because different plants can have different preferred pH and EC ranges (see Container Media Management; K. Bodman & Dr. K.V. Sharman which can be purchased from NGIQ).
The pH measures the hydrogen ions in the growing media, while EC (electrical conductivity) measures the soluble salts in the mix. The pH and EC of the growing media should be in accordance with the plant’s requirements because different plants can have different preferred pH and EC ranges (see Container Media Management; K. Bodman & Dr. K.V. Sharman which can be purchased from NGIQ).
Understanding pH management starts with your choice of growing media components, the crops you choose to grow in them and how you intend on irrigating them. Currently there is a wide range of media components available to the nursery industry. They may include but are not limited to: pine bark, peat, coir, sand, perlite, vermiculite, absorbalite, peanut shell, rice hulls and the list goes on. Some decisions on which components to use are dictated by what is available locally and for some it may be the cost of the growing media landed on your property.
In last week’s article we mentioned briefly that nurseries should have the correct physical, chemical and biological properties in their growing media. The question is have you actually tested them on site? Listed in the back of “Container Media Management” by K.Bodman and Dr.K.V.Sharman, 1993. This is a complete guide for nurseries to analyse their growing media. It discusses the analytical methods for determining Air Filled Porosity, Total Water Holding Capacity, Wettability, Volume and Bulk Density, pH and EC (Electrical Conductivity), Toxicity Index and Nitrogen Drawdown Index.