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Grow Me Instead

There have been some interesting discussions over the past month on why certain plant species are being nominated for the Grow Me Instead (GMI) program. The GMI program has been rolled out in all states and territories, with Queensland being the last state to have published GMI booklets. Within the program there are established protocols for determining whether a certain plant species should be included in the local GMI booklets. The subject plant must satisfy the following criteria to be considered as a GMI candidate;

 

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Growing Media Calculating Air Filled Porosity In-house

Why do you need to know the physical properties of your growing media?? Having visited more than a couple of nurseries over the years it becomes readily apparent that there are as many growing media recipes as there are growers who use them. This may become an issue if a grower from one nursery decides that they prefer the growing media of another nurseryman or if a particular grower decides he wants to change their media for whatever reason.

 

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Chemical Properties of Growing Media

Last month’s article was concerned with the physical properties of growing media and how to go about analyzing these characteristics. This month’s article will continue this theme but will look at the chemical properties of growing media. Understanding the chemical properties and their possible interactions is actually quite complex. Hence this article will only touch on a few key points, other key areas such as the buffering capacity of mixes will not be covered in this article.

 

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Grow Me Instead – Launch for Darling Downs and South West

The Grow Me Instead project has provided a wonderful opportunity for the Nursery and Garden Industry to put our environmental credibility on show. It is a real feather in our cap to take this proactive stance on invasive plants; showing government and the community we care about the environment and are prepared to take positive action to reduce the impact of invasive plants.

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Water Retention Efficiency of Growing Media

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.

 

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Growing Media pH and EC Testing

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).

 

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Growing Media Water Holding Capacity & Wettability Testing

Water Holding Capacity Testing
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).

 

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Growing Media Air Filled Porosity Testing

The air filled porosity (AFP) of a growing media is the percentage of its volume that is air after being saturated with water and just after it has stopped draining. Below is the method used in the Australian Standard for Potting Media for testing AFP.

 

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Growing Media: The Benefits of Coir Fibre

Coir or coconut fibre is the fibrous material that exists in the middle layer (mesocarp) of the coconut fruit. The long coir fibres are extracted from the coconut husk and used in the manufacture of brushes, twine and other products, while the short fibres have been shown to have excellent physical properties which can contribute to significant growth benefits for nursery plants.

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Growing Media Workshops Held in Far North Queensland

In response to requests by production nurseries in Far North Queensland (FNQ) for industry hands-on workshops about the use and testing of growing media in production nurseries, two Growing Media Workshops were held in May 2013 in Cairns and in the Atherton Tablelands. Both workshops were presented by Thea Pobjoy, the Northern Queensland Farm Management Systems Officer (FMSO) for the Nursery & Garden Industry Queensland (NGIQ).

 

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Growing Media pH and EC Testing: Method (for soil-less growing media)

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).

 

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Growing Media Physical Properties

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.

 

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Growing Media Air Filled Porosity Testing

The air filled porosity (AFP) of a growing media is the percentage of its volume that is air after being saturated with water and just after it has stopped draining. Below is the method used in the Australian Standard for Potting Media for testing AFP.

 

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Growing Media Calculating Air Filled Porosity In-house

Why do you need to know the physical properties of your growing media?? Having visited more than a couple of nurseries over the years it becomes readily apparent that there are as many growing media recipes as there are growers who use them. This may become an issue if a grower from one nursery decides that they prefer the growing media of another nurseryman or if a particular grower decides he wants to change their media for whatever reason.

 

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Chemical Properties of Growing Media

Last month’s article was concerned with the physical properties of growing media and how to go about analyzing these characteristics. This month’s article will continue this theme but will look at the chemical properties of growing media. Understanding the chemical properties and their possible interactions is actually quite complex. Hence this article will only touch on a few key points, other key areas such as the buffering capacity of mixes will not be covered in this article.

 

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Growing media and Irrigation

Nursery irrigation should be applied at a rate that matches the ability of the growing media to absorb and hold the water that is applied. The best designed irrigation layout operated at the correct pressure cannot deliver the required efficiency if a significant portion of the applied irrigation is quickly draining through the growing media without being absorbed and held in the container. Ensuring the application of water matches the absorption rate of the growing media will take full advantage of the water holding capacity of the growing media. This application of water is known as the Mean Application Rate (MAR) and the past results from a national survey of over 200 nurseries showed an average MAR of 20.2 mm/h. Production nurseries should be seeking to achieve a MAR of between 5 & 12mm/hr, but there are many variables that can have an impact on the absorption rate such as the makeup of the growing media, the physical components, the air-filled porosity, the addition of wetting agents and polymer gels and scheduling techniques. A well designed premium growing media can greatly improve irrigation efficiency.