March 2009

Welcome to the March 2009 edition of Fertile Minds, your source of everything soils.

In the last issue we met Issy, who is the first point of contact when your samples arrive at the lab. In this issue we meet Andrew, Jesse, Josh and Harry, who take your samples through the next step on their tour through the lab.

If you have any questions you would like answered in Fertile Minds, please write to info@sesl.com.au. If you have any special requirements, we would be pleased to talk with you and tailor a package and price. Please contact the office on (02) 9980 6554 or write to us at info@sesl.com.au.

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In this issue

• The Loam Ranger – Regulated deficit irrigation
• Waste reduction and avoidance
• What is cation exchange?
• Meet the staff – the Prep Lab
• Did you know ... ? – Reducing methane emissions with kangaroo microbes

The Loam Ranger – Regulated deficit irrigation

Dear Loam Ranger,

The drought is worsening and I recently read that irrigated rice planting in Australia had dropped by 93%. So how do we make our limited water resources go further?

Working smarter rather than harder can help. By scheduling irrigation to the periods when plants actually need the water, and by restricting the amount applied to less than luxury amounts, we can achieve the same yields with savings of up to 30% water. This practice is called regulated deficit irrigation, or RDI.

The CRC for Viticulture, in Adelaide, defines RDI as the use of irrigation to maintain plant water status within prescribed limits of deficit for part of the growth cycle of the plant. Mild to moderate plant moisture stress is allowed to develop at growth stages at which it has little or no effects on production. The ideal aim is to restrict plant growth while increasing harvestable yield, at the same time as improving water use efficiency.

Click here to find out how RDI works in practice (350 words, 2 minutes)

Waste reduction and avoidance

Waste disposal is wasteful:

• It costs you money.
• It makes potential resources unavailable for other purposes.
• It costs energy for no gain.
• It puts potentially harmful substances in a position where they could enter the environment.

The 3 R's

For many years now we have been encouraged to Reduce, Reuse, Recycle:

Reduce our use of resources. If a process can be performed with less input, it makes economic sense to do so, and this brings the added benefit of releasing resources, such as soil and water, for ecosystem functions.

Reuse materials instead of replacing them. For example, bricks, timber and tiles salvaged from demolished buildings can be reused more or less as is. Because they are not being made anew, their cost is obviously going to be less. This reduces society’s reliance on raw materials and our release of greenhouse gases.

Recycle materials into new materials. A good example is aluminium, which can be melted down and made into new products for only 1/10 of the cost of making new aluminium from bauxite. It makes economic sense, and it has broader benefits in reducing the release of pollutants from smelters.

To these we can add Avoid. If we don’t need something, why make it or pay for it?

Click here to read about how legislation governs waste disposal in NSW (650 words, 2 minutes)

What is cation exchange?

In a previous article we’ve discussed cation exchange capacity, or CEC, and why this is critical to the availability of plant nutrients in soil. In this article we look at how it works.

Surface adsorption

The surface of a clay particle or organic colloid is negatively charged. Therefore, it attracts and adsorbs positively charged ions, or cations. These cations can be exchanged between the particle surface and the soil solution. In solution they become available to plant roots.

The most important exchangeable cations are aluminium (Al³⁺), calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), ammonium (NH₄⁺), sodium (Na⁺) and hydrogen (H⁺).

To become available to a plant, a cation adsorbed on a soil particle must be replaced by a cation present in the soil solution (to balance the charge). Plant roots facilitate this process by excreting H⁺ into the soil solution. This displaces a cation and simultaneously acidifies the soil. The cation is then freed to be taken up by a root.

Click here to read about clay dispersion and ionic size (500 words, 2 minutes)

Meet the staff – the Prep Lab

In last month’s issue we met Issy Purwanto, who is the first point of contact for your samples at the lab. After Issy enters all the details in the system, the samples go off to the Prep Lab. In this article we meet the technicians there who prepare your samples for analysis and run the first tests.

What we refer to as the Prep Lab in fact consists of four separate rooms, each equipped for different tasks, dependent on the tests you specify.

Currently we have four technicians working in the Prep Lab. Although their responsibilities overlap and all can substitute for one another, each one looks after a particular area.

Meet Andrew Sheldon, Jesse Fenn, Josh Shaw and Harry Leake.

Click here to read about how your samples are prepared after arrival (600 words, 2 minutes)

Did you know ... ? – Reducing methane emissions with kangaroo microbes

Cattle and sheep in Australia account for 11% of Australia’s total greenhouse gas (GHG) emissions. Bacteria called methanogens in the rumen break down otherwise indigestible plant matter, releasing compounds that the animals can digest, but also releasing methane as a waste product. Not only does this contribute to global warming, but it also represents a 15% loss of energy, which equates to farm income.

Two solutions have been proposed. The first is to get rid of the cattle and sheep and to farm kangaroos. We’d all be a lot healthier not eating saturated fats, and the removal of the hard hooves from Australia’s fragile soils would reduce soil erosion and nutrient loss. The other solution is to replace the bacteria in the cattle’s and sheep’s rumens with the bacteria from kangaroos’ fore-stomachs.

Click here to read about the latest research into gut microbes (and farts) (550 words, 2 minutes)