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May 2010

Welcome to the May 2010 edition of Fertile Minds, the newsletter of Sydney Environmental & Soil Laboratory.

In this issue we feature disturbing news that over-reliance on glyphosate for weed control can lead to nutrient deficiencies, and explore how to use saline irrigation water successfully.

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In this issue

• The Loam Ranger – Salinity classes of irrigation water – how can they be used?
• Glyphosate – over-reliance leads to nutrient deficiencies
• Plant disease stages
• Soil formation and the soils of Sydney
• Did you know ... ? – Tea

The Loam Ranger – Salinity classes of irrigation water – how can they be used?

Dear Loam Ranger,

I cannot get access to enough clean water for irrigation. All I have is groundwater with some salt in it. Can I still irrigate with it?

The good news is that it’s possible to irrigate with moderately saline water if you are careful.

Irrigation water is conventionally divided into irrigation suitability classes according to the salinity content, from class 1 (low salinity, suitable for all uses) to class 5 (extremely high salinity; emergency use only).

Classes 1 and 2 don’t require much thought, because the water quality is considered excellent and good, respectively. Class 5 water is pretty much regarded as emergency irrigation water only, and the use of water of this quality is strongly discouraged.

That leaves classes 3 and 4. So what are the special management requirements, techniques and considerations required for their use?

Click here for how to irrigate successfully with saline water (700 words, 3 minutes)

Glyphosate – over-reliance leads to nutrient deficiencies

Glyphosate is to weed control what penicillin was to disease control in humans when it was first introduced. But as over-reliance on penicillin led (inevitably, as we now know) to resistance in disease organisms, so over-reliance on glyphosate has led not only to resistance in several weed species, but also to the gradual lessening of nutrient availability to plants. Both trends have worrying implications for crop production worldwide.

Click here to read why glyphosate can cause nutrient deficiencies (700 words, 3 minutes)

Plant disease stages

By the time you notice disease symptoms on your plants, the pathogen (disease organism) has already gone through four stages unnoticed. The development of symptoms is the last of five stages in disease development: inoculation, incubation, penetration, infection and symptoms. Understanding these stages and allowing for them in your management plans can reduce the incidence of disease in your crop or turf.

Click here for the 5 stages and how to minimise disease spread (650 words, 3 minutes)

Soil formation and the soils of Sydney

This is our second article in an occasional series on the origin of soils. In our first article, we saw how a soil develops into a series of layers, called horizons. Here we look at the crucial effect of geology on soil formation, with the resultant effects on modern land use in Sydney.

Click here for the history of the Sydney Basin (950 words, 4 minutes)

Did you know ... ? – Tea

Tea is made from the leaves of Camellia sinensis (= Chinese camellia). When tea was first discovered as an edible plant is anyone’s guess, but it was probably first used in herbal medicine in prehistoric times. Prehistoric peoples may even have eaten the leaves as a stimulant. At some point someone discovered that the boiled leaves made a pleasing drink.

The first records of tea as a drink come from China, and date back over 3000 years. Over the millennia, different forms of tea emerged. All start from the same plant, but the way the leaves are processed determines the final flavour.

Click here for a potted history of tea (570 words, 2 minutes)