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- As promised, armchair gardening this week and its water and salinity and
what to do about it.
- We garden in a Mediterranean climate here, which has some unique
peculiarities. For instance rain that falls in winter and little in the warm
summer, when most plants want to grow. So in our climate plants have to make
the bulk of their growth in autumn and spring unless you supplement water in
summer. The reticulated water you are likely to use is already loaded with
salt of at least 700 parts per million so the more water you add the more
saline your soil becomes, due to its inherent clay structure.
- That is unless you mulch. Which is why Adelaide gardeners are obsessive
about the benefits of mulching their flower beds and vegetable gardens in
summer. It reduces water use, by cutting evaporation, creates less salt
toxicity to your plants and provides a cool root run. However most mulch has
almost no nutrient value whatsoever. So don’t think mulch is nutrient.
- Now given all that, the fertilizers that you use to feed your bedding
plants and vegetables, become more critical than if you were to garden in
Melbourne or Sydney. Water-soluble fertilizers leave salt residues in the
clay soils in this region that elsewhere would not be a problem. Now you can
either add lots of organic material to your soil to provide a salt stable
buffer or use water-soluble fertilizers with specially formulated nutrients
that don’t leave loads of salt residue.
- At the risk of committing horticultural hara-kiri in the market place,
commercial nurseryfolk know and use Vitall® as their water soluble nutrient
of choice, because, it can be applied as a foliar spray as well as in the
soil, so less nutrients get tied up in the soil because of pH extremes, like
iron in alkaline soil. Most importantly Vitall® can be used on all plants
including phosphate sensitive plants like our native plants. The other great
benefit is that it does not leave salt residues in the soil, like most other
nutrients sold to home gardeners.
- In this city we only get water to move down the soil profile for six weeks
starting next week, the rest of the year it is evaporating and creating more
residual salts in your soil and in your containers, which cause that tell
tale dry leave margin on tips and edges of your favourite plants. The only
reason salt laden water soluble fertilizers are sold in Adelaide is because
they are made for other markets!
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