MAKE EVERY DROP COUNT
SOME SIMPLE STRATEGIES FOR INCREASING GARDEN WATER EFFICIENCY
THE horrendous weather of the last week has shown that our once fairly predictable climate is never to be taken for granted again.
This earth is in the grip of life-altering climate change and we in Eastern Australia are experiencing what could become the norm for many generations to come.
The current drought coupled with last week’s maelstrom has really tested the ability of gardeners to keep a steady supply of moisture to their plants, particularly vegetable gardens, fruit trees, potted specimens, lawns, annuals and shallow-rooted perennials, and especially those that have been newly planted and are in the the throes of establishing a root system.
I know that if I don’t water my larger potted plants at least every two days at this time of year, they will begin to show signs of water stress, and that affects some part of their growth, flowering or fruiting, relative to the amount of stress they suffer.
Examples of symptoms of water stress and inconsistent watering in vegetables can be “bolting” to flower and seed in silverbeet, spinach, beetroot and lettuce, bitter taste in leaf crops in addition to “corkiness” in root vegies, and splitting/blossom end rot in tomatoes. In fruit trees, symptoms will include a loss of leaf gloss/shine, leaf droop and subsequent loss of foliage, flower drop, fruit shrivelling and blackening, sometimes splitting and/or dropping.
Soft-stemmed annual and perennial plants will usually wilt, become stunted and prematurely flower, and sometimes drop leaves as a sign of moisture stress, with woody perennial plants showing a lack of leaf lustre and a “hang dog” or drooping foliage effect when lacking adequate moisture.
In extreme cases, some woody shrubs and trees will shed foliage or even large branches in a last-gasp effort to reduce water consumption, with a few simply looking crook one day, and carking it the next.
Water stress in most plants usually leads to nutrient deficiency, which produces weak and sickly growth, leading to inevitable pest and disease attack.
Lawns display their unhappiness by rolling their leaves and turning the blades to a vertical position, to reduce their exposed surface area and subsequent loss of moisture.
So, what smart strategies can gardeners put in place to improve water efficiency in their gardens?
As I’ve mentioned in many previous articles, your soil is the key to supplying adequate water for the longest possible time between rainfall or irrigation events.
Good structure is the aim, and for new garden beds, it’s relatively easy to achieve compared to existing planted beds and lawns.
Structural improvement for new beds (clays right through to sandy soils) means good organic matter levels, through incorporation of composts and manures and to a lesser extent organic fertilisers.
Simply increasing the organic matter content in your soils by 1% will help to retain a whopping extra 17 litres of water in every square metre.
Gypsum (the finer the better) will also improve clay-based soils, but not sandy or loamy soils.
For existing beds with established plants, the best you can do to improve structure is to lightly tickle your materials into the surface (without disturbing too many plant roots) and cover with a good mulch.
Speaking of mulch, remember that a chunky mulch about 50mm depth is best to maximise infiltration of water into your soil surface, without the mulch soaking it up.
For vegie gardens, a finer mulch like chopped lucerne is best, but keep it to no more than 25mm depth.
Water efficiency in potted plants is improved by the quality of the potting mix in which they’re planted.
Many gardeners have made the mistake of buying cheap, pine-bark dominated potting mix to save money, but it drains so freely that on hot days the plants need two waterings.
So don’t be a cheapskate, buy a quality peat (or coir) based potting mix for the best water-holding properties.
The application of a layer of mulch (e.g. gravel, stones, lucerne) on the top of the potting mix will help save water as well.
For existing lawns on dodgy soils, coring during late dormancy (around late August or September in our region) followed by the application of fine composts or organic soil improvers, a fine organic fertiliser, and gypsum (only for clays, remember), then a light topdressing, will greatly improve the infiltration of rainfall/irrigation and the retention of moisture for a maximum amount of time.
The six-monthly application of one of my favourite products, soil-wetting granules, to garden beds, lawns and pots will help to get maximum moisture into the root zone as well.
Water efficiency can be built into your garden design as well.
In earlier articles, I’ve mentioned the concept of creating permeable gravel paths, lower than the surrounding gardens, that collect and slowly distribute moisture, as well as making depressions in mounded garden beds to collect and slowly percolate rainwater to the surrounding soil.
In addition, hedges and windbreaks are ideal design features that can slow and divert prevailing winds to reduce evaporation from your garden, as well as the thoughtful placement of shade-producing trees and shrubs to prevent direct sunlight warming and drying the surrounding soil.
Implementing some of these techniques may significantly reduce water usage in your garden.