Many gardeners find watering their vegetable patches a therapeutic activity, but with the prospect of a drier summer, we need to get watering right. The timing, frequency and quantity are key to success. At the same time, smallholders need to be more scientific so they don’t waste this precious resource.
This also applies to how we set out our growing beds and our means of watering. Use landscaping techniques to use less water.
It is particularly important that garden staff are made aware of the importance of watering correctly.
Irrigation systems have a reputation of wasting water. However, through correct design and application of irrigation systems within a garden, vegetable patch or orchard you will actually be saving water.
When to water
Take care not to start watering programmes too early in the spring. Plants will normally only flourish after the first good rains. Rather spend time improving your soil.
Water when the soil in the root zone feels dry. Don’t allow the plant to start wilting.
Late afternoon or early morning is the best time to water. If you have the luxury of an automated irrigation system, set it to water at dawn.
Avoid watering in the heat of the day, when there is much more water loss through evaporation.
Water less if the weather is cool and more when it is hot. In cool seasons plants need less water. In hot dry weather and when windy, all plants use more water.
Vegetables need short, frequent watering, and as a rule, about double the amount required by shrubs and flowers.
When there is good rainfall, you don’t need to water for a few days.
Make sure to water your seedlings when the weather is dry, because they have not developed a strong root system yet and will soon droop.
Avoid using high pressure sprinklers on seedlings as they damage the young plants and waste water.
How to water
Apply the water as close to the roots as possible.
It is better to avoid wetting the foliage. Wet leaves are more vulnerable to disease.
A watering can is most effective when you need to target the water carefully.
Water dry spots individually, so that you don’t waste water by watering a large area unnecessarily.
Water slowly. This means that you prevent runoff, but you still penetrate the root zone.
Drip irrigation is very effective when used on vegetables and fruit trees.
Over-irrigation usually leads to poorer quality vegetables.
You can tell that you have watered too much when the stem base of plants is soft and spongy and the roots become weak or diseased. The foliage might wilt or the leaves turn pale.
Over-watering leads to the absence of subsoil microbe populations.
The presence of fungal growth is also a symptom of too much water.
Where you have not watered enough:
- leaf edges turn brown;
- flowers fall off;
- stems show signs of wrinkles;
- leaves lose their shine and take on a bluish lustre or they suddenly become yellow or crispy.
Ideally you should aim at moistening the soil to a depth of about 150 mm.
Watering fruit trees
Dig a shallow trench around the tree. This catches and holds the water.
Water trees separately. Check regularly and water as soon as the top 20-30mm of soil is dry.
If you don’t have a large number of fruit trees this is worth considering: when you plant a tree, place a water pipe from the base of the tree roots to just above the soil surface. This means that when you pour water into this pipe, it will take the water directly to the tree roots. This prevents wastage.
Do not over water your fruit trees, as this reduces their life-span.
Watering vegetables in grow-boxes and containers
Be guided by the size of the container, as different sized containers need varied amounts of watering.
Water directly into boxes, bags or pots, rather than generally watering the whole collection of containers.
The soil in raised beds can become very hot on sunny days, so paying special attention to watering this kind of bed is vital.
Water according to your soil type
Different soil mixes require varied amounts of water.
Water clay soils in short bursts or very slowly. This prevents run-off. Clay soils also hold water for longer, so water less frequently.
Sandy soils absorb water quickly, but also lose the water easily. Add organic matter such as compost to sandy soil. This will increase soil water retention.
Loamy soils are best as they hold water around plant roots.
Mulching the soil around plants will hold water in the soil for longer.
Using grey water
There is a move to encourage the use of grey water in the garden as a means of conserving this precious resource. Grey water is the waste from your showers, baths, sinks, laundry and kitchen, but not your toilets. Grey water can indeed be used for irrigation, with the following cautions:
- Take the trouble to build a simple gravel-and-sand filter through which to pass the grey water before using. This will remove fats, oils and greases, hair and other small particles which in time will clog your soil, sprinkler jets etc.
- Do not use grey water on crops that you eat directly, eg leafy greens, fruit that is eaten unpeeled etc.
- Remember that soaps and detergents contain significant amounts of phosphates and nitrates which, dissolved in the grey water, turn it into a liquid fertilizer. Using too much grey water in any one spot, or using it for too long, will result in a possibly unhealthy imbalance of these plant nutrients building up in your soil.
To read other articles about growing vegetables and crops click here.