Watering Vegetables Wisely
Everything is growing fast and temperatures are rising. Most veggies are thirsty, needing regular watering to produce juicy, tasty leaves or plenty of flowers for future fruit. How does the water-conscious gardener go about watering vegetables wisely to conserve water without depriving the plants, which would affect the yield and make them more susceptible to pests?
Mulching conserves the water in the soil, preventing the top layer from drying out and becoming hard. Here are some important mulching do’s and don’ts:
- Don’t make the mulch too thick, because it can suffocate plants and soak up the water, preventing it from reaching the plant. A layer of mulch should only be 1 – 2cm thick. The finer the mulch the thinner the layer. Rather have a very light mulch that is replaced often.
- Don’t pile the mulch up against the stems as this could cause them to rot and also prevent water from penetrating.
- Do mulch if grey-water is used. The mulch filters the solids out of the water.
- Do dry grass clippings before using them as mulch, otherwise they can form an impenetrable mat on top of the soil.
Rainwater can be harvested from homes with metal, corrugated iron, IBR or tiled roofs, via the gutters draining into a storage tank. Space permitting, opt for a 5000-litre tank. One or two heavy rainfalls will easily fill it. Where space is tight opt for slim-line 500-litre tanks. A 0.37kW pump provides enough pressure to run a sprinkler, handheld hose or even mist sprayers.
Water harvesting helps to make municipal water go a lot further.
Grey-water is wastewater collected from the shower or bath, hand basin, washing machine and, in some cases, from the dishwasher.
Do’s and don’ts
- Use grey-water within 24 hours, otherwise pathogens can develop.
- Use environmentally safe detergents.
- Wash vegetables that have been watered with greywater before use or just use grey water for fruiting vegetables rather than on leafy vegetables.
- Don’t use grey water exclusively. Supplement it with municipal or rainwater to flush away the residues from the grey-water.
Spongy soil minimises the amount of water that crops need, because every drop of water can penetrate to the roots and doesn’t run off. The more organic material in the soil, the better it retains moisture. Work well-rotted compost into the soil before planting.
More water doesn’t necessarily mean more flavour. The way you water can improve the flavour of tomatoes and other vegetables.
- Tomatoes should be well watered 2 – 3 times a week, while they are growing. Once the fruit starts to develop, reduce watering but not to the point where they wilt. The yield may be smaller, but the tomatoes will be tastier.
- Carrots, beetroot and other root crops taste better if grown in drier soil. This encourages the roots to penetrate deep into the soil looking for moisture and minerals, which produce a better flavour. Water root crops regularly for the first 3 – 4 weeks after sowing or planting, then taper irrigation to a minimum.
- Leafy crops, on the other hand, need plenty of water to prevent the leaves from becoming bitter. If there is a shortage of water, do not use a high-nitrogen fertiliser for Swiss chard, but rather a fertiliser with higher potassium (K) and and phosphorus (P). This encourages plant cell walls to thicken, enabling them to cope better in drought conditions.
Install a rain gauge. If there is less than 10mm rainfall then check the soil to see if watering is necessary. Less than 5mm of rain means that watering is still necessary. Don’t let the presence of puddles give you a false sense of security.
Over watering is as harmful as under watering. Check the moisture level of the soil every day, using the knuckle test. Test the soil by pushing your finger into the soil up to the first knuckle. The plants should be watered if the first 2 – 5cm of soil feels dry. Watering can be delayed by a day or so if the soil is still damp.
Know your soil type, because this determines the amount of time you need to water to achieve the best results. Test how long you can water before you start to see run-off. Clay soil should be watered in short bursts to allow the water to penetrate. Sandy soil drains fast and needs short, almost daily watering in hot conditions. Adding water retention granules will substantially reduce the need to water.
Group plants according to their water needs. For instance, plant veggies with deep roots (tomatoes, peppers) together because they like deep water less often than shallow-rooted plants (salad and leafy greens), which need less water more often.