How Much Water Do Tomatoes Need?
9 Dec
When growing tomatoes, getting the watering right is crucial for healthy plants.
Water thoroughly to encourage the tomato roots to seek water and nutrients deep in the soil. With an extensive, deep root system, the plants will hold up better during dry spells. When watering, soak the soil to a depth of at least 15-20 cm (6-8 inches).
- Water only when your plants need it. Tomatoes like moisture, but overwatering is harmful. You not only waste water, but soggy soil will prevent the roots from getting the air they need. If your plants look a little wilted on a hot, summer afternoon, that’s usually normal. They’ll perk up overnight. If plants are wilted in the morning, don’t wait — water them! (However remember that certain diseases can also cause wilting.)
- A thorough soaking every four to five days on light, sandy soils and every seven to ten days on heavy soils is a good general guide for irrigating if you don’t get enough rain.
- Water early in the day to cut down on evaporation losses and also to give your plants plenty of time to dry out. Wet foliage overnight may help trigger some diseases.
- With furrow irrigation, drip irrigation or soaker hoses, which all deliver water right at the soil surface and not on the leaves, you can water almost anytime. Try to avoid watering at midday though, because that’s when evaporation losses are highest.
- Trickle irrigation is the most easily controlled method of irrigation. The equipment is expensive, but is long lasting and saves growers time. It can also be scheduled to deliver constant amounts of water, which can help reduce the incidence of fruit cracking.
- Use mulch to reduce evaporation, improve water spread and uptake by the plants and reduce disease caused by rain and water splash.
If water is applied in a narrow band (through trickle irrigation) on sandy soils, the water will seep in quicker and deeper than on a heavier soil. On loams and clay, the water spreads out more and requires larger amounts to reach the same depth. Excess water on a sandy soil could leach below the area where most of the roots are found. Leaching water is also likely to take some soil nutrients with it, especially nitrogen. This means you will need to add more fertiliser than if your soil was loamy.
Full details on calculating exact watering requirements (how much, how often for size of plot) plus how to set up a simple irrigation system are provided in our book How to Grow Juicy Tasty Tomatoes.