The average amount of water that passes through a plant is extremely large.The water taken up by the plant from the soil is absorbed only by the young root ends that is, the root fibrils and hairs rather than by the whole surface area of the roots. Tomatoes need to mature quickly and the watering schedule should be as consistent as possible too little water will stress them out and can set them back beyond recovery.
Tomato Plants Require…
- Access to water 24/7 but not be over-watered
- Access to nutrients 24/7 without being over-fed
- Access to air (oxygen) in the root area
Watering Tomato Plants – The Wet/Dry Cycle
The usual advice is to keep compost or soil “just moist” and not too wet an almost impossible task especially on a hot day!The issue is that roots need both moisture and air not necessarily at the same time but roots will need air on a daily basis otherwise they will become diseased.The way to avoid the soil being too wet (saturated and air-less) over longer periods is to have a wet/dry cycle.This happens when, after watering, the soil is allowed to almost dry out, which allows air back into the root zone, between the soil particles.Of course if the soil should dry out completely, the plants will wilt.
Manual watering is always a bit “hit and miss” because plants use up moisture at different rates, depending on:
- light intensity
- air movement around the leaves
- amount of leaves a plant has
How Much Water To Give
Given that plants need enough water to get them through the day, but also need soil that contains air, here are a few tips for manual watering.
- Water mornings so that the entire soil area is fully wet, give it a thorough soaking!
- In the evenings, check to make sure that the soil, 5cm below the surface, is just slightly damp with your finger.
- If it is still wet, water less in the morning, if it is too dry, water more. Watering in the evening is best avoided because when temperatures drop at night, plants will be sat in cold water.
- On a hot day the soil will lose more moisture than on a cloudy, cold day.
If Soil Dries Out
The problem with watering a little and often when growing in soil, is that water will always find the quickest escape route. This may leave patches or pockets of dry soil beneath the surface. Roots in dry soil cannot absorb nutrients. This can lead to nutrient deficiency and result in Blossom End Rot which is caused by calcium deficiency. Irregular watering may also cause erratic growth and irregular fruit size. The stem thickness is a visual aid to the way a tall tomato plant has been fed and watered!
Over-Watering : You will often hear the words, “tomato plants need plenty of water” this is true when plants are mature and fruiting. Giving seedlings too much water can damage their roots. A common issue is over-watering, when air (oxygen) is removed from the soil, which becomes saturated, and roots become affected by disease. A plant with healthy roots will grow more quickly and produce a lot more tomatoes than a plant that has struggled because of receiving too much water and poor root growth. Too much water in the soil can also affect the taste of tomatoes.