Tomato plants benefit from consistent soil moisture with a partial or slight dry-down of soil between waterings to ensure that soil is not consistently wet. The amount of dry-down between waterings should be kept consistent, as irregular moisture swings and dry soil can lead to problems such as blossom end rot and fruit splitting. See GardenZeus Solutions to Common Abiotic Problems with Garden Tomatoes for more information about these issues.
Water tomatoes at soil level. Avoid watering with sprinklers or wetting foliage, which may encourage disease, although it can be helpful to rinse tomato leaves occasionally to clear dust and particle pollutants that may inhibit photosynthesis. Avoid applying strong streams of water that erode soil and expose roots, which may encourage pests and diseases, and reduce yield. The best method for watering tomatoes is generally drip irrigation, which allows for deep infiltration of water over time.
As tomato plants mature, water progressively more deeply and less frequently, to the full estimated depth of roots to encourage deeper rooting and reduce competition from weeds. Young plants should be watered to a depth of a few inches, while older plants should be watered slowly and for periods of 10 minutes to an hour or longer, depending on plant size and soil texture, to wet the top 8 to 18 inches of soil. Tomatoes in loose, fertile soil may develop roots to a depth of 2 to 3 feet or more. Deep watering is particularly important in hot-summer areas; plants with deep roots will be more tolerant of summer heat, more productive, and less prone to pests and diseases. Avoid overwatering or keeping soil wet, which may encourage disease.
Root depth and water penetration in soil can be evaluated by pressing a long screwdriver or thin metal probe into soil and noticing when soil resistance changes as dry soil is reached. A shovel can also be pressed carefully into the soil outside or at the edge of an established plant’s root system to expose the soil profile and gauge depth of roots.
Established tomato plants may go 1 to 6 weeks or longer between deep waterings in cool-to-warm weather. Healthy tomato plants with deep root systems may go 3 to 10 days or longer between waterings in hot weather.
To view customized information for growing tomato in your area, go to GardenZeus and enter your zip code, then go to tomato.
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