For best growth, keep the soil in the root zone moist enough to prevent wilting of tomatoes. This is especially important soon after transplanting when the plant is transitioning to garden conditions. Garden tomatoes will generally require 1 to 1.5 inches of water per week, but this number can change according to environmental conditions and plant size. Managing water in garden tomatoes is based on knowing the rainfall received on your site and then applying water if rainfall is not sufficient.
Most years in Tennessee there will be periods of the spring, summer and early fall when rainfall is insufficient or inconsistent for the best tomato plant growth. Tracking the volume over the season will help make irrigation practices more precise. When irrigating, it is best to apply 1/2 to 3/4 inch of water twice a week rather than the full amount in one irrigation event. This will reduce runoff and provide more consistent soil moisture but provide enough water to wet the soil for several inches. Likewise, it is best to deliver irrigation to the root zone of the plants through trickle or drip irrigation rather than overhead watering. Drip irrigation will be more efficient in water use and will keep the plants leaves dry. Soaker hoses are also common in the home garden and deliver water directly to plant roots. They can be purchased or constructed from used garden hose.
Soaker hoses can be cost-effective and versatile in the garden, but they do not deliver water as evenly as drip irrigation lines. If sprinkler irrigation is the only option, apply at a time when leaves will dry before nightfall to lower the risk of leaf disease.