Tomato Acid and Soil

Soil Acidity and Alkalinity

• Soil acidity and alkalinity are measured in pH units expressed in a logarithmic scale from 0 to 14. Acidity indicates an increase in hydrogen ions; alkalinity with an increase of hydroxyl ions. The difference in balance between these two chemical processes affects how molecules interact in the soil. Most garden plants thrive in soil with pH between 6 and 7. Tomatoes prefer slight acidity.

Beneficial Soil for Tomatoes

• Studies at the University of California at Davis show that tomatoes grown in organically managed soil have 79 percent more flavinoid content than conventionally grown tomatoes. Soil enriched with mature compost balances the soil’s pH factor and brings it to the optimum range for nutrient uptake. Tomatoes thrive in garden loam mixed with mature compost. Backyard compost is easily made from lawn clippings, kitchen vegetable scraps, dried leaves and paper waste.

Compost

• Sandy or rocky soil has high alkalinity. Compost added to sandy soil improves water retention and increases the pH acidity for tomato growth. Compost should be mixed into the soil to a depth of 8 to 12 inches a week before planting tomatoes. It is also used as a fertilizer when tomato plants set their first fruit. Compost is a slow-release fertilizer that supplies nutrients as the plant needs them.

Soil Microorganisms

• There are between 100 million and 1 billion microorganisms in each teaspoon of healthy soil. Organisms such as bacteria, fungi, insects and small arthropods decompose plant and animal matter, cycle nutrients to plants and perform services related to water and oxygen distribution through soil. Tomatoes thrive in soil with the high microorganism content that results from use of mature compost. Tomatoes are able to resist harmful pest infestation and disease when grown in slightly acidic soil that contains a healthy, sizable microorganism population.