Growing Vegetables and Fruits in the Red Clay Soil of the South

Red clay soils are technically categorized in US soil taxonomy as Ultisols.¹ Ultisols are strongly acidic soil varieties, having a pH often below 5.0. Although red clay soil is stable (and thus well suited for forestry and construction) it needs amendment in order to yield fine crops of vegetables and fruit. Fertilizer and lime are needed to increase nutrient levels and attenuate pH. Other materials may be added to improve texture and drainage.

Geology and Ultisols

What is the source of the red coloration of Ultisols? Soil Taxonomy (1975), published by the USDA Soil Survey Staff, says, "Well developed red color is one indication that the soils are relatively old or at least that the soil material has been subjected to relatively intense weathering for a considerable time." Weathering occurs where the climate tends to be hot and humid, leaching out calcium, magnesium, and potassium. Since all three of those minerals are essential to the growth of vegetables, and all are alkaline, fertilization and the increase of soil pH are essential.

Why Add Ingredients Other than Lime and Fertilizer?

Other problems relate to particle size. Weathered particles are smaller particles, so the soil tends to be rich in clay. The soil more readily packs, and moisture collects and doesn't drain efficaciously. The texture may be increased through the addition of peat, compost, and sand. Not only does drainage improve by so doing, but aeration as well. Of course compost is a fertilizer unto itself and adds nutrients.

Which Fruits and Vegetables Do Well?

Presumably, crops that are grown in abundance are crops that grow well in an area. For the state of Virginia, some of the top crops grown, including vegetables, are soy, tobacco, hay, cotton, wheat, peanuts, barley, tomatoes, and corn. Also grown abundantly are potatoes, snap beans, and cucumbers.² Fruit trees and vines do well, also. For the state of North Carolina, most of the vegetables and fruits doing well in Virginia do likewise in North Carolina. Some specialties are sweet potatoes, blueberries, peaches, and strawberries. Georgia-further south and hence warmer-decreases on a few of the above foods, but makes up for it by adding pecans, watermelons, and oats.³

¹ Ultisols are given five sub-categorizations: Aquults, Humults, Udults, Ustults, and Xerults. The southern states come almost completely within the Udults sub-category.
² Netstate: Virginia - Virginia Economy
³ Crops listed for North Carolina and Georgia are taken from the respective Netstate web site pages.

References and Resources:

University of Idaho, College of Agricultural & Life Sciences, Soil & Land Resources Division - Ultisols
USDA Natural Resources Conservation Service - Ultisols Map