What is the best soil type for sunflowers?

Just about any soil which drains well and is rich in macronutrients but poor in salt accumulation is the condition which sunflowers (Helianthus annuus) seek.

Specifically, this North American native plant accepts just about any combination of clay, sand or silt which does not leach nutrients on the one extreme or pool on the other. It does not tolerant nutrient loss, salt build-up, or waterlogging. It particularly flourishes with soils which already have, or which are fed, the six major nutrients calcium, magnesium, nitrogen, phosphorus, potassium, and sulphur.