Sunflowers’ deep taproot help to break the hardpan and produce roots in the lower subsoil zone. Drought tolerance is added to the mix through its ability to bring moisture up to share with companion plants that have more shallow roots. It, like Sunn Hemp, also promotes a Mycorrhizae that is very beneficial for plants growing with it and to the following crop. Mycorrhizal fungi are the hidden partner in the soil that helps plants take up more water and nutrients than they normally would be able to. This is most likely the main reason sunflowers are so good for your mixes.

Sunflowers attract and host beneficial insects, such as bees, with their beautiful, lengthy bloom. Birds love the seed while livestock and wildlife also benefit from them. 

One older farmer told me he was going to add sunflowers to his mix, simply because his wife enjoys seeing their beauty. So beautify your farm while improving your soil!