In a recent blog, Jake Mowrer, assistant professor and extension specialist at Texas A&M, tells us that the commonly held belief that the soil naturally provides everything a plant needs is incorrect, and that plants work hard to modify the soil to improve their chances of survival. 

"The soil is not a very welcoming environment for plant growth. It does not provide everything a plant needs freely and without reservation," he says. "In fact, left as is, the soil probably would not produce very many plants at all. Proof of this is found in the tremendous amount of soil modification plants engage in just to improve their chances of survival."
He goes on to explain how different root structures represent different survival strategies. For example, he says, "Taproots represent a survival strategy that relies on access to water nutrients held deeper in the soil. Fibrous roots represent a strategy that emphasizes exploration of soil closer to the surface and increased overall contact with soil particles to acquire nutrients with low mobility. The portion of the soil most explored, the depth, and the lateral reach of a plant's root system all affect how different plants physically modify soil in different ways."
To learn more about how different plant root architectures affect the soil, read his entire blog.