Soil feeds all plants, and plants, like us, require a large variety of nutrients, which the soil must therefore contain. Soil is immensely complex. Soil is a living complex biosystem, the most complex, diverse and poorly understood habitat on earth. If soil samples from only 2 cm apart are examined, they show many different microcomponents, which are even more diverse 1 metre away, and tremendously different 1 km away. Bacteria in soil help decomposition and maintain balance, and fungal activity may be even more beneficial than bacterial.
Pesticide use disrupts both.
There is a huge gap in our knowledge of soil microsystems, which scientists are not rushing to fill. Before destroying the soil with intensive agriculture, we need to understand it. Plant breeding and pesticide development have not included the below-ground impacts. For example, the most recent publication of Nature included a study from the University of New York that demonstrated that genetically engineered Bt corn leaks toxins through its roots. Build it and they will come.