As one person commented on the following story from TreeHugger.com:

The goal of most Organic or Natural farmers (I am not sure about the big guys) in the US is to improve the soil, and have a sustainable farm. Most of the methods were used for thousands of years, and were replaced with the quick fix.
The quick fix food does not feed us as well, degrades the soil over time (You need more and more nitrogen added as you kill the usefull fungi in the soil) and creates other problems like dead zones.

Quotes from TreeHugger:

Nearly One Quarter of World’s Farmlands Degraded
Prior data indicated that of the world’s 1.5 billion hectares of farmland, between 10-20% suffered from degradation. Now, after studying satellite imagery from 1981-2003, it is estimated that 24% of agricultural lands are degraded in some way.

The report points out that while tropical areas and developing nations have traditionally been connected with land degradation—nearly the entire nation of Swaziland has degraded soil—in the past 23 years, agricultural land degradation has spread in farther afield, with China, South Africa and Argentina experiencing increasing problems.

Sustainable Agriculture Needed to Combat Reduced Land Productivity
To combat this trend, the FAO recommends a “paradigm shift” owards sustainable agricultural practices, including government support for small-scale irrigation methods and greenwater technologies to combat land degradation.