Recently, Successful Farming published a feature article on the significance of topsoil (The Thin Black Line, Tim Gullickson, Successful Farming, April 2014). Gullickson emphasized the need for organic matter, but then went further and explored the need for carbon in that organic matter. Carbon feeds soil microbes, and that feeding activity can release 17-60 pounds of N per acre, and also spur the release of phosphorus and zinc. These nutrients are already in your soil; stimulating the bacteria can help release them to your crop.
Organic matter – and carbon to feed microbes that are present – are also important to soil structure and its ability to hold moisture. Soils too wet at planting and too dry afterward may be due to a lack of soil resilience… a loss of organic matter over time. Years of tillage and farming may deplete soil of organic matter, decreasing the soil’s ability to accept and retain moisture.
The no-till movement recognizes that tilling beats organic matter and pore space out of the soil, and loss of those two creates problems with water penetration, water retention, and microbial activity that supports root growth.
Bottom line: focus on increasing organic matter to foster an environment good for soil microbes. Then fuel those microbes with carbon to encourage them to release nutrients already tied up in your soil.