Fig. 3. Simplified N pools and pathways in long-term no-till ecosystems highlighting the changes in soil environmental conditions and management that increase plant available N over time. Organic N pools are increased by decreased decomposition rates; increased organic matter leads to greater N mineralization at a time when plants can use it, stimulated by plant growth and warmer weather rather than tillage. Inorganic N pools are maintained by N mineralization and also by reduced fertilizer N losses to the environment as changes in aggregation and porosity attenuate N losses via runoff, leaching, and denitrification. Plant available N is enhanced by increased inorganic N concentrations and by expanded producer expertise in applying appropriate N forms at times and in soil regions that maximize plant uptake, rather than environmental losses.