Illinois Agronomy Handbook - online For more than 25 years, farmers and their advisers have turned to the Illinois Agronomy Handbook for the research-based guidance they need. Since 1999 the web-based Interactive Agronomy Handbook (IAH) has supplemented the printed Handbook. The IAH adds value to the print version by providing useful decision tools like the The Illinois Soil and Nutrient Management Planner (SNMP).