The Sanborn Field Long-Term Experiment: A Continual Life-Long Learning Experience.

Sanborn Field is currently experiencing its 125^th cropping season making it the third oldest continuous research field in the world.  Originally initiated as the “Rotation Field” to assess the influence of crop rotations on yields and soil changes relative to monocultures, Sanborn Field has provided a life-term learning experience to the original objectives plus contemporary soil health and quality issues along with environmental applications.  Keys to making the Field a life-long learning experience have been: initial assessment of soil spatial variability, taking a whole soil profile soil sampling approach and well documented field notes of temporal crop response in addition to traditional yield and soil fertility data.  A sequential plan of detailed whole soil profile samples and analyses every 25 years in concert with the annual crop and soil variables collected has been valuable for assessing long-term changes.  This sequential plan has assisted in providing interpretations of long-term production agriculture changes from the diversified row crop, animal family farm using animals for cultivation through the introduction of mechanized agriculture, the inclusion of petroleum inputs to current production scenarios.  Some of the long-term lessons learned have been: rotations tend to maintain soil quality and larger yields relative to monocultures, ag lime is critical in the long-term sustainability crop production, manures are not a complete nutrient source, and addition of residues and manures after long-term residue removal will not increase soil carbon rapidly. The importance of properly archived soil, crop, and residue samples in concert with detailed meticulous notes are critical for the viability of the field for the original objectives plus contemporary applications.  Recent applications of long-term Sanborn Field data have assisted in assessment of radioactive fallout from past activities, the accumulation of Pb over time from internal combustion engines, and removal of residues on soil health and quality for biofuels.