Comparing Biological and Conventional Chemical Soil Tests in Long-Term Tillage, Rotation, N Rate Field Study

The Haney Soil Health Tool is a suite of tests integrating chemical and biological factors to provide a sophisticated analysis of soil nutrient availability. This research was conducted to determine if Haney tests (including H(3)A and water extracts, Solvita 24-h CO2 evolution, and Soil Health Calculation [SHC]) can add value to conventional chemical soil testing methods and increase knowledge of the effects of tillage systems, crop rotation, and N rate on soil health and corn grain yield. We studied rainfed continuous corn (Zea mays L.) and corn following soybean [Glycine max (L.) Merr.] under three tillage systems and three N rates in a long-term field experiment in northeast Nebraska. The H(3)A ammonium, H(3)A inorganic N, and water-extractable total N tests detected more differences (significant F tests for main effects and interactions involving all treatments) than conventional NO3-N analysis (which detected the interaction of rotation x N rate). Water-extractable organic C detected more differences than LOI. There was a three-way interaction of tillage x rotation x N rate for Solvita and SHC; high N and intensive tillage mostly corresponded to low Solvita and SHC values. We did not expect the treatments to affect P or K directly, but the tillage x rotation interaction was significant for Mehlich III P, tillage for H(3)A organic P, and N rate for H(3)A inorganic and total P. Correlation analysis confirmed linear relationships between many Haney and conventional soil tests, and we concluded via sensitivity ratio calculations that the tests offered similar precision.