A BIOLOGICALLY-BASED INDICATOR OF SOIL QUALITY

Soil quality indices are attempts to classify soil conditions and to c ompare these conditions to their historical use. From this information it may be possible to determine which uses of soils are better for th e long-range goals of agriculture and society. With many factors invol ved in the profitable production of safe foodstuffs without significan t degradation of the environment and soils, an indicator that represen ts a broad biological perspective of quality is appropriate. Among a g roup of biological indicators, the ratio of crop N uptake to mineraliz ed N as determined by microbial respiration plus net mineralized N fou nd over a growing season is an useful indicator of soil quality. An ev aluation of the 12-year-old Farming Systems Trial at the Rodale Instit ute Research Center indicated that soils in plots that had been conven tionally managed were of lower quality than soil treated with manure o r planted with legume-cash grain crops.