A PROPOSED METHOD FOR MEASURING THE EFFECT OF SOIL QUALITY ON PRODUCTIVITY

The evaluation of soil quality requires definitive, measurable criteri a. Our objective was to develop a field assay for identifying the spec ific soil attributes that govern the quality of soil for biomass produ ction. The technique involved the removal of surface soil and subseque nt deposition of soils with diverse attributes. As an initial evaluati on of this approach, 36 diverse soils were deposited in a replicated d esign at each of two sites (dryland and irrigated), and the soils were seeded to cereals for three subsequent years. Crop growth was highly responsive to variation in soil properties, Dry matter yields on dryla nd in the year after establishment, for example, ranged from 5.4 to 9. 4 Mg ha(-1) (excluding two subsurface soils). These findings demonstra te that variation in soil quality has a quantifiable influence on prod uctivity, and suggest a useful supplementary role for the proposed app roach in identifying soil quality criteria.