Management Systems Impact on Soil Quality.

Organic amendments are important to maintain and/or improve soil quality. The impact (2000 to 2007) of organic transition in field crops (conventional vs. organic) on soil quality was evaluated. Soil cores were collected at 0-15 cm depth, composited, 2-mm sieved, analyzed for total microbial biomass (Cmic), Cmic:Corg, basal (BR) and specific maintenance (qCO2) respiration rates, Cmic cell quotient (qD), and mineralizable C as biological indicators; total organic C (Corg), total N (TN), available N (AN), available P (P), glucose, active organic C (Cactive), particulate organic matter (POM), POM-P, POM-N, and POM-C as chemical indicators; and bulk density (rb), mean weight diameter (MWD), geometric mean diameter (GMD), macro-aggregates (Mag), microaggregates (Mig), and aggregate ratios (AR) as physical indicators of soil quality. An inductive additive approach, based on normalization, summation, and average of measured properties into biological, chemical, and physical soil quality indices, was used to calculate a simple soil quality index. Results showed that the values of soil quality indicator properties were significantly higher in organic system compared with conventional system. The organic soil had 29% higher biological quality, 36% higher chemical quality, and 16% higher physical quality. Likewise, 26% higher overall soil quality in organic soil than conventional soil. Regression analyses showed that biological, chemical and physical quality accounted 81, 84, and 74% variability in overall soil quality.