2.3. Soil collection and processing
Prior to establishing the experiment, 18 composite soil samples were randomly collected from the entire field for baseline data using GPS guided systematic sampling in early spring (May) of 2002. Ten soil cores were collected from 30 cm depth in plastic tubes for each composite sample using an environmental soil probe (1.9 cm internal diameter). The soil cores were segmented at 0–7.5, 7.5–15, 15–22.5 and 22.5–30 cm, respectively in the laboratory. The segmented soils at each depth were mixed to get composite samples and gentle sieving was done through a 4-mm mesh to eliminate stones, plants roots and large organic substances. After sieving, the composite field-moist soil was divided into two equal parts and each sub-sample was placed in a separate Ziplock plastic bag. The soil from one sub-sample bag was passed through a 2-mm sieve and homogenized to measure antecedent soil moisture content and incubate for 7 d at room temperature (25 °C) to stabilize microbial activity. After stabilization, the field-moist soil samples were then used to measure microbial biomass and/or incubated for biological properties. Soil from the second bag was spread on a polyethylene sheet and air-dried at room temperature for 72 h and analyzed for selected chemical and physical properties. In early spring (May) of 2007, a total of 18 composite samples were taken (using GPS) from same soil locations and depth, processed and analyzed for evaluation of temporal (2002 vs. 2007) effects of tillage on soil properties.