2.2. Experimentation and sampling
The management treatments were grazed pasture (GP), agroforestry
buffer (AgB), grass buffer (GB), and row-crop (RC). The AgB
and GB treatments were in the buffer areas of the small watersheds
with respective buffer type and the GP treatment was in
the pasture areas in the small watersheds with buffers. The experimental
design was completely randomized with a split plot for
soil depths (0–10 and 10–20 cm). There were two replicates for
treatments and three sampling locations per treatment plot. An
additional factor, landscape position, was evaluated for the GP and
RC treatments, resulting in soil samples collected at three landscape
positions.
Altogether, 96 total samples were taken from the four treatments
during June 2009. The sampling procedure was different
between buffer areas and the other two treatments. For GP and
RC treatments, soil samples were collected at three landscape
positions from each treatment: upper, middle and lower (three
sub-samples at each position) and in three transects. Since buffer
areas were narrow relative to GP and RC treatments, only three subsamples
were collected from the middle area within each buffer.
The soil samples for the GB buffer treatment were taken from
the center of the buffer. Samples for the AgB buffer treatment
were sampled about 40cm from the base of a tree trunk. Hence,
each buffer treatment consisted of six sample locations (three subsamples
and two replications).
Soils were collected with a soil auger and were placed in labeled
plastic bags. The sampling bags were sealed and transported to the
laboratory in a cooler. All samples were maintained at field moist
condition and were stored at 4 ◦C until analyzed. Three separate
sub-samples were taken from each sample. One sub-sample was
used for enzyme assays after passing through a 2-mm sieve. The
second sub-sample was air-dried for water stable aggregates and
soil carbon and nitrogen analysis. The third sub-sample was used
to determine soil moisture content.