Agriculture Reference
In-Depth Information
days after the fi rst tomato seeding, for a total of 16 evaluations. Extraction
was according to Tullgren's modifi ed method, which uses heat and desic-
cation to force the animals to leave the soil. Samples remained in the ex-
tractor for 72 hours. An alcohol:glycerin (1:1) aqueous solution was used
for specimen preservation. After extraction, the animals were counted and
separated into groups with the use of a stereoscopic microscope. Mites and
other smaller animals were fi xed on permanent slides for identifi cation.
Data were expressed as number of individuals per 785 cm
3
soil. Shannon's
diversity index (Shannon & Weaver, 1949) was calculated for a better un-
derstanding of the variations in the soil microarthropod populations.
Organic matter decomposition rate estimate: The decomposition rate
was estimated via loss of organic content from leaf litter confi ned in nylon
bags, 20 x 20 cm, with a 1 mm mesh, where 10 g of elephant grass dried
at 60°C for three days. The fi eld-collected samples, were collected every
20 days and transported to the laboratory, dried at 105°C for 24 hours and
ashed at 600°C for 4 hours. The loss of organic matter estimate was cal-
culated using the equation described by Santos & Whitford (1981), which
corrects for the adhesion of soil particles to the organic matter.
Evaluation of earthworms in the soil: The fi rst evaluation was carried
out 81 days before the fi rst planting, i.e., before plowing and liming. A
hand excavator was used to collect samples; two samples were collected
from each plot, up to a depth of 20 cm, with 20 cm diameter. Shortly after
planting the tomatoes, and 90 days later, samples were taken at about 40
cm depth, with a diameter of 10 cm. Three samples were collected from
the compost: one from the pile surface; another at a layer up to 35 cm, and
the third at a depth of 90 cm. The worm populations were determined 370,
407, and 471 days after the fi rst tomato planting.
2.3 RESULTS AND DISCUSSION
The populations of fungi, bacteria and actinomycetes were similar for
the two cropping systems over the entire period of study, with popula-
tions of fungi varying from 10
4
to 10
5
, whereas populations of bacteria
and actinomycetes varied from 10
5
to 10
7
CFU g
-1
dry soil (Figure 1).
