Agriculture Reference
In-Depth Information
After harvesting the corn, 'Débora' tomatoes were again cultivated, as
previously described. Transplantation was made 401 days after the initial
tomato planting.
2.2.1 SOIL MICROORGANISMS
A sample composed of 20 sub-samples of soil taken at the planting row
from the 0-7 cm depth layer was obtained for each plot. Samples were
placed in plastic bags and immediately transported to the laboratory. As-
sessments were performed within 24 hours after collecting the samples.
Populations of fungi, bacteria and actinomycetes: The populations of
fungi, bacteria and actinomycetes were quantifi ed through the serial-di-
lution method, followed by plating in culture medium. Martin's culture
medium (Tuite, 1969) added of 100 mg mL
-1
streptomycine was used for
fungi; for bacteria, the agar nutrient medium added of nistatin (42 mg
L
-1
) was used; for the actinomycetes, the alkalized agar-water medium
was utilized. Aliquots (0.1 mL) from three dilutions, for each soil sample,
were transferred to the culture media in three replications. Assessments
were performed by counting the number of colonies per Petri dish and
expressed as colony-forming units/g of dry soil (CFU g
-1
dry soil).
Total respiratory activity: Total microbial respiration was evaluated ac-
cording the method described by Grisi (1978). Soil samples (200 g) were
incubated for 10, 20, and 30 days within tightly sealed containers holding
10 mL of a 0.5 mol L
-1
(10 mL) KOH solution. At 10-day intervals, the
solution was substituted and titrated with 0.1 mol L
-1
of HCl. Incubation
was conducted in the dark, at 25°C. This parameter was expressed as g
CO
2
(g dry soil
-1
) (day
-1
). Since the more substantial changes happened
in the fi rst days, only readings up to the tenth day were used to determine
mean values. For the statistical analysis, data were transformed into square
root (x + 0.5) and subjected to analysis of variance and Duncan's mean
comparison test.
Soil microarthropods: Collecting was made with a Uhland-type, stain-
less steel auger 5 cm in diameter and 10 cm in height, totaling four sam-
ples per plot. Samples were placed in plastic bags and taken to the labora-
tory. Collecting was between 8:00 and 10:30 h, 82 days before and 325
