Agriculture Reference
In-Depth Information
under minimum tillage as compared to soils under conventional tillage.
Ladd et al. (1994) verifi ed that the C biomass of microbial populations
was greater in soils under crop rotation than in soils under continuous
monoculture; greater in soils where plant residues were incorporated or
remained on the soil surface than where they were removed; and smaller
in a nitrogen-fertilized soil than in non-fertilized ones. This information is
important because these are characteristics that contribute to soil biologi-
cal equilibrium, nutrient mineralization and suppressive capacity toward
plant pathogens, among others, making the system less dependent on ex-
ternal input.
The objective of this work was to evaluate the infl uence of the organic
and the conventional cropping systems, for tomato and corn, on the com-
munity of soil organisms.
2.2 MATERIALS AND METHODS
The experiment was carried out in Jaguariúna, SP, Brasil, latitude 22° 41'
S, longitude 47° W Gr., and an altitude of 570 m, on a dystrophic Ultisol,
with the following chemical properties of the 0-0.2 m topsoil layer, before
liming: pH (CaCl
2
) 4.4; OM 0.6%; P (resin) 1 mg cm
-3
; K 0.5; Ca 7; Mg 7;
H + Al 28; CEC 43 and S 15 mmol dm
-3
of soil; and V 35%. The studies
were conducted from January 1993 to September 1995.
The experiment was set up as randomized blocks with six replicates,
and plots measuring 25 x 17 m. Tomato planting pits were spaced 0.5 m
apart with 1.20 m between rows. Each plot was split in two halves, the
fi rst 12.5 x 17 m half being planted with the variety Débora and the other
planted with the variety Santa Clara. Therefore, each of the twelve rows
contained 17 planting pits for each variety. The edging between plots was
10 m wide and was planted with sorghum. Two tomato plants were trans-
planted per pit. The tomato crop was conducted using the stake system,
with one or two stems/plant. The number of stems was determined based
on the successful establishment of the seedlings. Furrow irrigation and
plant pruning were performed as often as necessary.
The entire area received 4.2 t ha
-1
lime and 2 kg per meter, 110 and 12
days before planting, respectively. Fertilization in the organic system em-
