soil - Lublin

Table 4.
Soil aeration indicators at different temperatures
Location
5 o C 10 o C 20 o C
t 300 t 400 t 300 t 400 t 300 t 400
1 A 49.5 0.1 34 0.1 5.5 0.1
1 B >60 0.1 30 0.1 2 0.5
2 A 35 15 19 3.5 3 0.5
2 B 34.5 12.5 20 4 6 0.5
3 A 21 0.125 8 1 1.75 0.25
3 B 34 0.1 13 0.1 3 0.25
4 A 19.5 0.1 8 0.1 1.25 0.1
At the incubation temperature of 10°C, the course of changes in the Eh of the
soils during the initial 21 days of incubation was similar to that at 5°C, though at
10°C the changes in Eh occurred at a faster rate. The lowering in the Eh value was
the greatest in the humus horizons of samples 3A (by 228 mV) and 4A (by 248
mV), less pronounced in sample 2A (by 120 mV) and the smallest in sample 1A
(by 47 mV). An exception here is the sample 4A, in which throughout the incubation
process the value of Eh decreased systematically, reaching 134 mV at the end
of the incubation process, on day 42.
At 20°C, the course of the redox processes during the incubation of the soils
studied was the fastest (till day 12) when compared to the changes occurring at 10
and 5°C. Lowering of Eh to the value of 150 mV in the characteristic sample 2A
occurred on the 9th day of incubation. The courses of the curves of the changes
were gentle, and the differences among the particular samples were the smallest.
In the characteristic days of incubation, the 7th and 10th, which were comparable
for the courses of all the incubation temperatures, both the surface horizons (A)
and the deeper horizons (B) did not differ with respect to the Eh values at the lower
temperatures of 5 and 10°C, while at 20°C the differences in soils samples from all
the three sampling sites were considerable, from 29 to 67 mV, in favor of the surface
horizons. Considerable differences between horizons A and B occurred also at
the smallest decreases in the value of Eh on the 40th day, 21st day, and in the period
of days 4-9, at incubation temperatures of 5, 10 and 20°C, respectively.
There is a noticeable overall tendency for Eh to decrease in the soils from the
upper towards the lower parts of the hill slope, the strongest effects of such
changes being observable at the incubation temperature of 20°C. In the soils from
the deeper horizons (B), however, the changes were not as clear cut as in the soils
from the humus horizons (A).
Values obtained from the measurements (n = 20) permitted the determination
of the dynamics of Eh in the course of the incubation process, and the determination
of indexes indicating the limits below which manganese and iron oxides (index
t 300 ) and nitrates (index t 400 ) are reduced (Table 4).
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