Abstract:
Investigations conducted
during 2004-2008 at the Podu-Iloaiei
Agricultural Research Station have studied
the influence of different rates of sewage
sludge on yield and soil agrochemical
characteristics. Sewage sludge was applied
annually at rates of 20, 40 and 60 t/ha,
together with mineral fertilizers,
differentiated according to the growing
plant. Applying rates of 20 t/ha DM sewage
sludge resulted in the accumulation of
mobile phosphate stock in soil of 58 ppm;
the microelement content (mobile forms
from soil) was of 19.0 ppm at Cu, 0.51 ppm
at B, 149 ppm at Zn and 397 ppm at
manganese. The obtained results have
shown that by applying a rate of 30 t/ha of
raw sewage sludge (18.5 l t/ha dry matter),
the allowable maximum limits stipulated by
Norm 86/278/EEC, were not exceeded. By
applying rates of 60 t/ha raw sewage sludge
(37 t/ha dry matter), the limits established
by Norm 86/278/EEC and Order no. 49
from January 14, 2004 have been exceeded
only at zinc. The application of the rates of
40 t/ha sewage sludge has resulted in
increasing the degree of plant supply by
mineral elements (especially, nitrogen and
phosphorus). It has also resulted in a mean
annual supply of 3.8 t/ha highly humificated
organic matter; this explains the increase in
soil humus content (after 4 years) from 2.82
to 3.79%. The use of fermented sewage
sludge, at a rate of 40 t/ha, has resulted in
getting mean yield increases of 65 % (1075
kg/ha), in winter rape, and of 63 % (937
kg/ha), in soybean. For slope lands degraded
by erosion, sewage sludge with other
organic resources may contribute to the
improvement in soil characteristics. The
application of rates of 20 t/ha sewage sludge
DM has resulted in the accumulation of
mobile phosphates in soil of 58 ppm, and
the content of microelements, mobile forms
from soil, was of 19.0 ppm at Cu , 0.51 ppm
at B, 149 ppm at Zn and 397 ppm at
manganese.
