Abstract:
Investigations conducted
during 2003-2009 at the Podu-Iloaiei
Agricultural Research Station, Iaşi County,
have studied the influence of different
sewage sludge rates, crop residues and
manure rates on yield quality and quantity
and soil agrochemical characteristics. Trials
were set up in a five year-crop rotation
(soybean-wheat-maize-sunflower-wheat).
Sewage sludge was applied every two years
at rates of 20, 40 and 60 t/ha, with different
mineral fertilizer rates, differentiated
according to the growing plant. In wheat,
we have used Gabriela Variety, and in
maize, Oana Hybrid. The mean yield
increases obtained during 2003-2009, by
applying the rate of 60 t/ha sewage sludge,
were of 1877 (93%) in winter wheat and of
2102 kg/ha (57%) in maize. After 7 years
since the application of a rate of 60 t/ha
sewage sludge, soil pH has increased 0.4
units, while phosphorus and potassium
content from soil has increased by 39 and
115 mg/ kg soil, respectively. Sewage
sludge from the Iaşi Water Treatment
Station, which was applied every two years
at rates of 40 and 60 t/ha, has determined
the increase in the organic carbon content
from soil by 3.4 g/kg (20.5%) and 4.7 g/kg
(28.3%), respectively, compared to the
unfertilized variant. Applying wheat and
maize residues, at the rate of 6 t/ha DM, has
determined the increase by 1.4-1.7 g/kg soil
(8.2-9.9%) in the content of organic carbon
from soil, compared to the mineral
fertilization (N80P60), and by 1.9-2.2 g/kg
(11.5-13.3%), compared to the unfertilized
control.
