Abstract:
The investigations conducted
at the Podu-Iloaiei Agricultural Research
Station, Iaşi County, Romania, have studied
the influence of different mineral fertilizers
rates on wheat and maize yield and soil
agrochemical characteristics. In bean-wheatmaize-
sunflower-wheat crop rotation, the
mean yield increases, obtained for each kg
of a.i. of applied fertilizer, were comprised
between 8.3 and 10.1 kg in wheat (N120P80-
N160P80) and between 10.8 and 11.0 kg in
maize (N150P80-N200P100). Generally,
nitrogen use efficiency is low and, to
achieve maximum yields, need for high
doses of nitrogen which can increase the
risk of environmental pollution. The N
agronomic efficiencies and physiological
efficiencies in wheat and maize declined
with the increase of nitrogen rate. Wheat
placed in rotation for five years, after
sunflower at recommended dose (N160P80),
physiological efficiency of nitrogen
utilization was 43.4 kg grain per kilogram of
nitrogen exported from soil, from fertilizer
applied. Mean annual amounts of nutrients
exported from soil by wheat in dry (14 yr.)
and favourable (11 yr.) years in five year
crop rotation have varied according to rates,
between 34.5 and 100.7 kg at nitrogen and
between 6.5 and 18.4 kg at phosphorus. The
long-term use of bean - wheat - maize -
sunflower - wheat rotation determined the
diminution by 43.4% (2,772 t/ha) in the
mean annual losses of eroded soil and by
38.5% (5.61 kg/ha) in nitrogen leakages by
erosion, compared with maize continuous
cropping.
