Abstract:
Investigations conducted at the Agricultural Research and Development Station
of Podu-Iloaiei, Iaşi County, during 2004-2008, have followed the influence of different crop
structures and different fertilization methods on crop yield, erosion and soil fertility. Within the
experiment, the following rotation schemes have been followed: wheat and maize continuous
cropping, 2-year rotation (wheat-maize), 3-year rotation (peas-wheat-maize) and 4-year
rotation + reserve field cultivated with legumes and perennial grasses (alfalfa + Lolium or
Sainfoin + Bromus). The use of 3 and 4 year- rotations with annual and perennial meliorate
plants has resulted in yield increases of 25 – 30 % (632 – 768 kg/ha) in wheat and 24-28%
(973-1161 kg/ha) in maize, as compared to continuous cropping. The fertilization of wheat and
maize crops at the rate of N60P40+30 t/ha manure has determined the increase by 3.0 g/kg
(17.9%) in the content of organic carbon from soil, as compared to the rate of N100P80. The use
of peas-wheat-maize-sunflower rotation + reserve field grown with legumes and perennial
grasses has contributed to the increase by 2.2 g/kg (13.4%) in the content of organic carbon.
The use of 4-year rotation + reserve field cultivated with perennial grasses and legumes on
slope lands, poor in organic matter has determined the increase by 47% in soil potential and by
34% in enzyme potential, as compared to wheat-maize rotation. On 11% slope lands, the use of
soybean-wheat-maize rotation + two reserve fields cultivated with perennial grasses has
determined the diminution of soil losses by erosion at 0.985 t/ha, and on 16% slope lands,
peas-wheat-maize rotation + two reserve fields, cultivated with perennial grasses has determined the diminution in soil erosion at 1.371 t/ha. On 16% slope lands, the crop structure,
which determined the diminution in mean soil losses by erosion until 1.371 t/ha/year included
20 % straw cereals, 20% annual legumes, 20% row crops and 40 % perennial grasses and
legumes.
