Abstract:
Investigations, set up in 1968, were carried out on a Cambic
Chernozem with a slope of 14%. They have shown the influence of different
crop rotations and fertilization on soil erosion and fertility. On slope lands
from the Moldavian Plain, a good supply in mobile phosphorus for field
crops (36-49 mg kg−1) was kept in case of the annual application of a rate of
N100P80, and a very good supply in mobile phosphorus (71-78 mg kg −1) and
mobile potassium (over 200 mg kg−1) was found at a rate of N80P60+30 t ha−1
of organic manure, applied in 3 or 4 -year crop rotations with legumes and
perennial grasses. The total carbon mass on Cambic Chernozem from the
Moldavian Plain has registered significant increases at higher than N140P100
rates, at organo-mineral fertilization and in 4-year crop rotation + reserve
field cultivated with perennial grasses and legumes. The mean yield
increases in wheat, during 1998-2009, were between 23 and 27 %, due to
crop rotation and between 58 and 104 %, due to applied fertilizer rates. The
determination of water runoff, soil, humus and nutritive element losses by
erosion in different crops was done by means of loss control plots, which are
isolated from the rest of the area by metallic walls and have basins and
devices for division; we took water and soil samples from plots, for
determining the partial turbidity and for analyses of chemical elements. On
16% slope lands, the crop structure, which determined the diminution in
mean soil losses by erosion until 2.3 t/ha/year included 20 % straw cereals
(winter wheat), 20% annual legumes (pea), 20% row crops (maize) and 40 %
perennial grasses and legumes.
