Abstract:
The paper presented the results of investigations concerning the influence of
long-term fertilization (39 years) on some physical and chemical characteristics of Cambic
Chernozem from the Moldavian Plain and on the yield of maize, placed under different crop
rotations with perennial grasses and legumes. The 39 year use of the crop rotation peaswheat-
maize-sunflower+reserve field, cultivated with perennial grasses and legumes, has
resulted in getting maize yield increase of 29% (1312 kg/ha), in comparison with maize
continuous cropping. On slope lands, the high rate fertilization of maize crop (N140P100) has
determined, in the latest ten years, an average yield increase of 93% (3086 kg/ha), against the
control, and applying a rate of N60P40+30 t/ha manure resulted in getting a very close yield
increase (95%, 3156 kg/ha). The long-term use of 4-year crop rotation + field cultivated with
perennial grasses and legumes has determined a maize yield increase of 16 %, respectively,
800 kg/ha, and the improvement of physical and chemical characteristics of soil. In maize
crop, fertilized with N60P40+30 t/ha manure, the rate of greater than 0.25 mm hydrostable
aggregates was higher by 26%, against the control; placing maize in crop rotations with
perennial grasses and legumes has resulted in increasing by 30% the rate of hydrostable
aggregates, compared to maize continuous cropping. The 39 year use of 3 and 4-year crop
rotations, which had perennial grasses and legumes in the crop structure, has determined the
increase in the content of total carbon and mobile phosphorus from soil by 10% (1.7 C g/kg),
respectively, 31% (11.8 P-AL mg/kg), in comparison with maize continuous cropping. A
minimum supply level of mobile phosphorus in soil (37-72 ppm) in maize continuous cropping
(39 ppm) and wheat-maize rotation (37 ppm) was maintained in case of annual application of a rate of N100P80. The total carbon content in Cambic Chernozem from the Moldavian Plain
has registered significant increases at higher rates than N140P100, in case of organo-mineral
fertilization and 4-year crop rotation + reserve field cultivated with perennial grasses and
legumes. In maize continuous cropping and wheat-maize rotation, very significant values of
the carbon content were registered only in case of organo-mineral fertilization, and in 4-year
crop rotation + reserve field, cultivated with perennial legumes, in case of N140P100
fertilization.
