Abstract:
Investigations conducted in long-term (39 years)
stationary experiments, under non-irrigated, followed the influence of
different fertilizer rates on the evolution of soil agrochemical
characteristics and yield obtained in main crops, placed in 2, 3 and 4 year
rotations. In maize crop, placed in 5 year rotations, the mean yield obtained
during 1980-2005 was of 5920 kg /ha. Rates of N100P100 have determined
yield increases by 94% (3030 kg/ha) and rates of N40P40 + 30 t/ha manure
resulted in a double yield, in hybrid Oana (9 %; 3180 kg/ha) compared to
unfertilized. The long-term use of 3 and 4 year rotation with ameliorative
plants resulted in getting yield increases by 46 - 48% (1120-1150 kg/ha) in
wheat and 27 - 35% (1180 – 1530) in maize, compared to continuous crop.
Annual application of rates of 80 kg/ha P2O5 determined the accumulation
of a reserve of mobile phosphates in soil, comprised, according to applied
nitrogen, between 47 and 66 ppm. The humus and nutrient content from soil
was maintained at a supply level proper to the requirements of plant
nutrition, only under 3 or 4 year rotation and in case of annual use of rates
of at least N100P100 or of mean rates of mineral elements with 30 t/ha
manure.
