LONG TERM NITROGEN AND PHOSPHORUS FERTILIZATION INFLUENCE UPON SOIL

The paper presents the results obtained in the SCDA Secuieni long term experimental field. The effect of long term (42 years) nitrogen and phosphorus fertilization upon soil fertility and yield was followed up with 0, 40, 80, 120, and 160 kg N/ha and 0, 40, 80, 120, 160 kg P/ha doses. Long term fertilization led to a statistically significant increase of grain yield. Maize grain yield increased from 5,569 kg/ha in the unfertilized control to 9,805 kg/ha in the N160P160 fertilized variants. Each kilogram of phosphorus brought a 6.78 kg maize grain gain, and for each kilogram of nitrogen a 15.28 kg grain increase was obtained. Phosphorus long term fertilization significantly increased the total and mobile soil phosphorus content: from 0.0160% in the unfertilized control to 0.094% in the variants fertilized with 160 kg P/ha, respectively from 8 mg P-AL/kg in the unfertilized control to 144 mg P-AL/kg in the variants fertilized with 160 kg P/ha, and didn't significantly change total and mobile potassium level. No significant humus and nitrogen levels modifications occurred under the influence of nitrogen and phosphorus long term fertilization.