INFLUENCE OF NITROGEN AND PHOSPHORUS FERTILIZATION ON SOIL ORGANIC MATTER CONTENT

Abstract

Influence of nitrogen (N) fertilization (in doses of 40, 80, 120, 160 kg/ha) and phosphorus (P) fertilization (in doses of 40, 80, 120, 160 kg/ha) on soil organic matter content was studied in a long term experiment at Drăgănești Vlașca. The studied soil was classified as a Cambic Phaeozem and the samples were collected from the surface layer (0-20 cm) after the wheat was harvested. The obtained results showed the following: none of applied nitrogen doses not significantly influenced the content of humus in the soil; when applying 40 kg/ha of phosphorus there was no influence on the content of humus in the soil, instead applying 120 and 160 kg/ha resulted in distinct significant increases of the humus content; simultaneous application of 80-160 kg/ha P and 40-160 kg/ha N led to distinct and very significant increases of the soil humus content; high doses of nitrogen (120 and 160 kg/ha) significantly increased the level of soil hydrolytic acidity. Applying high doses of N resulted in a drop of soil pH. Thus, the pH values decreased with 0.29 to 0.37 units, reaching the point where liming was necessary. In wheat culture, results obtained in 39 years of experiments showed that nitrogen and phosphorus fertilization has led to significant yields increases as compared with the unfertilized control. The highest yields were obtained when applying the maximum tested doses of fertilizers.