The aim of our research was to assess the impact of some chemical fertilizers on the acidity of the soil. Soil reaction, or pH, is an important agrochemical indicator of the growth medium, since it defines the conditions of bioavailability of nutritive elements for the plants as well as nutritional relationships. Following the large use of chemical fertilizers in the agricultural practice, as well as the acidification phenomenon signalled in the scientific literature, we tested the influence of a complex fertilizer type NPK (15:15:15) and of ammonium nitrate on soil pH. Both types of fertilizers are highly used in everyday practice. The soil the research was made on is a slightly gleized cambic chernozem found in Banat area, more specifically at Timișoara Didactic Station. Complex fertilizers were applied in three doses ensuring 50, 100 and 150 kg N active substance/ha. The nitrogen in the complex fertilizers was nitric and ammonia, in proportion of 6% and . Ammonium nitrate was applied on its own on the three agrofonds NPK ensuring a total of 50, 100, 150 and 200 kg N active substance/ha. We observed the changes in soil reaction at a depth of 0 – 20 cm, parted in 0 – 10 cm and 10 – 20 cm, in order to note the gradual influence of the fertilizers on the pH. Chemical fertilizers, whether applied separately or together, determined an acidification in soil reaction within the limits of  0.08 – 0.34 pH units for the depth of 0 – 10 cm and 0.09 – 0.31 pH units for the depth of 10 – 20 cm. After performing a comparative analysis of the two layers of soil we found gradual pH changes in relation to the infiltration of the ions coming from fertilizers on the surface of the soil. The mean change in soil reaction for the 0 – 20 cm deep layer is 0.09 pH units for a dose of 100 kg active substance N/ha ammonium nitrate. For fertilization type NPK 150 +N 50 (AA), the mean change is 0.32 pH units.

pH, soil, acidification, mineral fertilizers, ammonium nitrate, NPK

Presentation: oral