Dynamic of inorganic nitrogen in the soil in dependency on agrotechnical measures

In 2001-2003 years, a stationary field experiment was conducted to observe the influence of some agrotechnical interventions on the content of inorganic nitrogen in soil. The field trial was established on Orthic-Luvisol (content of inorganic nitrogen 20.65 mg per kg, of humus 2.10 -2.24 mg per kg and of oxidizable carbon 1.23 - 1.30 %) in a moderately warm and moderately arid climatic area in south-western part of the Slovak Republic (not far from Nitra city) where average temperature during growing season is 16.4 deg C and average annual precipitation is up to 561 mm. The experiment had two variants of cultivation with two fertilization levels (four-times repetition of treatments). Treatments of cultivation: A - conventional tillage up to the depth 0.25 m B - disk tillage Fertilization treatments: Al, Bl - unfertilized control A2, B2 - NPK-fertilization according to its content in the soil and nutrient requirements of winter wheat for a planned grain yield of 6 t per ha. Each month soil samples were taken from depths of 0-0.3 and 0.3-0.6 m for determination of N-NH4+ and N-NO3- contents (colorimetrically using a Nessler test solution or phenoldihydrosulphide). The content of inorganic nitrogen was calculated as a sum of N-NH4+ and N-NO3-. The results were evaluated using the tables and the statistical program Statgraphic, version 5.1. The weather conditions had expressive influence on the process and intensity of mineralization and nitrification, thereby on the content of inorganic nitrogen in the soil. Nitrate nitrogen predominated in the soil in the first year, normally rainy, whereas ammonium nitrogen predominated in the following, very dry, year. In confrontation of the systems of soil treatment was established slack increasing of both inorganic nitrogen forms in the soil treated by disk tillage (variant B), whereas this increasing was more important with nitrate nitrogen. Higher content of inorganic nitrogen was at amended variants (A2, B2).