THE EFFECT OF AGROTECHNICAL INTERVENTIONS ON SEASONAL CHANGES OF INORGANIC NITROGEN CONTENT IN THE SOIL

Abstract

We researched the influence of soil cultivation and fertilization on changes of nitrate, ammonium and inorganic nitrogen content in soil during the monitored vegetation periods (2004/2005 – 2005/2006). This experiment was realized on experimental bases of Slovak University of Agriculture in Nitra – Dolna Malanta on the winter/summer wheat (Triticum aestivum), variety Bonita, with red clover as its before-crop. In the field trial we used two types of tillage, B1 – conventional tillage up to the depth of 0,25 m and B2 – disc ploughing up to 0,15 m, with three variants of fertilization, 0 – unfertilized control, PH – fertilization according to its content in soil and PZ – fertilization according to its content in soil + plough down of post harvest residues. Samples of the soil were taken from the two soil depth (0,0- 0,3 m and 0,3-0,6 m) and in each vegetation period there were 8 takings of soil samples in four repetitions. During monitored vegetation period this dynamics was changeable. The content of nitrate nitrogen in the soil in autumn was about 40 % higher than content of ammonium nitrate. This tendency changed in spring, when the average content of ammonium nitrogen was higher than the content of nitrate nitrogen on average about 60 %. The cultivation had significant influence on dynamics of inorganic nitrogen. The average content of inorganic nitrogen in conventional tillage up to the depth of 0,25 m was 8,43 mg.kg-1 and in disc ploughing it was 7,60 mg.kg-1. The influence of fertilization on changes of inorganic nitrogen was significantly important. Monitored ways of fertilization within the content of nitrates in the soil had the following averages: in unfertilized soil 7,48 mg.kg-1, in fertilized soil NPK 8,20 mg.kg-1 and in the soil fertilized with plough down of post harvest residues 8,37 mg.kg-1. In the first and second variety of soil cultivation we found out a low increase of average concentration of nitrates in the fertilized soil in comparison with unfertilized one. High significant influence on dynamics of nitrate nitrogen in the soil had date of sample takings and also depth. In the first depth (0,0-0,3 m) the level of nitrate nitrogen was 9,18 mg.kg-1 and in the second depth (0,3-0,6 m) it was 6,85 mg.kg-1.