Prof. Milan Mesic1, Prof. Zeljka Zgorelec1, Dr. Aleksandra Percin1, Dr. Ivana Sestak1
1University Of Zagreb Faculty Of Agriculture, Zagreb, Croatia
There are numerous findings about the influence of mineral nitrogen fertilizer on SOC content. Results have not been consistent. Some authors report positive effects, however, some papers have shown a negative influence of nitrogen fertilization on total SOC content. Positive correlations are observed in semi arid, dry land areas in USA (Colorado and in Oklahoma). On the other hand, some scientists observed negative correlation after analyses of numerous long term cropping experiments. In addition, there are some results that conclude there is no influence of N fertilization on SOC. In our research with different amounts of mineral nitrogen (0 do 300 kg N ha-1) that was conducted on experimental field located within drained cropland in Western Pannonian subregion of Croatia, Europe (45°33´N, 16°31´E) we have found positive influence of nitrogen fertilization on SOC content. The soil type of trial site is drained distric Stagnosols. Objective of our work was to determine the effect of different nitrogen fertilization levels on changes in some soil chemical properties (pH, total N and SOC content). Soil sampling was carried out in 2010, 15 years later from the establishment of research field. Trial treatments included annual fertilization with different mineral nitrogen rates, respectively with 0, 100, 150, 200, 250 and 300 kg Nha-1. SOC and total nitrogen contents were determined by dry combustion method. SOC content in soil was in a range from 0.59-1.21 % in samples taken from treatments without applied nitrogen. In a treatment with 100 kg N ha-1 SOC content varied between 0.67 – 1.14 %. Increased rates of nitrogen increased SOC content up to maximum levels obtained in treatment with 300 kg of nitrogen – ranging between 1.00 – 2.14 %. Increased nitrogen rates caused decrease of soil pH and increase of TN content.
Prof. Dr. Milan Mesic, agricultural engineer, Dr.Sc., University of Zagreb Faculty of Agriculture, Department of General Agronomy, Full Professor.
Research: Assessment of soil quality through improved soil sampling schemes, precise information about soil properties, new possibilities for determination of soil properties including spectroradiometry and remote sensing, influence of nitrogen fertilization on water quality, soil properties and crop yields and quality, relations between nitrogen and carbon cycles in soils.