Soil organic carbon variability in stagnosol due to nitrogen fertilization

Redovita primjena mineralnih dušičnih gnojiva danas je uobičajena i nezamjenjiva praksa. Poznavanje doprinosa N gnojidbe na varijabilnost organskog ugljika u tlu od iznimne je važnosti kako bi se mjerama održivog gospodarenja tlom očuvala klimatsko regulacijska uloga tla. Cilj ovog rada bio je utvrditi utjecaj dubine tla, rastućih doza dušične gnojidbe i prisutnosti ratarskih kultura na vertikalnu varijabilnost organskog ugljika u pseudogleju. Istraživanje je obuhvatilo analizu uzoraka tla prikupljenih u 2007. (vegetaciji kukuruza) i 2008. godini (vegetaciji pšenice) sa višegodišnjeg poljskog pokusa smještenog u centralnom dijelu RH sa četiri rastuća gnojidbena tretmana u rasponu od 0-300 kg N/ha. Rezultati ukazuju da su rastuće doze apliciranog dušika značajno utjecale na povećanje organskog ugljika što je osobito bilo izraženo u površinskom sloju tla gdje je sadržaj ugljika varirao od 0,826 na N0 tretmanu do 1,797 % na N300 tretmanu u 2007. godini, te od 0,841 % na N0 tretmanu do 1,796 % na N300 tretmanu u 2008. godini. Vertikalna raspodjela organskog ugljika do dva metra dubine također je bila značajna i njegov sadržaj se smanjivao sa porastom dubine. Rezultati ukazuju da je u 2007. godini na tretmanu sa 300 kg/ha apliciranog dušika u tlu bilo pohranjeno 160,1 t/ha organskog ugljika, a godinu dana kasnije na tom istom tretmanu 196,6 t/ha. Sve ukupno istraživanje ukazuje na pozitivan doprinos dušične gnojidbe na sadržaj organskog ugljika u tla kao i na visok potencijal pseudogleja za pohranu ugljika.Regular application of mineral nitrogen fertilizers is a common and irreplaceable practice today. Knowledge of the contribution of N fertilization to soil organic carbon variability is very important in order to preserve the climate-regulating role of soil through measures of sustainable soil management. The aim of this master's thesis was to determine the influence of soil depth, increasing doses of nitrogen fertilization, and the presence of test crops on the vertical variability of organic carbon in stagnosol. The study included analysis of soil samples collected in 2007 (maize vegetation) and 2008 (wheat vegetation) from a field trial located in the central part of the Republic of Croatia with four nitrogen treatments in the range of 0-300 kg N/ha. The results indicate that increasing doses of applied nitrogen significantly influenced on increment of organic carbon, which was particularly pronounced in surface soil layer, where the carbon content varied from 0.826 at the N0 treatment to 1.797% at the N300 treatment in 2007 and from 0,841% on N0 treatment to 1,796% on N300 treatment in 2008. The vertical distribution of organic carbon up to two meters deep was also significant and its content decreased with increasing depth. The results indicate that in 2007, at treatment with 300 kg / ha of applied nitrogen, 160.1 t/ha of organic carbon was stored in the soil up to 2 m depth and one year later at the same treatment 196.6 t/ha organic carbon was recorded. Overall it pointed out positive contribution of nitrogen fertilization to soil organic carbon content and to the high potential of carbon storage of stagnosol