The effect of nitrogen fertilization on production and qualitative properties of sown grasslands in the system of sustainable production

Abstract

Nitrogen fixation in grass-leguminous mixtures is not sufficient to satisfy the nitrogen requirements of plants, therefore it is necessary to compensate this deficiency by nitrogen from mineral fertilizers. Objective of this study is to present the effect of N application in grass-leguminous mixtures on their production and qualitative properties, i.e. to give an answer to the question if application of nitrogen fertilizers results in the increase or decrease of yield, quality and changes in the structural composition of the grassland. N from mineral fertilizers, especially considerable amounts of nitrogen, changes the structural composition of grasslands - the share of leguminous plants decreases and share of grasses increases. Yield of dry matter increases with added nitrogen fertilizers. The amounts of nitrogen fertilizer which exceed the requirements of plants reduce the economical justification of fertilization and sometimes can have even opposite effect. Nitrogen fertilization increases the content of crude proteins and protein yield, whereas other quality parameters decrease or remain unchanged. Too much nitrogen in crops leads to nitrate accumulation in plants which is undesirable quality parameter.Azotofiksacijom u travno-leguminoznim smesama nije moguce zadovoljiti potrebe biljaka za azotom, pa je potrebno taj nedostatak nadoknaditi azotom iz mineralnih djubriva. Cilj ovog rada jeste da prikaze efekat primene N djubriva u travno leguminoznim smesama na njihove proizvodne i kvalitativne karakteristike, odnosno da da odgovor na pitanje da li upotrebom azotnih djubriva dolazi do povecanja ili smanjenja prinosa, kvaliteta kao i promena strukturnog sastava travnjaka. N iz mineralnih djubriva, narocito visoke kolicine azota, menjaju strukturni sastav travnjaka tako sto smanjuju udeo leguminoza, a povecavaju udeo trava. Prinos suve materije se povecava dodavanjem azota djubrivima. Kolicine koje prevazilaze potrebe biljaka za azotom smanjuju ekonomsku opravdanost djubrenja i nekad mogu da imaju suprotan efekat. Djubrenje azotom povecava sadrzaj sirovih proteina i prinos proteina, dok se ostali parametri kvaliteta smanjuju ili ostaju nepromenjeni. Prevelike kolicine azota u usevu dovode do nagomilavanja nitrata u biljkama kao nepozeljnog parametra kvaliteta. PR Projekat Ministarstva nauke Republike Srbije, br. TR-31053