| Popis: |
Cilj ovog rada bio je utvrditi utjecaj gnojidbe dušikom (N) na probavljivost, sadržaj sirovih proteina i metaboličke energije krme na poluprirodnom travnjaku. Tijekom tri godine (2002., 2003. i 2004 godine) na pokusnom pašnjaku „Centra za travnjaštvo“ Agronomskog fakulteta u Zagrebu provedeno je istraživanje na poluprirodnom travnjaku, u uvjetima rotacijskog napasivanja ovcama. Istraživan je utjecaj gnojidbe dušikom u količinama od 35 kg ha-1 god-1 dušika (N35), 100 kg ha-1 god-1 dušika (N100) i 150 kg ha-1 god-1 dušika (N150) na produktivnost pašnjaka i hranjivost dostupne biljne mase. Rezultati istraživanja pokazali su utjecaj ekstenzivnijih mjera gospodarenja pašnjakom na promjenu hranidbene vrijednosti dostupne krme. Utjecaj primjene N na hranidbenu vrijednost dostupne mase utvrđen je samo u smanjenom sadržaju sirovih bjelančevina (SB) kod gnojidbe sa 35 kg N ha-1 god-1 u usporedi s višim količinama primijenjenog N. Probavljivost organske tvari (OT) krme pokazala se najvećom kod primjene 100 kg N ha-1 god-1 gdje je iznosila 734,9 g kg-1 ST. Najveća probavljivost OT krme utvrđena je tijekom vegetacijske sezone 2003. godine (757,3 g kg-1 ST), dok je u 2002. i 2004. probavljivost OT iznosila 702,3 i 741,6 g kg-1 ST, respektivno. Sadržaj metaboličke energije (ME) nije se značajno mijenjao kod različitih količina N gnojidbe, kao ni s obzirom na vegetacijsku sezonu uzgoja. Unatoč tome, najveći sadržaj ME utvrđen je kod gnojidbe sa 100 kg N ha-1 god-1 (10 MJ kg-1 ST), te u vegetacijskoj sezoni 2003. godine (10,3 MJ kg-1 ST). The aim of this study was to determine the effect of nitrogen (N) fertilization on digestibility, crude protein and metabolic energy content in feed on semi-natural grasslands. Over the course of three years (2002, 2003 and 2004) a research was conducted on the Zagreb Faculty of Agriculture's "Center of Grassland" experimental pasture, on semi-natural grassland that was rotary grazed with sheep. The subject of study was the effect of nitrogen fertilization in quantities of 35 kg ha-1 yr-1 of nitrogen (N35), 100 kg ha-1 yr-1 of nitrogen (N100) and 150 kg ha-1 yr-1 of nitrogen (N150) on the productivity of pastures and nutritional values of available plant mass. The study results showed the effect that the more extensive pasture management measures had on the nutritional value of the available feed. The impact of the application of N on the nutritional value of available mass was found only in the reduced content of crude protein (CP) in fertilization with 35 kg N ha-1 yr-1 in comparison with higher levels of applied N. The digestibility of organic matter (OM) of the feed proved to be the highest in the application of 100 kg N ha-1 yr-1, where it amounted to 734.9 g kg-1 DM. The highest digestibility of the feed's OM was found during the growing season in 2003 (757.3 g kg-1 DM), while in 2002 and 2004, the digestibility of the OM was 702.3 and 741.6 g kg-1 DM respectively. The metabolized energy (ME) content was neither significantly changed by different amounts of N fertilization, nor with respect to the vegetation growing season. Nevertheless, the highest content of ME was determined in fertilization with 100 kg N ha-1 yr- 1 (10 MJ kg-1 DM), and in the growing season in 2003 (10.3 MJ kg-1 DM). |
