Effect of microbial nitrogen immobilization during the growth period on the availability of nitrogen fertilizer for winter cereals

摘要: Pot and field experiments were conducted to determine microbial immobilization of N fertilizer during growth periods winter wheat barley. In a pot experiment with wheat, Ca(15NO3)2 was applied at tillering [Zadok's stage (GS) 25)], stem elongation (GS 31) ear emergence 49). Rates 100 mg pot–1, 200 pot–1 or 300 each application date. At crop maturity, 15N-labelled highest the rate (3×300 pot–1). For N-rate treatment about 50% total immobilized from first dressing, 30% 20% 15N derived second third applications, respectively. trials (three sites) barley (one site) same stages as for trial. also fallow plots, but only GS 25. which not recovered (neither in crops nor soil mineral pools) considered represent net N. A clear effect (51–255 kg ha–1) on found. The found period between 25 (March) 31 (late April) amounted 54–97% harvest (July/August). 31, non-recovered be similar magnitude cropped indicating that C roots did affect immobilization. Microbial biomass (Nmic) determined plots 31. Although Nmic tended higher fertilized than unfertilized fertilizer-induced increases poorly correlated. It can concluded is particularly high after when uptake are low.