[Effect of enhanced ammonium nutrition (EAN) at different growth stages on wheat growth and nitrogen utilization]

Field experiments were conducted in 1998-2000 to investigate the effects of EAN applied at different growth stages (basal, tillering, jointing, booting and whole growth stage) on wheat growth and nitrogen utilization. Compared with single NO3-, EAN as basal fertilizer, tillering dressing and jointing dressing promoted dry matter and nitrogen accumulation after heading, LAI at booting stage, and chlorophyll content of wheat. Grain yield was also increased significantly. Nevertheless, there was no obvious promoting effect of EAN at booting dressing. No significant response of plant growth under EAN was observed over whole growth stage, compared with EAN at early stages, indicating that EAN after jointing was not effective to increase nitrogen utilization and wheat growth. But, it was more effective on decreasing N leaching than other EAN treatments. All EAN treatments increased nitrogen flow efficiency (NFE) and nitrogen recovery efficiency (NRE), compared with single NO-, but EAN treatments before jointing had significant effects on increasing nitrogen utilization. Besides these, EAN a sjointing dressing improved the leaf photosynthetic characteristics during the late developmental stage and the remobilization of dry matter to grain, while EAN a s basal fertilizer an d tillering dressing was more related to increased tillering.