Effects of different nitrogen fertilizers on available nutrients concentrations of greenhouse soils.

According to an incubation experiment,the effects of urea,ammonium bicarbonate and calcium nitrate on the content of available nitrogen,phosphorus and potassium in greenhouse soils were studied.The results indicated that:(i) The application of these three different nitrogen fertilizer forms can all increase the nitrate content in greenhouse soils and it increased with the increased fertilizer.The nitrate content in soil was mainly steady after 30 days of fertilizer application.The nitrate-N fertilizer showed no significant effect on the content of ammonium nitrogen.The ammonium nitrogen content increased after the application of ammonium-N and Amide-N fertilizer in greenhouse soils.The maximum value was observed at 3 days of the fertilizer application,then gradually declined and kept steady after 30 days;(ii)The application of three different nitrogen fertilizer forms showed no significant effect on the content of available phosphorus.A large portion of phosphorus was fixed in the soil after 1 day of the phosphorus fertilizer application;(iii) Available potassium content in greenhouse soils increased after the application of different nitrogen fertilizers.But the content of available potassium was only significantly positively correlated with the amounts of ammonium-N and Amide-N fertilizer application.Nitrogen fertilizers application could reduce potassium fixation,potassium fertilizer fixation rate in soils was:ammonium nitrogenamide nitrogennitrateno nitrogen fertilizer.Compared with no nitrogen fertilizer,the content of available potassium were increased 26.88 %,18.28 %,11.07 % by the application of ammonium nitrogen,amide nitrogen and nitrate fertilizer,respectively.Ammonium-N fertilizer was more benefit to potassium fertilizer use efficiency.