Effects of Different Ratios of NH_4~+/NO_3~- on Growth of Pinus koraiensis Seedings

The concentrations of NH4+-N,NO3--N and pH in vermiculite,the dry weight,total N,P and K contents of Pinus koraiensis seedlings grown with,Ammonium-N(ammonium sulfate) or Nitrate-N(calcium nitrate) and their different supply ratios were studied under pot culture in greenhouse.The results showed the higher growth were obtained at NH4+-N,NO3--N ratio of 4∶0 and 3∶1.The growth of seedlings declined with the increasing ratio of NO3--N.Excessive NO3--N inhibited root growth.There were no significant effects in the capability of supply NO3--N with NH4+-N.Increasing NH4+-N in nutrient solution led to the increase of phosphorus content in plant tissues,and the decreased of potassium contents.The pH of cultural medium(vermiculite) was affected markedly by the ratio NH4+-N and NO3--N,which was decreased with increasing NH4+-N and increased with increasing NO3--N.