Photosynthetic characteristics and leaf water potential diurnal variation of maize under plastic film mulching and different water nitrogen coupling

In order to provide a basis for improving crop water use efficiency through water and nitrogen interaction,the effects of different irrigation and nitrogen fertilizer combinations on photosynthetic characteristics and diurnal changes of leaf water potential of maize in oasis irrigation area was studied through field test.Results show that all of the NET photosynthetic rate of corn(Pn),tanspiration rate(Tr),stomatal conductance(Cond),leaf water potential(LWP)increased with the increasing of irrigation. But the WUEof leaf decreased with the increasing of irrigation.Under the same irrigation amount,applying with 360kg/hm2 nitrogen enhanced NETphotosynthetic rate,tanspiration rate,stomatal conductance and WUEof leaves,which were all decreased when applying with 540kg/hm2 nitrogen.Suitable nitrogen amount for high photosynthesis of maize was 360~540kg/hm2.Under low irrigation amount,increasing ni-trogen amount could reduce leaf water potential.But with the improvement of irrigation,leaf water potential increased with the increasing of nitrogen application.The interaction effects of irrigation and nitrogen on corn's net photosynthetic rate,transpiration rate and the leaf water potential and WUEeffects were all significant,which on stomatal conductance was not obvious.Effect of nitrogen on WUE was greater than water.The decrease of net photosynthetic rate and water use efficiency lead by water stress could be equalized partly by increasing nitrogen application.This suggested that water and nitrogen intermediation was the feasible method to optimize the photosynthetic characteristics of maize.