Effects Of Spatial-temporal Regulated Irrigation On Water Saving And The Greenhouse Gas Emissions Of Winter Wheat/summer Maize Rotation System

A pond-based experiment with winter wheat and summer maize was conducted under rainproof shelter during the growing seasons of 2016²017 to investigate the effects of spatial-temporal regulated irrigation on physio-biochemical characteristics,yield and greenhouse gas emission fluxes of winter wheat-summer maize.Six treatments were conducted,two irrigation methods such as border irrigation and furrow irrigation were included.Set full irrigation treatment and spring growth-stem elongation water deficit treatment under border irrigation.Set alternate furrow irrigation and spatial-temporal regulated irrigation under furrow irrigation.The soil water content was controlled at 55%⁶5%FC in spring growth-stem elongation,stem elongation-ear emergence,ear emergence-filling period of winter wheat and at 60%⁷0%FC in seedling-stem elongation,stem elongation-heading emergence,heading emergence-filling period of summer maize under spatial-temporal regulated irrigation,respectively.The treatments were replicated three times under completely randomized blocks experimental design.The soil moisture content,photosynthetic characteristics,proline and soluble sugar content of leaves,and greenhouse gas emission fluxes were measured.Based on the field experiment results and analysis,the conclusions are as follows:1.The results indicated that the net photosynthetic rate?P_n?and transpiration rate?T_r?of winter wheat and summer maize for the full irrigation were higher than those of alternate furrow irrigation and spatial-temporal regulated irrigation treatments,but a higher leaf water use efficiency under the alternate furrow irrigation and spatial-temporal regulated irrigation were demonstrated.The mean P_n of T4 was significantly lower than that of other treatments during later growth stage?P<0.05?,it was difficult to compensate effectively after rewatering,resulting in the substantial reduction of yield.2.The both proline and soluble sugar are the active substances to resist drought for winter wheat.The results indicated that the proline content of water stress treatment is generally higher than that of full water treatment.Compared with alternate furrow irrigation?T2?,the proline contents of winter wheat of T4,T5 and T6 were increased by an average of 13.14%,27.44%and 61.92%respectively,and the proline contents of summer maize of T4,T5 and T6 were increased by an average of 6.49%,23.59%and 83.25%respectively.It showed that the water stress in each growth period under patial-temporal regulated irrigation was beneficial to the accumulation of proline in the flag leaf of winter wheat and summer maize.The proline content in leaves can reflect the level of water stress for winter wheat and summer maize,but it seemed that the change of soluble sugar content was complicated,it may be related to the growth stage of wheat.3.The results indicated that the yield of the full irrigation was higher than those of alternate furrow irrigation and spatial-temporal regulated irrigation treatments in winter wheat and summer maize,but a lower water use efficiency for the border irrigation was demonstrated.In winter wheat experiment,The order of yield from high to low was T1>T3>T2>T4>T5>T6.In summer maize experiment,The order of yield was T1>T2>T4>T3>T5>T6,The yield of the border irrigation was higher than other treatments,but a lower WUE was founded.Compared with border irrigation?T1?,the yields of T2 and T4 were decreased by an average of 1.98%?P>0.05?and 5.68%?P<0.05?respectively,but their water consumptions were decreased by an average of 10.01%?P<0.01?and 16.91%?P<0.01?respectively,and their WUE were increased by 9.04%?P<0.05?and 15.82%?P<0.01?respectively.4.Under spatial-temporal regulated irrigation,winter wheat and summer maize had a lower CO₂emission flux during the stage of water deficit,but it increased significantly after rewatering,so there was no obvious emission reduction effect for spatial-temporal regulated irrigation.Over all,alternation of wetting and drying cycle increased the CO₂ emission of soil,soil that are too wet or dry would inhibit soil respiration rate.The emission flux of N₂O is mainly related to the rate of fertilizer application,but irrigation methods have no significant influnce on N₂O emission.During the experimental observation period,the CH₄ emission flux fluctuated greatly,but the absorption phenomenon of CH₄ was basically shown in each treatment,and the total absorption of CH₄ decreases with the increase of soil moisture.The effect of irrigation method on CH₄ emission was not obviously observed,and it still needs further research.Take the effects of saving water and environmental of different irrigation methods into account,the present results suggest that spatial-temporal regulated irrigation applying suitable water deficit?55%-65%FC?during returning green stage of winter wheat and applying suitable water deficit?60%-70%FC?during seedling stage of summer maize may be the better irrigation model to save water,fix carbon and reducedischarge of winterwheatandsummermaizerotation system in North China Plain.