Saline Water Management Effects On Soil Salinity,Physiological Responses And Crop Water Productivity Of Winter Wheat In The North China Plain

Brackish water used for irrigation can restrict crop growth and lead to environmental problems.Large amounts of underground water,often of 2?5 g L^-1 salt content,are available in the North China Plain?NCP?or shallow groundwater which require managing and,thus can be properly used in irrigated agriculture to realize the pressure on fresh water in this region for supplementary irrigation.At the same time,crop growth,grain yield and water productivity of winter wheat?WW?and physiological responses may be examined not only by the alternate irrigation with saline water at different growth stages but also confounded with long term salt accumulation by the alternate use of saline water.Furthermore,the effective water management in the NCP needs a tool to predict winter wheat production due to water quality.The SALTMED model is a generic modeling tool for efficient irrigation management strategies,especially for cyclic use of saline and fresh water as well as different water qualities,and it still needs further investigation for alternate irrigation using saline and fresh water at different growth stages of WW.Therefore,the field trials were conducted during the WW growing seasons at the experimental station of Institute of Dryland Farming,Hebei Academy of Agriculture and Forestry Sciences?Latitude:37°54?N;Longitude:115°42?E?in the NCP.The treatments comprised rain-fed cultivation?NI?,fresh and saline water irrigation?FS?,saline and fresh water irrigation?SF?,saline water irrigation?SS?and fresh water irrigation?FF?during the growth stages.The alternate irrigation with saline water at different growth stages is still not well understood.Therefore,field trials were conducted during 2015–2018 in the NCP to investigate whether alternate irrigation is practicable for winter wheat production.Results showed that the grain yield increased by20%under SF and FS treatments compared to NI,while a minor decrease of 2%in grain yield was observed compared with FF treatment.The increased soil salinity and risk of long-term salt accumulation in the soil due to alternate irrigation during peak dry periods was insignificant due to leaching of salts from crop rootzone during monsoon season.Although Na⁺concentration in the leaves increased with saline irrigation,resulting in significantly lower K⁺:Na⁺ratio in the leaves,the Na⁺and K⁺concentrations in the roots and grains were not affected.In conclusion,the alternate irrigation for WW is a most promising option to harvest more yield and save fresh water resources.The SALTMED model was used and evaluated to simulate the production of WW under different irrigation strategies.Three-year observed data were used for the validations of SALTMED model.The values of evaluation indices of relative error,RMSE,NRMSE,d-Index and r² between simulated and observed grain yield were 6.8%,0.8,10.7,0.9 and 0.9,respectively.The model results supported and matched the observed data and indicated similar differences among the rain-fed and irrigated treatments.It is concluded that the SALTMED model is able to predict grain yield of WW and its productivity under the alternate irrigation using saline and fresh water and their interaction in the climate condition of the NCP.The salt accumulation and physiologically responses of WW to the alternate irrigation strategies were examined during the growing seasons of 2017-2019.Results showed that the water treatments had no significant impact on mid leaf photosynthesis and stomatal conductance of winter wheat.However,stomatal conductance and transpiration significantly declined with increasing soil salt accumulation.At harvest,soil EC_1:5:5 significantly increased under SF,SS and SF compared to NI and FF treatments.Soil salt accumulation increased from the stem elongation stage and then decreased from the heading stage to maturity.The grain yield was increased by 24%and 32%under FS and SF treatments followed by NI treatment,while a slightly decrease of 12%to 6%in yield was recorded by FF.Furthermore,soil salt leached from upper soil layers by summer rainfall indicates that long-term use of supplementary alternate irrigation is feasible in the NCP for sustainable productivity.Crops alternately irrigated with saline and fresh water may experience multiple abiotic stresses in the field such as salinity and drought.Hence,the mutual effect of drought and salinity on crop WUE and the physiological mechanisms were investigated in a pot experiment in the glasshouse.The objective of the study was to investigate the growth,physiological responses,ABA signaling and WUE in two wheat cultivars under different drought and salinity conditions to unravel the mechanism for the physiological adaptation.The treatment comprised three levels of drought?80,60 and 40%SWHC?and salinity stress?0,100 and 200mM of NaCl?.Results showed that the increased drought stress along with soil salinity caused partial closure of stomata via decreased plant water potential and intensified root-to-shoot ABA signaling,resulting in improved WUE_int.Increased drought and salinity stresses enhanced WUE_p and leaf?¹³C,and the increased leaf?¹³C was due to the reduced A_n and g_s and vice versa in plant water consumption.However,soil salt altered the significant leaf stomata morphology and decreased total nitrogen in the both cultivars.Therefore,plant under environmental stresses enhanced root to shoot ABA signaling positively affect the plant hormones of WW cultivars and this could be one of important indicators for its better drought and salinity tolerance and improved water productivity.Furthermore,it is demonstrated that both stresses would increase in the plant level WUE.