| In China,fresh water resources is scarce in arid and semi-arid areas,and water use efficiency of salt resources is very low.From 2014 to 2015,field experiments were carried out to sudy water-salt distribution,water consumption characteristics,spring wheat growth index,and yield variation under the condition of different irrigation amount and water salinity in the Shiyang River Basin.Also,Feddes Model for root water uptake with the interaction of water and salt stresses was calibrated and validated.Three levels of irrigation amount: 355,280,and 205 mm(W1,W2 and W3)and four water salinity levels: 0.7,3,5 and 7g/L(S1,S2,S3 and S4)were settled in the experiments.There were 12 treatments and three replicates per treatment.The results are showed as follows:(1)Under the condition of fresh water irrigation(S1),the change of soil salt content was not high,the salt accumulation peak value was less than 0.6g/kg,and the soil salt accumulation rate was less than 15%.The degree of salt accumulation of soil profile was different.The more irrigation amount,the higher irrigation salinity,and the salt accumulation was also more obvious.The peak zone of salt accumulation in soil profile was in the 20-40 cm layer,and the value was up to about 2kg.About 40 to 80% of salt which brought by irrigation accumulated at 60 cm depth while the water salinity was higher than 3g/L.In addition,due to the salt accumulation in 2014,the initial salt content of W1S3 and W1S4 of 20 to 40 cm was up to 2g/kg in 2015.Irrigation time played an important influence on soil water content in the jointing stage.Irrigation time should be regulated reasonably.Under three irrigation amount levels,water content in root zone can be maintained with the range of 60 to 80% of field capacity.(2)Plant height,leaf area and yield of spring wheat increased gradually with increasing irrigation amount and decreasing water salinity.With the development of growth,the root length density of spring wheat increased from heading to filling stage,and reached the maximum at the grain filling stage and then decreased gradually after maturity.In the view of the vertical distribution of root length density,the root length of 0 to 30 cm soil depth accounted for more than 80% of the total root length.Under the same water salinity,compared with sufficient irrigation treatment W1,the yield reduction in W2 and W3 was less than 10% and 15%.Under the condition of the same irrigation amount,yield reduction of spring wheat was less than 10% while water salinity was 3g/L.While the salinity is above 5g/L,yield reduction was serious.Comparison of the experiments in two years,it can be found that when the salinity of irrigation was 3g/L,the yield of spring wheat in 2015 declined less than 10% than in 2014.Furthermore,ear length,grain number per ear and dry matter weight got the highest values at 3g/L irrigation in 2015.While the water salinity was higher than 5g/L,the plant height of spring wheat was reduced by more than 10% compared with that of 2014,which resulted in leaf presenility.The result indicated that water salinity of 3g/L can be used to save fresh water resources.The intensity of water consumption and water consumption of spring wheat are mainly related to irrigation amount,the greater irrigation amount,the higher the intensity of water consumption and water consumption.However,they were not significantly affected by irrigation salinity.Under the condition of full irrigation,irrigation water accounted for 59.83 to 80.01% of total water consumption.Under the condition of deficit irrigation(W3),crops will strengthen the absorption of soil water,and the proportion of irrigation water has decreased,accounting for 43.92 to 57.37%.While the salinity of irrigation was more than 5g/L,water use efficiency in 2015 was significantly lower than that in 2014.The result was dued to salt accumulation which was brought by irrigation.Water use efficiency of W1S3,W2S3,W1S4 and W2S4 were respectively decreased by 6.77%,6.52% and 28.99%,and 22.22%.(3)Based on the principle of water balance,we calculated spring wheat root water uptake in different treatment at different stages,and calibrated and verified Root Water Uptake Feddes Model in the interaction of water and salt.The results showed that under water stress,the differences between simulated and measured values of root water uptake were unobvious.Except the error of phase one and two in W3S1 respectively reached 31% and 32% in 2014,the rest of the phase error was less than 25%.Under the condition of salt stress,because the cardinal number of root absorption was small in phase two of W1S3 and W1S4 in 2014,the errors were 34% and 32%,respectively.Besides,in 2015,the relative errors reached 36% in phase three of W1S4,and that of the rest of the phase were less than 27%.Under the interaction of water and salt,the simulation results of Root Water Uptake Feddes Model were good,relative error was almost less than 20% and few values reached 30%,which basically meet the application requirements. |
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