Study On Water Consumption Strategies And Root-shoot Characteristics Of Winter Wheat Cultivars Under Different Irrigation Treatments

North China is one of the main wheat producing areas.Under the background of water shortage,reducing irrigation and screening high-yield and water-saving wheat cultivars are great significance for food security production in this region.In this study,water use and rootshoot characteristics of high-yield wheat cultivars were determined through two-factor split plot experiments of 10 cultivars and 3 irrigation treatments during the two growing seasons of wheat from 2020 to 2022.The results would provide theoretical basis and technical reference for screening high-yield and water-saving cultivars in this region.The main results are as follows:1.Irrigation at jointing stage(Ⅱ)got the higher grain yield and water use efficiency(WUE),and there were significant differences among cultivars in grain yield and WUE.Averaged across the 10 cultivars,the mean grain yield and WUE was increased by 16.0%-20.2%and 8.8%～10.0%from 10 to I1,respectively.The mean grain yield was only increased by 4.0%～4.5%from I1 to I2.While,the WUE decreased by 2.7%in 2020-2021,and only increased by 0.1%in 2021-2022.The yield among cultivars ranged from 7988.2 to 10089.3 kg/hm2 and the WUE ranged from 1.7 to 2.3 kg/m3 under I1 treatment.2.High-yield and water-saving cultivars increased the ratio of post-anthesis water use to seasonal crop water use and promoted soil water uptake in deeper soil layers after anthesis.Irrigation had significant effect on water consumption characteristics of different cultivars.Under I0 and I1 treatments,soil water storage before sowing was an important source of water consumption of wheat.Soil water depletion(SWD)accounted for 79.0%～83.5%and 59.6%～70.7%of total water consumption,respectively under the two irrigation treatments.Irrigation at jointing stage(I1)promoted the absorption of soil water after anthesis.The ratio of post-anthesis water use to seasonal crop water use was 20.1%～43.7%and 35.5%～50.2%under I0 and I1 treatments,respectively.Under I0 treatment,reducing water consumption before anthesis and increasing water consumption after anthesis are conducive to increasing dry matter accumulation after anthesis,and hance improving grain yield.3.High-yield and water-saving cultivars increased root length density(RLD)and root weight density(RWD)in deep soil layers(100～200 cm).Irrigation had significant effect on root distribution of different cultivars.The distribution of deep roots increased under I0 treatment.The RLD in 0～200 cm soil layers ranged from 15.4 to 28.7 km/m2,and the RWD ranged from 90.7 to 280.4 g/m2 under no-irrigation condition.The distribution of roots in the soil profile directly affects the absorption of soil water by crops.Under 10 treatment,cultivars with more deep roots is beneficial to promote the absorption of soil water in deep soil layers after anthesis and increased the yield.Under I2 treatment,cultivars with less deep root distribution are beneficial to increase yield.4.High-yield and water-saving cultivars had higher leaf relative water content(LRWC)and lower canopy temperature(CT).There were significant negative correlations between CT and yield under I0 and I1 treatments.Under I0 treatment,there were significant positive correlations between LRWC with RLD in 100～200 cm soil layers and grain yield,and there were significant negative correlations between CT with RLD and RWD in 100～200 cm soil layers.In this study,LRWC and CT can be used as alternative indexes for selection cultivars with deep root system under no-irrigation condition.In conclusion,soil water storage before sowing was the main source of water consumption of wheat under no-irrigation and limited irrigation conditions.Irrigation at jointing stage promoted the absorption of soil water after anthesis,then increased yield and WUE.The highyield cultivars increased the distribution of deep roots and promoted the uptake of soil water in deep soil layers after anthesis,then decreased CT,and increased LRWC and dry matter accumulation after anthesis,and thus increased grain yield.Under full irrigation condition,the high-yield cultivars increased above-ground dry matter accumulation and decreased RLD and RWD in deep soil layers,and thus increased grain yield.