Effects Of Different Water And Nitrogen Treatments On Population Root-shoot Growth And Nitrogen Utilization Of Winter Wheat

The coordination between the ability of wheat root to obtain water and nutrients and the photosynthetic performance of the canopy structure determined the yield and resource utilization efficiency of wheat.The cultivar ‘Fengdecun 5’ was selected as experimental material.A field experiment was conducted using split-plot on design two factors.Two main levels of water supply,W0(no irrigation during the whole growth period)and W1(irrigation once each at the jointing and flowering stages),and three secondary levels of N application [N0(0 kg hm-2),N180(180 kg hm-2),and N300(300 kg hm-2)] were set.The responses of population structure,photosynthetic performance,root characteristics,grain protein yield,nitrogen transport and utilization to water and nitrogen and the relationship between root and shoot of winter wheat were studied.This study provided a theoretical basis for building a reasonable population structure of winter wheat,promoting the coordinated growth of root-shoot and achieving high yield and efficiency.The main research results are as follows:1.Effects of different water and nitrogen treatments on yield and quality of winter wheatIrrigation and nitrogen application had significant effects on wheat yield and its component factors.The coupling of water and nitrogen had significant effects on spike number and 1000-grain weight.Compared with W0,W1 significantly increased spikes number and yield by 13.58% and 15.50%,decreased 1000-grain weight and protein content by 3.82% and 6.92%,and increased grain number per spike and protein yield by 4.49% and 6.94%.Nitrogen application increased spikes number and grain number per spike,decreased 1000-grain weight,and increased yield,protein content and its yield.In the treatments,W1N180 is beneficial to obtain high and stable yield2.Effects of different water and nitrogen treatments on population quality of winter wheatIrrigation and nitrogen application significantly affected the population structure and dry matter accumulation and transport of winter wheat.Compared with W0,W1 significantly increased total stem number,tiller heading rate and leaf area index by11.76%,4.92% and 7.73%,respectively.RVI and NDVI values were significantly increased by 4.34%-34.15% and 22.60%-37.25%.Aboveground dry matter accumulation and pre-flowering dry matter translocation amount significantly increased by 14.63% and 10.44%,but pre-flowering dry matter translocation rate and contribution rate were decreased.Total stem number,leaf area index,NDVI,RVI and dry matter accumulation increased with the increase of N application rate,while tiller heading rate decreased with the increase of N application rate.The dry matter translocation characteristics of pre-flowering vegetative organs showed N180>N300among nitrogen application levels.Compared with N300,N180 increased the translocation amount,translocation rate and contribution rate of pre-flowering dry matter of by 7.09%,8.92% and 10.44%,respectively.3.Effects of different water and nitrogen treatments on canopy light utilization of winter wheat populationIrrigation,nitrogen application and their interaction significantly affected light utilization characteristics of winter wheat.Irrigation was beneficial to improve the photosynthetic performance of winter wheat.Compared with W0,W1 increased extinction coefficient by 3.10%-12.54%,PAR interception ratio by 2.58%-7.12% and canopy photosynthetic rate by 5.14%-37.19%.The PAR interception ratio and extinction coefficient increased with the increase of nitrogen application rate,as N300>N180>N0.Increased nitrogen application significantly increased the canopy photosynthetic rate,but N180 was higher than that of N300.Especially under W1 treatment,the canopy photosynthetic rate of N180 treatment was significantly increased by 3.47%-12.78% compared with N300.In the treatment combination,W1N180 treatment maintained high the canopy photosynthetic capacity throughout the growth period.Correlation analysis showed that leaf area index,the canopy photosynthetic rate and PAR interception ratio were positively correlated with grain yield.The results indicated that the yield of winter wheat could be increased by increasing the canopy photosynthetic rate and PAR interception ratio.4.Effects of different water and nitrogen treatments on nitrogen translocation characteristics and utilization efficiency of winter wheatIrrigation could facilitate the translocation of nitrogen to grain before flowering and improve nitrogen use efficiency.Compared with W0,W1 increased pre-flowering nitrogen translocation amount and translocation rate by 29.92% and 2.02%,increased nitrogen uptake efficiency and the partial productivity of nitrogen fertilizer by 13.40%and 14.91%,respectively.Compared with N0,nitrogen application significantly increased the pre-flowering nitrogen translocation amount and contribution rate,while the pre-flowering nitrogen translocation rate and nitrogen use efficiency were the highest under N180 treatment.Compared with N300,N180 significantly increased the pre-flowering nitrogen translocation rate,nitrogen uptake efficiency and agronomic use efficiency of nitrogen fertilizer by 3.62%,44.51% and 39.37%,respectively.5.Effects of different water and nitrogen treatments on root characteristics of winter wheat and its relationship with abovegroundCompared with W0,W1 inhibited the increase of root length density,but was beneficial to the growth of root average diameter,promoted the increase of root surface area and root dry weight density in 0-20 cm soil layer,significantly increased root activity by 4.98%-22.7%,and decreased root-shoot ratio by 1.47%-11.25%.Nitrogen application promoted root growth of winter wheat.Compared with N0,nitrogen application significantly increased root average diameter,root length density,root surface area,root dry weight density and root activity,and decreased root-shoot ratio.N180 was more beneficial to root growth and improved root morphological indexes and root activity of winter wheat.Correlation analysis showed that root dry weight density was positively correlated with the canopy photosynthetic rate,grain grain yield and nitrogen utilization.There was a negative correlation between the canopy photosynthetic rate and nitrogen use efficiency at maturity stage.The root-shoot ratio was negatively correlated with the canopy photosynthetic rate,grain yield,but positively correlated with nitrogen utilization.The results showed that balanced root-shoot growth was beneficial to increase the population photosynthesis,yield and nitrogen utilization of winter wheat.In conclusion,reasonable irrigation and nitrogen application can optimize population structure and root morphological distribution of winter wheat,improve the canopy photosynthetic performance and root activity,coordinate dry matter distribution of root-shoot,and improve grain yield,protein yield and nitrogen use efficiency.In winter wheat production,once irrigation each of at the jointing and flowering stages combined with 180 kg hm-2 nitrogen application was beneficial to the construction of reasonable population root-shoot structure,the improvement of canopy photosynthetic capacity and root activity,the coordination of root-shoot dry matter distribution,and the synergic improvement of grain yield and nitrogen use efficiency.