Effects Of Nitrogen-saving Cultivation On Root System And Population Structure Of Spring Wheat Under Drip Irrigation

Two local spring wheat cultivars Xinchun 38 and Xinchun 49 in Xinjiang wheat region were selected as the materials.Under the condition of nitrogen reduction and combined application of organic fertilizer,the regulatory effects of different nitrogen changes in root layer on root morphology and physiological characteristics of spring wheat,the relationship between root biological characteristics and aboveground source and grain pool characteristics were studied.To clarify the coordinated effect of nitrogen reduction on root and aboveground growth and development under drip irrigation,so as to provide theoretical basis and technical support for nitrogen-saving cultivation and management of spring wheat under drip irrigation in Xinjiang.The main conclusions are as follows:1.Effect of nitrogen reduction combined with organic fertilizer on the root system of wheat under drip irrigation.Under different soil layers,the proportion of root volume and root length density of the two wheat varieties in the 0²0cm soil layer was the largest,indicating that the 0²0cm soil layer was the main soil layer of wheat root distribution,and also the soil layer where wheat roots were most active.Under different fertilization modes,the root morphology?root mass,root length density and root volume?and physiological characteristics?root activity,nitrate reductase,glutamine synthase?of Xinchun 38 and Xinchun 49 were treated with N15(nitrogen fertilizer 255 kg·hm^-2+organic fertilizer 2528 kg·hm^-2),which showed the best performance.Each treatment is represented by N15>N20>N25>N10>N5>NCK>N0,and N15 treatment was significant differences from NCK and N0 treatment.Root morphology and physiological indexes of strong gluten wheat Xinchun 38 was better than that of Xinchun 49,which increased by 4.91%to 9.74%,and the root morphology and physiological indexes of Xinchun 38 were higher than that of Xinchun 49 from the jointing stage to the flowering stage.The results showed that strong gluten wheat Xinchun 38 still showed strong root activity in the later growth stage.2.Effect of nitrogen reduction combined with organic fertilizer on population structure of drip irrigation wheat.Under different nitrogen application modes,the population structure indexes of Xinchun 38 and Xinchun 49 were the best under N15 treatment,The maximum total stem number was 722.67×10⁴ plant·hm^-2and 711.23×10⁴ plant·hm^-2 respectively,the leaf area index was 6.86 and 6.24,the contribution rate of dry matter after anthesis was 75.04%and 75.52%respectively,the grain-leaf ratio was 0.43 grain/cm² and 0.42 grain/cm²,and the grain weight-leaf ratio was 18.6 mg/cm² and 19.5 mg/cm²respectively,Each treatment is represented by N15>N20>N25>N10>N5>NCK>N0.N15 treatment was significantly different from NCK and N0 treatment.Under different varieties,the population structure of Xinchun 38 was the best.Compared with Xinchun 49,the number of tillers,leaf area index,grain weight-leaf ratio,grain-leaf ratio,maximum rate of dry matter accumulation,pre-anthesis dry matter and post-anthesis dry matter contribution rate of Xinchun 38 increased by 3.97%,11.64%,2.69%,5.83%,8.89%,1.66%and 1.45%respectively.3.Effects of nitrogen reduction combined with organic fertilizer on photosynthetic characteristics and fluorescence parameters of drip irrigation wheat.The SPAD values of Xinchun 38 and Xinchun 49 increased at first and then decreased from tillering stage to flowering stage.With the increase of nitrogen reduction level,Pn,Tr and Gs in flag leaves of spring wheat under drip irrigation increased at first and then decreased,while Ci decreased at first and then increased.The photosynthetic characteristics of strong gluten wheat Xinchun 38were better than those of the reinforcement in Xinchun 49,and the net photosynthetic rate,stomatal conductance,transpiration rate,intercellular CO₂ concentration,maximum photochemical efficiency and actual photochemical efficiency increased by 0.54%,7.52%,7.9%,8.28%,0.62%and 10.38%,and the photosynthetic capacity of the two wheat varieties under N15 treatment was the best.The net photosynthetic rate are 24.0?mol·m^-2·s^-1 and 22.6?mol·m^-2·s^-1,and the maximum photochemical efficiency is 0.846 and 0.838 respectively.4.Effect of nitrogen reduction combined with organic fertilizer on yield of drip irrigation wheat.Under different nitrogen application modes,with the increase of nitrogen reduction level,the yield of the two varieties increased at first and then decreased,the number of panicles and grains per panicle also increased at first and then decreased,while the 1000-grain weight decreased gradually.When the Xinchun 38 and Xinchun 49 were treated with N15,the yield reached the maximum,which were 7245.68 kg·hm^-2 and 7178.19 kg·hm^-2 respectively.Through the path analysis of the three yield components,it was found that the correlation coefficient of the three yield components on yield of the two wheat varieties was r_{panicle number}>r panicle grain number>r1000-grain weight,and the direct effect of the three yield components on yield of the two wheat varieties was Ppanicle number>Ppanicle grain number>P1000-grain weight.Therefore,among the yield and yield components,spike number and grain number per spike had a greater effect on yield,while 1000-grain weight had little effect on yield.Therefore,under the model of N15,the root distribution of spring wheat under drip irrigation could be significantly increased,the physiological activity of roots in the later growth stage could be prolonged,and the root growth could be promoted.Furthermore,the number of tillers,leaf area index,grain-leaf ratio and grain weight-leaf ratio of spring wheat under drip irrigation were increased,the SPAD value of leaves was increased,and the photosynthetic rate,maximum photochemical efficiency and actual photochemical efficiency were increased.So as to promote the distribution of dry matter accumulation to grains and increase the number of panicles,grains per spike and grain yield.