Effects Of Nitrogen Fertilizers And Population Densities On Growth Characteristics,Yield And Quality Of Hole-Sown Winter Wheat

Wheat is the most important food crop on the entire globe.The achievement of high efficiency,good character,and high output of wheat is of great meaning for guaranteeing grain production in China.Population densities and nitrogen application rate have a regulatory effect on wheat yield.In recent years,studies on the effects of nitrogen application rate and population density on wheat growth characteristics has primarily concentrated on drill sowing,wide-width sowing of wheat,and topdressing nitrogen fertilizer in late growth stage of wheat.However,studies on different nitrogen application rates and planting densities of wheat under hole-sown methods are relatively rare.Furthermore,the effect of nitrogen application amount and population densities on the growth,yield,and character of hole-sown winter wheat is unknown.Therefore,the winter wheat“Xinong 585”was employed as the experimental material between2020 and 2022,with three nitrogen application rates:210 kg·hm^-2（N210）,245 kg·hm^-2（N245）,280 kg·hm^-2（N280）,and five planting densities:312×10⁴ grains·hm^-2（D1）,425×10⁴ grains·hm^-2（D2）,600×10⁴ grains·hm^-2（D3）,706×10⁴ grains·hm^-2（D4）and 857×10⁴ grains·hm^-2（D5）,15treatments in total.The regulating influence of nitrogen application amount on leaf physiology,dry matter（nitrogen）build-up and allotment,stem characteristics,yield,and quality of hole sown winter wheat at various densities was investigated.The following main findings were made:1.As the growth period progressed,the total number of hole sown winter wheat tillers grew and eventually declined.The number of tillers was greatest at D4 density throughout the growth period;at the same planting density,nitrogen application rates showed N245>N280>N210 treatment.The maximum number of tillers in the population was attained at N280D3 and N245D5 during the two-year maturity period,indicating that increasing the planting population at a medium nitrogen application rate is also beneficial to shape a healthy population structure for hole sown wheat.2.Nitrogen fertilizer and density both have a considerable impact on the photosynthetic performance of hole sown wheat,with density being the most important element.The flag leaf SPAD value,Pn,Gs,and Tr perform best at N245,although there is a negative correlation with population density.Under the interaction of nitrogen fertilizer and density,the intercellular CO₂concentration and flag leaf area increased as nitrogen density increased;The SPAD value and Pn of flag leaf improved as nitrogen application amount advanced at D1-D2,but decreased as nitrogen application amount advanced at D4-D5 simultaneously.The photosynthetic capacity of wheat flag leaf was significantly lower under high density and high nitrogen treatment than under low density and high nitrogen treatment.3.Nitrogen fertilizer and density have a considerable impact on the internode properties of hole-sown wheat stems,and nitrogen and density have a large interaction effect.As population densities increased,plant height,centre of gravity height,and basal 1-5 internode length increased significantly,but the stem and stem wall became more delicate and weak,and bending resistance decreased;As nitrogen application amount increased,plant length,centre of gravity height,and basal 1-5 internode length increased significantly,but the stem and stem wall became more delicate and weak,and bending resistance decreased.4.The dry matter mass of stems,leaves,and panicles increased as nitrogen application amount increased,reaching a maximum at N280.The dry matter mass is greatest at D4 density during each growth cycle.Reduced nitrogen application rate and increased planting density,or decreased planting density and increased nitrogen application amount,can promote the amount of dry matter in the shoot and various organs during the mature stage when nitrogen fertiliser and density interact.N210D3 and N245D3 treatments were more conducive to dry matter buildup in hole seeded wheat over a two-year period.Nitrogen accumulation in stems,sheaths,and leaves was greatest during flowering when N280 was applied.The D1-D4 density range promotes wheat nitrogen accumulation.The nitrogen content of several organs in the mature phase increased when the nitrogen application amount was increased.Under the reciprocal effect of nitrogen fertiliser and population densities,medium and high seeding rates are more conducive to increasing nitrogen accumulation in wheat grains than low seeding rates,and nitrogen accumulation in wheat grains is greatest under N245D3 and N210D4 treatments in two years,respectively.As a result,the suitable seeding rate linked with medium and low nitrogen in support of wheat grain nitrogen buildup.5.The yield composition and quality of wheat under hole-sown showed significant differences under different nitrogen fertilizers and planting densities.The nitrogen application rate of 245-280 kg·hm^-2 increased the grain number per spike and processing quality of hole sown wheat,while reducing the effective spike number per unit area and 1000 grain weight.The effective panicle number improve with the elevate of population densities;The quantity of grains per spike and processing quality reached the maximum at D2 density;In the interaction between nitrogen fertilizer and density,under D1-D2 density,medium and high nitrogen application rates can promote the synthesis of the improvement of processing quality.During the two-years growing seasons,the yield reached the maximum under N210D3 treatment,which was 8287.64 kg·hm^-2 and 8703.27 kg·hm^-2,respectively.Research results of integration nitrogen application amount and population densities on growth peculiarity,output and quality of hole-sown winter wheat.Compared with high density（D4 and D5）,D2 and D3 treatments reduced plant height,center of gravity height,basal internode extent,improved stem diameter,stem wall thickness,and fracture resistance,thereby reducing the risk of lodging,and achieving higher grain numbers per spike and yield.Compared with high nitrogen（N280）application,245 kg·hm^-2 nitrogen application improved the tiller amount,flag leaf chlorophyll content,net photosynthetic rate,stomatal conductance,transpiration rate,processing quality,and yield of wheat population.In summary,from the perspective of cost saving and high yield,when the density is between 425-600 plants·hm^-2 and the nitrogen amount is 210-245 kg·hm^-2,it can guarantee the output of the hole sown winter wheat Xinong 585,while having better grain quality and lodging resistance.