Regulation And Physiological Basis Of Nitrogen Forms On Tillers And Yield Of Winter Wheat

In this experiment,multi-spike type winter wheat variety SN28 and large-spike type winter wheat variety TN18 were selected as test materials.From October 2018 to June 2019,pot experiments and field tests were carried out in the agronomic test field of Shandong Agricultural University.Seven nitrogen treatments were set up:no nitrogen?N0?,urea?N1?,nitrate nitrogen?N2?,ammonium nitrogen?N3?,nitrate nitrogen and urea 1:1 mixed application?N4?,ammonium nitrogen and urea 1:1 mixed application?N5?,nitrate nitrogen and ammonium nitrogen 1:1 mixed application?N6?.By studying the effects of different forms of nitrogen on the growth dynamics,thepercentage of ear-bearing tiller of tillers,dry matter and nitrogen accumulation in each stem,total carbon,total nitrogen content,nitrogen utilization rate,Endogenous hormone,yield and its constituent factors,etc.The physiological mechanism of nitrogen morphology to regulate tillering and panicle formation was analyzed in order to provide a theoretical basis for constructing a high-yielding population of winter wheat with different nitrogen morphologies.The main findings are as follows:1.Effects of nitrogen forms on endogenous hormone content,stem growth growth and earing rate of tillers in winter wheatCompared with the treatment without nitrogen application?N0?,the application of different forms of nitrogen can significantly increase the content of endogenous ZR+ZT and GA₇ and the number of tillers in the tillering nodes of two winter wheat varieties at each growth stage.The content of endogenous ZR+ZT and GA₇ and the response of?ZR+ZT?/GA₇ to nitrogen forms in the tillering section of the two varieties at each growth stage were basically consistent with the dynamic trend of stem growth.The total number of stems per unit area of SN28 and TN18 in the three-leaf stage and overwintering stage was significantly higher than that of 1:1 mixed application of nitrate nitrogen and urea?N4?.SN28 and TN18 at the jointing and heading stages had the highest number of stem borers per unit area under the mixed application of nitrate nitrogen and urea 1:1?N4?treatment,followed by nitrate nitrogen?N2?treatment.The total number of stems per unit area of the two varieties at the mature stage was the largest under the 1:1 mixed application of nitrate nitrogen and urea?N4?treatment,followed by the urea?N1?and nitrate nitrogen?N2?treatments,and the nitrate nitrogen and ammonium nitrogen 1:1 mixed application?N6?treatment was the smallest.Nitrate nitrogen and urea 1:1 mixed application?N4?treatment increased 12.39%and 7.56%respectively compared with urea?N1?treatment.Compared with other treatments,1:1 mixed application of nitrate nitrogen and urea?N4?significantly increasedthepercentage of ear-bearing tillerof SN28 and TN18.Although the ammonium nitrogen and urea 1:1 mixed application?N5?treatment promoted the occurrence of tillering at the early stage of growth,the conversion to effective tillering at the later stage was significantly reduced.The single application of ammonium nitrogen?N3?was not conducive to the occurrence of tillering of the two varieties,and it was also not conducive to the tillering and panicle formation in the later stages.2.Effects of nitrogen forms on dry matter accumulation in winter wheatThe 1:1 mixed application of nitrate nitrogen and urea?N4?treatment significantly increased the dry matter accumulation of the two varieties at each growth stage.In SN28,nitrate nitrogen?N2?treatment was the second,and in TN18,urea?N1?treatment was the second.The dry matter accumulation of SN28 and TN18 increased by 38.18%,34.68%,38.89%,12.13%and 12.49%,10.12%,12.74%and 6.90%respectively in overwintering period,rejuvenation period,jointing period and mature period compared with that of urea?N1?.Among all nitrogen application treatments,the 1:1 mixed application of nitrate nitrogen and ammonium nitrogen?N6?treatment was the most detrimental to the dry matter accumulation of winter wheat in each growth period.The grain weight and biomass of SN28and TN18 at the mature stage were the largest under the mixed application of nitrate nitrogen and urea 1:1?N4?,and the increase effect was more significant as the niche position increased.Compared with the conventional fertilization urea?N1?,the grain weight of SN28tillers of II,III and Ip increased by 21.90%,34.86%and 52.11%,respectively.TN18 increased by 15.88%,26.87%and 41.43%respectively.The responses of dry matter accumulation in leaves and stem sheaths of different stems to nitrogen forms were inconsistent.The 1:1 mixed application of nitrate nitrogen and ammonium nitrogen?N6?treatment was the most detrimental to the accumulation of dry matter in different organs of different stems and tillers of winter wheat varieties.3.Effects of nitrogen forms on the carbon and nitrogen content,nitrogen accumulation,and nitrogen efficiency of different organs of different stems of winter wheatNitrogen treatment significantly increased total nitrogen,total carbon content,nitrogen accumulation,and nitrogen efficiency in different organs of different stem borers of SN28 and TN18.Under the same nitrogen treatment,there was no significant difference in the total carbon and total nitrogen content in the grains of the stems of the two varieties.The 1:1mixed application of nitrate nitrogen and urea?N4?treatment increased the carbon and nitrogen content in the grains of each stem compared with other treatments.The amount of nitrogen accumulation in each organ of winter wheat is:grain>stem sheath>leaf.The nitrogen accumulation in the grains of the stems of the two varieties was the largest under the1:1 mixed application of nitrate nitrogen and urea?N4?treatment,which significantly increased the nitrogen accumulation in the high-level tiller.Compared with urea?N1?,the nitrogen accumulation of the two varieties II and III increased by 28.02%,49.32%,26.36%and 50.90%respectively,which had different effects on the nitrogen accumulation of stem sheath and leaf of each tiller.The 1:1 mixed application of nitrate nitrogen and urea?N4?treatment significantly increased the nitrogen utilization rate,nitrogen absorption efficiency,nitrogen harvest index,and nitrogen agronomic efficiency of SN28 and TN18,reduced nitrogen loss,and promoted Nitrogen is transported and distributed in wheat grains.4.Effects of nitrogen forms on winter wheat yield and its constituent factorsThe 1:1 mixed application of nitrate nitrogen and urea?N4?treatment significantly increased the effective panicles at the maturity stage,the number of panicles per panicle of?,?,and?p and the thousand-grain weight of?p,thereby further increasing wheat yield.Among them,the effective ear number contributed the most to the yield.Under the 1:1 mixed application of nitrate nitrogen and urea?N4?treatment,the effective ear number of SN28 and TN18 increased by 7.76%and 5.63%respectively compared with the urea?N1?treatment.The yield increased by 6.38%and 2.18%respectively.Although the treatment of ammonium nitrogen?N3?combined with ammonium nitrogen and urea 1:1?N5?increased the 1000 grain weight of low tiller,the effect of increasing 1000 grain weight of high tiller was not significant,and the number of effective ears of mature wheat was significantly reduced,so the effect of increasing yield was poor.