Effects Of Row Spacing And Nitrogen Fertilizer On Seed Yield And Nitrogen Use Efficiency Of Leymus Secalinus

Leymus secalinus is a perennial forage of the Gramineae,which has strong adaptability to the environment.The seed yield of L.secalinus is low in natural state,which is the biggest problem in production practice.In order to improve the seed yield of L.secalinus and to clarify the limiting factors of seed yield,the effects of cultivation techniques on the seed yield of L.secalinus were studied by using different row spacing and nitrogen application level,The experiment adopts Split zone test of row spacing and nitrogen application.Main area of nitrogen application amount is set as N0(0 kg·hm-2),N1(60 kg·hm-2),N2(120 kg·hm-2),N3(180 kg·hm-2)gradients,Sub district of the row spacing is set as R1(30 cm),R2(40 cm),R3(50 cm),R4(60 cm),each treatment is repeated for 4 times,and the area of the cell is 3m×5m.fertilization was carried out in the jointing period(May1,2020),and the effects of row spacing and nitrogen fertilizer on the seed yield and nitrogen utilization rate of L.secalinus were studied.The results are as follows(1)Under the same row spacing,with the increase of nitrogen application,the maximum photochemical efficiency(fv/fm),fv/fm value increased or decreased first,and the nitrogen addition amount significantly improved the efficiency of the energy,while the row spacing had no significant difference on the efficiency of the excitation energy.When the nitrogen application was 40 cm-60 cm,the net photosynthetic rate(Pn)of L.secalinus was increased when the nitrogen application was higher(120 kg·hm-2-180 kg·hm-2),and the dry matter accumulation was increased.The dry matter accumulation maturity > flowering stage > jointing stage,and reached the maximum under the treatment of 180 kg·hm-2 at the maturity stage.With the increase of nitrogen content,the contribution rate of dry matter accumulation before flowering was higher than that of post flowering.The maximum contribution rate of dry matter accumulation was 77.06% under the treatment of nitrogen application amount of 60 kg·hm-2 with 40 cm spacing of 40 cm,and the nitrogen application amount was 120kg·hm-2 line spacing of 30 cm.(2)The nitrogen accumulation in different periods was significantly different under row spacing and nitrogen treatment,which showed that maturity stage > flowering stage > jointing stage.From the significant level,except row spacing and nitrogen application single factor and interaction had no significant influence on nitrogen accumulation in flowering stage,row spacing and single factor of nitrogen fertilizer interaction had no significant effect on nitrogen accumulation of L.secalinus plants.The interaction between row spacing and nitrogen single factor had no significant effect on nitrogen accumulation of plants The amount of nitrogen accumulation has a significant influence.The results showed that the nitrogen accumulation of L.secalinus was mainly from the nitrogen absorption after flowering.From the significant level,the row spacing had no significant influence on the nitrogen contribution rate of the pre flower nutrition organs,and the nitrogen application had no significant influence on the nitrogen contribution rate after flowering.The nitrogen utilization rate increased with the increase of row spacing under the same nitrogen application.With the increase of nitrogen application,the nitrogen utilization rate of plants decreased obviously.The excessive application of nitrogen fertilizer was not conducive to the utilization of nitrogen,but it played a inhibitory role.The highest nitrogen utilization rate was 10.55 kg·kg-1,which was produced under the treatment of no nitrogen application line spacing of 60 cm.The lowest nitrogen utilization rate was 1.88 kg·kg-1 under the treatment of 180 kg·hm-2 line spacing of 30 cm,and the nitrogen utilization efficiency and nitrogen absorption efficiency decreased with the increase of nitrogen application and row spacing.(3)The seed yield of L.secalinus was increased with the increase of row spacing.When the nitrogen application was 120 kg·hm-2,the seed yield of L.secalinus was 403.95 kg·hm-2,and the excessive nitrogen application would cause the seed yield to decrease.The row spacing was 30 cmunder the nitrogen application of 60 kg·hm-2 The minimum yield of L.secalinus was 180.56 kg·hm-2,which was far from the maximum seed yield.Under the same row spacing treatment,the yield of rice grass seed increased with the increase of nitrogen application.Compared with the actual seed yield,the potential seed yield of L.secalinus is larger,and the row spacing and nitrogen fertilizer have a great influence on the potential seed yield of L.secalinus.Under the same nitrogen application,the potential seed yield of L.secalinus increases with the increase of row spacing.The potential seed yield of L.secalinus is 2157.74 kg·hm-2 when the line spacing is 60 cm.The germination rate and vigor index of L.secalinus seeds increased significantly with the increase of nitrogen application and row spacing.With the increase of nitrogen application,the germination rate of seeds increased gradually under the same row spacing.The row spacing and nitrogen fertilizer single factor had significant influence on germination index and vigor index of L.secalinus(P < 0.05)In conclusion,the nitrogen application amount is 120 kg·hm-2,and the line spacing is 60 cm treatment can effectively improve photosynthesis and photosynthetic products of L.secalinus,increase the accumulation of dry matter,effectively improve the seed yield of L.secalinus,and reduce the use of nitrogen,and improve the nitrogen utilization rate of L.secalinus.Excessive application of nitrogen will cause the seed yield to be reduced,nitrogen utilization rate will be reduced,nitrogen pollution and other problems.