Effects Of Nitrogen Fertilizer Management On Oat Growth And Nitrogen Utilization Under Grass-grain Planting Pattern

In view of the problems of"one season is surplus,two seasons are insufficient"and insufficient utilization rate of nitrogen fertilizer,the regeneration characteristics of"grass-grain"mode（that is,after harvesting green and recycled grain）was adopted to study the growth,yield,quality and utilization of oats.Two oat varieties were selected in the experiment:Ding yan 2（A）and Zhang yan 4（B）;Set up no nitrogen treatment（N0）,base urea（N1）,base slow-release nitrogen fertilizer（N2）,basal application of slow-release nitrogen fertilizer+urea（N3）,basal application of slow-release N fertilizer+tiller catch-up application of urea（N4）,basal application of slow-release N fertilizer+gestation catch-up application of urea（N5）,Basic application of slow-release nitrogen fertilizer+topdressing of 1/2 urea at tillering stage+topdressing of 1/2 urea in the gestational stage（N6）,a total of 7 treatments.the total nitrogen application was 71.25kg/hm².Through the analysis of the agronomic traits,yield,quality and soil nitrogen of oat,the influence of nitrogen fertilizer transportation on the growth and development and nitrogen utilization of oats is explored,in order to provide certain theoretical basis and technical support for oat production.the results show that:1.1.After nitrogen application,the plant height,stem diameter and flag leaf area of o at cutting stage,regeneration oat heading stage and regeneration oat filling stage were signi ficantly higher than those without nitrogen application.The highest plant height was 108.82 cm,which was 28.63%higher than the lowest treatment BN0.The highest stem diamete r was 5.78 mm,which was 24.57%higher than the lowest treatment AN0.The highest flag leaf area was 32.66 cm²,which was 70.19%higher than that of AN0.There were differen ces between the two varieties,but the effects of nitrogen fertilizer were consistent.2.After nitrogen application,the photosynthetic characteristics of oats were significan tly improved.The net photosynthetic rate reached 29.09μmol·m^-2·s^-1in N4 treatment,th e intercellular CO₂concentration and stomatal conductance were 418.50μmol·mol^-1and316.44 mmol·m^-2·s^-1in N5 treatment,and the transpiration rate was 7.59 mmol·m^-2·s^-1in N6 treatment.The highest net photosynthetic rate of regenerated oats at heading stage w as 22.99μmol·m^-2·s^-1under N5 treatment,the highest transpiration rate was 5.84 mmol·m^-2·s^-1under N2 treatment,and the highest intercellular CO₂concentration and stomatal conductance were 330.4μmol·mol^-1and 252.87 mmol·m^-2·s^-1under N6 treatment.The highest net photosynthetic rate of regenerated oats was 29.24μmol·m^-2·s^-1under N6 trea tment.The highest transpiration rate and intercellular CO₂concentration were 6.95 mmol·m^-2·s^-1and 349.00 mmol·m^-2·s^-1under N4 treatment,respectively.The highest stomatal conductance was 296.55 mmol·m^-2·s^-1in N2 treatment.Comprehensive analysis showed that N4,N5 and N6 treatments significantly improved the photosynthetic characteristics of oats,and the photosynthetic characteristics of oats under the’basal fertilizer+topdressing’fertilization mode were significantly higher than those under the one-time basal nitrogen fertilizer mode.3.After nitrogen application,the total yield and grain yield of oats were significantly increased.The yield of green hay and the yield of regenerated oats were the highest in N5 t reatment.The straw yield of regenerated oats was the highest in N2 treatment.The highest total grass yield treatment BN5 was 37175.62 kg/hm²,which was 33.16%higher than the lowest treatment BN0,and the difference was significant.The grain yield of AN5 was 2529.00 kg/hm²,which was 41.55%higher than that of AN0.4.Oat grass quality and grain quality were significantly improved.The crude protein content,neutral detergent fiber and acid detergent fiber of N5 treatment were the best in gr een hay at cutting stage,straw at regeneration maturity stage and regenerated oat grains,an d the crude fat content was the highest in N3 treatment.The soluble sugar content of green hay in oat mowing stage was the highest in N4 treatment,and the soluble sugar content of s traw and regenerated oat grains in regeneration maturity stage was the highest in N5 treatm ent.5.After nitrogen fertilizer application,the contents of soil total nitrogen,nitrate nitrogen and ammonium nitrogen decreased gradually with the growth period of oats.The nitrogen content of each soil layer in the mowing period reached the optimum and then decreased gradually,and the soil nitrogen content decreased with the increase of soil depth.The nitrogen content of N5 treatment in 0～20 cm soil layer and 20～40 cm soil layer was the highest in oat cutting stage and regeneration oat heading stage.The nitrogen content of N2 treatment in 0～20 cm soil layer and 20～40 cm soil layer was the highest in the filling stage of regenerated oats.6.The nitrogen use efficiency,relative feed value and economic benefit of each treat ment were significantly improved.The highest nitrogen partial productivity treatment N5was 551.17 kg/kg,which was 21.45%higher than the lowest treatment N6,and the differ ence was significant.The highest relative feeding value of green hay at cutting stage was 151.42,the highest relative feeding value of straw at mature stage was 114.72,and the highe st relative feeding value of regenerated oat grain was 429.55,which was 41.59%-49.82%higher than the lowest treatment.The highest economic benefit treatment BN5 was 55439.21 yuan/hm²,that is,the nitrogen use efficiency,relative feed value and economic benefit of oats were the highest under the treatment of basal slow-release nitrogen fertilizer+topdr essing urea at booting stage（N5）.In summary,the effect of topdressing at booting stage under oat straw-grain planting mode is better.Using slow-release nitrogen fertilizer base application（33.75kg/hm²）and booting stage topdressing urea（37.5kg/hm²）（N5）,Zhangyan 4（B）was selected as the variety.The yield of oat forage was the best and the economic benefit was the best,reaching 55439.21 yuan/hm².