Effect of nitrogen fertilizer on nitrogen balance index,photosynthetic characteristics and yield of wide-range densely planted oats
[Objective]To identify the optimal nitrogen fertilization mode to maximize the yield of wide-range densely planted oats in the southern foothills of Yinshan Mountains in Inner Mongolia.[Methods]A two-factor experimental design was employed with five nitrogen levels(N1:35 kg/hm2,N2:70 kg/hm2,N3:105 kg/hm2,N4:140 kg/hm2,N5:175 kg/hm2)and two topdressing stages(T1:tillering stage,T2:booting stage).The impact of different nitrogen application levels and topdressing stages on nitrogen balance index(NBI),photosynthetic characteristics and yield of oats at each growing stages were analyzed.[Results]During the middle and late growth stages,both the net photosynthetic rate and NBI of oats increased first and then decreased with rising nitrogen levels.At grain-filling stage,N4 nitrogen level in the T2 treatment had best photosynthetic efficiency,but no significant difference(P>0.05)with N3 nitrogen level.At the same nitrogen level,compared with T1 treatment,T2 treatment enhanced the net photosynthetic rate and NBI of middle and late growth period stages oats by 1.40%-11.97%and 9.82%-23.26%,respectively,with N3 nitrogen level having the most significant increasing.In comparison with T1 treatment,oat yield components of T2 treatment had synergistic improvement,with grain yield increased by 3.99%-9.10%.The grain yield of N4 nitrogen level was highest at 3 901.13 kg/hm2.However the difference with N3 nitrogen level was not significant(P>0.05).Correlation analysis revealed that chlorophyll index(Chl)and NBI of oat had extremely significant positive correlations with yield during the heading and grain-filling stage,with grain filling stage having a higher correlation coefficient.[Conclusion]The optimal nitrogen application rate for wide-range densely planted oats in the southern foothills of Yinshan Mountains in Inner Mongolia was 105-140 kg/hm2.Booting stage was the most effective timing for nitrogen application.
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