氮肥用量对烟草群体发育和群体光合的影响

为了揭示氮肥用量与烟草群体光合的关系,以烤烟品种K326为材料,设置3个氮肥用量处理:N1(75.0kg·hm~(-2))、N2(97.5kg·hm~(-2))、N3(120.5kg·hm~(-2)),研究了氮肥用量对烟草群体叶面积动态、冠层辐射和群体光合作用的影响。结果表明,烤烟群体发展动态表现为圆顶期叶面积指数(LAI)最大,行间叶尖距和冠层透光率最低,以后随着叶片的成熟采收,LAI逐渐减小,行间叶尖距和冠层透光率逐步增大。与此相应,群体光合速率(RCP)也以圆顶期最高。圆顶期,3个施氮量处理的LAI大小顺序为N3N2N1,但N2和N3之间差异不显著;下二棚收获后,以N2的LAI最大。2个生育阶段(圆顶期到下二棚叶采收、下二棚叶收获到中部叶采收)的叶面积持续期(LAD)均以N2处理较高。冠层透光率以N3处理最低,N2与N1差异不显著。群体光合速率(RCP)以N1最低,N2和N3差异不显著。不同发育阶段的群体叶源量(CLSC)以N1处理最低,圆顶期到下二棚采收阶段,N2略高于N3,后期N3略高于N2。随着施氮量的增加,烟叶产量提高,上等烟比例和产值则以N2最高。从群体发展及生产成本等综合考虑,种植烤烟品种K326时,以采用18 182株·hm~(-2)左右的种植密度,97.5株·hm~(-2)左右的氮肥用量较为适宜,有利于群体协调发展,增强群体光合能力。

Effect of Nitrogen Fertilizations on Population Development and Canopy Photosynthesis of Flue-cured Tobacco

Canopy photosynthetic capacity is the basis for the yield and quality of flue‐cured tobacco ;and ,nitrogen fertilization is critical in regulating the individual growth and canopy development of the plants .To determine the relationship between the fertilization and the canopy photosynthesis ,3 nitrogen fertilizer application rates ,i .e .,N 75.0 kg · hm-2 (N1 ) ,N 97.5 kg · hm -2 (N2 ) and N 120.5 kg · hm -2 (N3 ) ,were applied on the tobacco cultivation .The effects of the varied fertilizations on the leaf area index (LAI) ,light transmittance (LT ) ,and photosynthesis of K326 tobacco were monitored .The results showed that ,in the course of canopy development , LAI was the highest ,but the distance between leaf tips of adjacent lines (DLT ) and LT was the lowest at the round top stage ;and afterwards ,LAI decreased ,DLT and LT increased as the leaves were harvested .Meanwhile ,the canopy photosynthetic rate was the highest at the same stage ,and LAI in the order of N3 ,N2 and N1 ,with no statistically significant difference found between N 2 and N3 .After the lower leaves were harvested from the plants , LAI of N2 became greater than those of N2 and N3 .Additionally ,the leaf area duration of N2 was the longest among the treatments during the two periods from the round top stage to the lower leaves harvest ,as well as ,from the lower leaves harvest to the middle leaves harvest . The canopy LT of N3 was the lowest , with no significant difference between N1 and N2 ,and the canopy photosynthetic rate and canopy leaf source capacity of N 1 were the lowest with no significant difference between N2 and N3 . The tobacco yield increased with increasing nitrogen application .However ,the proportion of top‐quality tobacco and output value were found to be the highest under treatment N2 .Thus ,an intermediate nitrogen fertilization rate (approximately 97.5 kg per hm2 ) was considered economically appropriate for K326 cultivation at a planting density of 18 , 182 plants per hm2 as used in this experimentation .