粘土掺砂对烤烟氮、钾含量和光合特性及产量的影响

以秦烟96为材料，采用盆栽试验，设置5个不同质量分数粘土掺砂水平，分别为S0（对照，0%）、S1（10%）、S2（20%）、S3（30%）、S4（40%），研究粘土掺砂对陕西烟区土壤物理特性、烤烟氮、钾含量和光合特性及产量的影响。结果表明，随掺砂质量分数升高，土壤体积质量降低，孔隙度增大；根系活力、根系和烟叶氮、钾含量、烟叶净光合速率（Pn）、叶绿素含量、蒸腾速率（Tr）和胞间CO₂摩尔分数（Ci）及产量均呈先提高后降低的趋势，且均以S3（30%）最大。由掺砂质量分数与产量模拟方程得出，该试验条件下，最佳掺砂质量分数为23.62%。掺砂质量分数为0%~30%时，掺砂质量分数与土壤体积质量呈显著负相关，而与根系活力、根系和烟叶氮、钾含量、烟叶光合特性指标和产量呈显著正相关，在30%~40%时均呈显著负相关（根系氮含量除外）。因此，粘土适当掺砂(30%)，可改善其土壤物理特性，提高烟株根系活力，改善氮、钾营养，有利于光合作用，提高烟叶产量。

Effects of Sand mixed Clay on Nitrogen and Potassium Contents, Photosynthetic Characteristics and Yields of Flue cured Tobacco

Pot experiments were conducted using flue cured tobacco cultivar Qinyan 96 to investigate effect of different mass fraction of sand mixed into clay soil, i.e. S0 (control, 0%), S1 (10%), S2 (20%), S3 (30%) and S4 (40%) on soil physical properties, nitrogen and potassium contents of roots and leaves, photosynthetic characteristics and yields of flue cured tobacco in Shaanxi Province. The results showed that with the increasing of mass fraction of sand mixed in clay soil, soil bulk density decreased whereas soil porosity increased. The root activity, nitrogen and potassium contents of roots and leaves, net photosynthetic rate (Pn), chlorophyll content, transpiration rate (Tr) and intercellular CO₂ concentration (Ci) and yield production all showed the trend of increase firstly and then decrease. The best performance occurred in S3 (30%) treatment. From the simulation equation, the optimal mass fraction of sand mixed in clay soil was 23.62% under the current condition. In the range of 0%-30% mass fractions , the mass fraction of sand mixed in clay soil was negatively correlated with soil bulk density while positive with root activity, nitrogen, potassium contents of roots and leaves, leaf photosynthetic characteristics index and yield. As for the range of 30%-40%, the corresponding responses were all negative correlative (except nitrogen contents of roots). Hence, S3 (30%) treatment can improve soil physical properties, increase root activity, improve nitrogen and potassium nutrition, and benefit for photosynthetic capacity for high yield of flue cured tobacco.