氮对水培生菜营养液元素动态变化及产量与品质的影响

Effects of Different Nitrogen Levels on the Nutrient Elements Dynamic Change,Yield and Quality of Hydroponic Lettuce

氮素是生菜最重要的营养元素之一，影响生菜的产量和品质，通过动态监测水培生菜生长及营养液矿质元素变化过程，为水培生菜合理有效的营养液管理提供理论依据。采用深水培方法，在5个氮素浓度9,8,6,4,3mmol/L条件下对生菜产量、品质及营养液元素动态变化过程进行了试验观测，分析了氮对水培生菜生长、矿质元素利用效率及动态吸收量的影响。不同氮素处理生菜的干物质积累量随时间差异越来越显著，在氮素水平为6mmol/L时生菜可获得最大产量；硝酸盐含量随氮水平的增高先增高后稍有降低，氮素浓度为8mmol/L时最高；Vc和可溶性蛋白不断增高，在氮素浓度为9mmol/L时含量最高；可溶性糖先增高后减小，氮素浓度为6mmol/L时含量最高；不同氮素浓度显著地影响了生菜对氮的吸收，高浓度氮素水平有利于生菜对氮、磷的吸收，较低氮素水平则有利于生菜对钾、钙、镁的吸收。生菜对氮、磷的吸收主要集中在定植后的20.30d，平均吸收量分别占到全生育期的64.81%和61.88%，对钾的吸收在定植后30.40d较多，平均吸收量占到全生育期的44.46%，生菜对钙、镁的吸收在定植后都较均勻。生菜对磷、钾、钙、镁的利用效率呈现出先增大后减少的趋势，对氮的利用效率线性减小。当氮素水平为8mmol/L时，生菜全生育期对矿质元素的吸收量最大，为582.31mg/株，此时生菜获得较好的产量和品质，较高的磷、钾、钙、镁利用效率，但是氮的利用效率较低。

Through dynamic monitoring on hydroponic lettuce growth and mineral nutrient change,provide theoretical basis for reasonable and effective management of hydroponic lettuce nutrient. By adopting deep hydroponic method,setting five nitrogen concentration,respectively 9,8,6,4,3 mmol / L,systematically learned the influence of different nitrogen levels on lettuce yield,quality,utilization efficiency and dynamic absorption of mineral elements.The results showed that under different nitrogen level the difference of lettuce dry matter accumulated more and more significant over time,when nitrogen levels was 6 mmol / L,lettuce obtained maximum yield. Lettuce nitrate increased first and then slightly decreased as the nitrogen increasing,and reached the maximum when the nitrogen level was 8 mmol / L,Vc and soluble protein increased constantly as the nitrogen increasing,and the content reached the highest when nitrogen level was 9 mmol / L,the soluble sugar increased first and then decreased as the nitrogen increased,and gained the maximum levels when nitrogen level was 6 mmol / L. As the nitrogen level increased,the utilization efficiency of P,K,Ca,Mg of lettuce showed a trend of increase first and then decrease,nitrogen utilizationefficiency of lettuce linear decreased. High concentration of nitrogen level helped improve the lettuce on the absorption of nitrogen and phosphorus,while low nitrogen level helped improve the absorption of potassium,calcium and magnesium. The absorption of nitrogen and phosphorus were mainly concentrated in the 20- 30 d after planting,average uptake respectively accounted for 64. 81% and 61. 88% of the whole growth period,the absorption of potassium reached the maximum in the 30 ~ 40 d after planting,the average absorption was 44. 46% of the whole growth period,the lettuce on the absorption of calcium and magnesium were relatively uniform after planting. When nitrogen level was 8 mmol / L,lettuce absorption of mineral elements gained highest in the whole stages,which was 582. 31 mg / plant,by this time,the lettuce obtained good yield and quality,higher efficiency utilization of P,K,Ca,Mg,but the nitrogen use efficiency was lower.