【摘要】 采用盆栽试验方法探讨利用手提式叶绿素计预测菠菜氮含量、硝酸盐含量的可能性。试验分尿素氮4个浓度水平,4个重复,每盆施土2kg。收获期菠菜生物量、叶片和根的干重及含氮量的分析表明,在100mg·kg-1施氮浓度时获得最大生长量和最低硝态氮含量。SPAD值与菠菜叶片的含氮量、硝态氮含量显著相关,表明利用便携式叶绿素计测定菠菜叶片叶绿素的SPAD(Soil-PlantAnalysisDevelopment,土壤-植物分析模式)值对菠菜叶片的含氮量、菠菜硝态氮含量具有潜在的预测作用。SPAD读数随着时间的延续而下降,表明还可能用于有效控制菠菜的最佳收获时间。更多还原

【Abstract】 This study is aiming at investigating possibility of predicting concentration of nitrogen, nitrate in spinach using a pocket apparatus chlorophyll meter (Minolta, Japan) based on a pot experiment. Spinach was grown in plastic pots filled with 2 kg brown soil per pot with urea as only nitrogen fertilizer. Four fertilizer application rates (0, 100, 200, 400 mg· kg- 1 urea- N) were used in this study with four replicates for each treatment. After pre- treatment, seeds of spinach were sown on 21st March and plants were harvested on 7th May in 2003. SPAD values were read once a week 20 days after seedling emergence. Furthermore, plant biomass, leaf and root dry weights, total nitrogen content in leaf and root, NO3- N in leaf were measured after harvesting. The results showed that SPAD readings in the control started to drop on 25 th April and continued to decrease through the rest of the growth season. The readings for 100 and 200 mg· kg- 1 urea- N fertilizer treatment began to decrease on 2nd May.For the treatment with 400 mg· kg- 1 urea- N, the SPAD readings showed a decrease only on 2nd May. Plant biomass (including leaf and root dry weights) all reached their highest value when N was applied at the rate of 100 mg· kg- 1 as urea- N. The total nitrogen concentrations in leaves and roots increased significantly (α =0.001) with increasing rates of urea- N fertilizer application. NO3- N in leaf also increased significantly (α =0.001) with increasing N application rates, except that there was no significant difference between the control and the treatment of 100 mg· kg- 1 urea- N. Based on all parameters investigated in this experiment, it was suggested that 100 mg· kg- 1 urea- N fertilizer be the best rate and 200 mg· kg- 1 urea- N be the second. Meanwhile, SPAD readings in leaves of spinach were significantly correlated to their nitrogen and NO3- N concentrations. This may be concluded that SPAD readings of spinach was useful for estimation of NO3- N concentrations of spinach, and practical for field use to assist the decision- making for N management and harvest arrangements. Field experiment is needed to verify the findings from this greenhouse study.更多还原