Weightman R M, Dyer C, Buxton J, Farrington D S
Centre for Sustainable Crop Management, ADAS UK Ltd, Battlegate Road, Boxworth CB3 8NN, UK.
Food Addit Contam. 2006 May;23(5):462-9. doi: 10.1080/02652030500522606.
Seven commercial crops of lettuce and one crop of endive were sampled in order to study the variability in plant tissue nitrate concentration (TNC). Assuming that an appropriate sampling pattern was employed, ten plants were sufficient to give an acceptable estimate of the mean TNC. Short-term shading (24-48 h) had no significant effects on mean TNC, unlike the increase in TNC known to occur following dull periods 10-14 days before harvest. The effect on TNC of time of day harvested was significant, but there was no obvious pattern of diurnal variation. Averaged over all experiments, the coefficient of variation for TNC was in the order of 35%. Increasing the sample size from ten to 40 plants would only be expected to decrease the standard error of measurement of TNC from 16 to 12% of the mean because of the underlying analytical error, which would remain constant.
为了研究植物组织硝酸盐浓度（TNC）的变异性，对七种商业种植的生菜作物和一种苦苣作物进行了采样。假设采用了合适的采样模式，十株植物就足以对平均TNC做出可接受的估计。短期遮光（24 - 48小时）对平均TNC没有显著影响，这与收获前10 - 14天阴天期后已知的TNC增加情况不同。收获时间对TNC的影响显著，但没有明显的昼夜变化模式。在所有实验中平均，TNC的变异系数约为35%。由于潜在的分析误差保持不变，将样本量从十株增加到40株预计只会使TNC测量的标准误差从平均值的16%降至12%。
