基于叶片SPAD估算不同水氮处理下温室番茄氮营养指数

为了探讨临界氮稀释曲线模型在西北地区温室番茄不同水分处理下的适用性以及采用SPAD仪快速准确诊断氮营养状况,该研究以"丽娜"番茄为材料,2013-2015年在陕西省杨凌区温室内进行水分和氮素处理试验,水分处理设置4个水平,分别为全生育期充分灌水处理、仅苗期亏水50%、苗期开花期连续亏水50%和全生育期亏水50%;氮素处理设置3个水平,施氮量分别为0、150和300 kg/hm2,通过2013-2015年试验数据对临界氮浓度稀释曲线模型进行率定和验证,并将该模型参数与番茄全生育期平均日耗水量建立相关关系,提高了临界氮浓度稀释模型在不同水分条件下的适用性。结果表明通过番茄全生育期平均日耗水量和临界氮浓度稀释曲线模型估算得到的临界氮浓度估算值和实际计算值有较好的一致性,其绝对误差为0.13~0.34 g/(100 g),标准误差为0.14~0.39 g/(100 g),决定系数为0.94~0.99,因此采用该方法可以对西北地区温室番茄不同水分处理下临界氮浓度稀释进行准确估算。通过2013-2015年试验数据分析番茄不同叶位叶片SPAD值和氮营养指数(nitrogen nutrition index,NNI)之间相关性,结果表明番茄中位叶片SPAD值与氮营养指数(NNI)有良好的线性相关性(决定系数为0.77~0.98),且该相关系数值与番茄日耗水量呈极显著相关关系,因此通过番茄日耗水量可以估算出NNI与中位叶片SPAD值之间的线性关系,估算出NNI=1时的中位叶片SPAD值,并以此SPAD值进行氮营养诊断。该研究可为西北地区温室番茄实时氮营养诊断和优化氮素管理提供了较好的理论参考。

Estimation of nitrogen nutrition index of greenhouse tomato under different water and nitrogen fertilizer treatments based on leaf SPAD

Water and nitrogen have great influences on the production of tomato in greenhouses. This study aims to determine the applicability of the critical nitrogen concentration dilution curve model in different water conditions, and to suggest a rapid and accurate method of identifying the nitrogen condition of tomato. Greenhouse experiments with different water-nitrogen combinations were conducted in 2013-2015 in Yangling, Shaanxi. Four water treatments were investigated, i.e., full irrigation through the whole life span of tomato, deficit of 50% at seedling stage, deficit of 50% at flowering stage, and deficit of 50% through the whole life span. Three nitrogen treatments were investigated, i.e., 0, 150, and 300 kg/hm2. We validated and verified the critical nitrogen concentration dilution curve model with the data in 2013-2015. We verified the applicability of the model under different water treatments of greenhouse tomato in Northwest China. We built relationship between the model parameters and the average daily water consumption of tomato during the whole growth stage, and improved the applicability of the critical nitrogen concentration dilution curve model under different water treatments. Both the parameter a and the parameter b of the critical nitrogen concentration dilution curve model decreased first and then increased with the increase of the average daily water consumption during the whole growth period of the tomato. We analyzed the relationship between SPAD (soil and plant analyzer development) values and nitrogen nutrition index (NNI) at different leaf positions with the test data in 2013-2015. There was a linear correlation between SPAD and NNI at different leaf positions of tomato under different water treatments. The fitting relationship between the SPAD values and the NNI of the upper and lower leaves was poor, and the degree of fitting was greatly affected by the year and the treatment. The fitting relationship between the median leaf''s SPAD value and NNI was a significant linear positive correlation relationship and had good stability. Therefore, the tomato median leaf can be used as a suitable diagnostic leaf for nitrogen diagnosis. The results showed that: 1) The model could well estimate the critical nitrogen concentration of tomato with the absolute error of 0.13-0.34 g/ 100 g, the standard error of 0.14-0.39 g/ 100 g, and the decisive factor (R2) of 0.94-0.99. 2) At the median position of canopy, there was a good linear correlation between the SPAD value and NNI, and the SAPD values of the middle leaves can be used to determine the nitrogen conditions of tomato. 3) The SPAD values of middle leaves at the NNI of 1 can be the indicators for appropriate nitrogen fertilizing. When the SPAD value of the median leaf in the different treatments is greater than the appropriate SPAD value, it indicates that the application of nitrogen in the treatment is excessive and should be appropriately reduced. When the SPAD value of the medial leaf in the test treatment is less than the appropriate SPAD value, it indicates that the application of nitrogen should be appropriately increased. Therefore, we have determined and validated the applicability of the critical nitrogen concentration dilution curve model under different water treatments of greenhouse tomato in Northwest China and constructed a nitrogen nutrition diagnosis method based on the daily water consumption of tomato, which can support nitrogen diagnosis and nitrogen management of tomato in greenhouses in this region.