基质栽培番茄临界氮浓度和氮营养指数研究

Critical Nitrogen Dilution Curve and Nitrogen Nutrition Index for Soilless Tomato

为了确定番茄的需氮量以及利用氮营养指数估测番茄氮盈亏水平的可行性,分别建立了基质栽培番茄临界氮浓度、氮营养指数和氮亏缺模型,为番茄精确施肥提供理论依据。采用基质栽培番茄,营养液氮素形态设置3个硝铵比为100∶0、75∶25和50∶50,标记为N100、N75+A25和N50+A50;氮素水平设置为Hoagland氮浓度(15mmol/L)的1/4、1/2和3/4。实验采用完全随机区组设计,共9个处理,每个处理15个重复。分别构建了不同氮源下番茄地上部生物量的临界氮浓度稀释曲线模型。结果表明,不同氮源处理番茄临界氮浓度和地上最大生物量间均符合幂指数关系,不同氮源模型间存在一定差异,参数ac(ac为地上部生物量为1g/株时的临界氮浓度)差异表明对于相同的地上部生物量,N75+A25处理番茄的氮累积能力高于N100和N50+A50;b值(b为曲线斜率)不同说明N75+A25处理植株衰老缓慢,叶氮浓度下降较N100和N50+A50慢,因而其曲线斜率低。基于临界氮浓度的氮营养指数(NNI)和氮亏缺模型Nand对番茄的适宜氮源和浓度诊断结果一致,均以N75+A25(1/2)s为最佳施氮组合。根据模型推算的NNI与相对地上部生物量、相对氮累积量和相对产量均呈显著相关性。临界氮稀释模型具有明确的生物学意义,该模型得出的分析结果是合适和可靠的。

In order to determine the nitrogen requirement of tomato and the feasibility of N nutrition index（NNI） in evaluating N nu- trition status of tomato, this paper established the models of critical nitrogen dilution curve, nitrogen nutrition index and nitrogen deficit, which would provide a tool to precise fertilization management in tomato. Soilless tomato experiment consisted of three dif- ferent nitrate/ammonium ratios： 100 ： 0.75 ： 25 and 50 ： 50 （named N100.N75＋A25 and N50＋A50, respectively）, and three dif- ferent nutrient concentrations （1/4） s. （1/2） s and （3/4） s. There were 9 treatments in total with randomized block design with fif- teen replications. Three models of critical nitrogen concentration dilution curve were constructed for the aboveground dry matter in tomato with different nitrate/ammonium rate. A negative power function relationship was found between shoot maximum dry matter and critical nitrogen concentration in different nitrate/ammonium rate treatments and there existed some differences between models of different nitrate/ammonium rates. The difference of the coefficient a, which represents the plant N concentration when shoot bio- mass is 1 g/plant for soilless tomato, between three models showed that the capacity of nitrogen uptake in N75 ＋A25 was higher than that in N100 and N50＋ A50 for the same aboveground biomass. The parameter b, which is the slope of the relationship, showed N75＋A25 could slow plant senescence, and the leaf nitrogen concentration of which decreased slower than N100 and N50＋AS0, so the slope of N75＋A25 was low. According to the N nutrition index and N deficit model under critical N concentration, N75 ＋A25 （1/2） s could be used as the optimum N application combination. The calculated NNI based on the critical N dilution curve model had a significant correlation with relative aboveground biomass, relative N accumulative uptake amount and relative yield. The critical nitrogen concentration dilution curve model had specific biological meaning. The results calculated based on the model were suitable and reliable.