水氮耦合条件下番茄临界氮浓度模型的建立及氮素营养诊断

Simulation of critical nitrogen concentration and nitrogen nutrition index of tomato under different water and nitrogen conditions

【目的】临界氮浓度是指在一定的生长时期内获得最大生物量时的最小氮浓度值,具有明确的生物学意义。探究不同水氮供应对番茄地上部生物量、氮素累积的影响,构建临界氮浓度稀释曲线模型,并基于氮素吸收和氮营养指数模型进行番茄氮素营养诊断,可为番茄水肥一体化提供一定的理论依据。【方法】于2013年在日光温室内进行了盆栽试验,供试番茄品种为金鹏M6088。设置3个灌水量为低水W1(60%70%θf)、中水W2(70%80%θf)和高水W3(80%90%θf),θf为田间持水率;施氮量设置3个水平为低氮N1(N 0.24 g/kg土)、中氮N2(N 0.36 g/kg土)和高氮N3(N 0.48 g/kg土),试验采用完全随机区组设计,共9个处理,每个处理重复15次,研究了不同水氮条件下番茄的地上部生物量、氮素累积及氮浓度的动态变化,构建了番茄不同水分条件下的临界氮浓度稀释曲线模型。【结果】番茄地上部生物量、氮累积量随移栽时间的动态变化符合Logistic模型,不同水氮供应对番茄地上部生物量理论最大值的影响不同,中水和高水条件下,番茄地上部生物量理论最大值随着施氮量的增加呈先增加后减小的趋势;而在低水条件下呈递增趋势,说明适量增施氮肥可以减轻干旱对干物质量累积的抑制;番茄地上部生物量快速累积起始日较氮快速累积起始日晚8 17 d,且不同水氮处理番茄地上部生物量最大生长速率、氮累积量最大累积速率均出现在中水中氮(W2N2)处理;在相同的水分条件下,番茄地上部生物量氮浓度随施氮量的增加而提高,随生育进程的推移呈下降趋势;氮浓度与地上部生物量之间符合幂指数关系,适当增大灌水量可以提高植株对氮的容纳能力,并且可以缓解氮浓度随植株生物增长量下降,使植株稳步有序地生长;不同的水氮供应对番茄产量影响显著,随着灌水量和施氮量的增加,产量显著提高,但当灌水量和施氮量达到一定数量时产量不仅没有提高反而随其增加而降低。【结论】基于临界氮浓度构建的氮营养指数、氮吸收模型对番茄的适宜施氮量诊断结果一致,均以中水中氮(W2N2)为最佳条件,即当灌水量和施肥量分别为62.1 L/plant、15.1 g/plant时,番茄单株产量达到最大(1602 g),构建的模型合理可行。

[Objectives] The critical nitrogen （ N ） concentration in plant aboveground biomass is defined as the minimum N concentration required for maximum plant growth. This study investigated the effects of different water and nitrogen supply on tomato aboveground biomass, nitrogen accumulation, and drew a critical N concentration dilution curve. The N status of tomato plant was analyzed based on a model of N uptake and nitrogen nutrition index （ NNI ） , which provided a theoretical basis for optimal water and nitrogen management. [Methods]A pot＆amp;nbsp;experiment was conducted in greenhouse of the Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Area of Ministry of Education in Northwest Agriculture and Forestry University in 2013 . Cultivar of tomato（M6088）was used in this experiment. The treatment comprised three levels of irrigation（W1, 60%-70% θf;W2, 70%-80% θf;W3, 80%-90% θf）,θf is the field capacity, and three levels of nitrogen（N1, N 0. 24 g/kg;N2, N 0. 36 g/kg;N3, N 0. 48 g/kg）. For determining the critical N concentration dilution curves under different water conditions, the treatments were replicated fifteen times in random complete block designs to examine the dynamic changes of tomato aboveground biomass and nitrogen accumulation under different water and nitrogen conditions. [Results] The aboveground biomass and N accumulations presented a Logistic curve over time. Different water and nitrogen supply had different effects on maximum theoretical value of tomato aboveground biomass：the maximum theoretical value of tomato aboveground biomass increased firstly and decreased with the increase of nitrogen rate under two levels of irrigation （ W2 , W3 ） . It also increased with the increase of nitrogen rate under the level of irrigation（W1）, which indicated that moderate nitrogen supply could enhance the inhibiting effect of drought on aboveground biomass accumulation of tomato. The beginning time of fast accumulation period for nitrogen was 8-17 days earlier than those for biomass, the maximum accumulation rates of tomato aboveground biomass and nitrogen were both found in W2N2 treatment. Under the same water supply condition, the nitrogen concentration of tomato aboveground biomass increased with the improving of applied N rates, and decreased in the growing process. The relationship between the aboveground biomass and N concentration could be described by the power equation, appropriate irrigation could improve the capacity of plant for nitrogen absorption and relieved the decline of nitrogen concentration with the aboveground biomass growth to ensure a steady and orderly growth of tomato. The yield was significantly affected by water and nitrogen supply, appropriate condition of water and nitrogen achieved maximum yield. [Conclusions] Based on the model of nitrogen nutrition（ NNI） and the model of N uptake, the W2N2 treatment was the optimal option with irrigation amount of 62. 1 L/plant, nitrogen rate of 15. 1 g/plant, and the highest yield was 1602 g/plant. Thus, the models built in this study were reasonable and feasible for the research objectives.