滴灌番茄临界氮浓度、氮素吸收和氮营养指数模拟

作物的氮浓度随生物量的增加而下降,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。该文在滴灌条件下,基于3a不同的氮素水平试验,构建了加工番茄地上部生物量的临界氮浓度稀释曲线模型。结果表明,临界氮浓度与地上部最大生物量之间符合幂指数关系,相关系数为R~2=0.947,加工番茄最高(%Nmax)、最低(%Nmin)临界氮浓度稀释模型亦符合幂指数关系,相关系数分别为R~2=0.959、R~2=0.925。基于临界氮浓度建立了加工番茄氮素吸收模型(Nupt)、氮素营养指数模型(NNI),可作为加工番茄氮素营养状况的判别指标,氮素吸收和氮营养指数模型对新疆北疆加工番茄种植区的适宜施氮量诊断结果一致,均以300kg/hm2为最佳施氮量。该研究所建立的临界氮浓度稀释曲线模型较前人建立的模型更具机理性,因此,该模型所得出的分析结果是合适和可靠的,并且可用于指导加工番茄动态精准施肥及为氮素优化管理的建立提供参考。

Simulation of critical nitrogen concentration, nitrogen uptake and nitrogen nutrition index of processing tomato with drip irrigation

Abstract: In many crops, nitrogen concentration decreases with increasing plant mass. A critical N concentration in plant above-ground biomass, which is defined as the minimum N concentration required for maximum plant growth, can be found at any time in the growth cycle. To determine the critical N concentration dilution curve for drip-irrigated processing tomato, three years of field experiments with five levels of N applications (0, 75, 150, 300, 450, 600 kg/hm2) were carried out in Shihezi city, northern Xinjiang. Results showed that N concentration in above-ground biomass declined with accumulated physiological development time after emergence. The relationship between the above-ground biomass and critical N concentration can be described by the power equation (%Nc=4.352DW-0.274), with ac=4.352 and b=0.274 for three experiments. Taking into account all data from the three experiments, we observed a large variability in total N concentration for a given biomass. Using the observed maximum, %Nmax and the minimum N concentration, %Nmin at each sampling date, the following two boundary curves were determined. The boundary curve model also followed a power equation (%Nmax=5.063DW-0.246, %Nmin=3.522DW-0.163), with amax=5.063, bmax=0.246, and amin=3.522, bmin=0.163 for all three experiments. Based on the critical N concentration dilution model, a model of the allometric relationship between crop N uptake at each N application level and above-ground biomass, and a model of nitrogen nutrition index (NNI), were developed. The former can be used as an index for controlling N application, and the latter can be used to express the N status of the drip-irrigated processing tomato plants. If NNI=1, N nutrition is considered to be optimum; NNI>1 indicates excess N, and NNI<1 indicates N deficiency. Based on the critical N concentration model, the model of N uptake at growth period for potential growth and yield was developed. According to the N-uptake model coefficient, NNI, and N uptake under critical N concentrations, we concluded that 300 kg/hm2 could be used as the optimum N application rate of drip-irrigated processing tomatoes in northern Xinjiang. Furthermore, there existed agreement between our model and the reference relationship for C3 crops. Thus our results could be used to guide the dynamic precision fertilization and provide a theoretical basis for optimal nitrogen management of drip-irrigated processing tomato in Xinjiang.