棉花蕾花铃生物量、氮累积特征及临界氮浓度稀释模型

在大田栽培条件下，于河南安阳（黄河流域黄淮棉区）和江苏南京（长江流域下游棉区）设置了棉花氮素水平试验，对不同氮素水平条件下棉花蕾花铃的生物量、氮素累积及氮浓度的动态变化进行分析，并依据Justes的临界氮浓度稀释模型确定方法，研究棉花蕾花铃临界氮浓度稀释模型。结果表明：棉花蕾花铃的生物量增长和氮吸收累积均受氮素水平的影响，其动态变化符合S型曲线，氮累积的快速起始时间较生物量早1～5d；氮浓度过高或过低均不利于产量形成，蕾花铃等器官存在氮奢侈消费现象；氮浓度随施氮量的增加而升高、随生育进程的推移而降低，其生物量累积量与氮浓度间符合幂函数关系，两试点蕾花铃氮稀释曲线模型形式相同，但模型参数a不同，不同生态区存在独立的临界氮稀释曲线模型。由于临界稀释模型具有明确的生物学意义，可以作为定量诊断蕾花铃氮营养动态变化的指标之一。

Accumulation characteristics of biomass and nitrogen and critical nitrogen concentration dilution model of cotton reproductive organ

Several nitrogen (N) field experiments were carried out in Nanjing and Anyang, China, to study the dynamic characteristics of biomass accumulation and N uptake, and to define the dilution curve for critical N concentration in cotton reproductive organ over the growth period. The results show that the total biomass and N accumulation were affected significantly by the rate of N application, exhibiting a sigmoid curve over time. The beginning time of fast N accumulation was 1–5 d earlier than that of biomass accumulation. The cotton lint yield was correlated with N concentration in the reproductive organ and fluctuated with varying N concentration, indicating the existence of luxurious N consumption in the cotton reproductive organ. The N concentration increased with increasing N application rates, and decreased gradually during the growth period. The relationship between biomass and N concentration can be described with a power equation. The patterns of the N concentration dilution model were consistent at both experimental sites, but the model parameter values of a differed. The results presented in this paper indicate that a critical N concentration dilution curve for cotton reproductive organ is independent of ecological region and can be described with a power equation.