棉花临界需氮量动态定量模型

在大田栽培条件下，于江苏南京和河南安阳两个生态区设置棉花氮素水平试验，基于作物临界氮浓度稀释模型和干物质动态累积模型，建立了棉花花后动态临界氮吸收速率、临界氮需求量的定量化模型.结果表明，两生态区的临界最大氮吸收速率均出现在花后42 d，分别为5.3和4.4 kg·hm^-2·d^-1,临界快速氮累积期分别在花后的23～59 d和23～61 d，安阳的最大临界日需氮量明显大于南京.根据模型得到：安阳生态区适宜施氮量在240～360 kg·hm^-2 之间,且360 kg·hm^-2 条件下其氮累积接近临界需求，南京生态区240 kg·hm^-2施氮量的氮累积与临界值相近.两区域基肥施用量分别占总施肥量的26%和27%，且适宜的追肥时间应在花后22 d左右.由于模型的建立是基于不同氮处理试验，有合理可靠的生理依据，为定量确定不同气候区域的动态施肥量提供了理论依据.

Dynamic quantitative model of critical nitrogen demand of cotton

In this paper, field experiment of different nitrogen application levels for cotton was conducted both in Nanjing of Jiangsu Province and in Anyang of Henan Province. The quantitative dynamic models of critical nitrogen uptake rate and demand of cotton after flowering were established, based on the models of crop critical nitrogen concentration dilution curve and dry matter accumulation curve. The results showed that in Nanjing and Anyang, the maximum critical nitrogen uptake rate of cotton was 5.3 kg x hm(-2) x d(-1) and 4.4 kg x hm(-2) x d(-1), respectively, and appeared at 42 days after flowering. The 23 - 59 days and 23 - 61 days after flowering were the periods of rapid nitrogen accumulation in cotton plant, and the critical nitrogen demand per day was higher in Anyang than in Nanjing. By comparing the nitrogen uptake rate and accumulation amount with their critical values, the appropriate N application rate for cotton was slightly lower than 360 kg x hm(-2) in Anyang, and 240 kg x hm(-2) in Nanjing. 26% and 27% of total fertilizer nitrogen should be applied as basal, and the supplemental nitrogen should be applied at 22 days after flowering. Because the model in this paper was established on the basis of critical nitrogen concentration model and linked to the cotton aerial biomass rather than time, it had a sound eco-physiological basis, and was consequently superior to other models. It also offered a tool to determinate the nitrogen application rate for cotton in different ecological regions.