太湖地区稻田持续高产的减量施氮技术体系研究

Nitrogen reduction technique system for sustaining high yield of paddy fields

在系统总结前人研究的基础上,结合课题组多年来15N同位素示踪研究以及水稻前后期用肥比例、适宜基蘖肥比例的盆栽试验和大田小区试验结果,提出了稻田持续高产低污的减量施氮技术体系方案。该技术体系包括稻季施氮量的合理计算、基于土壤肥力的前后期适宜施肥比例以及基蘖肥的合理运筹、基于作物长势的穗肥实时调控等,明确了氮肥减量首先应依据目标产量计算合理施氮量,然后根据土壤肥力水平高低对前后期用肥比例以及基蘖肥的分配进行优化,根据作物长势对穗肥用量进行实时微调,从而确保水稻高产可持续。氮肥减量重点在于减少前期用肥即基蘖肥的用量。在同等施氮量下,水稻适宜基蘖肥比例随肥力水平的增加而下降,低肥力下60%最佳,中肥力下50%为宜,高肥力下可降低至40%;此外,低肥力下需保证一定的基肥用量,并调整适宜的基蘖肥比例以确保高产。

A nitrogen reduction technique system was put forward based on the previous research results including the15 N isotope trace, different split ratios of basal, tiller and panicle N fertilizer experiments. The N reduction technique system included the determination of theoretical N rate, the suitable split ratio of basal, tiller N fertilizer, and the real-time adjustment of panicle topdressing N rate based on the rice growth status. The theoretical N rate should be calculated based on the target yield and N requirement per unit grain. Then, the split ratios of N fertilizer at different growth stages should be optimized according to the soil fertility. Nitrogen rate reduction should be emphasized on basal and tiller N. At the same N rate, the suitable basal and tiller N ratio decrease with increasing soil fertility level, and should be 60%,50% and 40% for low, medium and high soil fertility, respectively. Under low soil fertility, a certain amount of basal N rate should be applied and the ratio of basal to tillering should be kept at 3∶7 to ensure the high yield and N use efficiency. However, no obvious influences was observed for different split ratios of basal to tiller N under high soil fertility. Finally, in order to ensure a high yield, the panicle topdressing N should be adjusted based on the crop growth and target yield using the leaf color or canopy reflectance spectra as the non-destructive diagnostic tool.