太湖地区氮肥用量对土壤供氮、水稻吸氮和地下水的影响

利用矿化培养与田间试验的方法,探讨了太湖地区长期施氮条件下,氮肥用量对土壤供氮、水稻吸氮与环境的影响。初步试验结果表明:多年施用氮肥能够提高土壤的供氮能力,并随施N量的增加而增加。增加氮肥用量能够提高稻株含氮量和吸氮量,但氮素向谷粒的转移率降低,试验区水稻氮肥用量以225～270kghm-2左右为佳。稻田田面水和渗漏液的N素养分动态变化显示,施N会造成田面水NH4 N和NO3-N含量的短暂升高,但不同施N量之间相差并不显著。稻田渗漏液中的氮以硝态氮为主,通常在淹水泡田后的7d内有一个NO3-N含量的峰值期,NO3-N含量在1.62～2.75mgL-1之间,约10d后降至0.5mgL-1以下;NH4 N含量变化有随施N量而增加的趋势,高峰期通常出现在分蘖末期,其余时间NH4 N含量在0.2mgL-1以下。

EFFECTS OF FERTILIZER-N APPLICATION RATE ON SOIL N SUPPLY, RICE N UPTAKE AND GROUNDWATER IN TAIHU REGION

Ananaerobic incubation and field experiment of fertilize-rN application of different rates were conducted in the Taihu region to determine effects of fertilize-rN on soil N supply, rice N uptake and groundwater.The results show that soil N availability could be considerably enhanced after years of N-fert ilization.N content in rice and N uptake by rice increased with the N application rate, but the rate of N transferred to grain decreased.The optimum fert ilize-rN application rate ranged from N225 to 270 kg hm^-2 for rice in this region.The concentrations of both NH₄⁺-N and NO₃^--N in the surface water of paddy field rose temporarily as a result of fertilize-rN application, but they were not significantly correlated.NO₃^--N was the main form of nitrogen in the leachate from paddy field.Its concentration rose quickly arriving at a peak around 1.62~2.75 mg L^-1 within the first 7 days after the field was flooded for transplanting, and then dropped to below 0.5 mg L^-1 after 10 days or so.NH₄⁺-N concentration in the leachate seemed increasing with the N application rate and peaked at the end of the rice tillering stage, but usually remained lower than 0.2 mg L^-1 in the rest of the growing season.