Abstract: Solution culture experiments were conducted to study N uptake kinetics and the relatively uptake of ammonium- and nitrate-N by rice (Oryza sativa) at different growth stages. The relative uptake or the ratios(NH₄-N/NO₃-N) of ammonium-N to nitrate-N absorbed by rice varied with its growth stages. At different stages, rice plant had different preference to either ammonium-N or nitrate-N when both NH and NO were present equally in the nutrient solution. From transplanting to initial tillering, the absorbed ratio was 1. 15 on average, and the absorbed ammonium-N accounted for 53. 48% of the total uptake nitrogen during the same period. During the tillering period, the absorbed ratio was 2. 55 on average, and the absorbed ammonium-N accounted for 71. 8% of the total at this stage. This phenomenum that rice preferred ammonium-N to nitrate-N during the vegetative growth period could be explained by kinetic parameters(Vmax and K) of absorption. During the reproductive period from elongation to maturity, the absorbed ratios tended more or less towards 1, and either of the nitrogen forms could be taken up efficiently by the crop. For the whole growth duration, the absorbed ratios ranged from 0. 98 to 2. 62 with 1. 28 on average, the accumulated ammonium-N absorbed being 56. 1 % of the total nitrogen.

Key words: ammonium nitrogens kinetic parameter, nitrogen uptake, nitrate nitrogen, solution culture

摘要： 采用水培方法, 研究了水稻不同生育期对铵、硝态氮的吸收特性。水稻虽为较强的喜铵作物，累积吸收的铵态氮多于硝态氮，但并不完全依赖于铵态氮。在铵、硝态氮等量共存条件下，水稻对铵、硝态氮的相对吸收量表现出明显的阶段性。从移栽到分蘖终期的营养生长期，吸收的铵态氮多于硝态氮，占营养生长期吸氮总量的68.9%；铵态氮营养主导作用在分蘖期表现得更为明显。从拔节到成熟的生殖生长期，两者的吸收比例在1左右，趋于稳定，可以同等有效地吸收铵态氮和硝态氮。在施肥实践中，应充分考虑水稻不同生育阶段吸收铵态氮、硝态氮的营养特点，合理调控土壤中铵、硝态氮比例，以满足水稻不同生育期对各种氮源的需求。

关键词: 溶液培养, 吸氮量, 铵态氮, 硝态氮, 动力学参数