氮肥有效性与土壤水分胁迫关系

Relationship between the Availability of N Fertilizer and Water Stress

利用￣(１５)Ｎ同位素进行了土壤盆栽试验，研究了土壤水分胁迫与甜菜吸Ｎ能力、强度及Ｎ素肥效间的关系，明确了：１）土壤湿度为２０％左右时对甜菜的生物效应以Ｎ素为主，反之则以土壤水分为主；２）使Ｎ肥对甜菜有效的最低土壤湿度为１５％；３）甜菜吸Ｎ在各器官中分布比例为，叶：叶柄：根为１０：２：１；４）甜菜吸Ｎ强度随土壤含水量增加而增加，并在２５％时达到最大；５）甜菜吸收的总氮中，来自肥料Ｎ的比例在土壤含水量为２０％～２５％时为最大。

The relationship of N uptake ability. intensity and the efficiency of N fertilizer with soil water stress in sugarbeet was investigated by the use of 15N isotop in greenhouse. The results clarified: 1)When soil moisture was about 20%. N was the main actor on the biomass of sugarbeet,or else the soil moisture was on the dominated position; 2)The lowest soil mois- ture which was needed by sugarbeet was about 15% in the process of N uptake; 3)The ratio of uptaked N which distributed in blade. petiole and root was about 10:2:1;4)The intensi- ty of N uptake was increased with the inerease of soil moisture . and reached the highest level when the soil moisture inereased to 25%;5)The soil moisture had a great effects on the ratio of fertilizer N to soil N in the total uptaked nitrogen by sugarbeet. when the soil moisture ranged from 20%～25%, the ratio had a highest value.