评价土壤有效氮测定方法的生物指标

研究表明,作物吸收的氮素总量能客观地反映土壤的供氮能力,是评价化学浸取氮的唯一准则。作物含氮百分数只有在生育期长时才有较大变动,反映出土壤供氮水平的差别。对于生育期短,吸氮不多的作物,干物质与吸氮量有一致关系,可用来衡量浸取法的适合程度;而对于生育期长、吸氮多的作物,则有较大偏差。以两种方式表示的浸取氮与作物吸收氮间的相关系数基本一致。作物吸氮量与两种方式表示的全氮间的相关系数无显著区别;而以每盆毫克数表示的有机质与作物吸取的氮素有密切稳定的相关。

THE BIOLOGICAL INDICES FOR EVALUATION OF CHEMICAL EXTRACTION METHODS DETERMING AVAILABLE NITROGEN IN SOILS

Pot experiment results show that the total nitrogen uptake by plants coulil objectively reflect soil N supplying capacities, and is the only criteria for evaluating extratcd N from soil by chemical methods. The percentage of plant nitrogen may reflect the differences of soil supplying N levels only when piants grow for a long period; As to the short-term growing plart with less N up take, plant dry matters are well correlated with its N uptake, and may be used as an evaluation indicator to judge the fitness ci .extracted N by chemical methods; but for long-term growing plants with more N uptake,, dry matter; are not well matched with plant uptake N, The correlation coefficients be ween extracted soil N expressed in two ways and plant uptake N are principally in agreement, and so are the coefficients between plant uptake N and total soil N expressed in two ways. A close, stable relationship is found between pianl uptake N ajid soil organic iratter when the later is expressed in mg per pot.