Microbial Biomass in Paddy Soils-Its Measurements and Significances in Turn-over of Bioelements and Energy

土壤微生物在生物元素的周转和维持能量方面起着重要的作用。但目前对水稻土微生物生物量及其活性的研究还很有限。本研究旨在建立水稻土生物量的测定方法，探讨水稻生物量与养分吸收的定量关系，并测定腺苷酸能荷（AEC）作为微生物活性的指标。研究结果如下：1.水稻土微生物生物量的测定：采用氯仿熏蒸提取法和有机碳分析仪，可快速、准确地测定11种水稻土的生物量C（碳）（变异相关系数< 5%）。用顺序秋兰法对土壤提取液及葡萄糖和邻苯二甲酸氢钾标准溶液进行了校正。生物量C与ATP（5 '-三磷酸腺苷）的相关性极显著.微生物量氮（N）、土壤无机氮和水稻吸氮量：采用盆栽试验，研究了水稻土-植物生态系统中N的动态变化。生物量氮和无机氮在种植区显著低于未种植区，表明活性氮通过土壤无机氮库从生物量向植物转移.淹水和未淹水水稻土中的AEC：ATP和另外两种腺苷酸（ADP和AMP）通过荧光素酶反应和肌激酶、磷酸烯醇丙酮酸和丙酮酸激酶的酶来测定。由ATP、ADP和AMP计算的AEC在淹水过程中呈下降趋势，而在未淹水土壤中保持较高水平，表明耐厌氧微生物只能在淹水土壤中存活。

The roles of soil microorganisms are very important in the turn-over of bioelements and maintenance energy. But there are limited knowledge of microbial biomass and its activity in paddy soil. Aims of this research are to 1) establish the methods of biomass in paddy soil, 2) examine the quantitative relationship between biomass and nutrient uptake by rice plant, and 3) measure the adenylate energy charge (AEC) as an index of mirobial activity. Results are summarized as follows.1. Determination of microbial biomass in paddy soil : Biomass C (carbon) in 11 kinds of paddy soils could be measured rapidly and precisely (correlation of variance < 5%) by chloroform fumigation-extraction method and total organic carbon analyzer. Calibration with the ordinal Tyurin method was carried out for soil extrct as well as standard solutions of glucose and potassium hydrogen phthalate. Correlation between biomass C and ATP (adenosin 5'triphosphate) was highly significant.2. Microbial biomass N (nitrogen), inorganic soil N and N uptake by rice : Two kinds of paddy soils were used with or without rice plant for the pot experiment to elucidate N dynamics in paddy soil-plant ecosystem. Biomass N and inorganic N remained significantly lower in planted plots than in unplanted plots, implying active N turn-over from biomass to plant through inorganic soil N pool.3. AEC in flooded and unflooded paddy soils : ATP and two other adenylic acids (ADP and AMP) were determined by luciferin-luciferase reaction and enzymes of myokinase, phosphoenol pyruvate and pyruvate kinase. AEC calculated from ATP, ADP and AMP decreased during flooding, while it kept high level in unflooded soil, indicating that microorganisms resistant to anaerobic condition could only survive in flooded soil.