有机物料对水旱轮作红壤磷素微生物转化的影响

EFFECT OF AMENDMENT OF ORGANIC MATERIALS ON TRANSFORMATION OF P IN RED EARTH SOIL UNDER FLOOD DROUGHT CULTIVATION

室内培养研究了添加有机物料后水旱轮作红壤的微生物生物量变化和磷素转化状况。结果显示 ,加 5gkg-1葡萄糖 (G5 )、5和 10gkg-1稻草 (S5、S10 )处理的土壤微生物生物量碳 (MB C)在前 3d大幅度增加 (2 15 %、74 %、16 3% ) ;此后G5和S10处理的MB C经过一个下降阶段 (3～ 14d和 3～ 7d)后转为稳定 ;而S5处理的MB C基本保持稳定。G5和S10处理的土壤微生物生物量磷 (MB P)分别在前 3d或 7d大幅度提高 ,此后基本稳定 ;S5处理的MB P一直保持稳定 ,但到培养结束时 (4 3d)比对照约高 1倍。G5处理的土壤提取磷 (鲜土 ;Olsen法 )在前 3d内显著下降 ,此后基本稳定 ;S5和S10处理的提取磷基本稳定 (略低于对照 )。在第 4 3天 ,G5处理土壤的Al、Fe结合态磷含量和固定态无机磷总量显著减少 ,说明添加有机物料在提高土壤微生物生物量和磷素吸收的同时 ,促进了固定态无机磷特别是Al、Fe结合态磷的活化。进一步分析发现经过微生物利用的磷约有 30

Changes in the microbial biomass C (MB C) and P (MB P), Olsen P, and fixed inorganic P fractions in red earth soil under flood drought cultivation were investigated after amendment of organic materials (glucose and rice straw) and incubation at 25℃ and 100% humidity. Results showed that soil MB C increased by 215%, 74% and 163%, respectively, by 3 days for the treatments of adding glucose (G5, at 5 g kg -1 soil) and straw (S5, at 5 g kg -1 soil; S10, at 10 g kg -1 soil). Thereafter, soil MB C in Treatments G5 and S10 underwent a decreasing process for a period of 3～14 days and 3～7 days, respectively, and then leveled off, but in Treatment S5, it remained relatively constant till the end of the incubation. However, soil MB P in the former increased considerably during the early phase (by 3 or 7 days), and followed by a stable trend throughout the remaining incubation period. Soil MB P in Treatment S5 remained relatively constant during the entire incubation period, and by the end was about 2 times greater than that in the control (without amendment) as soil MB P in it decreased significantly during the period. A significant decrease (3.5 mg kg -1 soil) in Olsen P occurred in Treatment G5 during the first 3 days. Differences between the content of Olsen P in Treatments S5 and S10 and that in the control were limited (generally under 1 mg kg -1 soil). It was found that, by the end of the 43 d incubation, the contents of Al and Fe bonded P, and total fixed inorganic P in the soil of Treatment G5 were significantly lower than those in the control. It was concluded that the amendment of organic materials enhanced the microbial biomass and MB P in the soil under flood drought cultivation, and consequently activated some fixed inorganic P (mainly Fe bonded P) for utilization. A further analysis of the data obtained suggests that a considerable part (over 30%) of the P used by the microbial biomass was transformed into organic P pool, and that P released from decomposing straws could preferentially be used by microbial biomass and generally filled up its need. Thus, the influence of straw incorporation on soil P availability may be limited.