添加水稻秸秆对油菜(Brassica napusL.)幼苗生长的影响

近几年,水稻秸秆直接还田对油菜幼苗生长的负效应受到关注。有许多研究在水稻残体或腐解物中检测出了酚酸等被广泛证实具有化感作用的物质,因此在水稻秸秆产生的负效应中,化感抑制作用不容忽视。本研究以酚酸为目标化感物质,以湖北省油菜主栽品种"中双11号"为受体,采用4种采自典型稻油轮作系统中的土壤进行盆栽试验,研究水稻秸秆对油菜幼苗生长的影响。结果表明:(1)整体看来,添加秸秆对油菜幼苗总生物量的主效应在进贤土为正,在汉川土为负,在阳逻和麻城土为无明显影响;(2)功能叶片光合色素含量在全部土壤下的显著降低均出现在播种后33 d之内,与水稻秸秆腐解速率最大值的出现与存在时间上的重叠。秸秆处理对油菜幼苗的负效应在早期强于后期;(3)土壤水溶态酚酸含量为3.3~49.0μg·g-1soil。添加秸秆虽导致土壤中水溶态酚酸浓度增加,但其明显增加主要发生在试验后期,且增量与幼苗生物量化感效应指数呈正相关关系。因此酚酸含量的变化不能解释水稻秸秆的负效应,为揭示秸秆处理的负效应机制,需要转换目标化感物质。

Allelopathic Effect of Rice Straw on Rape(Brassica napus L.)Seedlings

In recent years, negative effects of rice straw on rape(Brassica napus L.)were verified in rice-rape(Brassica napus L.)rotation system in Yangtze River Basin in China. Allelopathic effect could contribute to the negative effects, as soluble phenolic compounds were frequently identified in decomposing rice straw. To gain a better understanding, seedlings of rape cultivar Zhongshuang 11 were treated with and without rice straw in 4 typical soils sampled from rice-rape rotation system. Our results were as follows:(1)Across the whole experiment period, rice straw treatment showed marked positive and negative main effect in Jinxian soil and Hanchuan soil, respectively, while showed no effect in the other two soils;(2)Significant decrease in photosynthetic pigment contents of functional leaves were observed in all the soils from 20 d to 33 d after sowing. The peak decomposition rates of rice straw were also verified during this period.(3)Total phenolic acid contents ranged 3.3~49.0μg·g-1 soil in this study. Significant increases in total phenolic acid content of soil extractions were observed in later stages. The marked(P<0.01)positive correlation between the increases and RI(allelopathic response index)of total biomass suggested positive effect of the phenolic acids on biomass accumulation. Thus, dynamic changes of water soluble phenolic acids were not valid to illuminate the mechanism of negative effect of rice straw on rape seedlings. Allelochemicals other than phenolic acids should be included in further studies on this issue.