Abstract: The effects of soil bulk density (SBD) on both leaf water use efficiency (WUEl) and plant water use efficiency (WUEp) of maize (Zea mays L.) under different water regimes were studied. Split-root experiments were conducted under both low (-0.86 MPa) and high (-0.17 MPa) soil matrix potential conditions. Four types of soil treatments were imposed: low density (both compartments packed to 1.20 g/cm³), middle density (both compartments packed to 1.33 g/cm³), high density (both compartments packed to 1.45 g/cm³), and mix density (one compartment packed to 1.20, the other to 1.45 g/cm³). The results showed that under drought condition (-0.86 MPa), WUEl increased and WUEp decreased with increasing SBD, whereas under wetting condition (-0.17 MPa), both WUEl and WUEp increase with increasing SBD. The correlation analysis showed that WUEl had positive correlations with soil mechanical resistance (Rs) under both drought and wetting condition. There were positive correlations between WUEp and Rs under wetting condition, but significant negative correlation under drought stress. Under both drought and wetting condition, the WUEl and WUEp of plant grown in mixed density soil maintain higher level. It is suggested that high SBD and low matrix potential influence water use efficiency (WUE) independently, but the effects of low matrix potential is more profound, and there is also an interactive effect of them upon WUE. Meanwhile the spatial change of SBD is beneficial for WUE improvement.

Key words: soil bulk density (SBD), soil matrix potential, Zea mays L., water use efficiency (WUE), soil mechanical resistance (Rs)

摘要： 用‘陕单9号’玉米为试材进行分根实验,研究土壤干旱和湿润条件下,土壤容重对玉米单叶水分利用效率(WUEl)和单株水分利用效率(WUEp)的影响。土壤容重分4种处理:低容重(两边容重都为1.20g/cm³)、中容重(两边容重都为1.33g/cm³)、高容重(两边容重都为1.45g/cm³)和混合容重(一边为1.20g/cm³,另一边为1.45g/cm³)。土壤水分控制在高基质势(-0.17MPa)和低基质势(-0.86MPa)两个水平。结果表明,在干旱条件下,WUEl随容重的增大而提高,而WUEp随容重的增大而降低;在湿润条件下,WUEl和WUEp都随容重的增大而提高。相关分析表明,无论是干旱还是湿润条件下,WUEl与土壤机械阻力(Rs)呈正相关;在湿润条件下WUEp与Rs呈正相关,但在干旱条件下WUEp与Rs呈显著负相关。无论是干旱还是湿润条件下,生长在混合容重土壤的植株能维持较高的WUEl和WUEp。因此,土壤水分和容重都会影响植物水分利用效率,并存在交互作用,但土壤水分的作用更大;同时,土壤容重空间变化有利于提高水分利用效率。

关键词: 土壤容重, 土壤基质势, 玉米, 水分利用效率, 土壤机械阻力