不同土壤水分条件下容重对玉米生长的影响

用玉米作为实验材料。进行分根实验研究不同土壤水分条件下容重对玉米生长的影响，种子根平分在装有塿土的分隔的白铁皮桶中，土壤容重分4种处理：低容重(两边容重都为1．20g·cm^-3)、中容重(两边容重都为1．33g·cm^-3)、高容重(两边容重都为1．45g·cm^-3)和混合容重(一边为1．20g·cm^-3，另一边为1．45g·cm^-3)，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，当植株生长在紧实土壤或土壤基质势从-0．17MPa降到-0．86MPa时。根长、根干重和地上部干重都显著降低，并且地上部干重的降幅更大，紧实土壤使根长降低的同时还使根的直径增大，无论是容重增大还是土壤水分含量降低所引起的高土壤阻力都使叶片扩展速度降低和植株变小，生长在紧实土壤中的植株变小不仅是因为叶片扩展速度降低，同时是成熟叶片叶面积缩小的结果。然而，当植株生长在混合容重土壤中时，处在低容重土壤中的根系生长得到加强，补偿甚至超补偿高容重土壤中根系生长的不足，整个植株的生长状况与低容重土壤中生长的植株接近。

Effect of soil bulk density on maize growth under different water regimes

Split-root experiments were conducted with maize under both low (-0.86 MPa) and high (-0.17 MPa) soil matrix potential conditions, in which, maize roots were divided equally between two compartments in partitioned galvanized steel containers containing Lou soil. Four treatments were installed, i.e., low bulk density (both compartments packed to 1.2 g.cm-3), medium density (both compartments packed to 1.33 g.cm-3), high density (both compartments packed to 1.45 g.cm-3), and mixed density (one compartment packed to 1.2, the other to 1.45 g.cm-3). The results showed that high soil bulk density and low matrix potential had a significant effect on root and shoot growth, but the effect of low matrix potential was more profound. There was a significant decrease in root dry matter and shoot dry weight, but the shoot growth was reduced more significantly than root growth, when the plants were grown on compacted soils or the soil matrix potential reached -0.86 MPa from -0.17 MPa. Both leaf expansion rate and plant size reductions occurred under high soil mechanical resistance caused by increased bulk density or lowered soil water content. The smaller size of plants in compacted treatments was due to the reduced leaf expansion rates and the smaller maximum size of individual mature leaf. In contrast, when plants were grown in soil with mixed bulk density, there was an enhanced growth of root in low-density soil to compensate or even overcompensate the reduced growth in high-density soil, and hence, the plant growth was comparable with that in low bulk density soil.