不同N源对马尾松幼苗根/土界面pH及P素有效性的影响

Effect of different nitrogen sources on pH and phosphorus availability in the root-soil interface zone of Pinus massoniana

用根垫—冰冻切片法研究了不同N源处理对马尾松幼苗根/土界面pH及P有效性的影响。结果表明:较对照处理,施加硝态N(NO3--N)与铵态N(NH4+-N)时,根/土界面pH分别增加和降低;不同N源配施易溶性P(PS)时,近根面处pH变化很小,有效P含量均明显增加;配施难溶性矿物P(PR)时,硝态N引起的根/土界面pH增加的幅度增大,近根面处有效P含量未表现出增加,而铵态N引起的根/土界面pH降低的幅度减小,近根面处有效P含量明显增加,表明铵态N处理引起的根系质子(H+)分泌是根/土界面处难溶性矿物P活化的主要因素。

The effects of different nitrogen sources on pH and the phosphorus availability in the root-soil interface zone of Pinus massoniana were studied by means of root-mat method. The results revealed that the addition of NH4^＋-N decreased the pH in the root-soil interface, while the addition of NO3 -N increased the pH in contrast with the control treatments. When fertilized with soluble P （ PS）, the pH change in the root-soil interface induced from different nitrogen forms changed little and the content of available P increased obviously. When fertilized with insoluble rock phosphate （PR）, the extent to which the pH in the root-soil interface in- creased was bigger and the content of available P near the root plane changed little compared with the addition of only NO3^- -N, while the extent to which the pH in the root-soil interface decreased was obviously smaller and the contents of the available P increased remarkably very near the root plane compared with the addition of only NH4^＋ -N. The results showed that the protons excreted by the roots were the main activating factors for the solution of the rock P in the root-soil interface.