不同N、P源对红松根/土界面pH及磷有效性影响

用根垫法研究了不同形态N源与P源对红松苗木根/土界面pH及磷有效性的影响.结果表明，铵态N处理使根/土界面pH降低，硝态N处理使根/土界面pH升高.不同N源处理引起根/土界面pH变化的幅度受P源种类及距根面距离的影响，施加矿物P时，铵态N引起的根/土界面pH下降的幅度明显减小.不同P源处理时根/土界面有效P含量受N源种类的影响，铵态N处理时，加入易溶性P近根面处有效P含量显著增加，而加入难溶性P时仅距根面0～2 mm处有效P含量显著增加；硝态N处理时，仅在加入易溶性P时近根面处有效P含量显著增加，而加入难溶性P时，近根面处有效P含量与不加P处理时相近，表明铵态N处理引起的根系分泌质子是根/土界面处难溶性矿物P溶解的主要驱动力.根/土界面处P浓度与苗木叶中P浓度具有较好的相关性. 

Effects of different nitrogen and phosphorus sources on pH and availability of P in the root/soil interface of Pinus koraiensis seedlings

The effects of different nitrogen and phosphorus sources on pH and P availability in the root/soil interface of Korean pine seedlings were studied by means of the root-mat method. The results show that the addition of NH 4--N decreases the pH in the root/soil interface, while the addition of NO - 3--N increases the pH compared with the control treatment. The type of P sources and the distance from the root plane reamarkably influence the changes of pH in the root/soil interface induced by the addition of the nitrogen sources. Compared with the addition of only NH 4--N, the extent to which the pH in the root/soil interface decreases is obviously smaller when treated by NH 4--N and rock P. When treated with different P sources, the contents of available P in the root/soil interface are affected by the types of the N sources. The content of the available P in the root/soil interface obviously increases when treated with NH 4--N and soluble P, whereas the content of the available P increases only in the area 1--2 mm from the root plane when treated with NH 4--N and rock P. When treated with NO - 3--N, the contents of available P in the root/soil interface increase only when applied with soluble P, whereas the contents of the available P change little when applied with rock P. The results above show that the protons excreted by the roots are the main activating force for the solution of the rock P in the root/soil interface. The concentrations of P in the root/soil interface are remarkably correlated with those in the needles of the seedlings.