用根垫-冰冻切片法研究不同氮源对石灰性潮土中黑松幼苗根-土界面无机磷形态转化及有效性的影响.结果表明:铵态氮(NH+4-N)处理后幼苗根-土界面pH值较对照处理明显降低,而硝态氮(NO3-N)处理后幼苗根-土界面pH值较对照处理升高,不同氮源引起的幼苗根-土界面pH值变动的幅度取决于氮源的质量分数.铵态氮处理明显降低了幼苗根-土界面Ca2-P,Fe-P和A1-P质量分数,100,200和400mg·kg-1的铵态氮处理后,距根表0～1mm处Ca2-P较土体亏缺率分别为37.1％,45.9％和57.7％,Fe-P较土体亏缺率分别为23.4％,29.1％和38.2％,AI-P较土体亏缺率分别为25.1％,28.0％和33.2％；硝态氮处理增加了幼苗根-土界面Ca2-P,Fe-P和AI-P质量分数,但不显著.铵态氮与硝态氮处理后幼苗根-土界面Ca8-P的亏缺程度较对照分别加大或降低,但不明显.铵态氮与硝态氮处理后幼苗根-土界面Ca10-P和O-P质量分数较对照处理变化很小.铵态氮引起的黑松幼苗根-土界面pH值的降低,促进了幼苗根-土界面处无机磷的形态转化,提高了根-土界面无机磷的生物有效性,显著增加了根系对磷的吸收.%The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozen-slicing method in laboratory. The pH in the root-soil interface with the control treatment was just slightly lower than in the bulk soil. However, the addition of NH1-N significantly decreased the pH value in the root-soil interface and the addition of NO3 -N slightly increased the pH value in the root-soil interface. The magnitude of pH changes in the root-soil interface depended upon the concentrations of the nitrogen sources added. The contents of Ca,-P, Fe-P and Al-P in the root-soil interface were much lower after treated with NH4+ -N and slightly higher after treated with NO3- -N compared with control treatment. After treated with 100, 200 and 400 mg·kg-1 NH4+-N, the deficiency rate9 of Ca2-P in the area0 - 1 mm from the root plane were 37. 1% , 45.9% and 57.1% , respectively, the deficiency rates of Fe-P were 23. 4% , 29. 1% and 38.2% , respectively, and the deficiency rates of Al-P were 25. 1% , 28.0% and 33.2% , respectively. Compared with the control the deficiency rates of Ca,-P in NH4+ -N and NO, -N treatments decreased and increased, respectively, but the differences were not obvious. The contents of Ca10-P and O-P in the root-soil interface did not significantly change after treated with NH4+-N or NO3-N, suggesting that Ca10-P and 0-P were remarkably difficult to be mobilized even at the presence of high concentration of NH4+ -N. The lowered pH in the root-soil interface induced by the addition of the NH4+-N promoted the transformation of phosphates in the root-soil interface, enhanced the mobilization and bioavailability of phosphates, and thereby remarkably increased the absorption of phosphorus by roots.
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