The pH change in rhizosphere ofPinus koraiensis seedlings as affected by different nitrogen sources and its effect on phosphorus availability
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Root mat method described by Kuchenbuch and Jungk was used to study the rhizosphere processes. The experiment was carried out on two years oldPinus koraiensis seedlings. Soil samples collected from the upper 20-cm soil layer in Changbai Mountain were treated with three different forms of nitrogen fertilizers: NO3 −−N, NH4 +−N and NH4NO3. The results showed that the soil pH and available P near the roots were all lower than in the bulk soil in control treatment. NH4 +−N application greatly decreased the soil pH near the roots compared to the control treatment and promoted the absorption of phosphorus, which led to a more remarkable depletion region of available P. On the contrary, the rhizosphere soil pH was higher than in the bulk soil in treatments with NO3 −−N and retarded the P absorption, which led to a nearly equal available P contents to the bulk soil. In treatment with NH4NO3, the rhizosphere soil pH was only a little lower than that in the control treatment and its effects on P absorption is mediate between the treatments with NH4 +−N and NO3 −−N.
KeywordsNitrogen sources Rhizosphere pH Available P
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