The rhizosphere pH change of Pinus koraiensis seedlings as affected by N sources of different levels and its effect on the availability and uptake of Fe, Mn, Cu and Zn

摘要

Dark brown forest soil was collected from the upper 20 cm soil layer in Changbai Mountain Research Station of Ecosystem, Chinese Academy of Sciences. The soil was amended with two different forms of nitrogen fertilizers: NO_3~- as Ca(NO_3)_2, NH_4~+ as NH_4CI at the concentrations of 50, 100, 200 and 400 mg kg~(-1) respectively. The experiment was carried out with 2-yr-old Pinus koraiensis seedlings in pot. The pH change of rhizosphere soil and the contents of available Fe, Mn, Cu, and Zn in soil and leaves were analyzed. The result indicated that the addition of NH_4~--N decreased the rhizosphere pH value, while the addition of NO_3~--N increased the rhizosphere pH value in contrast with the control treatment. The direction and extent of the pH change mainly depended on N source and its concentrations applied. The rhizosphere pH change had a remarkable influence on the availability of the micronutrients in the rhizosphere, and thereafter affected the nutrient uptake by the seedlings. The contents of available mineral nutrients had a negative correlation with the pH value in the rhizosphere soil. The contents of available mineral nutrients in leaves were positively correlated to the levels of the available nutrients in the rhizosphere soils.