The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing method in laboratory. The pH in the root-soil interface with the control treatment was just slightly ...The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing 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 NH<sub>4</sub><sup>-</sup> -N significantly decreased the pH value in the root-soil interface and the addition of No<sub>3</sub> -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<sub>2</sub>-P,Fe-P and Al-P in the root-soil interface were much lower after treated with NH<sub>4</sub> -N and slightly higher after treated with No<sub>3</sub> -N compared with control treatment.After treated with 100,200 and 400 mg·kg<sup>-1</sup>NH<sub>4</sub><sup>+</sup> -N,the deficiency rates of Ca<sub>2</sub>-P in the area 0-1 mm from the root plane were 37.1%,45.9%and 57.7%,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<sub>8</sub>-P in NH<sub>4</sub><sup>+</sup> -N and No<sub>3</sub>-N treatments decreased and increased,respectively,but the differences were not obvious.The contents of Ca<sub>10</sub> -P and O-P in the root-soil interface did not significantly change after treated with NH<sub>4</sub><sup>+</sup> -N or No<sub>3</sub> -N,suggesting that Ca<sub>10</sub>- P and O-P were remarkably difficult to be mobilized even at the presence of high concentration of NH<sub>4</sub><sup>+</sup> -N.The lowered pH in the root-soil interface induced by the addition of the NH<sub>4</sub> -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.展开更多
文摘The calcareous fluvo-aquic soil was collected and a microcosm study was carried out with root-mat and frozenslicing 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 NH<sub>4</sub><sup>-</sup> -N significantly decreased the pH value in the root-soil interface and the addition of No<sub>3</sub> -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<sub>2</sub>-P,Fe-P and Al-P in the root-soil interface were much lower after treated with NH<sub>4</sub> -N and slightly higher after treated with No<sub>3</sub> -N compared with control treatment.After treated with 100,200 and 400 mg·kg<sup>-1</sup>NH<sub>4</sub><sup>+</sup> -N,the deficiency rates of Ca<sub>2</sub>-P in the area 0-1 mm from the root plane were 37.1%,45.9%and 57.7%,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<sub>8</sub>-P in NH<sub>4</sub><sup>+</sup> -N and No<sub>3</sub>-N treatments decreased and increased,respectively,but the differences were not obvious.The contents of Ca<sub>10</sub> -P and O-P in the root-soil interface did not significantly change after treated with NH<sub>4</sub><sup>+</sup> -N or No<sub>3</sub> -N,suggesting that Ca<sub>10</sub>- P and O-P were remarkably difficult to be mobilized even at the presence of high concentration of NH<sub>4</sub><sup>+</sup> -N.The lowered pH in the root-soil interface induced by the addition of the NH<sub>4</sub> -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.
