| Phosphorus is an essential element for plant growth, while the amounts of availabile phosphorus that could be used by plant in soil was limited. Since most of phosphorus in soil is fixed and insufficient for plant growth. This resulted in more and more phorsphorus fertilizers being applied into soil. Long-term excess phosphorus fertilizer application resulted in the accumulation of phosphorus in arable soils, leading to the waste of phosphorus fertilizer resource and polluted environment. This study aims to characterize the distribution pattern of phosphorus and its potential of reuse in soil under long-term fertilization, as well as further provide scientific evidence for optimizing management of soil phosphorus in agricultural production on regional scales. Three typical arable soils in China such as Black soil, Red soil and Meadow cinnamon soil were selected and their phosphorus distribution patterns were studied.Soil samples were collected from three ecological stations of Chinese Academy of Sciences. Black soils in the Northeast were from Hailun Agro-Ecological Experimental Station, Red soils in the South were from Yingtan Agro-Ecological Experimental Station, and Meadow cinnamon soils in Huang-Huai-Hai Plain were from Luancheng Agro-Ecological Experimental Station.. Results were as follows:(1) Long-term application of chemical fertilizer and chemical fertilizer amended with organic manure increased both total and available P contents in three typical soils. Compared with no fertilization, long-term application of chemical fertilizer increased total P contents 19.1, 58.1 and 30.3%, available P contents by 2.5, 3.5, 2.4 times, respectively in the three types of soils by; long-term organic amendment increased total P contents of black soil and red soil by 54.2% and 161%, available P contents by 8.4,11.4 times, respectively.(2) Long-term fertilization also increased inorganic P contents to different degrees for black soil, red soil and meadow cinnamon soil, respectively. Organic amendment decreased O-P accumulation which was not available for plant growth. In addition, long-term fertilization changed the composition of inorganic P of different forms in black soil and red soil; in contrast, the composition of different forms of inorganic P kept relatively stable for meadow cinnamon soil. Fe-P and O-P accounted for a relatively large proportion of inorganic P, while Ca10-P and Ca8-P were dominant fractions of inorganic P in meadow cinnamon soil. (3)Long-term fertilization increased organic P contents in both whole soil and the relative fractions; labile organic P and intermediately stable organic P increased significantly as compared with other fractions. Inorganic P contributed more to total soil P than organic P in red soil and meadow cinnamon soil, the proportions of inorganic P were between 67.4-75.9% and 79.1-83.5%, respectively. In contrast, soil P mainly comprised of organic P in black soil with a higher proportion, which was between 50.1-59.2%. In three types of soils, organic P was mainly of intermediate lability. Long-term fertilization did not change the stabilization of various organic P fractions in red soil and meadow cinnamon soil, but long-term fertilization resulted in the redistribution of various organic P fractions in black soil.(4)The adsorption and desorption of P increased quantitatively with the increase of P concentration in equilibrium solution differing in fertilizer application for the three types of soils. P adsorption was highest in red soil under the same concentration of P solution, while the highest P desorption was found in black soil. Long-term fertilization decreased P adsorption to soils and enhanced P desorption from soils. P adsorption to soils of the three types under different fertilizer treatments was well fitted to Langmuir equation with strong correlation. Long-term no fertilizer application increased soil Qm, K, and MBC values, and the adsorption capacity of P to soils as well, but it decreased the supply capacity of available P. By contrast, long-term fertilization decreased soil Qm, K, and MBC values, i.e., decreased P adsorption to soils and increased supplying capacity of P. Of the three types of soils, red soil had the highest capacity of P adsorption. P adsorption and desorption dynamics of three types of soils can be well fitted to Langmuir equation with significant correlation. |
