Effects Of Long-term Fertilization On Speciation And Available In Brown Soil

This research aimed to study the effect of long-term fertilization on pH、 Eh and various speciations of iron, manganese at different plant growth stages or in different soil depth, and their relationships based on long-term located fertilization experiment in brown soil. The main results were as follows:1. Effect of Long-term fertilization on soil pH, Eh and the content of various iron, manganese in topsoil(0-20cm). Long-term application of organic manure can improve soil pH, but reduce soil Eh, while long-term application of chemical fertilizers decreased soil pH and increased soil Eh. Organic fertilizer and inorganic fertilizer co-application can alleviate soil acidification caused by long-term chemical fertilizer. Long-term application of organic fertilizer reduced the content of free iron oxide, but balanced application of N1PK and organic fertilizer could effectively increase the content of free iron oxide in soil; Long-term application of organic fertilizer can increase the contents of free manganese oxide, amorphous iron oxide, amorphous manganese oxide, ferrous iron, manganous manganese and available iron, especially when co-used nitrogen fertilizer, content of free manganese oxide and available manganese were increased more significantly; Long-term applicaton of chemical fertilizer increased the content of available manganese in soil, and long-term application of nitrogen fertilizer more markly increased the content of manganous manganese.2.The variation of soil pH, Eh and various iron, manganese speciations with growth stages. All treatments’pH in 0-60cm layer was significantly decreased at branching stage, while all treatments’Eh declined at the seedling stage and rised at the flowering pod period. Content of free iron oxide and free manganese oxide in 0-60cm layer at all fertilizer treatments showed obvious rising trend at pod stage and branching stage respectively; The contents of amorphous iron oxide and amorphous manganese oxide in 0-60cm layer both showed a downward trend at branching stage; The content of ferrous iron in 0-60cm layer increased at the branching stage, while the manganous manganese increased at the branching and decreased at filling period; The content of available iron and available manganese in 0-60cm layer kept declining from early sowing to branching period to reach a minimum value.3.The spatial changes of pH, Eh and virous Fe, Mn speciation in 0-60cm profile at harvest. The order of pH value was as 40-60cm>20-40cm>0-20cm at all treatments apart from M1N1P and M1N1PK treatments; The value of Eh increased with the raise of soil depth. The content of free iron oxide increased with soil depth rising at most fertilization treatments indicating downward gatheration; The content of amorphous iron oxide was the highest in 20-40cm layer; The content of ferrous iron in the chemical fertilizer area had no obvious variation with soil depth among treatments, while those in the lower organic manure area and the higher organic fertilizer area were decreasing with soil depth; The content of available iron declined with soil depth; The content of free manganese oxide aggregated in 0-40cm layer and was the lowest in 40-60cm layer only the CK and N1PK treatments had a reverse pattern; The content of amorphous manganese oxide aggregated in 40-60cm layer at most treatments; The content of manganous manganese of most treatments was decreasing with soil depth; The content of available manganese deeper decreased with soil depth with highest content in topsoil.4. There is a certain correlation between the various iron, manganese and soil physical and chemical properties. Content of free iron oxide and soil Eh, pe+pH were positively related; Content of amorphous iron oxide and soil Eh, pe+pH and organic matter were positively related; Content of ferrous iron and pH, pe+pH had significantly negative correlation; Content of amorphous manganese oxide showed positively correlation with soil Eh, pH, and significantly negative correlation with soil pe+pH; Content of manganous manganese presented a significantly negative correlation with soil pe+pH, pH, and a significantly positive correlation with soil Eh; Content of available manganese showed significantly negative correlation with soil pH, and significantly positive correlation with soil Eh; There was significant correlation between various manganese speciations, betweenvarious iron speciations, as well as between various manganese and iron speciations indicating these index were related to each other.