Effects of long-term fertilization on forms of Fe and Mn and their distributions in soil profiles

The BCR Continuous Extraction was used to study the iron and manganese content changes and their profile variations in brown soils after 31-year fertilization treatments in long-term localization experimental field of Shenyang Agricultural University. The results show that compared with the baseline, the contents of the Water soluble and the Weak acid soluble Fe and Mn are increased, while the contents of their oxidizable and the residual forms are decreased. The main forms of both elements are residual and oxidizable. As for the profile distribution, with increase of soil depth, the contents of the weak acid soluble and the reducible Fe and Mn are reduced, while the contents of residual pools are increased. It is concluded that manure can alter the forms of Fe and Mn and manure can activate the residual Fe and Mn.