Phosphorous Transformation and Fixation of Some Main Soils in Vietnam

Phosphorus is a very important nutrient for plant growth, and phosphorus deficiency is often observed in tropical soils because of high concentration of iron (Fe), aluminum (Al), and fixation capacity of soils. So that farmers usually apply with high rates of phosphate to improve crop yields. However, the effects and dynamic of phosphorus in soils are not understood. To investigation these effects, the research is carried out on some main soils of Vietnam. The results showed that most of the studied soils have high phosphorus fixation capacity. The fixation capacity of soil decreases from Ferralic Acrisols to Xanthic Ferrasols, Gleyic Fluvisols, Eutric Fluvisols and Haplic Arenosols. In term of fractions, the fraction of Fe-P is predominant in most of the studied soils, except Xanthic Ferrasols. The fraction of Al-P is higher than Ca-P in soil with highly ferralitic intensity of Rhodic Ferrasols, but lower in soils with weakly ferralitic intensity of Eutric Fluvisols and Haplic Arenosols. Water logged has high effects on phosphorous fractions in soils. The contents of Org-P, Ca-P and Al-P decrease but the contents of Fe-P increases due to logged soils. Phosphorous applies also have significant effects on the sorption capacity as well as the fractions of phosphorous in soils. At high rates of phosphate applied, all the fraction of phosphorus increases significantly, especially Fe-P and Ca-P.