The chelation process in the soil Soluble chelates increase the availability of micronutrient cations: Fe Zn, Mn, and Cu. The chelates help protect the ions from precipitation or adsorption reactions
Soluble chelates increase the availability of micronutrient cations: Fe, Zn, Mn, and Cu. The chelates help protect the ions from precipitation or adsorption reactions. The chelation process in the soil
Factors that affect micronutrient availability a) Solubility of the micronutrient (affected by factors such as pH) b) Percent of exchange sites that are occupied by the micronutrient c)Soil organic matter (1)Affects the balance between adsorption and desorption (2) Organic matter is also involved in the chelation process
a) Solubility of the micronutrient (affected by factors such as pH) b) Percent of exchange sites that are occupied by the micronutrient c) Soil organic matter (1) Affects the balance between adsorption and desorption (2) Organic matter is also involved in the chelation process Factors that affect micronutrient availability
Iron Fe in the soil Fe is one of the most abundant elements in the surface of the earth. It makes up about 5% weight of the earth's crust and is invariably present in all soils
Iron • Fe in the soil Fe is one of the most abundant elements in the surface of the earth. It makes up about 5% weight of the earth’s crust and is invariably present in all soils
Iron forms in soil Mineral bearing iron Primary mineral olivine, augite(辉石), hornblende and biotite(黑云母) Minerals fe oxides Geothite(a- FeOOH针铁矿), haematite(赤铁矿)and ferrihydrate(HFe5O84H2O水化铁)etc
Iron forms in soil • Mineral bearing iron • Primary mineral: • olivine, augite(辉石), hornblende and biotite(黑云母). • Minerals Fe oxides • Geothite (α-FeOOH针铁矿), haematite（赤铁矿) and ferrihydrate（HFe5O8·4H2O水化铁）etc
Iron in the soil solution 1. Soil solution concentrations are very low The concentration of fe3+ in the soil is 10-15to1020M. Soluble inorganic forms include Fe3+, Fe(oH)2+, Fe(oH)2+ and Fe2+ Iron solubility is largely controlled by the ph and Eh Fe3+ +30H =Fe(OH)3 At higher pH levels Fe3t activity in solution decrease 1000 fold for each ph unit rise
Iron in the soil solution 1. Soil solution concentrations are very low. The concentration of Fe3+ in the soil is ~10-15 to 10-20 M. • Soluble inorganic forms include Fe3+, Fe(OH)2+ , Fe(OH)2+ and Fe2+ • Iron solubility is largely controlled by the pH and Eh. • Fe3+ +3OH-= Fe(OH)3 • At higher pH levels Fe3+ activity in solution decrease 1000 fold for each pH unit rise