The researchers studied how different soil pH levels affect the forms of cadmium in paddy, purple, and yellow soils. They found that when the pH is below 6.5, the amount of dissolvable cadmium increases significantly. In acidic conditions, the percentage of exchangeable cadmium goes up, while it decreases in alkaline conditions. Cadmium bound to carbonates and Fe-Mn oxides increases with higher pH, and cadmium bound to organic matter also increases slightly. To reduce the harmful effects of cadmium, it is suggested to keep soil pH above 6.5 and use organic manure for fertilization.