Reactions of copper with soil affecting its availability to plants. II. Effect of soil pH, soil sterilization and organic matter on the availability of applied copper

Abstract

Incubation of copper with warm, moist soils reduced its effectiveness for uptake by wheat plants when compared to copper freshly applied. On two soils (Gingin, Dongara), the relative effectiveness of incubated compared to freshly applied copper was lower at higher pH. On the third soil (Lancelin) relative effectiveness was unaffected by changing soil pH from 6.7 to 7.8. Soil sterilization before incubation increased the effectiveness of incubated copper compared with that freshly applied on two soil types (Lancelin, Dongara), while on the other soil (Newdegate) soil sterilization did not affect relative effectiveness. The addition of cereal straw decreased the effectiveness of copper both freshly applied and when incubated with the soil. The effect of cereal straw was more marked where the copper was incubated with the soil, suggesting that organic matter is strongly involved in reducing the effectiveness of incubated copper compared with that freshly applied. The same reactions which reduce the availability of freshly applied copper appear to continue to decrease the availability of copper throughout incubation.