Availability of nutrients in wood ash amended tropical acid soils

A greenhouse study was conducted to assess nutrient availability in wood ash when applied to surface soil samples of three tropical add soils (Kandiudult) from Cameroon Amendments were applied at rates to attain target pH values of 5.5, 6.0 and 6.5. Lime treatments were included as a control. Rye grass (Lolium perenne L.) was grown as an indicator plant for three successive cycles of 40 days each Data on total harvested dry matter, nutrient uptake, nutrient additions and extractable soil nutrients from treated soils have been used for availability investigations. Application of wood ash resulted in neutralisation of soil acidity, increased exchangeable nutrient bases and decreased extractable micronutrients. Wood ash was in general more effective than lime in increasing dry matter production, mainly because of higher P and K uptake. phosphorus, Ca, Mg, K,Mn, Zn and Cu from wood ash were used by plants. Wood ash application increased the availability of P, Ca, Mg and K and decreased that of Mn and Zn for plant uptake. Both nutrient additions and nutrient extractions from treated soils provided a reliable measure for plant available nutrients. Soil pH and ECEC affected the availability of P, Ca, Mg and K positively and that of Mn and Zn negatively. Field studies, conducted on a larger number of tropical add soils, are required to establish prediction models.