Availability of nutrients in wood ash amended tropical acid soils

A greenhouse study was conducted to assess nutrient availability in wood as h when applied to surface soil samples of three tropical add soils (Kandiud ult) from Cameroon Amendments were applied at rates to attain target pH val ues of 5.5, 6.0 and 6.5. Lime treatments were included as a control. Rye gr ass (Lolium perenne L.) was grown as an indicator plant for three successiv e cycles of 40 days each Data on total harvested dry matter, nutrient uptak e, nutrient additions and extractable soil nutrients from treated soils hav e been used for availability investigations. Application of wood ash result ed in neutralisation of soil acidity, increased exchangeable nutrient bases and decreased extractable micronutrients. Wood ash was in general more eff ective than lime in increasing dry matter production, mainly because of hig her 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, M g and K and decreased that of Mn and Zn for plant uptake. Both nutrient add itions and nutrient extractions from treated soils provided a reliable meas ure for plant available nutrients. Soil pH and ECEC affected the availabili ty of P, Ca, Mg and K positively and that of Mn and Zn negatively. Field st udies, conducted on a larger number of tropical add soils, are required to establish prediction models.