Comparison of sewage ash, crushed limestone and cement kiln dust as ameliorants for acid soils

Abstract

A field experiment and a glasshouse experiment showed that crushed limestone, cement kiln dust and sewage ash were all effective in ameliorating adverse soil factors associated with acid soils. Pasture plant yield could be more than doubled by the addition of up to 6 t of ameliorants/ha. Twenty-six months after incorporating ameliorants in the top 10 cm of soil in the field experiment pH had substantially increased, however, there was a much smaller effect in the 10-20 cm zone. In the glasshouse experiment, clover yield on the strongly acid (pH 4.1 in CaCl2) well-buffered soil from the field experiment site responded to the addition of up to 4 t of ameliorants/ha. On a slightly acid (pH 4.7 in CaCl2) poorly buffered soil from another site, ameliorant rates above 2 t/ha reduced clover yield because of factors associated with an increase in pH (CaCl2) to 6.6 and above. Sewage ash tended to be better than the other ameliorants in improving plant yield. This was attributed to the presence of about 3% of P in the ash, which increased soil extractable P, and P content and yield of the herbage.