Nutrient Availability in a Calcareous Soil Amended with Different Types of Biomass Ash

An incubation experiment was conducted to evaluate the effects that three types of biomass ash, each applied at two doses, exert on the nutrient availability in a calcareous soil. The application of the ash from dry olive cake or greenhouse vegetable wastes significantly increased soil ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable phosphorus (P), potassium (K), sodium (Na), copper (Cu) and zinc (Zn) as well as exchangeable and non-exchangeable K and Na. Wood ash was effective only for increasing soil ABDTPA-extractable Zn and Cu. By contrast, the three types of biomass ash hardly increased soil ABDTPA-extractable Fe or Mn. The high content in carbonate of the soil appears to minimize the potential of the ash to increase the micronutrients availability, which shortened with longer incubation time. Soil ABDTPA-extractable heavy metals were not detected in the different treatments tested. Other parameters of the soil, as pH and organic carbon, were scarcely affected by the ash, while conductivity and dehydrogenase activity increased.