RHA-based waste recycling: a cheap alternative for improving phosphorus availability while restoring acid soils

Abstract

Soil acidity constrains crop productivity in the northern floodplain regions of Bangladesh under intensifying cropping, where yields often decline despite increased fertilizer inputs. Acid soil limits the availability of essential plant nutrients and may induce toxicity. Given the inconsistent supply and quality of conventional liming materials, rice husk ash (RHA) was evaluated as an alternative for managing soil acidity and increasing phosphorus availability. A three-month laboratory incubation study (25-30°C); soils maintained at field capacity) was conducted using composite soils from Rangpur (AEZ 2) and Kurigram (AEZ 3) to assess the changes in soil pH and available P following application of RHA and dololime at graded rates 0 to 4.0 t ha-1 equivalents with three replications. Treatment effects were analyzed statistically at the end of the incubation period. Soil incubation with Dololime at 2.0 t ha-1 delivered the strongest pH correction, raising pH to ~6.8 in Rangpur and in Kurigram. High rates of RHA also increased pH to a favorable range for crop production; @4.0 t ha-1, the pH increased to 6.18 in Rangpur and 6.02 in Kurigram.  Incubation results showed a significant increase in soil pH and enhanced P availability after amendment, confirming a strong link between pH correction and improved P dynamics in soil. Long-term trials integrating economic, biological and physical soil indicators are recommended to optimize the amendment strategies (quantify residual effects and application intervals) for the acid soils of Bangladesh. Res. Agric. Livest. Fish. 13(2): 285-294