Recovery and management of actual acid sulphate soils in Boyacá (Colombia)

Acid sulphate soils (ASS), having very res­tricted use due to their extreme acidity, have been iden­tified within the upper Chicamocha river basin, Boyacá (Colombia). This situation has led to increasing degra­dation of the land, rendering around 3,000 ha of land unproductive. Production alternatives are thus being sought for recovering these flat upland areas, currently suffering from ASS, as they do have agricultural poten­tial. Soils were initially characterised and identified in a problem area so that possible management of such ASS could then be inferred from the initial study. Increasing doses of calcium hydroxide (Ca(OH)2) (5 to 100 t· ha-1) were then evaluated and determined for neutralising extreme acid conditions in laboratory incubation assays (5-100 t· ha-1). Greenhouse and field tests (random block experimental design with 10 treatments and 4 repeats) were used for observing the response of Avena sativa as an indicator plant; just hen-dung (5-10 t· ha-1) and hen-dung mixed with lime (dry and wet matter) were also evaluated as amendment material. The experiments re­vealed the soils’ chemical changes and reactions following these treatments: pH, Al, ECEC, % AL, % Ca, total S, Mn, Fe and P (i.e. after statistical correlations had been made). These studies led to the soils being recognised as non-coast actual ASS and classifying them as Typic Sulfaquept. The findings indicated that Ca(OH)2 12.5 t· ha-1 mixed with 10 t· ha-1 organic matter (hen-dung) represented the best treatment for obtaining the best A. sativa performance in terms of dry matter production, reflected in positive ASS chemical changes.