Phosphorus leaching from soils amended with thermally gasified piggery waste ash

In regions with intensive livestock farming, thermal treatment for local energy extraction from the manure and export of the P rich ash as a fertilizer has gained interest. One of the main risks associated with P fertilizers is eutrophication of water bodies. In this study P and K mobility in ash from anaerobically digested, thermally gasified (GA) and incinerated (IA) piggery waste has been tested using water loads ranging from 0.1 to 200 ml g(-1). Leaching of P from soil columns amended with GA was investigated for one P application rate (205 kg P ha(-1) corresponding to 91 mg P kg(-1) soil dry matter) as a function of precipitation rate (9.5 and 2.5 mm h(-1)), soil type (Jyndevad agricultural soil and sand), amount of time elapsed between ash amendment and onset of precipitation (0 and 5 weeks) and compared to leaching from soils amended with a commercial fertilizer (Na(2)HPO(4)). Water soluble P in GA and IA constituted 0.04% and 0.8% of total ash P. Ash amended soil released much less P (0.35% of total P applied in sand) than Na(2)HPO(4) (97% and 12% of total P applied in Jyndevad and sand, respectively).