Effect of varying static and changing moisture levels during incubation on extractability of soil phosphate

Summary A sandy loam (pH 6.5) was incubated at 28°C at static moisture levels, ranging from 10 per cent saturation to 133 per cent saturation (waterlogging), for 6 and 12 weeks; other samples covering the same moisture range were first incubated for 6 weeks, and after changing all moisture levels to 50 per cent saturation were incubated for a further 6 weeks.With increasing static soil moisture level during incubation there was a slight reduction in Morgan-extractable phosphate up to 70 per cent saturation, but thereafter, due to anaerobic effects, there were considerable increases in extractable phosphate with increasing moisture level.With changing moisture level during incubation the effects of anaerobiosis became apparent where original moisture level was greater than 50 per cent saturation; extractable phosphate was reduced to levels lower than those occurring where the soil was maintained continuously at 50 per cent saturation. The extent of reduction in extractable phosphate increased with original soil saturation level.