The Potential for Direct Application of Papermill Sludge to Land: A greenhouse study

Papermill sludge (PMS) is the waste product from the paper manufacturing industry and is produced in considerable quantities worldwide. This investigation characterised a PMS from a papermill plant in South Africa and investigated the potential for direct land application of the PMS to soil. In a pot experiment, application of PMS to three contrasting soils at equivalent rates of 0, 10, 20 and 40 Mg/ha resulted in an overall decline in ryegrass yield. Plant germination was reduced at an application rate of 40 Mg/ha, which was attributed to the high EC of the PMS. The nitrogen content of the ryegrass foliage declined with an increase in PMS application rate, this attributed to assimilation of N by organisms in the presence of excess C from the PMS. Other foliage nutrient and metal concentrations were generally either within critical ranges or below detection limits. This was attributed, in part to either low initial concentrations in the soil and PMS, the liming effect of the sludge or, for some nutrients, microbial assimilation processes. An equilibration time period between land application and crop planting is recommended.