Greenhouse and field response of southern pine seedlings to pulp mill residues applied as soil amendments

Abstract

Pulp and paper mills produce organic wastewater treatment residuals, inorganic process residues, and ash that have potential value as soil amendments in southern pine plantations. Chemical characteristics of 18 organic and 10 inorganic residues from 11 southern US pulp and paper mills were determined, and loblolly pine seedling growth response to their use as soil amendments was evaluated in two greenhouse studies. Fourteen of these 28 residues were then used in field studies in which they were incorporated into soil during establishment of pine plantations at three different sites. Under greenhouse conditions, seedling growth was increased by soil incorporation of most of the secondary wastewater treatment residuals at rates equivalent to 22.4 or 134.4 Mg · ha-1. In contrast to these greenhouse studies, under field conditions seedling growth was either unaffected or reduced when secondary wastewater treatment residuals were incorporated into soil at these same rates at plantation establishment. Seedling growth in soil amended with primary wastewater treatment residuals was generally no greater and in some cases significantly less than in the untreated control in both greenhouse and field studies. However, some evidence for growth improvement was observed when these residuals were added to sandy soils of a flatwoods site. We observed little short-term growth benefit from incorporation of inorganic causticizing residues or ash in either the greenhouse study or in field studies of pine plantation establishment. Recycling pulp mill wastewater treatment residuals and process residues to forestland may be a viable recycling/reuse alternative, but growth responses will vary among materials and soil types and are relatively small. Secondary wastewater treatment residuals have the greatest potential to improve growth, but current silvicultural operations would need to be adapted to effectively use these materials. © 2012 by the Society of American Foresters.