Comparative rooting of deciduous landscape shrub cuttings in media amended with paper mill biosolids from four different sources: Summary

Abstract

Pulp and paper, a $20 billion industry in Canada, generates large quantities of effluent waste. For disposal purposes, the waste is typically dewatered into raw sludge or biosolids (30-45% total solids). About 1 million tonnes of this waste product is generated annually.Like other industrial wastes, the disposal of paper mill biosolids is a major concern. Landfilling has been restricted or has become prohibitively expensive. Environmentally friendly and sustainable disposal alternatives are being sought.Since the 1950s, research has assessed the use and benefits of using paper mill biosolids in land reclamation, forestry, and in agriculture. More recently, biosolids have been used successfully to amend soils for field-grown horticultural crops, or used raw or composted in substrates for container nursery crops.In an investigation conducted at the Horticultural Research Institute of Ontario, paper mill biosolids from one source (QUNO) were used effectively as a medium amendment for rooting nursery cuttings under mist. Since biosolids are derived from widely different manufacturing sources, often with different end-uses, can other sources of biosolids be used similarly in nursery rooting media?Current season terminal cuttings were taken in early summer from six deciduous woody shrubs: coralberry, flowering almond, honeysuckle, mock orange, purple-leaf sandcherry, and viburnum. The cuttings were treated with a rooting hormone (5000 ppm indolebutyric acid) and inserted in flats filled with 100% perlite medium, or perlite mixed with 15, 30, 45 or 60% by volume of raw paper mill biosolids from one of four sources (Atlantic, Domtar, Thorold, and QUNO). Rooting occurred under mist and 50% lath shade. The response of species in each treatment was assessed 3 to 4 weeks later in terms of the percent of cuttings rooted, number of roots per rooted cutting, and length of the longest root per cutting.Despite wide variability in rooting response among species, source, and/or amount of biosolids in the rooting media, statistical (regression) analysis showed remarkable consistency in the results. There was little or no discernable adverse affect of the biosolids on the cuttings. With few exceptions, optimum rooting occurred when between 30 and 60% (the highest level tested) of biosolids were present in the rooting media. There was no clear indication that any one of the sources was consistently or substantially better than the other in promoting rooting.In this study, physical analysis indicated that the pore space characteristics of the biosolids-amended media were comparable to, or exceeded, those of perlite. Also, chemical analysis showed that the initial concentrations of all nutrients in the unamended biosolids were relatively low or within acceptable ranges, and values in electrical conductivity (EC, a measure of the soluble salts content) ranged from 0.2-0.7 dS m -1 . After preparation of the mixes and initial watering of the flats, and throughout the rooting period, the EC values in the amended mixes were within an accept...