By Calvin Chong and Peter Purvis, University of Guelph, Department of Plant Agriculture — Vineland Horticultural Research Institute of Ontario, Vineland Station, Ontario


Cuttings from seven deciduous species were rooted in media consisting of municipal waste compost (15 to 75 per cent by volume) mixed with perlite or with peat. Cuttings of most species rooted as well as or better in the compost-amended media compared with 100 per cent perlite or 100 per cent peat. Best rooting occurred with between 45 and 75 per cent compost in the rooting medium. A tendency for better rooting in compost mixed with perlite than with peat was due largely to lower water and higher air porosities with perlite than with peat. High salt levels — a concern in some unmixed compost — was not an influential factor since the media were leached.


Introduction
Since inception 16 years ago, the Ornamental Nursery Research Program at Vineland has been investigating the use of uncomposted and composted organic farm and industrial wastes as field soil amendment and in nursery potting mixes (1, 2). In a previous article in Landscape Trades, we reported on rooting of evergreen shrub cuttings in unleached municipal waste compost media (4). This related report summarizes results on rooting of deciduous shrub cuttings in leached waste compost media.


Procedure
Current season stem cuttings were taken at the end of June from the following test species: coralberry (Symphoricarpos × chenaultii ‘Hancock’), snowberry (Symphoricarpos albus), European cranberry bush (Viburnum opulus), lilac (Syringa velutina), purple osier (Salix purpurea ‘Nana’), purple-leaf sandcherry (Prunus × cistena), and winged spindle-tree (Euonymus alata ‘Compacta’). The trial required 500 cuttings of each species for a total of 3,500 cuttings.

     The basal portions of the cuttings were quick-dipped in 5000 ppm indo­lebutyric acid dissolved in wind­shield washer fluid (3). Cuttings were then inserted in flats filled with 100% sphagnum peat or 100% perlite, or mixtures of 15, 30, 45, 60, and 75 per cent by volume of municipal leaf and yard waste compost with peat or perlite, and rooted under lath and intermittent mist. To determine rooting response, we recorded the percentage of cuttings with roots longer than 1 mm, root number per cuttings, and length of the longest root per cutting.


Results and discussion
Chemical analysis and salts

• The batch of compost used in this study had concentrations of soluble salts measuring 1.7 dS/m, due primarily to excess of potassium and chloride (Table 1).
• However, immediately after preparing the experimental rooting media and watering the flats several times, the salt values in all media were at or below 0.2 dS/m, the desirable salt threshold for rooting of most nursery cuttings.

Rooting response
Table 2 summarizes the results for the percentage of cuttings rooted, the number of roots per rooted cutting, and the length of the longest root per cutting. For each measurement, we (a) compared the responses occurring in 100 per cent perlite or 100% peat with those occurring in compost (i.e. the best response within the range of 15 to 75 per cent compost) mixed with perlite or peat, respectively; and (b) indicated if differences were positive (+) or negative (-), or if there was no difference (0).

• With few exceptions, there was no adverse effect of the compost on rooting.
• On the contrary, the presence of compost often resulted in increased rooting.
• The best rooting generally occurred when there was between 45 and 75 per cent of compost in the medium.
• More species rooted better in compost mixed with perlite than in compost with peat (Table 2).
• This result was due largely to higher air and lower water porosities with perlite than with peat which are more favourable for rooting (Table 3).

Recommendation
The results of this trial confirm the efficacy of municipal waste compost as an alternative rooting medium amendment. With leaching, volumes up to 75 per cent can be satisfactorily used. Mixtures with perlite were generally better than corresponding mixtures with peat.

     Since different sources of compost, or even batches from the same source, may differ, we recommend that you check the salt reading of the compost and/or pre­pared medium before sticking the cuttings. If the reading is higher than 0.2 dS/m, simply leach it (once or more) until the reading is below or very close to this value. Salts leach very quickly from propagating medium in shallow flats or plugs. Often, just leaving the media in flats under mist for a day or two will result in leaching sufficient to lower salts to acceptable levels.


Acknowledgments
This trial was conducted with the cooperation of Caesar J. Corvinelli, Engineer, Solid Waste Management Division, Metropolitan Works Department, The Municipality of Metropolitan Toronto, Keele Valley Landfill, Vaughan, Ont. Unrooted plant material was donated by Willowbrook Nursery, Fenwick, Ont. Technical assistance was provided by Bob Hamersma, Linda Oulevey and Sarah Wheeler.


References
1. Chong, C. 1996. Growing on wastes: A success story and horticultural resource. In: Ground Works ‘96 Proceedings. R. Khana and M. Stager (editors), The Evergreen Foundation, Toronto, ON. pp.36-43.
2. Chong, C. 1999. Experience with the utilization of wastes in nursery potting mixes and as field soil amendments. Canadian Journal of Plant Science 79:139-148.
3. Chong, C. and B. Hamersma. 1995. Further studies with inexpensive root-promoting solutions. Landscape Trades 17(4):28-29.
4. Chong, C. and P. Purvis. 2001. Municipal waste compost: A potential rooting medium amendment. Landscape Trades 23(1):(January issue).