During the last 10 yr, research was established in the Niagara region of Ontario to assess the use of paper sludge on agricultural land. Compositionaily, the sludges are relatively free of chemical contaminants. These sludges are used primarily as an organic amendment rather than as fertilizers, because of low mineral nutrient contents. Greenhouse, nursery container media, and field experiments showed increased growth and yield of various horticultural and agricultural crops, thus demonstrating the beneficial effects of paper sludges as organic amendments to potting media and field soils. Small to moderate deficiencies in N in certain sludges are readily compensated by adding fertilizer to soil or sludge. From field plot studies, increases in growth and yield for selected crops have been realized with a recommended sludge application rate of 12 dry Mg ha -~ provided sufficient N fertilizer is applied.

`Eight deciduous ornamental shrubs-deutzia (Deutzia gracilis Siebold & Zucc.), dogwood (Cornus alba L. `Argenteo-marginata'), forsythia (Forsythia × intermedia Zab. `Lynwood Gold'), ninebark [Physocarpus opulifolius (L.) Maxim.], potentilla (Potentilla fruticosa L. `Red Ace'), privet (Ligustrum vulgare L.), rose (Rosa L. `John Frank. lin'), and weigela [Weigela florida (Bunge) A. DC. `Variegata Nana']—were grown in trickle-irrigated containers with 100% bark (control) or with bark and 33%, 67%, and 100% (by volume) of each of three sources of spent mushroom compost (unweathered, weathered, and unweathered compost leached with water). Despite large variation in species growth response to sources and levels of compost, most grew equally well or better in the compost-amended regimes than in 100% bark and were influenced little, or not at all, by initial or prevailing salt levels in the media. Shoot and root dry weight of dogwood, forsythia, ninebark, rose, and weigela (all sources), and shoot dry weight of deutzia and potentilla (weathered source only), increased linearly or curvilinearly with increasing compost levels. The reverse relationship occurred (all sources) in shoot and root dry weight of privet and root dry weight of weigela and potentilla. Leaf nutrients (N, P, K, Ca, Mg, Fe, Mn, and Zn) tended to increase with increasing compost levels, but not all species showed this response with all nutrients. Regardless of compost source or level, all shrubs were of marketable quality when harvested, except privet, which showed leaf chlorosis in all compost-amended regimes.

Postbloom applications of benzyladenine (BA) thinned young fruitlets of mature `Empire' apple trees (Malus domestica Borkh.) as well as or better than NAA or carbaryl (CB). BA increased fruit weight more effectively than either NAA or CB. Promalin (PR) was less effective than BA for both thinning and fruit-weight increase. In 1990, both BA and PR reduced fruit set up to 29 days after full bloom, but PR showed less thinning activity. BA and NAA produced independent and additive thinning responses when tank-mixed. Effects of all thinners on foliar mineral-nutrient concentrations were associated with changes in fruit load. BA increased return bloom as much or more than NAA or CB. PR did not affect return bloom. Chemical names used: N -(phenylmethyl)-1 H -purine-6-amine [benzyladenine (BA)]; BA plus gibberellins A, and A, [Promalin (PR)]; 1-naphthaleneacetic acid (NAA); 1-naphthalenyl methylcarbamate [carbaryl (CB)].

Benzyladenine (BA) applied postbloom at 125 and 250 mg·liter-1 thinned `Empire' apple (Malus domestica Borkh.) trees below commercial crop levels but thinned less than thidiazuron (THI) at 62 and 125 mg·liter-1. Ethephon (ETH) applied up to 250 mg·liter-1 reduced fruit set only slightly. When BA was tank-mixed with ETH, thinning was the same as with BA alone. Although THI thinned more, BA resulted in a larger increase in fruit weight. Seed development was nearly eliminated by THI, but was unaffected by either BA or ETH. Thinner effects on foliar nutrient concentrations were associated with changes in fruit load but not shoot growth. The effects of BA and ETH on fruit-flesh nutrient concentrations were similar to their effects on foliar nutrient concentrations. Although THI thinned strongly and produced large changes in foliar nutrient concentrations and seed count, THI resulted in virtually no changes in fruit-flesh nutrient concentrations. Chemical names used: N-(phenylmethyl)-1 H-purine-6-amine (benzyladenine); 2-chlorophosphonic acid (ethephon); N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron).

Four deciduous ornamental shrubs {`Coral Beauty' cotoneaster (Cotoneaster dammeri C.K. Schneid.), `Flaviramea' dogwood (Cornus sericea L.), `Lynwood' forsythia (Forsythia ×intermedia Zab.), and `Variegata' weigela [Weigela florida (Bunge) A. DC.]} were grown in trickle-irrigated containers with 100% pine bark (control) or with 10 other pine-bark-amended media, including two sources [Noranda Forest (NF) and Quebec and Ontario (QO)] of raw paper mill sludge mixed at 15 % or 30% (by volume). All species grew equally well or better in the sludge-amended media than in the control or other nonsludge media. Cotoneaster and forsythia grew more in NF sludge media than in corresponding QO media due primarily to the greater quantities of N and other nutrients released from the NF sludge.