Biosolids and Hybrid Poplar

Biosolids are treated waste materials from various sources, including paper mills, animal product processing plants, beef and pork feedlots, and city sewage treatment plants. Public awareness of pollution and landfill problems have led to increased interest in cycling wastes back into natural systems.

Effects of Biosolids on the Growth of Cottonwoods
Biosolids have been shown in numerous similar experiments that they have a positive effect on hybrid poplar production. Wastewater effluent improved biomass production in plantations on abandoned pasture lands (Carslon 1992). Cole (1982) showed a seven-fold increase in mass accumulation over a control plot after five years of municipal wastewater irrigation.

Relative Effects of Different Treatments
A number of experiments have been done to test the relative effects of various biosolids on the performance of hybrid poplar. Zabek (1995) showed that fish compost, municipal waste biosolids, and pig manure all induced a positive growth response in hybrid poplar and were more effective than inorganic fertilizer.
Paper mill "mulch"- high fiber, low nitrogen waste mixed with wood ash- was shown to be less effective in hybrid poplar stands at higher levels of application than at lower, leading the authors to the conclusion that it was more useful as a mulch for insulative purposes than as a nutrient supplement.

Various Sources of Biosolids
Organic residuals can come from a great number of sources, including municipal sewage, fish- or meat-processing sites, and pulp and paper mills. Dredged harbor sludge has even been shown to have a positive effect on the growth of hybrid poplar (van den Burg 1978, de Vos 1989).


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