Paper Mill Sludges (Biosolids) Applications in Agriculture: Agronomic and Environmental Impacts, 2002 Environmental Conference Proceedings

A. N’Dayegamiye, S. Huard and Y. Thibault

Environmental technologies in the paper industry are recognized as important tools in water pollution control and generate high quantities of paper mill sludges (PMS). Large PMS volumes have been used more and more in agriculture for almost five years in the province of Québec, reducing landfilling of these organic materials. In the present study, the agronomic potential and environmental impacts of PMS have been evaluated since 1997 in field experiments in Central Québec on corn, soya, and barley crops. Paper mill sludges were applied at rates varying from 20 to 60 t/ha on wet basis, and compared to mineral fertilizer treatments and to a control without any fertilizer and PMS. Results indicated that PMS applied alone significantly increased corn and barley yields, compared to the control treatment. Lower effects were observed on soya bean. Corn and barley highest yields were obtained when PMS were combined with reduced fertilizer rates (50% to 75% NPKMg) leading to higher yields than those obtained with a complete fertilizer application (100% NPKMg). PMS effects on corn and barley yields were mainly due to their high nutrient contents and efficiency and also to their significant effect on soil properties. PMS significantly increased soil microbial biomass, microbial respiration (CO2), nitrogen mineralization (NO3-) as well as phosphatase and urease activities. PMS applications also increased soil organic matter content and earthworm abundance (data not presented). Results also indicated that three successive PMS applications did not increase soil metal content (Ni, Cr, Co, Cu, Cd and Pb) in the 0-40 cm soil layer, as a result of their low contents in those constituents. Results on E.coli and coliforms also showed lower populations in soil treated with PMS, compared to the control and mineral fertilizer treatments. From this point of view, PMS could be considered safe for use in agriculture when they meet environmental standards. Due to their high nutrient and organic matter contents, PMS are recommended as fertilizers and organic amendments for a sustainable agriculture.