DEINKING SLUDGE INFLUENCES BIOMASS, NITROGEN AND PHOSPHORUS STATUS OFSEVERAL GRASS AND LEGUME SPECIES

Fierro, A., Norrie, J., Gosselin, A. and Beauchamp, C. J. 1997. Deinki ng sludge influences biomass, nitrogen and phosphorus status of severa l grass and legume species. Can. J. Soil Sci. 77: 693-702. In a greenh ouse study, deinking sludge was evaluated as a soil amendment suppleme nted with four nitrogen (N) fertilization levels for the growth of the grasses Agropyron elongatum (Host.) Beauv. (tall wheatgrass), Alopecu rus pratensis L. (meadow foxtail), Festuca ovina var. duriuscula (L). Koch (hard fescue), and four levels of phosphorus (P) for the growth o f the legumes Galega orientalis Lam. (galega), Medicago lupulina L. (b lack medic), Melilotus officinalis (L.) Lam (yellow sweet clover). Fer tilizers were applied on the basis of sludge level to maintain uniform carbon (C)/N or C/P ratios across sludge treatments. In one experimen t, sand was mixed with 0, 10, 20 or 30% sludge while, in a second expe riment, mineral soil was mixed with 0, 27, 53 or 80% sludge (vol/vol). In sand mixtures of 30 and 20% sludge, grasses had similar or greater growth than in unamended mineral soil when N was added at about 6.5 a nd 8.4 g kg(-1) deinking sludge, respectively. For all legumes but Med icago lupulina, P at about 0.8 g kg(-1) sludge was required for these sand mixtures. In soil mixtures of 53 and 27% sludge, grasses grew wel l when supplemental N was about 5.3 and 6.9 g kg(-1) sludge, respectiv ely. Legumes required P at 0.5 and 1.2 g kg(-1) sludge, respectively. In general, growth was closely related to total amount of added N or P in spite of the wide range of C/N or C/P ratios. When growing in medi a amended with sludge, grasses needed higher tissue N concentration fo r an equivalent growth than in control soil; legumes had similar tissu e P concentration. The grasses Agropyron elongatum and Alopecurus prat ensis as well as the legumes Melilotus officinalis and Galega oriental is are promising species for field testing, based on dry matter produc tion. Deinking sludge can be used as soil amendment when adequate N an d P supplements are provided.