USE OF RAW AND COMPOSTED PAPER SLUDGE AS A SOIL ADDITIVE OR MULCH FORCOTTONWOOD PLANTS

Pulp and paper sludge is a by-product of paper production and may be s uitable in agricultural applications as a soil amendment or mulch. The objective of this study was to evaluate raw and composted pulp and pa per sludge as soil additives or mulches for cottonwood plants. Primary sludge, a combination of by-products from bleached kraft and neutral sulfite semichemical paper, was mixed with tailings, slaughterhouse pa unch, and 10 percent wood ash (by volume), and used raw or composted a nd cured in the field for 39 weeks. Cuttings of two cottonwood (Populu s deltoides Bartr. ex Marsh) clones were planted in a field soil (Quin cy loamy fine sand) that was mixed (incorporated) or mulched (placed o n top the soil) with raw or composted sludge mixtures at application r ates of 0, 45, 90, 135 and 180 Mg/ha. The plants were grown in a plast ic house for nine weeks. Electrical conductivity (EC), cation exchange capacity (CEC), soluble Cl and extractable Na in soil amended with 18 0 Mg/ha of compost were 37, 22, 197 and 138 percent higher, respective ly, than those of soil amended with the raw sludge mixture at the same rate. bulk density of amended soil decreased, whereas soil aeration a nd water-holding capacity increased as sludge application rate increas ed. After nine weeks, raw or composted sludge applied at a rate of 135 Mg/ha, whether used asa mulch or incorporated, improved cottonwood pl ant height by 40 percent and stem diameter by 20 percent compared to p lants grown in nonamended, nonmulched (control) soil. These results in dicate that the pulp and paper sludge mixtures, whether raw or compost ed, improved soil characteristics and aided establishment of cottonwoo d cuttings.