Title: MULTIPLE APPLICATIONS OF PAPER MILL WASTES IN AN AGRICULTURE SYSTEM: SOIL EFFECTS
Submitted to: Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 10, 2000
Publication Date: N/A
Interpretive Summary: This study was undertaken to determine whether paper mill wastes could provide agricultural benefits, thereby reducing environmental problems regarding disposal of the wastes. Large amounts of wastes are produced annually in the production of paper and most of this is currently disposed in landfills. However, growing concerns regarding long-term environmental safety of landfills has spawned interest in alternative methods of disposa and possible methods of utilization of wastes. One alternative to landfilling of paper mill wastes is land utilization. These high organic matter wastes may benefit agriculture by supplying nutrients or promoting soil productivity. The present study was designed to evaluate paper mill wastes for such a use. A five-year study was conducted to determine if paper mill wastes could improve soil fertility and productiveness. Varied amounts of paper mill wastes were added to cornfields in every year, in every other year, or only once in five years. Impacts on soil organic matter level, soil bulk density, soil aggregates, and on the amount of water held in the soil were measured. Addition of paper mill wastes to the soil increased soil organic matter, in some cases, more than doubling the amount in the soil. Marked improvements in the capacity of soil to hold water for plants was observed during the course of the study. Similarly, improvements in soil aggregate formation, a property that helps the soil resist erosion and improves soil aeration, occurred when paper mill wastes were used. Along with the increase in soil water holding properties, soil density was reduced, thus improving soil tilth. In some cases, however, over-application of paper mill wastes reduced soil bulk density too much and the soil became too "fluffy".
A five-year field study was undertaken to determine the long-term effects of land application of paper mill wastes on an agricultural soil. Little information exists regarding the effects of field-scale application of paper mill sludge on soil properties. The goal of this study was to determine the responses of soil chemical and physical properties to multiple application of wastes under three management protocols: wastes applied once, applied in alternate years or applied annually. Five rates of waste application were tested, ranging from 0 to 225 Mg ha-1. Results indicate strong relationships between added sludge C and several soil physical properties. Increases or maintenance of soil C were observed when sludge was applied annually or biannually, but little residual effect of sludge applied only once was seen after five years. Increases in soil structure, particularly in the larger size fractions (1 mm and 2 mm), were significantly related to sludge C added. Sludge C effects on water holdin capacity was greatest in the lower moisture tension classes; the effect on gravimetric water content ranged from approximately 50% to near 90% in the -0.067 MPa class. Lesser increases were seen in higher tension classes until cumulative C addition reached approximately 225 Mg ha-1. At these higher levels, gravimetric water content increased from near 15% to over 30% in the -1.5 MPa range. Paper mill sludge has been shown to effect positive changes in soil physical properties that are related to soil quality.