SOIL COMPACTION BY MANURE SPREADERS EQUIPPED WITH STANDARD AND OVERSIZED TIRES AND MULTIPLE AXLES

Abstract

A study was conducted on a heavy clay soil to evaluate soil compaction induced by different traffic treatmentsassociated with liquid manure spreader systems. Five spreader weights (from 96 to 218 kN), two running gears (tandemand tridem, i.e., three axles) and two types of tire (conventional low section tire and oversized tire) were combined toobtain six traffic treatments, representative of liquid manure spreading operations in Quebec. Soil dry bulk density ( b)and cone index (CI) were measured to evaluate compaction. Tire rut depths and the lateral influence zone were alsoinvestigated in the study.<br><br>For a single pass of a spreader, soil compaction was confined to the tilled layer (about 0-250 mm depth) regardless oftraffic treatments, and this did not affect emergence rates and yields of soybean under the particular soil and climateconditions that prevailed at the time of the study. Neither tandem nor tridem running gears were found to adequatelycontain soil compaction within the tilled layer for total spreader weights exceeding 154 kN. The acceptable limitation fora tandem spreader with conventional 21.5L-16.1 tires would be a total load of about 96 kN, resulting in average groundpressures of 150 kPa or less. If medium capacity spreaders are required, oversized tires are recommended for manurespreading on prairies or post-seeding applications on small grain crops. Finally, the recourse to multiple-axle runninggears for larger spreaders to maintain or reduce unit load per axle or ground pressure does not result in less soilcompaction than lower capacity tandem spreaders with comparable axle loads and ground pressure.