EFFECTS OF STONE REMOVAL AND STONE CRUSHING ON SOIL PROPERTIES, EROSION, AND POTATO QUALITY

Abstract

Effects of rock removal (stone picking) and rock crushing on soil properties, erosion, and potato (Solanum Tuberosum) quality were examined on a Carleton gravelly loam till soil (Typic Haplaquod) in New Brunswick, Canada. The objective was to evaluate applicability of these operations to reduce tuber injury when a mechanical harvester was used in a stony field. Seriously injured tubers were reduced from 38% under existing field conditions (control) to 17% after the field was crushed with a rock crusher. In the rock-crushed field, no stones over 50 mm in diameter were found in the top 50 mm of soil. Rock removal reduced coarse fragments greater than 50 mm in diameter from 6.8% to 0.6% by weight. Although these operations facilitate the use of mechanical harvesters, they also adversely degrade soil quality and increase the potential for surface runoff and soil loss. Rock removal reduced soil temperature whereas rock crushing deteriorated soil quality by reducing the number of water-stable aggregates greater than 0.5 mm in diameter, which significantly lowered soil aggregate mean-weight diameter. For two rainfall events monitored shortly after plot establishment, average runoff from stone crushed plots was 3.0 and 1.5 times higher than the control; runoff from the stone removal treatment was 1.7 and 1.4 times higher than the control; and soil loss from the crushed and removed treatments was 2.0 and 1.5 times, respectively, higher than from the control. It was concluded that both rock crushing and rock removal operations are at present detrimental to soil and water conservation. However, if better soil/rock separation can be achieved during rock crushing, use of the crusher in stony fields is promising.