Characterization of soil physical properties and organic matter under long-term primary tillage in a humid climate

Chisel ploughing is considered to be a potential conservation tillage method to replace mouldboard ploughing for annual crops in the cool-humid climate of eastern Canada. To assess possible changes in some soil physical and biological properties due to differences in annual primary tillage, a study was conducted for 9 years in Prince Edward Island on a Tignish loam, a well-drained Podzoluvisol, to characterize several mouldboard and chisel ploughing systems (at 25 cm), under conditions of similar crop productivity. The influence of primary tillage on the degree of soil loosening, soil permeability, and both organic matter distribution throughout the soil profile and organic matter content in soil particle size fractions was determined. At the time of tillage, chisel ploughing provided a coarser soil macrostructure than mouldboard ploughing. Mouldboard ploughing increased soil loosening at the lower depth of the tillage zone compared to chisel ploughing, These transient differences between primary tillage treatments had little effect on overall soil profile permeability and hydraulic properties of the tilled/non-tilled interface at the 15-30 cm soil depth. Although soil microbial biomass, on a volume basis, was increased by 30% at the 0-10 cm soil depth under chisel ploughing, no differences were evident between tillage systems over the total tillage depth. Mouldboard ploughing increased total organic carbon by 43% at the 20-30 cm soil depth, and the carbon and nitrogen in the organic matter fraction less than or equal to 53 mu m by 18-44% at the 10-30 cm soil depth, compared to chisel ploughing.