EFFECTS OF TILLAGE, LIME, AND PHOSPHORUS ON SOIL-PH AND MEHLICH-3 EXTRACTABLE NUTRIENTS

In Eastern Canada, barley yields are often restricted by soil acidity and low fertility as well as by structural degradation. The addition of lime and fertilizers and reduced tillage are proposed practices which may have a large impact on soil reaction and nutrient extractability. The objective of this work was to assess the impact of three years of differential tillage intensity (minimum, MT; chisel plow, CP; and moldboard plow, MP) and of lime and P additions on pH and Mehlich-3 extractable nutrients in the 0-7.5, 7.5-15, 15-30, and 30-45 cm soil layers of a Courval clay loam (fine, mixed, frigid, Aeric Humaquept). This study has shown that lime reaction was limited to the depth of incorporation in this clay soil. Lime, when added at moderate amounts, resulted in significant increases in soil phosphorus (P) extractability under all tillage intensities and reductions in extractabile zinc (Zn) and manganese (Mn), whereas potassium (K) and magnesium (Mg) were not significantly affected. Subsoil-extractable Mg was brought closer to the surface in the plow treatments. The use of the chisel plow as primary tillage has resulted in increased soil P, K, and Mn extractabilities. Extractable Zn was larger under moldboard plowing. It is possible that, because of a better distribution of plant residues, larger microbial biomass activity under CP is responsible for these observations. Chisel plow is a good alternative to moldboard plowing in this soil as it incorporated lime and plant residues more evenly while reducing fixation of added fertilizers.