BURNING CROP RESIDUES: EFFECT ON SELECTED SOIL CHARACTERISTICS AND LONG-TERM WHEAT YIELDS

Abstract

Soils from a long-term spring wheat — spring wheat — fallow crop rotation study at Lethbridge, Alberta, and two similar crop rotations at Indian Head, Saskatchewan, were analyzed for pH, organic C, total N, chelating resin-extractable C, polysaccharides, water-stable aggregates, NH 4 -N, NO 3 -N, and available P. Several agronomic practices, including straw burning, have been tested in the rotations. At Lethbridge, soil samples from the straw-burning treatment showed a decrease (P < 0.05) in soil polysaccharides and in the percentage of water-stable aggregates. At Indian Head, where straw was burned, organic C and polysaccharide content of all soils were decreased (P < 0.05), and NH 4 -N and available P were decreased (P < 0.05) in some soils. The other soil characteristics examined were not affected by burning of the previous crop residue or, as with available P, reacted differently at different sites. Long-term wheat yields tended to be greater in all experiments when straw was not burned. On the basis of the results obtained, burning of crop residues on a long-term basis must be discouraged.