EFFECT OF SPRING SEEDLING RESIDUES ON THE AGRONOMIC PERFORMANCE OF SUBSEQUENT FLAX AND BARLEY CROPS SEEDED WITH AND WITHOUT PRIOR TILLAGE

Field experiments were conducted to determine the effect of spring seedling residues of canola (Brassica napus L. and B. campestris L.), barley (Hordeum vulgare L.), flax (Linum usitatissimum L.) and a weed mixture on the growth and yield of subsequent crops of flax and barley seeded after tillage of the seedling plots. Some treatments were also tested without tillage, the seedlings being killed with paraquat. The large quantities of spring seedling residues had variable effects on flax yields, resulting in increases in some years and decreases in others compared to seedling-free plots. Flax yields were generally reduced by canola, flax and weed seedling residues, and increased by barley seedling residue. Averaged over 6 yr, canola seedlings reduced flax yields by 2% and barley increased flax yields by 3% with conventional tillage. On the other hand, barley yields were reduced 7% by conola and 17% by barley seedling residues. Yields of flax and barley were higher without than with tillage of the seedlings prior to seeding. The results are discussed in relation to the effects of the seedling residues on soil crusting, toxic compounds in the residues and toxic compounds formed during decomposition of the residues.Key words: Flax, Linum usitatissimum L., barley, Hordeum vulgare L., plant residues, tillage systems