EFFECTS OF TIME OF SOWING OF SPRING WHEAT AN D DEFOLIATION OF AGROPYRON REFENS (L.) BEAUV. ON COMPETITION BETWEEN THEM

Summary. Spring wheat, sown at three different times, and Agropyron repens, defoliated at the same three times, were grown separately or together in pots kept in an open‐sided cage. The pots were widely spaced and adequately watered. Early sowing of wheat gave a greater grain yield than late sowing, and lessened the loss from competition with Agropyron. Early defoliation of Agropyron slowed its subsequent early growth more than did late defoliation, and plants defoliated early suffered more from competition with wheat. Competition, probably mainly for nitrogen, decreased tillering and the number of ears produced by wheat, more when sowing was late than early, but grain dry weight per ear was decreased equally at the three times of sowing. The rate at which wheat produced leaves was affected by competition only at the last date of sowing. In competition with wheat, Agropyron produced fewer shoots and ears, had lighter shoots and rhizomes, and ear emergence was slightly delayed.