WINTER-WHEAT GROWTH AND NITROGEN DEMAND IN SOUTH COASTAL BRITISH-COLUMBIA

Winter wheat, Triticum aestivum, is a new crop in south coastal Britis h Columbia. The purposes of this study were to characterize plant deve lopment, dry matter accumulation and N uptake under low input and inte nsively managed systems as well as to assess the capability of some of the region's soils to supply N to the crop. Grain yields, crop develo pment and dry matter and N accumulation were similar to those reported from southern England. High amounts of winter rainfall (November-Apri l precipitation ranged from 523 to 1111 mm) leach virtually all residu al NO3 from south coastal B.C. soils and, without N fertilization, res ult in uniformly N deficient winter wheat. The low input N regime, 75 kg N ha(-1) at Zadoks growth stage 31, plus soil N mineralized subsequ ent to the winter leaching period were sufficient in this study to max imize grain and total aboveground crop dry matter yields, but not to a chieve adequate grain protein contents. The soils in the study were ca pable of supplying N in amounts sufficient to support only 30-53 % of the maximum N uptake between growth stages 31 and 78. Appropriate quan tities and timing of N are critical to successful production of high-y ielding, good-quality wheat in south coastal British Columbia. Nitroge n management is likely to be most efficient when guided by the stage o f crop development and demand and not by spring soil sampling and mine ral N analysis.