ACCUMULATION AND REDISTRIBUTION OF DRY-MATTER AND NITROGEN BY SPRING BARLEY

The grain protein content of barley (Hordeum vulgare L.) is derived from the retranslocation of vegetative N, as wed as from the continued uptake and assimilation of N during grain filling. Field trials were conducted at the E.A. Lods Agronomy Research Centre of McGill University on a a Bearbrook soil (fine, mixed, nonacid, frigid Humaquept) to study the effects of fertilizer N on grain and total plant N accumulation, vegetative N retranslocation, and post-heading N uptake, and also to evaluate the importance of pre- and post-anthesis N uptake in determining grain protein concentration (GPC). 'Cadette' and 'Leger', which are adapted feed types, and 'Argyle', an unadapted malting type, were grown with N rates of 0, 50, 100, 150 and 200 kg N ha(-1) broadcast at seeding as NH4NO3. Two other treatments consisted of applying 100 kg N ha(-1) at seeding and 50 kg N ha-L as NH4NO3 (broadcast) or urea (foliar solution) 6 to 10 d after awn emergence. Retranslocation of vegetative N to the grain generally decreased with increased N application in 1988 and 1989, but not in 1990, when it increased. The proportion of vegetative N retranslocated to the grain decreased with increasing rates of fertilizer N in all years. Post-heading N uptake and assimilation increased with fertilizer N, and appeared to be the major contributor of N to the grain. Cultivar differences in GPC were not related to differences in total N uptake, grain Ei, N harvest index, and apparent post-heading N uptake or N retranslocation.