POST-HEADING NITROGEN UPTAKE, RETRANSLOCATION, AND PARTITIONING IN SPRING BARLEY

In cereals, N provided to the developing grains comes from continued N uptake and assimilation after anthesis and from the retranslocation of previously accumulated vegetative N. This study investigated management and cultivar effects on post-heading N uptake and their relationship with total plant and grain N accumulation and grain protein concentration (GPC). Twenty six-rowed spring barley (Hordeum vulgare L.) cultivars were grown on a Chateauguay clay soil(fine loamy, mixed nonacid, frigid, Typic Hapludalf) in 1988 under conventional management (recommended N, no fungicide or growth regulator) and on a Bearbrook clay soil (very fine silty, mixed nonacid, frigid, Humaquept) in 1989 and 1990 under conventional and intensive (high N, fungicide and plant growth regulator) managements. Post-heading N uptake was generally not related to N concentration and N per plant at awn emergence but was highly correlated with total dry matter accumulation after anthesis and moderately to highly correlated with total plant and grain N per plant at harvest. Post-heading N uptake seemed related to the amount of tillering that occurred after anthesis. High-GPC cultivars did not accumulate more N after heading than low-GPC cultivars. Nitrogen retranslocation was correlated with total dry matter and N per plant at awn emergence, but the relationship varied with growing season and management. Nitrogen retranslocation and N harvest index were not correlated with GPC. Post-heading N uptake and N retranslocation were negatively but moderately correlated with each other.