The influence of fertiliser nitrogen application on development and number of reproductive primordia in field-grown two- and six-rowed barleys

A field experiment using different 2- and 6-rowed barley cultivars grown at two contrasting nitrogen supply rates (40 and 150 kg N/ha) without water restrictions was carried out to explore how the number of leaf primordia and the rate of leaf emergence interact to modify the duration of different pre-heading phenological phases, and to analyse the dynamics of initiation and mortality of different subcomponents of grain number per unit area, in response to different fertiliser nitrogen regimes. The lower nitrogen supply (40 kg N/ha) delayed heading time as a consequence of higher phyllochron, without any effect on the final number of leaves initiated in the apex. The different fertiliser nitrogen rates only altered the co-ordination between tiller appearance and leaf emergence in two of the 6-rowed cultivars, whereas for the rest of the cultivars, co-ordination between leaf emergence and primary tiller appearance was not altered by fertiliser nitrogen rate. The lower nitrogen supply resulted in less fertile florets per ear due to a reduction in floret primordia survival, without any effect on the maximum number of spikelet primordia initiated in the apex. The higher floret abortion observed in 6-rowed compared with 2-rowed cultivars could be associated with the fact that lateral floret primordia, in those apical and basal positions within the ear in 6-rowed cultivars, are poorly developed with respect to the central spikelets.