GRAIN-YIELD AND QUALITY OF WHEAT AS AFFECTED BY NITROGEN-FERTILIZER APPLICATION TIMED ACCORDING TO APICAL DEVELOPMENT

Optimal yield and quality of wheat (Triticum aestivum L.) depend to a large extent on the rate of nitrogen (N) fertilizer application, which may often be inadequate. Uptake and utilization of N by wheat plants are influenced by environment and variety, and consequently supplement ary N may be needed during the growing season according to variations in these factors. Additional N can be applied at specific stages of pl ant development (phenology) for maximum effect. However, timing supple mental N application according to growth stage scales may not result i n maximum yield as the scales do not provide sufficiently precise indi cation of spikelet and floret formation, which critically affect the s ink capacity of the plant. In this review it is proposed that knowledg e of apical development offers a means to identify the initiation and formation of those plant organs that are indicators of specific stages of plant development. Aspects of the general usage of apical developm ent stages in timing N, and how they vary according to growing conditi ons, are discussed.