USING A CHLOROPHYLL METER TO OPTIMIZE NITROGEN-FERTILIZER APPLICATIONFOR INTENSIVELY-MANAGED SMALL-GRAIN CEREALS

Most methods used to estimate N status require collection, processing and analysis of soil and/or plant tissue samples. In this study, leaf chlorophyll content of cereals, determined in the field with a portabl e chlorophyll meter (Minolta SPAD-502), was used to predict N availabi lity of wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat s (Avena sativa L.) and rye (Secale cereale L.). The results indicated that accurate nitrogen (N) fertilizer recommendations based on chloro phyll content have both environmental and economic advantages. Determi nation of leaf chlorophyll content with a chlorophyll meter accurately indicated plant N status allowing N fertilizer requirement to be accu rately determined and resulting in increased N uptake efficiency. Appl ying N fertilizer on this basis improved production economics and impr oved physical input-output ratio during grain yield formation. Using a chlorophyll meter, responsive and non-responsive categories can be de termined at the stage of maximum number of florets per ear primordium (Zadoks' GS 37-41) and at pollination (i.e. pollen grains on well-deve loped stigmatic hairs, GS 52-58).