Use of Minolta SPAD-502 Chlorophyll Meter for Estimating Leaf N Concentration and Grain Protein Content in Three Varieties of Wheat

Non-destructive approaches that can rapidly estimate the nitrogen (N) status of plant could be useful in N fertilizer management practices.  This study was conducted to assess leaf N concentration and grain protein content of three varieties of winter wheat (Triticum aestivum L., cv. Zarin, Alvand, Durum) using portable non-destructive Minolta SPAD-502 chlorophyll meter. Measurements were made on the midpoint of the last fully developed leaf at Zadoks growth stages GS 31 and GS 41 collected from an irrigated wheat N response trial in a factorial randomized complete block design with three varieties and six N treatments in three seasons (2008-2010). The chlorophyll meter distinguished grain yield differences between N fertilizer treatments at both growth stages GS 31 and GS 41. Significant differences in chlorophyll meter readings were found between winter wheat cultivars. Chlorophyll meter SPAD-502 readings gave a poor prediction of grain yield (R², 0.01-0.06), but it predicted successfully the nitrogen status of total leaf N content (0.63^**>R²>0.88^**). Significant regression equations were established between grain protein content and SPAD value for all varieties studied in this experiment (0.40^**>R²>0.79^**). The best correlation between the SPAD meter readings with foliar N concentrations and grain protein contents were obtained at GS 41. The results indicate that SPAD meter can be a useful tool for nondestructively assessing foliar N status of winter wheat to make N recommendations and protein content in grain, but SPAD readings should be calibrated for wheat dominant varieties cultivated in west Azerbaijan regions.