Knowledge about nutrient demands of plants at different growth stages is important in scheduling the fertilizer application. This study was conducted to determine the influence of three phosphorus (P) levels [0, 25, and 50 mg kg-1 soil as (Ca (H2PO4)2] and two organic matter (OM) levels (0 and 2% w/w as feedlot cattle manure) on winter wheat (Triticum aestivum L.) characteristics and P status in different parts at various growth stages under greenhouse-conditions. Number of tillers, grains, and spickles; spickle-length, grain-yield, and 1000-grain weight increased with P and OM applications. Maximum shoot-dry-matter-yield (SDMY) was obtained with 50 mg P kg-1 soil application at stage 8 (dough development). Shoot-P-concentration was the highest at early stages, but decreased later on. Shoot P uptake increased with P and OM applications and also with growth stages. Phosphorus and OM applications increased P uptake of stem, spickle, and flag-leaf. Furthermore, effects of P and OM treatments on flag-leaf DMY were similar to those of stem. Stem and flag-leaf P uptake decreased at dough development to ripening stages, but spickle-P-uptake increased. Critical P concentration of shoot and flag-leaf decreased with plant growth; whereas, that of spickle increased. Results confirmed that wheat-plants required much more P at early stages. The tentative conclusion is that flag-leaf P analysis, instead of stem, may be used to evaluate the nutritional status of winter wheat.
Key words: Flag leaf analysis, phosphorus nutrition status, crop characteristics, wheat growth stages.
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