Abstract

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.