The influence of phosphorus fertilizer aplication on growth and elemental composition and distribution in sunflower (Helianthus Annuus L.)

The effect of P fertilization on dry matter (DM)roduction Jarelemental composition and distribution in sunflower (Helianthusannuus L.) was studied at different stages of growth. Two varieties (H345 and Issanka) were used in the study. Phosphorus fertilizer significantly increased DM production in the Leaves but had no significant effect on DM J'I accumulation in roots, stems and heads. A H345 had higher seed yield and oil concentration than Issanka. Phosphorus fertilizer application affected seed yield and oil concentration significantly in both varieties. The highest seed yields were obtained with the application of P at 31.5 and 63.0 kg ha-l in Issanka and H345, respectively. The highest oil content in both varieties was obtained with the application of P fertilizer at -1 63.0 kg ha . Calcium concentration in the leaves was increased significantly by P fertilizer application. Similarly, P concentration in the stems of H345 was significantly higher in plots applied with P fertilizer than those with no P fertilizer application. In otner plant parts, P fertilization did not have significant effect on P and Ca concentrations. Nitrogen concentration in the leaves, stems and heads was significantly reduced by P fertilizer application but not in the roots. Also, K concentration in the stems was significantly reduced by P fertilizer application. With the exception of seedling stage of growth, the roots hadthe highest percent DM and stems had the lowest. Leaves had the highest concentrations of N~ Ca and Mg during most of the grow1ng season. The heads had the highest P concentration from heading to maturity stage. Roots and stems had the lowest l .- Z concentration from heading to maturity stage. 1\\ the lowest concentrations of N~ P~ Ca and Mg throughout the Roots and stems had growing seasono Sunflower seeds had the highest K and Ca concentrations when compared with other plant parts at maturity. Nitrogen~ P, K, Ca and Mg concentrations in the roots declined during the growing season. Nitrogen concentration in the stems declined throughout the growing season while P and K concentrations did not have a consistent trend during the early stages of plant growth but declined from flowering stage onward. Calcium concentration increased slightly during the early stages of plant growth but remained relatively constant from flowering stage \\:".0 maturity. Magnesium concentration in the stems remained relatively constant upto the flowering time, then declined. Nitrogen, P, K and Ca concentrations in the heads declined throughout the growing season but Mg concentration increased slightly upto the flowering time, then declined in H345 and Issanka. Nitrogen concentration in the leaves declined throughout the growing season while Ca concentration increasedo Phosphorus and Mg concentrations remained relatively constant upto flowering time and then declined at maturity in both varieties. Also, in the leaves, K concnetration increased upto flowering time then declined at maturity.