The influence of phosphorus fertilizer application on growth and elemental composition and distribution in sunflower (helianthus annuus L.)
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The effect of P fertilization on dry matter (DM) production and eleillen 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 accumulation in roots, sternsand heads. Phosphorus fertilizer application affected seed yield and oil concentration significantly in both varieties. The highest seed yields were -1 obtained with the application of P at 31.5 and 63.0 kg ha in Lssanka and H345, respectively , The highest oil content in both varieties was obtaned with the application:ofP fertilizer at 63.0'kg ha -'. Calcium concentration in the leaves was increased significantly by P fertilizer application. S~similarly, P concentration~ in the stems of'H345 was significantly higher ~n plots applied with P fertilizer than those with no P fertilizer application. In other plant parts,P fertilization did not have significant effect Oil 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 had the highest c;lry. matt·'~rprbdttctibJ1.;allil;.:.,hsa1J:atuhies lowest';'Leaves had the highest concentrations ·of N, Ca and .Mg during most of the growing season. The heads had the highst P concentration from heading to maturity stage. Roots and st e.as had the lowest concentration from heading to maturity stage. Roots and stems had the lowest concentrations of N, P, Ca and Mg throughout the growing season. 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 duri.ngthe growing season. Nitrogen concentration an 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 floY:'e'rin.gs:.tgae .onward, Calcium concentration increase~ slightly during t.heearly stages of plant growth but remained relatively constant from flowering stage to maturity. Magnesium concentration in the stems remained relatively constant up to the flowering time, then declineJ. Nitrogen, P,K and Ca concentrations ~n the heads declined throughout the growing season but Mg concentration increased slightly up to the flowering time, then declined. Nitrogen concentration in the leaves declined throughout the growing season while Ca concentration increased. Phosphorus andMg concentrations remained relatively constant up to the flowering time, then declined at maturity ~n both varieties. Also, in the leaves K concentration increased up to flowering time ,:·the.nd..ecli.ned-itamaturity.