Variation in acquisition of soil phosphorus among wheat and barley genotypes

To assess the extent of variation in phosphorus acquisition efficiency of some winter wheat (Triticum aestivum L.), winter and spring barley (Hordeum vulgare L.) genotypes, depletion of inorganic phosphorus (P) extractable with 0.5 M NaHCO3 (NaHCO3-P-i) from the rhizosphere soil was studied. Nutrients supply, rhizosphere soil pH and soil water content was kept equal for all the genotypes with the aim to reduce the confounding variation due to these factors. The experimental set up implied that no difference in the relative growth rates, nitrogen, potassium and calcium content of shoot dry matter occurred among the genotypes. The winter wheat, winter barley and spring barley genotypes differed significantly (p>0.05) in their efficiency to acquire NaHCO3-P-i from the rhizosphere soil. The efficiency of the winter wheat genotypes to acquire NaHCO3-P-i from rhizosphere soil ranked Kraka > Gawain > Foreman > Sleipner = Obelisk > Kosack > Pepital > Arum. Winter wheat genotypes differed in extent of P depletion profiles in the rhizosphere, indicating variation in root hair length. The winter barley and spring barley genotypes also showed significant differences in their P depletion profiles near roots. The efficiency of the winter barley genotypes to acquire soil P in the rhizosphere ranked Hamu > Frost > Marinka > Astrid > Clarine = Angora. The efficiency of spring barley genotypes to acquire NaHCO3-P-i in the rhizosphere ranked Canut > Etna similar or equal to Riga > Digger > Peel > Semal > Alexis. The rhizosphere pH remained unchanged, suggesting that additional mechanisms such as root hair formation and root exudates play a significant role in causing variation in P acquisition among the genotypes.