Phosphorus (P) acquisition of cereal cultivars in the field at three levels of P fertilization

Low phosphorus (P) availability in soils and diminishing P reserves emphasi ze the need to create plants that are more efficient P users. Knowledge of P efficient germplasm among the existing cereal varieties may serve as the basis for improving soil P use by selection and breeding. We had identified some cereal cultivars (winter wheat: Kosack and Kraka; winter barley: Hamu and Angora; spring barley: Canut, Alexis, Salka, Zita;) which differed (p< 0.05) in P depletion from thin slices (0.2 mm) of the rhizosphere soil unde r controlled conditions. In the present study, the same cultivars were stud ied under field conditions at three levels of P supply (no-P, 10 and 20 kg P ha(-1)) and the differences in P uptake as found in the previous work wer e confirmed. Under both conditions, the variation between the cultivars was greatest in soil without P fertilizers (no-P) for about 30 years. The vari ation in P uptake with most cultivars disappeared when 10 kg P ha(-1) was a pplied. Root development did not differ between the cultivars much, but the re was wide, consistent variation in their root hairs, regardless of growth media (solution, soil column and field). Increase in soil P level reduced the length of root hairs. The variation in root hairs between the cultivars was largest in no-P soil. When 10 kg P ha(-1) was applied, the root hair l engths did not differ between the cultivars. Barley cultivars with longer r oot hairs depleted more P from the rhizosphere soil and also absorbed more P in the field. The relationship between root hairs and phosphorus uptake o f the wheat cultivars was less clear. The wide variation in P uptake among the barley cultivars in the field and its relationship to the root hair dev elopment confirms that root hair length may be a suitable plant characteris tic to use as criterion for selecting barley cultivars for P efficiency, es pecially in low-P soils.