Analysis of the response of two tall fescue cultivars of different origin to P deficiency

Soil phosphorus (P) availability commonly limits crop growth and forage production. Furthermore, there is a concern about the use of fertilizers, both because of the risk of environmental degradation and P being a non-renewable resource. Some experimental evidence would indicate that certain cultivars of tall fescue of Mediterranean origin would have a higher root:shoot ratio than temperate ones. This characteristic could improve P efficiency. Since P fertilization is a crucial issue in forage production, enabling grass crops to use the soil resources more efficiently represents an important agronomical goal. The objective of the present work was to compare the response of two tall fescues of different origin to low P availability and to analyze the interactions between morphological traits, P uptake efficiency and P use efficiency. Two cultivars of tall fescue ( Schedonorus phoenix (Scop.) Holub (formerly Festuca arundinacea (Schreb.)), one of temperate origin, Palenque Plus INTA (PP), and the other of Mediterranean origin, Fraydo (F), subjected to three different P treatments (P1, P2 and P3 obtained by adding 0; 10 or 100 mg P kg −1 soil–sand mixture 1:1 by weight) were studied in a glasshouse experiment. Four destructive harvests were performed from 24 to 54 days after emergence (dae) and the following determinations were performed: root and shoot components dry matter (DM), leaf area, tiller production, root length and diameter, root and shoot components P concentration. Tissue turnover measurements were performed from 19 to 53 dae. In general, responses to low P availability were in agreement with the literature (e.g. low DM accumulation, higher root:shoot ratio, low leaf elongation rate, low tiller production). Conversely to what was expected, PP had a higher root:shoot ratio than F under low P availability and tended to show higher values of P uptake during the whole experimental period. However, the P uptake efficiency per unit of root length was higher in F than in PP. By the end of the experimental period PP accumulated a higher amount of total biomass than F under P2 and P3. Under moderate P deficiency (P2), shoot growth was less reduced in PP than in F. Under the experimental conditions of the present study PP showed a higher growth potential and a more plastic response to P availability. Experiments at lower temperatures that would favor Mediterranean cultivars growth should be performed to study possible effects of P-temperature interactions