RELATIONSHIPS BETWEEN BETWEEN IRON, SULFUR, NITROGEN AND PHOSPHORUS IN LAWNS GROWN ON A CALCAREOUS SOIL IRRIGATED BY SLIGHTLY SALINE WATER

In calcareous soils, Fe availability is highly restricted. On the other hand, Fe metabolism is intimately related to S, N, and P ones, whilst intensive agronomic activity requires significant S inputs. How these relationships are shaped in the commonly used for lawns species Cynodon dactylon, Pennisetum clandestinum, Festuca arundinacea, Festuca rubra, Lolium perenne, Poa pratensis, Dichondra repens, and Trifolium repens, when they are grown in a medium-textured calcareous soil irrigated with slightly saline water? In this system, [S-org] presented a wide range among the studied lawns, and two groups were distinguished: one with [S-org] above 70 mu mol g(-1)DM and the other with [S-org] below 50 mu mol g(-1)DM. All binary combinations of N/S-org, P/S-org, S0(4)(2 -)/S-org, Fe/S-org ratios were in very strong linear relationships, along with N/Fe vs P/Fe ratios. S-org/Fe ratio suggested more acquisition of S relative to Fe, by the warm season grasses. The relationship between S-org/Fe and S0(4)(2 -)/S-org ratios suggested that Fe and S0(4)(2-)were interconnected via the required content of S-org and the following scenario seems to be supported: P nutrition was adjusted to N nutrition; iron was adjusted to both of them, so that N/Fe was in linear relationship to P/Fe. S-org was adapted to both N and Fe.