THE EFFECTS OF OXALATES PRODUCED BY SALSOLA-TRAGUS ON THE PHOSPHORUS-NUTRITION OF STIPA-PULCHRA

Oxalic acid is produced by some species of plants and mycorrhizal fung i and it may solubilize unavailable soil phosphorus (P) bound by catio ns (Ca++, Al++, Fe+++). Field and greenhouse experiments were conducte d to show whether oxalate produced by the annual Salsola tragus or add ed oxalic acid would solubilize P from the inorganic-bound soil P pool , making it available for uptake by Stipa pulchra. Oxalate could be le ached in the laboratory from the senescent canopy of Salsola, and leac hing hv rainfall was hypothesized to be a source of potential increase d soil P under the Salsola canopy. Both oxalate leached from the canop y of Salsola and added oxalic acid increased the availability of soil P in greenhouse experiments. The source of the increase in available s oil P in the greenhouse experiment was shown to be the inorganic-bound : P pool, as the total P concentration of the soil decreased with incr easing oxalate. There were significant increases in Stipa shoot P in r esponse to Salsola leachates and in response to added oxalate in the g reenhouse studies. These results suggest an important role for oxalate in P cycling. On disturbed sites where Salsola invades it may act to facilitate the establishment of later seral species like Stipa by crea ting a nutrient island of available P.