DIFFERENTIAL CAPACITY OF WHEAT CULTIVARS AND WHITE LUPIN TO ACQUIRE PHOSPHORUS FROM ROCK PHOSPHATE, PHYTATE AND SOLUBLE PHOSPHORUS SOURCES

We characterized varying capacity of two wheat cultivars ('Brookton' and 'Krichauff') and white lupin to acquire and utilize phosphorus (P) from different P resources [P-0, rock phosphate, composted rock phosphate, phytate and soluble P) at 200 mg P kg(-1) soil]. In all three genotypes, shoot P concentration and content were highest in the phytate treatment and lowest in P-0. Roots of wheat cultivars exuded only traces of organic acid anions, whereas lupin root exudates contained high concentration of citrate. Phosphorus utilization efficiency (PUTE) was highest in P-0 and lowest in the phytate treatment for all three genotypes. Phosphorus acquisition efficiency (PACE) ranged from 1 ('Brookton' in P-0) to 355% ('Brookton' supplied with phytate). In conclusion, the availability of P in rock phosphate was not influenced by microbe and organics supplementation in the composting process and wheat cultivars were not as efficient as lupin in using P from sparingly soluble P sources.