Faba bean (Vicia faba L.) varieties reveal substantial and contrasting organic phosphorus use efficiencies (PoUE) under symbiotic conditions

Background: The excessive use of inorganic P (Pi) in soils is alarming as it is causing numerous environmental problems and may lead to the depletion of rock phosphate reserves earlier than expected. Hence, to limit the over-dependence on Pi, there is the need to investigate organic phosphorus (Po), which is the dominant P form of soil P pool, as an alternate P source for plant growth. Aim: The present study seeks to investigate organic P use efficiency of eight varieties of faba bean grown symbiotically. Methods: The plants were grown in pots (6 kg soil) under greenhouse condition with three P source, namely, phytic acid (organic P, Po), KH2PO4 (inorganic P, Pi), and no-P. The P was applied at the rate of 1.79 g kg(-1) soil. Results: The plants grown with Po and Pi produced similar amounts of root, shoot, and total dry matters. Despite producing statistically similar dry matters, P uptake by Pi-fertilized plants was twofold higher than by Po-fertilized plants. Meanwhile, Pi differed significantly from Po in terms of nodulation characteristics such as nodule dry biomass and individual nodule dry biomass. However, Po varied significantly from Pi in P utilization and acquisition efficiencies. Principal component analysis of Pi and Po revealed no significant variation and close association, confirming the nonsignificant differences between the two P treatments. Among the varieties tested, Tiffany tended to accumulate more dry matter, coupled with highest organic P utilization efficiency (0.48 g mg(-1)) as well as the highest organic P beneficiary factor (80%). Conclusion: These results provide a solid basis for further comparisons at physiological, biochemical, and molecular levels between Tiffany (Po-efficient) and Fuego (Po-inefficient) varieties, offering deep insights into and making it easier to understand the mechanisms that allow soil Po to be utilized under symbiotic conditions.

Automated summary

This study investigated the organic phosphorus use efficiency of eight varieties of faba bean. The results showed that although plants grown with organic phosphorus and inorganic phosphorus produced similar amounts of dry matter, the phosphorus uptake by inorganic phosphorus-fertilized plants was twice as high as that by organic phosphorus-fertilized plants. Additionally, significant differences were observed between organic phosphorus and inorganic phosphorus in terms of nodulation characteristics and phosphorus utilization efficiency. Among the tested varieties, Tiffany had higher organic phosphorus utilization efficiency and organic phosphorus beneficiary factor.