Effects of phosphite and phosphate supply in a weathered tropical soil on biomass yield, phosphorus status and nutrient concentrations in common bean

Recent studies have indicated that phosphite (Phi) is harmful for phosphate (Pi)-starved plants, but no effect has been noticed for Pi-sufficient plants. However, there is no knowledge about the effects of Phi in weathered tropical soils and its consequence for yield of the crops. In this study, it was investigated the potential effect of Phi and Pi supply in a weathered tropical soil on biomass yield, phosphorus status and nutrient concentrations in common bean (Phaseolus vulgaris L.) plants. The experiment was conducted under greenhouse environment with pots containing 6 dm(3) of a low-fertility Oxisol, using 2 Pi levels (Pi-starved and Pi-sufficient plants) combined with 7 Phi levels (0, 3.125, 6.25, 12.5, 25, 50 and 100 mg of P per dm(3) of dry soil). Supply of Phi at low levels did not affect the growth of common bean. On the other hand, further increase in Phi levels in the Oxisol resulted in a progressive decrease in biomass yield of the plants in both phosphate levels. Moreover, these plants exhibited higher concentrations of P in shoot and root tissues, although the accumulated P was not increased. Elevated levels of Phi enhanced the P uptake efficiency but reduced the P utilization efficiency of the plants, regardless of the soil Pi status. In general, concentrations of other nutrients in shoot also were affected by applied treatments. Our results indicate that high input of Phi into the weathered tropical soils may potentially limit the growth of common bean, even under adequate Pi fertilization.