Foliar Phosphorus Applications in the Forms of Phosphate and Phosphite Have Contrasting Effects on Wheat Performance Under Field Conditions

Since phosphite (Phi) cannot replace phosphate (Pi) as source of phosphorus (P) for plants, and grain crops might experience P deficiency after anthesis, this study hypothesized that Phi and Pi sprays during the reproductive period would have contrasting effects on wheat productivity. The treatments consisted of a factorial combination of P sources applied at three rates (1.0, 2.0, and 4.0 kg ha-1 P in the form of Pi or Phi), plus a control without P. Foliar P application influenced wheat grain yield and post-anthesis shoot dry matter (SDM) production in a source-dependent manner, with Phi and Pi linearly decreasing and increasing these parameters, respectively. Foliar Pi application increased post-flowering shoot P uptake, but Phi usage produced the opposite result. However, internal P efficiency did not vary across treatments, revealing that P acquisition rather than its conversion into biomass governed yield responses. Moreover, SDM remobilization and contribution to grain yield were linearly increased and decreased, respectively, following Phi and Pi spray, suggesting alterations in the plant’s capacity to sustain carbon assimilation. It is concluded that while foliar Pi application during reproductive growth could be a suitable option to improve wheat grain yield, Phi usage might be detrimental for crop productivity. © 2019, Korean Society of Crop Science and Springer.