Uptake and translocation of foliar applied phosphite and its effect on growth and development in cool season turfgrass

Abstract

Phosphate (PO4 3-, Pi) is the sole phosphorus (P) containing compound utilized for plant growth, leading to the widespread use of Pi containing fertilizers. An alternative form of P, phosphite (PO3 3-, Phi) has increasingly been used in many crop systems, including amenity turfgrass, not only as a nutrient source but also as a pesticide and biostimulant. There are, however, conflicting reports of the efficacy and benefits of Phi as a source of P. This study was conducted to determine the rate of uptake, translocation and fate of Phi when applied as a foliar treatment to amenity turfgrass, and to assess its role as a source of P nutrition, determining the effect Phi treatments have on turfgrass growth, P deficiency responses, tissue and soil P accumulations. Analysis of Phi treated turfgrass using High Performance Ion Chromatography determined that Phi is rapidly taken up and translocated, that sequential Phi treatments lead to cumulative increases in meristematic tissues, an increase in soil P levels and no in planta conversion to Pi. In P sufficient rootzones (> 35 ppm), foliar applied Phi increased biomass in shoot, crowns, and roots, but also led to a reduction in root to shoot ratios. In phosphorus deficient rootzones (< 5 ppm), foliar applied Phi led to growth reductions in leaf, crown and root, and repression of P deficiency responses.