Polyphosphate fertilizer use efficiency strongly relies on soil physicochemical properties and root-microbial activities

Abstract

Limited phosphorus (P) bioavailability restricts global agriculture and food production. This element is considered the least plant-available nutrient, and it is highly susceptible to immobilization in the soil matrix. Among the mineral fertilizers used to increase soil P fertility, polyphosphates (PolyP) consist of polymers of OrthoP residues and have been shown to improve crop P uptake and resulting yields more than other forms of P amendments. PolyP fertilizers are also known for their progressive hydrolysis, improving P availability in the rhizosphere and plant P uptake throughout crop growth stages. However, PolyP behavior in soils is still understudied, including rhizosphere traits likely to be involved in PolyP use efficiency within the soil-root-microbe interface. To improve our knowledge of PolyP behavioral properties in the soil–plant continuum, this review is among the first studies to compile, discuss, and propose ideas regarding this research while focusing on the key soil biochemical factors responsible for PolyP hydrolysis and use by crop roots. A combination of exuded P-hydrolyzing enzymes and acidification of the rhizosphere can presumably mobilize available P from PolyP and thereby improve crop P acquisition. The importance of root-associated microbes (exhibiting high P-mobilization capacities) is also discussed as a promising rhizosphere trait that could contribute greatly to boost PolyP hydrolysis and thus increase PolyP agronomic efficiency.