Phosphorus (P) loss from agro-ecosystems impinges upon
P use efficiency
by plants and thereby constitutes both agronomic and environmental
nuisances. Herein, we report on the potential for controlling P leaching
loss and application in crop fertilization through repurposing and
nano-functionalizing tripolyphosphate (TPP) as a sole P source. The
developed TPP-Chitosan and TPP-Chitosan-ZnO nanofertilizers exhibited
positive surface charges, 5.8 and 13.8 mV, and hydrodynamic sizes
of 430 and 301 nm, respectively. In soil, nanoformulations of TPP-Chitosan
and TPP-Chitosan-ZnO significantly reduced cumulative P leaching during
72 h, reaching 91 and 97% reductions, respectively, compared to a
conventional fertilizer, monoammonium phosphate (MAP). Cumulative
P leaching after 72 h from these nanofertilizers was, respectively,
84 and 95% lower than from TPP alone. TPP-Chitosan-ZnO was, overall,
65% more effective in reducing P leaching, compared to TPP-Chitosan.
Relative to MAP, the wheat plant height was significantly increased
by TPP-Chitosan-ZnO by 33.0%. Compared to MAP, TPP-Chitosan and TPP-Chitosan-ZnO
slightly increased wheat grain yield by 21 and 30%, respectively.
Notably, TPP-Chitosan-ZnO significantly decreased shoot P levels,
by 35.5, 47, and 45%, compared to MAP, TPP, and TPP-Chitosan, respectively.
Zn release over 72 h from TPP-Chitosan-ZnO was considerably lower,
compared to a control, ZnO nanoparticles, and averaged, respectively,
34.7 and 0.065 mg/L, which was 534 times higher for the former. Grain
Zn was significantly higher in the TPP-Chitosan treatment, relative
to MAP. TPP-Chitosan also significantly mobilized the resident K,
S, Mg, and Ca from soil into the plant, helping to improve the overall
nutritional quality and supporting the role of chitosan in nutrient
mobilization. Taken together, our data highlight the potential for
repurposing a non-fertilizer P material, TPP, for agricultural and
environmental applications and the effect of applying nanotechnology
on such outcomes. Broadly speaking, the reduction in P loss is critical
for controlling the eutrophication of water bodies due to nutrient
overload and for sustaining the dwindling global P resources.