Coupling phosphate type and placement promotes maize growth and phosphorus uptake by altering root properties and rhizosphere processes

Nutrient distribution and phosphate fertilizers can impact maize growth, but how to match the type of phosphate fertilizer and the application method to enhance root-foraging capacity for phosphorus (P) is unclear. This study was aimed at characterizing the effects of different phosphate fertilizers and placements on maize growth, grain yield, root properties and rhizosphere processes on calcareous soil. A soil column experiment with five different phosphate fertilizers [single superphosphate (SSP), monoammonium phosphate (MAP), diammonium phosphate (DAP), urea phosphate (UP) and ammonium polyphosphate (APP)] applied either uniformly or locally 10–20 cm deep in a greenhouse. In addition, a 2-year field experiment with five P fertilizer treatments (non-fertilization and broadcast MAP, DAP, UP or APP) was conducted. In the soil column experiment, localized application of SSP, MAP, UP and APP significantly promoted the growth and P uptake of maize by modifying the root morphology. Localized application of each P fertilizer increased (by up to 74 %) the first-order lateral root density and first-order lateral root length of maize in the fertilizer-enriched layer, resulting in a significant increase in the efficiency of root P acquisition by maize. In the field experiment, the rhizosphere pH of maize supplied with MAP, UP or APP was reduced by 0.5–0.7 units in comparison to DAP in 2018. Compared with MAP and DAP, application of UP or APP in the field did not show significantly improve maize growth and P uptake. These results show that optimizing P fertilizer types and placement modified root morphology and physiology, and consequently promoted maize growth and P accumulation, but further characterization of the localized application of different P fertilizers in the field is needed. Engineering root properties and rhizosphere processes by manipulating fertilizer types and placement improves fertilizer-use efficiency and reduces environmental footprint of food production.