Effects of phosphorus application in different soil layers on soil phosphorus fractions and the root of Platycodon grandiflorum

Abstract

The enhancement of phosphorus (P) acquisition through deep P application has been documented in crops with fibrous root systems, but little is known about this effect on the morphology of a taproot system. A four-year field experiment with P application was conducted using Platycodon grandiflorum with a taproot system as the experimental material at two P rates of 40 and 60 kg ha⁻¹ with middle and deep P application patterns. The biomass and P accumulation of P. grandiflorum were greater with deep P application than with middle P application at the same P rate. Regardless of whether the root diameter being greater or less than 2 mm, the root length, volume and surface area of P. grandiflorum increased due to P application, and they were greater with deep P application than with middle P application at the same P rate. Four-year consecutive P application increased the concentrations of soil NaHCO₃-P, HCI-P, NaOH-P and residual-P, resulting in soil P accumulation, especially HCI-P. This is the first report that deep P application was more favorable to the growth of P. grandiflorum with a taproot system than middle P application. And this research provided evidence that deep phosphorus application is also suitable to crops with a taproot system.

Keywords:

• hierarchical phosphorus application
• Platycodon grandiflorum
• root
• soil phosphorus fraction

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

Financial support provided by Natural Science of Foundation of Shandong Province, China (No；ZR2015HM017) was gratefully acknowledged.