X-ray fluorescence spectrometry-based approach to precision management of bioavailable phosphorus in soil environments

Purpose: Managing declining nutrient use efficiency in crop production has been a global priority to maintain high agricultural productivity with finite non-renewable nutrient resources, in particular phosphorus (P). Rapid spectroscopic methods increase measurement density of soil nutrients and improve the accuracy of rates of additional P inputs. Materials and methods: Soil P was measured by a multi-element energy-dispersive X-ray fluorescence spectroscopic (XRFS) method to estimate the spatial distribution of soil total (XRFS-P) and bioavailable P in a Fluvisol occurring on a 20-ha contiguous area comprised of seven elongated field strips under a wheat-maize rotation near the Quzhou Agricultural Experiment Station in the North China Plain. Results and discussion: Soil XRFS-P was highly variable along the length of the field strips and across the entire area after decades of continuous cultivation. A linear relationship existed between XRFS-P and bicarbonate-extractable P or Mehlich 3-extractable P, allowing a description of the spatial distribution of bioavailable P based on XRFS, in both directions of a two-dimensional grid covering the entire area (p > 0.05). Distinct management zones were identified for more precise placement of additional P. Conclusions: Direct element-specific analysis and a high sample throughput make XRFS an indispensable component of a new approach to sustainably manage P, and other macronutrients of low atomic number Z such as K, Ca, or Cl in production fields, based on their site-specific variations in the soil. Concerning P, this rapid precision approach provides a promising avenue to manage soil P as a regionalized variable while preventing zones of deficiency or surplus P that can affect plant productivity or potential loss from a field, respectively.