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

Abstract

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 multielement 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.

Quantifying spatial variability of indigenous nitrogen supply for precision nitrogen management in small scale farming

“…Across different fields, however, the spatial dependence was stronger than within a field, with the ratio of sill over total variance, range of spatial dependence and MCD being 70.9%, 375 and 99.7 m, respectively (Table 2). In spatial analysis of soil properties in these fields, Dao et al (2011) found that the range of spatial dependence for bicarbonateextractable P was 103 m. Its spatial distributions showed a strong north-south trend within each field with significant differences between different fields in the east-west cross direction. However, other reported soil properties (Soil pH, organic carbon, X-ray Fluorescence Spectrometry (XRFS) estimated Ca and Fe concentrations, etc.)…”

“…Factors other than N may also be limiting crop growth and yield in this field. An examination of the soil data indicated that Fields 2 and 4 had the lowest and second lowest bicarbonate-extractable P concentrations (Dao et al 2011), which may contribute to the high variability in Field 2 and low biomass in Field 4.…”

“…above-ground biomass) and thus the interpretation of INS variability. After harvest in 2007, soil samples were collected from the same grid points and the average values of several soil parameters for each field have been reported by Dao et al (2011). Soil pH did not vary much in that average values were 8.2-8.3.…”

“…Organic carbon was lowest in Field 3 (5.9 g kg -1 ), and similar in other fields (6.5-7.0 g kg -1 ). Average bicarbonate-extractable phosphorus (P) concentrations were all very low (less than 8 mg kg -1 ), with Fields 2 and 6 having the lowest (4.3 mg kg -1 ) and highest (7.9 mg kg -1 ) values, respectively (Dao et al 2011).…”

Manure and Mineral Fertilizer Effects on Seasonal Dynamics of Bioactive Soil Phosphorus Fractions

“…The Ap horizon of the Pullman soil (0–0.15 m) is noncalcareous, has a clay content of 38%, 10 g kg −1 organic C, and a cation exchange capacity (CEC) (NaOAc; pH 8.2) of 28 cmol c kg −1 with 70% of the exchange sites occupied by Ca (Schwartz and Dao, 2005). Within the experimental plots of this study, Me3P concentrations averaged 52 mg kg −1 and total P, determined by energy‐dispersive X‐ray fluorescence spectroscopy (Dao et al, 2011), averaged 400 mg kg −1 . The plots were cropped in continuous grain sorghum with supplemental irrigation and no fertilizer P since 2000.…”