Submitted to: Journal of Soils and Sediments
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/25/2011
Publication Date: 3/15/2011
Publication URL: DOI 10.1007/s11368-011-0347-2
Citation: Dao, T.H., Miao, Y., Zhang, F.S. 2011. X-ray fluorescence spectrometry-based approach to precision management of bioavailable phosphorus in soil environments. Journal of Soils and Sediments. 11(4):577-588. Interpretive Summary: Phosphorus is a critical plant nutrient for early seedling growth. However, soil P often is highly variable within a field and contributes to extremes in P availability that can be detrimental to plant growth and the environment. While numerous analytical techniques can provide the needed information, they differ widely in limits of detection, labor, time, and the cost of chemicals used per analysis. With recent technological advances, measurements of light elements with x-ray fluorescence, although still difficult, are becoming more feasible. These light elements include many plant nutrients such as P, magnesium, calcium, and K. Because of the rapid and non-destructive nature of the analysis, X-ray fluorescence spectroscopy (XRFS) is adapted to rapid non-destructive laboratory analysis of soil, plant tissue, and animal manure samples. However, the quick measurement of plant-available P in soil remains difficult because their estimates remain tied to laborious laboratory extraction methods. We sampled a 54-acre field located near the Quzhou Agricultural Research Station in Heibei Province, China on a 75 by 75 ft. grid to determine soil P. There were a number of significant advantages over traditional wet chemistry techniques, including minimal sample preparation, rapid analysis times thus high throughput, multi-element detection to allow such a detailed view of the nutrient distribution of the field. Soil available P was highly variable in both directions of a two-dimensional grid after decades of continuous cultivation. A significant relationship existed between the P measured by x-ray fluorescence and plant-available P to derive and map the spatial distribution of soil available P across the large field. Distinct nutrient management zones were identified for more precise added P placement. The high sample throughput and minimal sample processing makes x-ray fluorescence spectroscopy an indispensable component of a novel approach to derive soil available P and sustainably manage P, and by and large mineral macronutrients in production agriculture based on their site-specific variations in the soil.
Technical Abstract: Declining nutrient use efficiency in crop production has been a global priority to preserve high agricultural productivity with finite non-renewable nutrient resources, in particular phosphorus (P). Rapid spectroscopic methods increase measurement density of soil nutrients, and the availability of more precise data can improve the calculation of appropriate application rates of fertilizer P inputs. A multi-element analytical x-ray fluorescence spectroscopic (XRFS) method was evaluated for P detection in soil samples collected from contiguous field strips under wheat cultivation near the Quzhou Agricultural Experiment Station in the North China Plain. Soil available P was highly variable in both directions of a two-dimensional grid after decades of continuous cultivation. A linear relationship existed between XRFS-P and bicarbonate-extractable P or Mehlich 3-P to generally depict the spatial distribution of soil available P across a 22-ha field (p < 0.001). Distinct nutrient management zones were identified for more precise added P placement. The high sample throughput and minimal sample processing makes XRFS an indispensable component of a novel approach to sustainably manage P, and by and large mineral macronutrients in production agriculture based on their site-specific variations in the soil. These approaches and their limitations may provide a promising avenue to improve use efficiencies of P and other inorganic macronutrients to attenuate the within-field variations in P distribution and avoid zones of deficiency or surplus P that can affect plant productivity across the field.