Abstract
Phosphorus availability in soils is an important parameter influencing primary production in terrestrial ecosystems. Phosphorus limitation exists in many soils since a high proportion of soil phosphorus is stored in unavailable forms for plants, such as bound to iron minerals or stabilized organic matter. This is in spite of soils having a high amount of total soil phosphorus. The feasibility of silicon to mobilize phosphorus from strong binding sites of iron minerals has been shown for marine sediments but is less well studied in soils. Here we tested the effect of silicon on phosphorus mobilization for 143 Artic soils (representing contrasting soil characteristics), which have not been affected by agriculture or other anthropogenic management practices. In agreement with marine studies, silicon availabilities were significantly positive correlated to phosphorus mobilization in these soils. Laboratory experiments confirmed that silicon addition significantly increases phosphorus mobilization, by mobilizing Fe(II)-P phases from mineral surfaces. Silicon addition increased also soil respiration in phosphorus deficient soils. We conclude that silicon is a key component regulating mobilization of phosphorous in Arctic soils, suggesting that this may also be important for sustainable management of phosphorus availability in soils in general.
Highlights
Phosphorus (P) is a key element for metabolic pathways and carbon (C) turnover on Earth
The distribution of inorganic P between Ca, Fe, Al or Si fractions is highly dependent on soil pH in combination with the mineral composition depending on parent material and soil diagenesis stage
near edge X-ray absorption fine structure (NEXAFS) measurements indicated a mobilization of P from mineral surface-bound Fe(II)-phosphate phases by Si and Ca
Summary
Phosphorus (P) is a key element for metabolic pathways and carbon (C) turnover on Earth. The P content of soils is not necessarily low, a high proportion of this P is stored in plant unavailable forms such as organic P5, or is bound/adsorbed as inorganic P to e.g. aluminum (Al), iron (Fe) oxides, or calcium (Ca) minerals, depending on soil pH6, soil diagenesis stage[7] and mineral composition. The distribution of inorganic P between Ca, Fe, Al or Si fractions is highly dependent on soil pH in combination with the mineral composition depending on parent material and soil diagenesis stage. The Si fractions in soils are composed of dissolved Si (free in soil solution or adsorbed to Fe or Al oxides/hydroxides), amorphous forms (e.g. the biogenic phytoliths or the minerogenic silica nodules), poorly crystalline forms (e.g. secondary quartz), and crystalline forms (the primary silicates like mica, feldspars or quartz and the secondary silicates e.g. clay minerals)[10]. Si availability in terrestrial soils (especially those used by agriculture) is potentially declining due to effects of ecosystem management[15,16,17] and the yearly withdrawal by crop harvest, since many crop plants are Si accumulators[11]
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