EGU2020-6926
https://doi.org/10.5194/egusphere-egu2020-6926
EGU General Assembly 2020
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Amorphous silica increases the water holding capacity and the phosphorus mobility in soils - solving the two main problems of agriculture

Jörg Schaller1, Benjamin Gilfedder2, and Sven Frei3
Jörg Schaller et al.
  • 1Bayreuth, Environmental Geochemistry, Bayreuth, Germany (joerg.schaller@uni-bayreuth.de)
  • 2Limnological Station, Bayreuth Center of Ecology and Environmental Research (BAYCEER), University of Bayreuth, Germany
  • 3Department of Hydrology, Bayreuth Center of Ecology and Environmental Research (BAYCEER), University of Bayreuth, Germany

The two primary problems currently facing agriculture are drought and the availability of mineable phosphorus minerals used for fertilization. More frequent and longer drought periods are predicted to threaten agricultural yields in future. The capacity of soils to hold water is a highly important factor controlling drought stress intensity for plants during the growing phase. High phosphorus availability in soils is necessary for high agricultural yield. For both drought and phosphorus availability in soils amorphous silica (ASi) has been suggested to be able to mitigate these problems. Amorphous silica pools in natural soils are in the range of 0-6%. However ASi pools have declined in agricultural soils since the development of high intensity agriculture to values of <1% due to yearly crop harvests, decreasing water the holding capacity of the soils. Here, we analyzed the effect of ASi on the water holding capacity (WHC) of soil and how the ASi effects the mobilization of phosphorus.  ASi was mixed at varying rates with different soils. Afterwards, the retention curve of the soils was determined. Here we show that ASi increases the soil water holding capacity substantially, by forming silica gels with a water content at soil saturation higher than 700%. An increase of ASi by 1% or 5% (weight) increased the water content at all studied water potentials and plant available water increased by >40% and >60%, respectively. Additionally, we fertilized soils with ASi and measured phosphorus mobilization from the solid phase into the soil pore waters. We found a strong mobilization of phosphorus by ASi. In a lysimeter experiment we found that ASi strongly increased the WHC of soils. Furthermore, as expected from the batch experiments the ASi is decreased phosphorus sorption to soil minerals and consequently increased its mobilization. Our results suggest that ASi addition to soils enhances the water availability, potentially decreases drought stress for plants as well as increasing phosphorus mobility in soil of terrestrial ecosystems.

How to cite: Schaller, J., Gilfedder, B., and Frei, S.: Amorphous silica increases the water holding capacity and the phosphorus mobility in soils - solving the two main problems of agriculture, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6926, https://doi.org/10.5194/egusphere-egu2020-6926, 2020

Display materials

Display file

Comments on the display material

AC: Author Comment | CC: Community Comment | Report abuse

Display material version 1 – uploaded on 29 Apr 2020
  • CC1: Comment on EGU2020-6926, Valeria Arenas, 05 May 2020

    Hello Jörg,

    Very interesting research and promising results. I wonder if the only mechanism of P mobilization you have studied or identified is related to iron oxide - phosphate ligand. Have you found any P mobilization related to phosphate bound to aluminium or calcium?

    • CC2: Reply to CC1, Jörg Schaller, 05 May 2020

      there is apaper showing the effect alos for Al minerals. see:

      Koski-Vähälä J, Hartikainen H, Tallberg P. 2001. Phosphorus mobilization from various sediment pools in response to increased pH and silicate concentration. Journal of Environmental Quality 30(2): 546-552.

      Cheers,

      Joerg

      • CC3: Reply to CC2, Valeria Arenas, 05 May 2020

        Great! Thanks for sharing.