Abstract
Two 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 the future. The capacity of soils to hold water is a highly important factor controlling drought stress of plants during the growing phase. High phosphorus availability in soils is also necessary for high agricultural yields, however over application has also led to a range of environmental problems, foremost being the eutrophication of waterways. Amorphous silica (ASi) has been suggested as one solution to mitigate both water and phosphorus availability. In this work we analyzed the effect of ASi on phosphorus mobility and the soil water storage of a sandy soil. In a lysimeter experiment we found that ASi strongly increased the water storage capacity of soils (up to 180 % by addition of 3 wt. % ASi). Furthermore, the ASi is in direct competition with phosphorus for sorption sites on iron oxides and other soil minerals increasing nutrient mobilization and increasing potential bioavailability for plants. Following calibration to the lysimeter experiment a process based hydrological model was used to extrapolate experimental results to a sandy agricultural soil with and without ASi for one year. For the soil with ASi, the water storage capacities for the yearly scenario were up to 40 kg/m² higher compared to the untreated soil. Our results suggest that ASi enhances the water storage capacity and phosphorus mobility in soil and that this may be one way to mitigate the predicted climate change related drought stress in sandy soils.
Highlights
Low phosphorus (P) availability as well as longer and more frequent droughts are known to reduce terrestrial ecosystem performance and crop production (Engelbrecht et al, 2005; Elser et al, 2007; Michaelian et al, 2011; Elser, 2012; Fahad et al, 2017)
It is clear that the different concentrations of amorphous Si (ASi) in soils in combination with different substrates have to be analyzed in future to obtain a more generalized picture on how ASi is affecting water storage capacity (WSC) of soils
The strong effect of ASi increasing the soil WSC and water availability for plants during drought periods may be used in future agriculture practices to mitigate plant stress due to water limitation and associated harvest losses
Summary
Low phosphorus (P) availability as well as longer and more frequent droughts are known to reduce terrestrial ecosystem performance and crop production (Engelbrecht et al, 2005; Elser et al, 2007; Michaelian et al, 2011; Elser, 2012; Fahad et al, 2017). A high proportion of this P is stored in inaccessible forms such as organic P (Bünemann et al, 2010), or is bound/adsorbed as inorganic P to, e.g., aluminum, iron oxides, or calcium minerals, depending on soil pH (Beauchemin et al, 2003), soil diagenesis stage (Crews et al, 1995), and mineral composition. At lower pH values P tends to be bound/adsorbed by hydrous oxides of iron, Amorphous Silica for Sustainable Agriculture manganese, or aluminum (Brady and Weil, 2008). Soils differ quite substantially in regard to amorphous Si (ASi) content in soils (0.1 to ∼6%; Saccone et al, 2007) depending on climate regions, parent material, and vegetation cover
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