Silicate Fertilizer Amendment Alters Fungal Communities and Accelerates Soil Organic Matter Decomposition

Abstract

Soil microorganisms play a crucial role in organic matter decomposition and nutrient cycling in cropping systems. Compared to bacteria, fungal community composition and the role of fungi in organic matter decomposition and nutrient cycling in agro-systems are, however, elusive. Silicon (Si) fertilization is essential to improve agronomic performance of rice. The effects of the Si fertilizer application on the soil fungal community composition and their contribution in soil organic matter (SOM) decomposition are not yet studied. We investigated the short-term (120 days) slag silicate fertilizer (SSF) amendment impacts on plant photosynthesis and soil biochemical changes, soil fungal communities (assessed by ITS amplicon illumina sequencing), hydrolytic and oxidase enzyme activities, CO 2 emissions, and bacterial and fungal respiration in diverse eco-geographic races of rice (Oryza sativa L.), i.e., Japonica rice (O. sativa japonica) and Indica rice (O. sativa indica). The short-term SSF amendment significantly increased the relative abundance of saprotrophic fungi and accelerated organic matter decomposition. The increase in saprotrophic fungi was mostly attributed to greater labile C availability and Si availability. Higher organic matter decomposition was accompanied by an increase in both hydrolytic and oxidative enzyme activities in response to the SSF amendment. The stimulation of oxidative enzyme activities was explained by an increase in root oxidase activities and iron redox cycling, whereas stimulation of hydrolytic enzyme activities was explained by the greater labile C availability under SSF fertilization. We conclude that the short-term SSF amendment increases saprotrophic fungal communities and soil hydrolytic and oxidative enzyme activities, which in turn stimulates SOM mineralization and thus could have negative feedback impacts on soil C storage in submerged rice paddies.

Silicon in the Soil–Plant Continuum: Intricate Feedback Mechanisms within Ecosystems

“…With the changes in plant nutrient concentration by Si, an effect on plant litter and organic matter decomposition is possible. It was shown that leaf material from reed [ 394 , 395 ] and rice [ 348 , 396 ] with high Si concentration decomposed faster than a litter of conspecific plants with a lower Si concentration. However, Emsens et al [ 397 ] found no effect of plant material Si concentration on decay rate.…”

“…Furthermore, it was shown that an increase of Si in soil pore water might also be able to mobilize carboxylic groups from soil organic matter particles, hence potentially additionally increasing litter decomposition [ 399 ]. Another potential explanation for how Si is accelerating organic matter respiration is by a change in soil microbial decomposer community, as shown for reed litter decay—where Si reduced the concentration of ergosterol as a measure of sporulating fungi [ 395 ]—and for rice litter—where the abundance of increase in saprotrophic fungi increased with increasing Si availability [ 396 ]. Hence, how Si is altering the soil microbial decomposer community is currently unclear, as the existing studies partially contradict each other.…”

Divergent taxonomic responses of below-ground microbial communities to silicate fertilizer and biofertilizer amendments in two rice ecotypes

“…The increased abundance of several genes related to the carbon cycle, nitrogen fixation, and heavy metal reclamation functions was associated with the silicate fertilization (Das et al, 2019a). The same group reported the alteration in the saprotrophic fungal communities and accelerated organic decomposition under the silicate fertilizer application (Das et al, 2019c). In another study, silicon fertilizer increased crop yield while decreasing the heavy metal content in multiple metals contaminated soil and modifying the structure and heterogeneity of the bacterial community associated with the metal-resistance (Wang et al, 2020).…”

“…Several studies have demonstrated that applying slag-based silicate fertilizer in agriculture has tremendous potential for improving rice productivity, plant disease resistance, and metal detoxification (Ning et al, 2014;Das et al, 2019b;Wang et al, 2020). At the microbiome level, recent studies have shown the positive effects of silicate fertilizer on bacteria and fungi populations (Das et al, 2019c;Wang et al, 2020). It has been revealed that several bacterial phyla were enriched and depleted while exposed to silicate fertilizer.…”

Silicate Fertilization Improves Microbial Functional Potential For Stress Tolerance in Arsenic-Enriched Rice Cropping Systems

“…Overall, total soil enzyme activities remarkably increased, indicating an improvement of nutrient cycling in response to silicate fertilizer application in rice paddy grown on Asenriched soils. Silicon-fertilization to improve soil enzyme activities in arable and forest soil has been proved effective [18,19].…”