Silicon elution from three types of steel slag fertilizers in a paddy field analyzed by electron probe micro-analyzer (EPMA)

Abstract

Elution of silicon (Si) from three types of slag fertilizers was tested in a paddy field. They were made from granulated blast furnace slag, dephosphorization slag and decarburization slag, respectively. Each fertilizer, embedded in epoxy resin to expose the cross section, was analyzed to get initial two-dimensional distribution images of Si, calcium (Ca), oxygen (O), magnesium (Mg), aluminum (Al), manganese (Mn) and iron (Fe) by electron probe micro-analyzer (EPMA). These resin specimens were set in a paddy field for 75 d. Then the second two-dimensional distribution images of Si, Ca, O, Mg, Al, Mn and Fe at the same site were analyzed again by EPMA. A comparison of the two-dimensional distribution images before and after setting in paddy field elucidated the following results: (1) Si eluted clearly from dephosphorization slag and decarburization slag; (2) Si, Ca, Mg and Al distributed homogeneously in granulated blast furnace slag. X-ray diffraction (XRD) clarified that granulated blast furnace slag was amorphous. The content of plant-available Si in each slag fertilizer was evaluated by the cation exchange resin extraction method. It was the highest in dephosphorization slag fertilizer. This result corresponded to Si elution from dephosphorization slag observed by EPMA. The content of plant-available Si was low in granulated blast furnace slag but high in air-cooled blast furnace slag. Although the content of plant-available Si in decarburization slag was low, the efficacy of Si elution was the highest in decarburization slag. From X-ray diffraction analyses, calcium silicate or larnite (Ca 2 SiO 4 ) was considered to be the causative substance for efficient Si elution from decarburization slag and dephosphorization slag. Because of the high content of plant-available Si, dephosphorization slag and aircooled blast furnace slag are recommended as silicate fertilizers in paddy fields.

Converter slag causes gradual collapse of chlamydospore of the rice false smut fungus and suppresses hyphal invasion into rice roots

“…This coincidence may be explained by the mechanism of the disease suppression. Application of converter slag in paddy soil might cause chlamydospore walls to melt because of the continuous release of calcium ions from converter slag (Ito et al, 2015). Therefore, this application was preferred during the previous year to decrease the number of living chlamydospores before rice planting.…”

Sustainable soil management in East, South and Southeast Asia

“…The effect of steel-making slag on rice yield was seen in some field experiments in Vietnam, especially in soils with low available silicate, measured using the incubation method (JSSSPN 1986) (Figure 3). Silicon elution from steel-making slag fertilizers into a paddy field has also been visualized using an electron probe microanalyzer (EPMA) (Ito, Shiratori, and Inubushi 2015). To mitigate methane emissions from paddy fields, measuring the rate of methane oxidation and methanotrophs activity are also important, particularly in rice plant-soil systems that have different rice cultivars and growth stages (Inubushi et al 2002b).…”

Investigation of negative effects of rice husk silica on komatsuna growth using three experiments

“…Silicon has also been reported to have good effects on humans; it improves bone health and accelerates healing (Henstock et al 2015) as well as improves the immune response and tissue health (Farroq and Dietz 2015). Since 1950s, there have been numerous researches on how silicon affects rice production (Yoshida et al 1959(Yoshida et al , 1962Krishnarao and Godkhindi 1992;Savant et al 1996;Klotzbücher et al 2015;Ito et al 2015;Siregar et al 2016;Waseem et al 2016;Song et al 2017).…”