Release of potassium accompanying the dissolution of rice straw phytolith
In
rice, Si assimilated from the soil solution is deposited in inter- and
intracellular spaces throughout the leaf and stems to form silicified
structures (so-called phytoliths). Because K is also present in
significant concentrations in rice stems and leaves, the question arises
if K is immobilized in the mineralized silica during the precipitation
of Si. This work determined whether desilification of the phytolith is a
factor regulating K release by implementing batch experiments.
Solubility of Si and K of the rice straw heated at different
temperatures were examined to identify effect of pretreatment.
Analyses of phytoliths using SEM-EDX and X-ray tomographic microscopy in
conjunction with the results from batch experiments revealed that K
might co-exist with occluded organic matter inside the phytolith
structure. In the kinetic experiments, corresponding increases of K and
Si concentrations in the supernatants were observed which suggested that
desilification of the phytolith is a main factor regulating K release.
The extent of heat pretreatment of the rice straw is of significant
importance with respect to dissolution of the phytolith by affecting
organic removal and surface modification. At temperatures lower than 600
degrees C, corresponding increases of the soluble Si and K with heating
temperature have been obviously observed. In contrast, the solubility
of Si and K gradually decreased at temperatures above 600 degrees C.
This work provides insights into factors that control release of K and
Si from phytolith and a practical recommendation for practices of
burning rice straw that may maximize subsequent release of Si and K for
crops.
Nhận xét
Đăng nhận xét