Silicon 'Plant Stones' for Strong Rice
Silicon 'Plant Stones' for Strong Rice
Silicon quite literally pumps up the
strength of a rice plant. Rice takes up Si with the soil solution and forms
amorphous Si dioxide bodies within the plant tissue, the so-called phytoliths
(literally translated "plant stones"). These phytoliths make the
plant stem and leaves stronger and more rigid. Thus, a sufficient Si supply
enhances the plants' resistance against heavy rain and wind and against attacks
of pests and fungi.
Undoubtedly, an indispensable
element for sustainable rice production, the processes which control Si
availability in the soil remain rather understudied. In their paper Anika
Marxen from the Helmholtz Centre for Environmental Research -- UFZ and her team
study rice soils in Vietnam in order to understand these processes, providing
scientific base for future recommendations for sustainable rice production.
Silicon is contained in most soil
minerals and mineral weathering slowly releases the important element into the
soil solution. In Vietnam, soils are strongly weathered due to high
temperatures and precipitation which means that Si availability is very low.
The study shows that Si
application to the soil increased Si uptake by rice and rice grain yield. When
the produced rice straw (that is Si-rich) is left on the field after harvest, a
large proportion of the Si is released during straw decomposition and is
available for the upcoming rice crop. Thus, Si is recycled and Si supply for
rice plants can be maintained on a high level with one single fertilizer
application for many cropping seasons.
Lignin, a hardly degradable
carbon compound in plant cells, has the same function than phytoliths have,
which is to give the plant stability. The formation of lignin is energetically
much more expensive for the plant than the formation of phytoliths. Therefore,
increased Si availability and uptake by rice probably lowers lignin formation
and thus fastens decomposition and nutrient release of the produced straw.
Hence, Si fertilization might also exert effects on the cycling of other
important nutrients, with yet unknown consequences for rice plant growth.
"Our study showed positive
effects of Si fertilization on rice growth and decomposability of the produced straw;
however Si cycling must be understood in more detail before applying Si
fertilizer at a large scale. More research is certainly needed, but these first
steps seem to take us in the right direction,"