Agriculture Reference
In-Depth Information
Fig. 2.4 TEM image of
ZnO nanoparticles used in
study on peanut plants.
Inset
: dramatic increase in
root growth of peanut plant
after nano-ZnO treatment
(
right
: 1,000 ppm) after
110 days in comparison to
bulk zinc (
left
: 1,000 ppm)
over the same time period
(Prasad et al.
2012
).
Reproduced with
permission from Taylor and
Francis
crop grain yields, other expected advantages of the nano-form of this nutrient have
not been demonstrated. For example, a study on the uptake of zinc using a variety of
Zn materials, including 40 nm ZnO, noted that the use of the nano-form did not lead
to greater Zn content in roots compared to bulk Zn treatments (Watts-Williams
et al.
2014
). A second study examined the dissolution kinetics of nano-ZnO and
bulk Zn as coating for a phosphate fertilizer and found that the kinetics of Zn
dissolution and release were not affected by the form of Zn used (Milani
et al.
2012
). These data, in conjunction with the data found on IAA levels and
enzyme activity after nano-ZnO application, appear to suggest that nutrient and
physiological factors alone or combined help explain the effects on plant growth.
Further research is warranted to determine the exact mechanisms by which micro-
nutrient fertilizers affect plant growth and metabolism.
Selenium nanoparticles used as micronutrient fertilizers have been described in
several patents and papers (Yu
2005b
;Li
2007
; Wu et al.
2008
; Hu et al.
2008
; Tong
et al.
2008
; Wei et al.
2012
; Xuebin et al.
2009
; Tian et al.
2012
). In these studies or
inventions, the selenium content in the specific crop was generally found to be
increased when the nanoselenium was applied. For example, in the patent by Hu
et al., Se particles milled down to approximately 400 nm in size were investigated
as a foliar fertilizer for green tea (Yu
2005b
). Higher selenium levels were found
when compared to those exposed to selenium salts. Iron is another micronutrient
that is being investigated in a nano-form. For example, a plant tonic comprised of
nano-iron has been patented (Hong and Shim
2006
). A 2004 patent describes nano-
iron oxide mixed with peat and CaCO
3
, leading to improved crop quality
(Wu
2004a
). Rare-earth element (REE) fertilizers have been applied as microele-
ment fertilizers in Chinese agriculture since the 1980s (Wang et al.
2008b
). REE
