Agriculture Reference
In-Depth Information
fertilizers have been reported to improve nitrogen fixation efficiency and reduce
water loss by plants (Brown et al.
1990
). Several patents describe the use of nano-
REE fertilizers (Wang et al.
2005a
,
b
,
c
). For example, seed soaking or foliar
treatment with REE (e.g., La(OH)
3
, Nd(OH)
3
, and Ce(OH)
3
) nanoparticles is
claimed to lead to increased yield and quality of crop, with less REE than that
required to see effects with the bulk treatment.
Table
2.1
lists all the patents and patent applications whose inventions fall under
this category, grouped in terms of their nano-content. In cases where more than one
component of the formulation is described, the patent is listed under each nano-
component.
2.2.2 Nanoscale Additives
In this category, a nanomaterial is included in crop rhizospheres not necessarily as
the nutrient itself but perhaps as an additive to enhance plant growth, such as a
binder or water retention material, or plant defense against soil pathogens. Note that
while pesticides are not described in this chapter as a separate category, nanoscale
additives to a fertilizer product used to provide pest resistance or antimicrobial
properties have been included.
One of the first, widely cited, examples of the use of nanotechnology to improve
crop yields investigated the effects of carbon nanotubes (CNTs) on the growth of
tomato seedlings (Khodakovskaya et al.
2009
; Biris and Khodakovskaya
2011
).
The nanotubes were found to penetrate the tomato seed coat and a dramatic increase
in seed germination and growth was observed.
1
More recently a similar effect was
demonstrated in chickpea using water-soluble carbon nanotubes (Tripathi
et al.
2011
). An increase in water absorption and retention was observed as a result
of channels and capillaries created by the CNTs (see Fig.
2.5
). Similar results were
noted in mustard plants exposed to 30 nm diameter multiwalled CNTs (Mondal
et al.
2011
). In the root tissue exposed to CNT, dramatic uptake of black CNT was
observed. In recent work examining the effects of CNTs in tomato (Khodakovskaya
et al.
2013
) and tobacco plants (Khodakovskaya et al.
2012
), there are data to
indicate that the CNTs may be involved in the upregulation of genes involved in a
number of processes, such as water transport, cell division, and cell-wall extension.
In this case, then, the CNTs themselves could be considered as a plant growth
promoter or protector of crops under drought conditions. Furthermore, if carbon
nanotubes are used as transporters for crop nutrients, these materials would also fall
under Category 3. Several carbon-based nanomaterials have found applications in
patents on nanofertilizer formulations (Biris and Khodakovskaya
2011
; Lewis
2013
; Liu and Wangquan
2012
; Zhang and Chen
2012
; Xie and Liu
2012
; Li and
Guan
2011
; Zhang and Liu
2010
).
1
Note that this paper has since been retracted for copyright reasons.
