Agriculture Reference
In-Depth Information
Fig. 2.6 Hydroxyapatite nanoparticles for urea delivery. (a) SEM image of urea-modified
hydroxyapatite nanoparticles. (b) Comparison of %N released over 60 days for (a) the
nanofertilizer and (b) a conventional fertilizer (Kottegoda et al.
2011c
). Reproduced with permis-
sion from Indian Academy of Sciences
structures filled with commercial plant food have been tested on marigolds and
compared to controls of the plant food alone. Larger foliage, more blooms, and
more buds were noted in the cochleate-treated sample, suggesting improved deliv-
ery of the plant nutrients via foliage application (Yavitz
2006
).
Other porous materials such as mesoporous silica and layered double hydroxides
(LDHs) have been investigated for fertilizer delivery. The release of nitrogen via
urea hydrolysis has been controlled through the incorporation of urease into
nanoporous silica (Hossain et al.
2008
). LDHs are a class of layered nanomaterials
with positively charged crystalline inorganic layers (thickness of a few nm) and
charge balancing anions located in the interlayer region. The anions located in the
interlayer regions can be easily replaced, leading to an intense interest in the use of
LDH intercalates for advanced applications such as controlled-release systems. A
2002 study examined the use of LDHs for the release of a plant growth regulator
found that slow release of the compound could be controlled by pH (Hussein
et al.
2002
). Patents have described LDHs loaded with nitrate for use in fertilizers
(Kottegoda et al.
2011a
).
Also found within Category 3 are nanoscale polymer films, either wholly
polymer based or composites with other materials such as humic acid cementing
agents or clays. Several patents have been filed on nano-polymer fertilizer coatings,
for example, those prepared from lignosulfonate particles (Zhang et al.
2003a
;Du
2007
), polyvinyl alcohol particles (Zhang et al.
2005a
,
e
), polystyrene (Zhang
et al.
2005d
), polyolefin-starch conjugates (Zhang
2004
), cellulose (Lin
2008
),
and polyelectrolytes (Li et al.
2010
). Patents on polymer conjugates with zeolites
(Barati
2010
), palygorskite (Cai
2007
), kaolin, and montmorillonite (Zhang
et al.
2003b
; Dong et al.
2006
) have also been described. Several studies have
been published related to the characterization of these clay-polymer
nanocomposites and their slow-release properties (Liu et al.
2006
; Zhang
et al.
2006a
,
b
). Mixtures of a poly(acrylic acid-
co
-acrylamide) polymer and kaolin
