Agriculture Reference
In-Depth Information
30 h in an aqueous medium. In addition, the modified rubber was easily applied to
encapsulate the urea fertilizer. The resulting polymer membrane of the capsule was
degraded in natural soil after use. The advantages of this value-added NR product and the
biopolymer are its environmental friendliness and low production cost.
Keywords:
Encapsulation, Fertilizer, Natural rubber, Modification
1.
I
NTRODUCTION
Fertilizers are one of the essential agrochemical agents required to supply nutrients to
sustain plants and promote their abundant and fruitful growth. The current agricultural
systems may be unable to supply the exploding world population in the future. Farmers
depend heavily on fertilizer to improve their crop yields. Many crops in tropical countries
such as rubber, rice, corn and vegetables are illustrated in Figure 1. There are three major
components of fertilizers: nitrogen, phosphorus, and potassium. However, the efficiency of
the use of the fertilizers is poor (Riyajan, et al., 2012). Less than half of the fertilizer applied
to the crop soil is actually recovered in crops. In conventional agriculture many of the losses
of fertilizer occur through volatilization or leaching by rain, and this can lead to some
important environmental problems. In addition, the parameters that affect the efficiency of
fertilizer use are the nature of the soil, the climate, the technique of application of the
fertilizer and the nature of the crops. One way to improve the efficiency of fertilizer
utilization could be to encapsulate the fertilizers within a polymer membrane that would
control the rate of release of the water-soluble active agents (Riyajan et al., 2012). One such
polymer membrane for controlling the release of fertilizer can be made by modifying natural
rubber (NR) with a biopolymer (Riyajan, et al., 2012a) and demonstrate its ability to control
its release in the water and soil of an agriculture field. Factors e.g., modification methods to
the NR, the NR content, the NR layer, the ratio between NR and biopolymer on the release
rate of urea, the form of the fertilizer confined within such capsules that can be made with an
enclosing membrane formed from an NR biopolymer membrane have now been investigated.
The properties of NR were altered by chemical modification, e.g., crosslinking, grafting and
epoxidation. In parallel, NR was blended with other polymers, e.g., poly (vinyl alcohol)
(PVA) (Riyajan et al., 2008), polyacryamide (Riyajan and Wongsa, 2013b), starch (Riyajan et
al., 2010) or sodium alginate (SA) Riyajan et al., 2009b), and natural fibers (Riyajan et al.,
2013c) to increase its use in agriculture The results of some of these experiments have been
described in this manuscript.
2.
M
ODIFICATIONS OF
NR
NR, consisting mainly of 93-95%
cis
-1,4-polyisoprene is an elastomer, produced from
latex of the rubber tree. Natural rubber latex (NRL) is a brand of NR and it consists of two
main components including hydrocarbon bonds (30-35% rubber) and non-rubber components
such as water, protein, carbohydrate, fatty acid and other chemical agents (Riyajan and
Santipanusopon, 2010b). Fresh latex from the
Hevea brasiliensis Muell. Arg
tree contains 30-
35% rubber. After collection, the NRL is usually stabilized with NH
3
to aid its dispersion in a
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