Transcript PENTINGNYA SILIKAT BAGI TANAH DAN TANAMAN TEBU

PENTINGNYA SILIKAT
BAGI
TANAH DAN TANAMAN TEBU
Bahan kajian MK Pupuk dan Pemupukan
Diabstraksikan oleh Prof Dr Ir Soemarno MS
Jur Tanah FP UB Oktober 2011
Sumber: dirujuk dari beragam sumber referensi ilmiah, selengkapnya
pelajari artikel aslinya
APLIKASI SILIKAT PADA TEBU
Aplikasi Si dilakukan dengan dosis 0, 55, 110 dan
165 kg ha-1 Si, bahan yang dipakai Ca-Mg silicate
(262,1 g kg-1 Ca; 56,8 g kg-1 Mg; 108,4 g kg-1 Si),
diaplikasikan dalam larikan pada saat tanam.
Hasil tanaman terbaik dicapai pada dosis 103,2 kg ha1 Si (952 kg ha-1 silicate).
Aplikasi silikat meningkatkan kandungan Si-tersedia
dalam tanah, yaitu ekstraksi 0.5 mol L-1acetic acid
dan 0.01 mol L-1 CaCl2.
Konsentrasi Si dalam daun tebu ditentukan oleh
kultivar nya (A =3 g kg-1; B =2.18g kg-1).
Dalam batang tebu, ternyata biomasa dan seapan Si
terbaik diperoleh pada aplikasi dengan dosis 89 kg ha1 Si, tidak ada efek pada keruskaan akibat penggerek
batang.
Sumber: …
Rancangan Percobaan Aplikasi Si
The experiment was set up in a completely randomized
factorial scheme with four silicon rates (0, 55, 110
and 165 kg ha-1 Si), two cultivars (IAC 87 3396 and SP 89
1115), and 4 replications.
The source of silicon was Ca-Mg silicate containing 262.1
g kg-1 Ca; 56.8 g kg-1 Mg; 108.4 g kg-1 Si. All plots
received the same Ca and Mg quantities with additions of
dolomitic lime (320g kg-1 Ca, 29.5 g kg-1 Mg) and/or MgCl2
(11.9% Mg) when necessary.
The cultivars were chosen based upon yield potential,
precocity, good number of sprouts under sugarcane
mulch residue and differences on stalk borer tolerance
(Diatraea saccharalis): low tolerance (SP 891115;
Coopersucar) and intermediate tolerance (IAC 87 3396;
Landell et al., 1997).
Added Si as calcium magnesium silicate increased the
amounts of extractable Si in a Quartzapsament soil, as well as
increasing the yield and Si uptake in stalks of cultivar SP 89
1115. Rates of 103 kg ha-1 Si and 89 kg ha-1 Si provided the
best yield and absorption of silicon of SP 89 1115, respectively,
but it did not promote less stalk borer damage.
Sumber: …
Pentingnya Si bagi Tebu
Silicon fertilization has been shown to improve
chlorophyll and structure of leaves, reduce lodging, and
minimize biotic and abiotic stress, but there is little
information in Brazil, the major world sugarcane producer.
Positive results have been obtained with silicon
application in many countries, including Brazil (Berthelsen
et al., 2002; Kingston et al., 2005; Elawad et al., 1982;
Korndörfer et al., 2000; Brassioli et al., 2009). Most of
these results were not exclusive from silicon because the
high rates of silicate can improve pH, Ca, and Mg contents
(Alcarde, 1992). The silicate fertilization applied in furrow
planting could be useful to reduce the cost of this product
used in rates similar to lime (>2 or 3 t ha-1) and study the
direct effects of Si on sugarcane.
Another beneficial advantage of silicon to sugarcane is
the possibility of reducing damage of insects. Studies
conducted in pots and field conditions with Si has shown
positive effects to control of African stalk borer Eldana
saccharina. Stalk borer (Diatraea saccharalis) is a problem
in Brazil controlled by biological methods and/or resistent
cultivars. Good characteristics in sugarcane such as low
fiber and high sugar are generally related to stalk borer
tolerance. An increase of silicon uptake in sugarcane with
silicate applications could reduce the damage of ‘brazilian’
stalk borer.
Sumber: …
Hubungan antara Si-tanah yang terekstraks 0.5 mol L-1 acetic acid
dan 0.01 mol L-1 CaCl2 ( kedalaman contoh tanah 0-25cm dan 25-50
cm) dengan serapan Si batang tebu dengan dosis Ca-Mg silicate.
Sumber: …
Si PADA DAUN TEBU
The variability of silicon absorption in sugarcane cultivars can be
associate with its yield and sugarcane borer (D. saccharalis)
incidence. The objective of this work was to evaluate silicon uptake
by the leaves and accumulation in total aerial plant and its
relationship to yield, quality and stalk borer in sugarcane cultivars.
Yields were superior to 100 t ha-1 at 16 months of age and IAC 911099 and RB 86 7515 cultivars showed the highest diameter and
height, respectively. The IAC 91-1099 showed the highest values of
sugar and lowest to fiber content.
Silicon content in leaves collected at 6 months showed not
significant differences. The IACSP 93-3046, IACSP 93-6006 and IAC
91-1099 showed the highest silicon content in the leaves at 8
months and they were superior to 10 g kg-1 Si.
Higher silicon content in the leaves was found for IAC 91-1099 at 10,
14 and 16 months and, in bagasse, to RB 86-7515 at 10 and 12
months. The foliar analysis collected at 8 months and the total
aerial plant, collected just before harvest, were efficient to show
differences on silicon uptake among cultivars.
There was no relationship among Si uptake and yield and borer
stalk incidence, which was reduced with increase of fiber content .
Sumber: Bragantia vol.69 no.4 Campinas Dec. 2010
Beberapa jenis tanah di perkebunan tebu telah lama sekali
digunakan untuk budidaya tebu, beberapa tanah
mempunyai kandungan Si-tersedia yang rendah.
The objectives were to evaluate silicon availability in soils
and the relationship between availability and uptake.
Therefore, we assessed the dry matter yields of sugarcane
cultivated in three soil types, with and without silicon
fertilization.
The experiment was set up in a completely randomized
factorial scheme (4 x 3 x 2) with four silicon rates (0, 185,
370 and 555 kg ha-1 Si) as Ca-Mg silicate and three soils:
Quartzipsamment (RQ), Rhodic Hapludox (LV) and Rhodic
Acrudox (LVdf), in four repetitions.
All plots (100 L) received same Ca and Mg quantities with
additions of dolomitic lime and or MgCl2. The LVdf soil
showed the higher soluble silicon concentration, followed
by LV and RQ.
Added Si applied increased the amounts of soluble
content in all soils but Si uptake in leaves of sugarcane
were just increased to RQ and LV.
However, addition of Si to the soils did not promote
changes in dry matter yields and Si uptake
on stalks of sugarcane.
Sumber: The Proceedings of the International Plant Nutrition
Colloquium XVI, Department of Plant Sciences, UC Davis, UC Davis
Si bagi Tebu
Silicon is not an essential element (Epstein, 1999),
but its fertilization to Si accumulating plants, such
as sugarcane, could exhibit increased yields (Fox
et al., 1967, Elawad et al.,1992; Anderson et
al.,1991; Korndörfer et al., 2002).
Soils cultivated with sugarcane were classified in
four groups (Berthelsen et al.2002) as a function of
the amount of soluble Si in CaCl2 0.01 Mol L-1 (mg
kg-1 Si):
very low (0-5), low (5-10), limited (10-20), and
sufficient (20 to >50).
Several classes of soils in Brazil are classified as
low silicon content (Korndörfer et al., 2002) and
these soils are cultivated with sugarcane.
Sumber: …
Concentration uptake in leaves and stalks after harvest of sugarcane and
soluble silicon in soils with silicon (*p<0.05).
(Sumber: Silicon absorption by sugarcane: effect of soils type and
silicate fertilization. The Proceedings of the International Plant Nutrition
Colloquium XVI, Department of Plant Sciences, UC Davis, UC Davis
Sumber: …
APLIKASI Si:
EFEK FISIK DAN FISIOLOGIS
Silicon is an integral part of cell walls, and has a similar
role to lignin, in that it provides compression-resistance
and rigidity in cell walls, thus providing structural strength
to the plant.
An ample supply of Si has been reported to reduce
lodging (drooping, leaning or becoming prostrate) in grass
crops due to improved mechanical strength. The improved
rigidity of the cell walls also promotes a more erect habit
and disposition of the leaves, resulting in better light
interception and photosynthetic efficiency.
Sugarcane cultivars high in Si may also show enhanced
sucrose synthesis, due to improved photosynthesis, as
shoots are not as likely to become prostrate following
wind and rain.
Sumber: Sugar Research and Development Corporation
Final Report . SRDC Project CLW009 . CSIRO 2003
Varieties have changed substantially between 1970 and
1990, and lodging, once a factor selected against, is now
considered a less important selection criterion, with the
use of mechanical chopper harvesters. Consequently,
plant-breeding programmes may have been inadvertently
selecting varieties with lower concentrations of Si in the
stalk. As there is evidence that lodging can result in loss
of cane yield and reduction in sugar content, this
highlights the possibility that low plant and soil Si levels
may be a causal factor in declining sugarcane yields
observed over recent years.
Adequate Si nutrition may also assist crops withstand the
effects of drought conditions in areas reliant on rainfall, or
declining water quality in irrigation areas. Plants with a
well-thickened layer of Si associated with the cellulose in
cell walls of epidermal cells have been observed to be less
prone to wilting and have improved drought resistance.
Silicon may also reduced stress to salt in a similar way
that it alleviates water stress. Work with cereal crops
suggest that Si can both increase photosynthesis and
decrease the permeability of plasma membranes of leaves
of salt-stressed plants. In addition, Si has been shown to
inhibit the uptake of Na and increase the uptake of K, thus
alleviating the effect of salt toxicity and improving
vegetative growth.
Sumber: …
Ketahanan thd Stress Biotik
Improved resistance to disease and pathogenic fungal attack,
due to Si applications, has been reported for a number of
crops. It is generally agreed that as most parasitic fungi
penetrate the host by boring through the epidermal cell wall, Si
in these walls may act as a mechanical barrier. In addition, Si
may also protect the plant by its association with the cell wall
constituents, minimizing the enzymatic degradation that
accompanies the penetration of the cell wall by the fungal
hyphae. The highly silicified leaves of grasses can not only
make the plant more resistant to attack by pathogenic fungi,
but also to attack by predaceous chewing insects, as they can
suffer a high mortality when their mandibles and maxillae
become worn down, rendering their mouthparts ineffective.
It is relevant, therefore, that recent history of yield decline in
sugarcane dates back to the recognition of ‘Northern Poor
Root Syndrome’ (NPRS) as a problem in sugarcane on
Queensland’s wet tropical coast (Egan et al., 1984). Although,
it has been suggested that the build-up and susceptibility to
root pathogens may be the ultimate expression of other factors
being out of balance in the farming system, it is plausible that
low soil and plant Si levels have allowed increased
susceptibility to pathogen attack.
Sumber: …
Ketahanan thd stress Abiotik
Adequate Si nutrition is reported to have a major effect
on the absorption and translocation of some
macronutrient and micronutrient elements, assist in the
negative effects resulting from nutrient imbalances,
and also have the ability to alleviate, or in some cases
to eliminate, the adverse effects of heavy metals,
excess phosphorus and salinity.
Current sugarcane production systems often apply
nitrogen at rates far in excess of what may be
considered necessary for maximum yield, and with
high soil concentrations of phosphorus, may result in
unbalanced nutrient supply on many sugarcane soils.
That yield decline can be temporarily reversed by
increasing N fertilizer rates to soil Si-depleted systems.
However, for sustained yields, Si fertilisation is
required to balance applied nutrients, particularly N,
when high rates can result in increased problems with
lodging.
Although Si additions are reported to improve P
nutrition, conversely, continued use of superphosphate
may have also resulted in accelerated depletion of soil
Si reserves, since P effectively competes with Si for
specific sorption sites, thereby resulting in the loss of
Si through leaching.
Si dalam Tanah
Soil Si status, indicative of potential soil productivity
Silicon is recognized as a major constituent of soils. It is
present in the solid phase of soils as alumino-silicate clay
minerals and crystalline minerals, and also in a number of
amorphous forms such as plant phytoliths. In the soil
solution, or liquid phase, Si is present as mono- and polysilicic acids, and also present as complexes with
inorganic and organic compounds.
While it is the mono-silicic acid component that is taken
up by plants and has a direct influence on crop growth,
the poly-silicic acids, and probably the inorganic and
organic Si complexes, are important as sources/sinks of
Si which can replenish the soil solution following crop
use, but importantly, they can have a significant effect on
soil properties such as improving soil aggregation and
increasing soil water holding capacity and also increasing
the exchange and buffering capacity of soils. It has also
been suggested that the organosilicic compounds play a
specific role in organic matter formation.
Sumber: …
Reaksi-reaksi Si dalam
tanah
Sumber: …
Ketersediaan Si dalam tanah
In general, most soils have appreciable amount of
be adequate for crop growth. Although quartz is a major
source of Si in many soils, the rate of dissolution of this
mineral is very slow and therefore does not contribute
significantly to the labile pool of soluble Si. For plant
growth the important forms of soil Si are the soluble
forms, mainly monosilicic acid (Si(OH)4), various polymers
and silica gels, Si adsorbed onto sesquioxidic surfaces,
and that present in crystalline and amorphous soil
minerals. The quantity present in each of these forms is
largely controlled by the dominant soil mineral and the
amount of Si lost (desilication) through weathering.
The solubility of Si in the soil is influenced by several
factors including, particle size, soil pH, organic
complexes, the presence of aluminium, iron and
phosphate ions, temperature, exchangeable/dissolution
reactions, and soil moisture.
Sumber: …
APLIKASI BAHAN-BAHAN SILIKAT
METODE APLIKASI Si
Aplikasi kalsium-silikat pada pertanaman tebu dapat
dilakukan dengan cara disebar dan kebudian dibenamkan
ke tanah sebelum penanaman bibit.
Sumber: …
Manfaat aplikasi pupuk silikat pada tanaman tebu:
1.
Menetralisir kemasaman tanah: Ini akan memperbaiki
aktivitas mikroba tanah dan ketersediaan N,P, S dari
bahan organik tanah; mereduksi toksisitas Fe, Al, Mn
dalam larutan tanah
2. Mensuplai unsur hara Ca, Si, P, K, Mg,S dan unsur
mikro
3. Meningkatkan hasil tebu dan hasil gula: diameter dan
panjang batang, jumlah batang, daun-hijau, ineks
pertumbuhan
4. Memperbaiki fotosintesis dan produksi klorofil
5. Regulator ensim dalam sintesis gula, dan simpanan
sukrose dalam tanaman
6. Mereduksi kerobohan tanaman, habit tumbuh tegak,
sehingga efisien cahaya
7. Meningkatkan ketahanan tanaman terhadap gangguan
hama dan penyakit
8. Mereduksi transpirasi sehingga air lebih efisien
9. Mereduksi toksisitas Mn dan mencegah akumulasi Mn
di daun
10. Memperbaiki nutrisi P: Mereduksi fiksasi P,
meningkatkan kelarutan P-tanah, efisiensi
pemanfaatanP oleh tanaman
11. Memperbaiki kesuburan tanaman
Sumber: …
Pangaruh dosis aplikasi Ca-silicate terhadap tinggi
batang dan jumlah batang tebu
Sumber: …
Pengaruh aplikasi Ca-silikat terhadap Konsentrasi Si
(%) dalam daun muda yang telah mekar sempurna
(TVD) pada tanaman umur 7 bulan; hasil batang tebu,
ccs dan bobot segar umur 8 bulan setelah tanam; dan
hasil akhir tebu, ccs dan hasil gula
Pengaruh aplikasi Ca-silikat terhadap kadar
serat (%) batang tebu, persen daun yang
terinfeksi penyakit karat-orange dan becak
kuning pada umur 8 bulan setelah tanam
Sumber: …
Pengaruh aplikasi Ca-silikat terhadap hasil tebu ratoon
pertama, ratoon ke dua, tebu tanaman, dan
kumulatifnya
Sumber: …
Hubungan antara hasil relatif tebu dengan indeks
ketersediaan Si-tanah
(a) Si(sol) ekstraksi 0.01 M CaCl2
(b) Si(ext) ekstraksi 0.005 M H2SO4.
Sumber: …
Hubungan antara hasil relatif tebu dengan indeks
ketersediaan Si-tanah (AEC / 100g clay) pada dua jenis
tanah yang berbeda
(sol)
(a) Si
dari ekstraksi 0.01 M CaCl2
(b) Si(ext) dari ekstraksi 0.005 M H2SO4.
Sumber: …
Pengaruh aplikasi calcium silicate terhadap
tingkat hijauanya daun (SPAD units), tebu ratoon
pertama dan ke dua.
Sumber: …
Pengaruh aplikasi bahan silikat terhadap tingkat
hijaunya daun (SPAD units) pada tanaman tebu
Sumber: …
Reaksi-reaksi yang terjadi dalam tanah setelah aplikasi
calcium silicate slag (Kato and Owa, 1997a).
Sumber: …
Karena calcium silicate reaksinya lambat untuk
menghasilkan asam mono-silikat (H4SiO4) yang tersedia
bagi tanaman (reaksi 1 - 4), Ca2+ dan Ca(OH)2 hasil dari
reaksi akan diserap pada koloid tanah (reaksi 5 dan 6).
Permukaan hidroksilasi pada permukaan tanah akan
melepaskan proton, secara bertahap akan mengasamkan
tanah. Kalau pH tanah menurun maka kelarutan Si dari
terak kalsium silikat akan meningkat.
Sumber: …
Reaksi kondensasi dan pengendapan polimer Si
(Drees et al., 1989)
Sumber: …
Flokulasi Si-polymorphs dengan
pembentukan ion-ion hidroksida logam
yang bermuatan positif (MOH+) (Drees et
al., 1989).
Sumber: …
Pengaruh aplikasi Ca-silikat terhadap KTK tanah
permukaan 0-10cm, diukur setelah tanaman tebu
(2000) dan setelah ratoon pertama (2001).
Sumber: …
Hubungan antara hasil tebu (ton/ha) ratoon
pertama dengan kadar Si (%) daun muda
(TVD) tanaman tebu umur 7 bulan.
Sumber: …
Si Memperbaiki Produksi Tebu
Tebu sangat respons terhadap aplikasi bahan-bahan
sumber silika.
Aplikasi bahan-bahan silikat dengan dosis 0, 5, 10, 15,
dan 20 metric tons/ha, brupa bahan-bahan TVA slag,
Florida slag, dan Portland cement.
Bahan-bahan silikat disebar di permukaan tanah dan
dicampur rata dengan tanah menggunakan bajak “disc
harrow”.
Aplikasi silikat meningkatkan tinggi tanaman, diameter
batang, jumlah batang, hasil tebu dan hasil gula, baik
pada tanaman tebu maupun ratoonnya.
Aplikasi bahan silikat sebanyak 15 metric tons/ha
meningkatkan hasil tebu dan hasil gula masing-masing 68
dan 79% untuk tebu tanaman; sebesar 125 dan 129% pada
tebu ratoon.
Peranan vital Si dalam pertumbuhan tanaman tebu
terbukti dengan meningkatnya ukuran tanaman dan
jumlah anakan akibat aplikasi bahan silikat.
Sumber: Agronomy Journal Vol. 74 No. 3, p. 481-484
PENTINGNYA Si BAGI TEBU
Silicon (Si) is one of the most abundant elements found in
the earth's crust, but is mostly inert and only slightly
soluble. Agriculture activity tends to remove large
quantities of Si from soil.
Sugarcane is known to absorb more Si than any other
mineral nutrient, accumulating approximately 380 kg ha-1
of Si, in a 12-month old crop. Sugarcane (plant growth and
development) responses to silicon fertilization have been
documented in some areas of the world, and applications
on commercial fields are routine in certain areas. The
reason for this plant response or yield increase is not fully
understood, but several mechanisms have been proposed.
Some studies indicate that sugarcane yield responses to
silicon may be associated with induced resistance to
biotic and abiotic stresses, such as disease and pest
resistance, Al, Mn and Fe toxicity alleviation, increased P
availability, reduced lodging, improved leaf and stalk
erectness, freeze resistance, and improvement in plant
water economy.
Sumber: J. Plant Nutr. 22 (12):1853-1903. 1999
FUNGSI Si BAGI TANAMAN
Tanaman tebu mengakumulasikan sejumlah besar Si
dalam bentuk silica gel (SiO2.nH2O) yang dilokalisir dalam
tipe-tipe sel tertentu.
Fungsi Si dalam tanaman tebu adalah:
i) Memperkuat dinding sel (ketahanan terhadap lodging);
ii) Ketahanan terhadap hama dan penyakit;
iii) Reduksi evapotranspirasi;
iv) Reduksi toksisitas logam berat
v) Unsur esensial bagi pertumbuhan tanaman normal.
PEMUPUKAN Si
Kajian-kajian tentang hara Si pada tanaman tebu telah
banyak dilaporkan di Australia, South Africa, Brazil,
Taiwan, India, Mauritius, Puerto Rico, the United States
dan negara-negara lain produsen tebu.
Pemupukan Si juga telah dipraktekkan untuk memperbaiki
produktivitas tebu di berbagai perkebunan tebu di dunia.
Efisiensi pemupukan Si ternyata sangat ditentukan oleh
karakteristik fisika dan kimia bahan pupuk-silikat ;
teknologi aplikasinya, waktu aplikasinya dan dosis
aplikasinya.
SERAPAN Si TANAMAN TEBU
Sugarcane absorbs large amounts of Si from soil.
According to Samuels (1969), at 12-months the above
ground parts contained 379 kg ha-1 of Si, compared with
362 kg ha-1 of K and 140 kg ha-1 of N.
Ross et al. (1974) reported the removal of 408 kg ha-1 of
total Si from soil by a sugarcane crop (tops + millable
cane) yielding of 74 t ha-1.
The removal of Si from soil could be more important in
intensively cultivated areas. As a result of the Si export of
this magnitude, a temporary depletion of bio-available Si
in soils could also be a possible factor of declining yields
of ratoon crops.
In other words, there may be an apparent need for
consideration of Si nutrient management in developing
appropriate integrated nutrient management system for
sustainable sugarcane production, especially in certain
ecoregions having Si deficient weathered soils and
organic soils.
Sumber: …
NUTRISI SILICON TANAMAN TEBU
There is ample evidence that different species uptake greatly
different amounts of Si. Legumes and other dicotyledons
have much lower levels than monocotyledons, for example,
the Gramineae. Sugarcane is a Si accumulator plant, which
strongly responds to Si supply.
The Si form that which sugarcane usually absorbs has no
electric charge (H4SiO4) and is not very mobile in the plant.
Because the uptake of undissociated H4SiO4 may be
nonselective and energetically passive, and its transport from
root to shoot is in the transpiration stream in the xylem, the
assumption has sometimes been made that the movement of
Si follows that of water (Jones and Handreck, 1965). The
silicic acid is deposited mainly in the walls of epidermal cells,
where it is integrated firmly into the structural matter and
contributes substantially to the strength of the stem.
The distribution of Si within the shoot and shoot parts is
determined by the transpiration rate of the part (Jones and
Handreck, 1967). Most of the Si remains in the apoplasm
mainly in the outer walls of the epidermal cells on both
surfaces of the leaves as well as in the inflorescence bracts
of graminaceous species and is deposited after water
evaporation at the end of the transpiration stream, (Hodson
and Sangster, 1989). Silicon is deposited either as amorphous
b (SiO2. hH2O, 'opal') or as socalled opal phytoliths with
distinct threedimensional shapes (Parry and Smithson, 1964).
The preferential deposition of Si in the apoplasm of epidermal
cells and trichomes is reflected in similarities between
surface features of leaf and structure of Si deposits (Lanning
and Eleuterius, 1989).
Si DAN PENINGKATAN HASIL
TANAMAN
Research work demonstrating the use of silicate slag as a
source of Si for sugarcane has been largely conducted in
Hawaii, Mauritius, and Florida. Yield responses are great
enough that sugarcane grown in the Everglades (South
Florida) is routinely fertilized with calcium silicate when
soil tests indicate the need. However, Si fertilization
requires large quantities of slag (generally 5 Mg ha-1),
making it quite costly (Alvarez et al., 1988).
Yields of cane and sugar in Hawaii have been increased
10-50% on soils low in Si, and many sugar plantations
regularly apply calcium silicate in responsive fields
(Ayres, 1966; Clements, 1965a; Fox et al., 1967b).
Increased yields of sugarcane in fields have been reported
in Mauritius (Ross, 1974) and Puerto Rico (Samuels, 1969);
while in South Africa (Preez, 1970) and Brazil (Gascho and
Korndörfer, 1998), several sources of silicate increased
sugarcane yields in pots.
Si DAN KONTROL PENYAKIT
In sugarcane, small rust-colored or brownish spots on the
leaves of cane growing on highly weathered soils
characterize a leaf disorder called freckling.
In severe cases, affected lower leaves may die
prematurely and can affect cane yield.
Freckled plants are less efficient in performing
photosynthesis not only because they have less leaf but
also because many leaves are freckled. This leaf disorder
was corrected by application of silicate materials
(Clements, 1965b).
Ayres (1966), Fox et al. (1967b), and Wong You Cheong et
al. (1972) have also noticed that leaf freckling symptoms in
sugarcane were gone following Si treatments.
Elawad et al. (1982a) observed significant decrease in
percent freckling in the plant crop as well as the ratoon
crop with application of 20 t ha-1 of TVA slag to muck soil.
The mechanism for the disappearance of leaf freckling in
sugarcane following Si application is still not well
understood.
Clements et al. (1974) attributed leaf freckling mainly to
the presence of toxic levels of Fe, Al, Mn and Zn in the soil
solution. However, Gascho (1978) stated that the
development of freckled leaves is an expression of the
plant's need for Si.
Silicon deposited in the epidermal tissue mechanically
deters hyphae invasion (Takahashi, 1996). Furthermore, Si
Si DAN PENGENDALIAN HAMA
While studying the influence of UVB radiation and soluble
Si on growth of sugarcane, Elawad et al. (1985)
additionally observed increased resistance of sugarcane
to stem borer (Diatraea saccharalis F.) with improved Si
nutrition. Newly hatched D. saccharalis larvae, when
starting their attacks on sugarcane plants, do so by
feeding on epidermal tissue of the sheath, leaves and
developing internodes in the immature top of the plants.
The presence of Si crystals in these tissues should hinder
the feeding of the insect, which in this phase has rather
fragile mandibles. Plants like sugarcane and rice, with
high Si contents, seem to interfere in the feeding of larvae,
damaging their mandibles. It is possible that plants with
higher Si contents in their tissue would have a higher level
of resistance to the infections by such pests.
The high Si levels in Na2SiO3 treated plants may have
served as a deterrent to the borers. A significant negative
relation was observed between leaf Si content and shoot
borer incidence.
Sugarcane varieties with a higher number of Si cells per
unit area in the leaf sheath portion 5 to 7 cm from the base
were found resistant to the shoot borer. The percentage of
the incidence of borer damage was less in sugarcane (var.
GPB 5) treated with bagasse furnace ash and silicate slag
than in untreated sugarcane. It is interesting to note that
increased application of N fertilizers alone increased the
incidence of sugarcane stalk borer, and that of another
borer (Chilo auricilius Dudgeon) in India.
Si MEMPERBAIKI EKONOMI AIR
Water stress under field conditions is common and
affects cane yields. Improved Si nutrition may reduce
excessive leaf transpiration.
One of the symptoms associated with Si deficiency is the
excessive rate of transpiration. The rate of transpiration of
Si deficient plants increased by about 30% over the rate
of control plants (rates were measured as grams of water
lost through transpiration per gram of dry weight per day).
Okuda and Takahashi (1965) obtained a similar result, but
found that in barley the effect was small (less than a 10%
difference between Sideficient and control plants). This
observation suggests a role for Si in the water economy of
the plant. An increased rate of transpiration in Si-deficient
plants could explain the wilting that may occur,
particularly under conditions of low humidity, and could
also help to explain the increased accumulation of Mn and
other mineral nutrients in the aerial parts of Si deficient
plants. The rate of transpiration is presumably influenced
by the amount of silica gel associated with the cellulose in
the cell walls of epidermal cells. Hence, a well thickened
layer of silica gel should help to retard water loss, while
epidermal cell wall with less silica gel will allow water to
escape at an accelerated rate.
Since this role of Si nutrition may result in water economy
and may be important in water management, field
research on this potential beneficial has merit.
Si MEREDUKSI KEROBOHAN DAN
MEMPERBAIKI KETEGAPAN TEBU
One other effect of increased plant Si content, which has
been reported in literature, is the increased mechanical
strength of plant tissue, which results in reduced lodging.
Under field conditions, particularly in dense stands of
sugarcane, Si can stimulate growth and yield by
decreasing mutual shading by improving leaf erectness,
which decreases susceptibility to lodging.
Leaf erectness is an important factor affecting light
interception in dense plant population and, hence,
photosynthesis.
In rice, Si supply increased the photo-assimilation of
carbon, especially after heading, and promoted the
translocation of assimilated carbon to the leaves.
This effect of Si on leaf erectness is mainly a function of
the Si depositions in the epidermal layers of the leaf
panicle.
INVERSI SUKROSE
Few investigations of the role of Si in sugarcane have
considered the mechanism by which it affects sugarcane
tonnage production. However, Alexander et al. (1971) has
undertaken the task of finding the role that Si plays in the
synthesis, storage and retention of sucrose in the
sugarcane plant. He found that sucrose inversion in
sugarcane juice samples was delayed for several days by
adding sodium metasilicate immediately after milling.
Chromatographic evidence suggests that at low levels
metasilicate forms a physical complex with sucrose which
prevents the union of invertase with its substrate. The
hypothetical fructose-silicate configuration is retained
even after sucrose is inverted, thereby preventing fructose
from being metabolized by microorganisms. Fructose
appears to be the preferential hexose for microbial growth,
i.e. most suitable carbon source.
The effective preservation of fructose by silicates may
constitute a bacterial repression operating in addition to
the invertase-inhibitory action.
Next to K, Si is the most extensive constituent of ash in
sugarcane juice. It is the highest component of millable
stalks ash and represents an even greater percentage in
leaves. However, silicates in cane are believed to be one of
the major contributors to mill roll wear.
BAHAN SUMBER SILIKAT
The usual carrier for Si is calcium silicate and this material
can also supply Ca to a Ca-deficient soil. The Hawaiian
Cement Corp. first manufactured calcium silicate in
August 1965.
Gascho and Korndörfer (1998) working with four different
soils groups from Brazil and several Si sources
(Wollastonite, thermal-phosphate, calcium silicate and
basic slag) concluded that thermal-phosphate was the
most effective source to supply both Si and P to the rice
plant.
In several studies, no attempt was made to maintain
constant Ca levels with increasing calcium silicate
applications. It is important to separate Si from Ca effects.
Ayres (1966) reasoned that since both calcium silicate and
calcium carbonate treatments had increased yields, the
calcium supply probably was not the factor causing higher
yields in their studies. Teranishi (1968) concluded that
yield increases from calcium silicate applications could
not be attributed to Ca supply in his experiment since
plant Ca was above the critical level for sugarcane and
also since calcium carbonate had been added to the zero
Si plots to maintain pH and supply adequate Ca.
According to Ross et al. (1974), calcium silicate applied to
low Si soils at planting increase annual cane yield over a 6
year cycle (TABLE 4) and well demonstrated the residual
effect from this source.
KALSIUM METASILIKAT
Calcium metasilicate was generally much more soluble
and readily available to sugarcane than calcium orthosilicate.
Mini-granules of calcium metasilicate, which were small,
spherical (50 to 150 mesh) made from fine (100 to 200
mesh) material using 2% sodium oxide as a binder, were
agronomically equivalent to fine ungranulated calcium
metasilicate (HSPA, 1982).
A fine grade of Si fertilizer was best for increasing Si
content and grain yield. Rice yields increased relative to
the control by 20-26%, 18%, and 4-11% for the fine,
standard, and pelletized forms, respectively in 1990/1991.
Agronomic feasibility of mini-granulation of CaSiO3 has
been confirmed. When containing high amounts of Si,
both granular and powered slag are equally efficient.
These are useful findings because they offer potential the
option of mini-granulation of fine silicate sources for
solving their handling problem.
DOSIS APLIKASI SILIKAT
Dosis aplikasi Si sangat dipengaruhi oleh komposisi
kimiawi dari sumber Si, kandungan Si-tersedia dalam
tanah, dan kandungan Si dalam tanaman.
Rekomendasi aplikasi silikat tanaman tebu di Hawaii 7.5
tons ha-1 bahan terak TVA (Tennessee Valley Authority).
Rekomendasi lainnya adalah 4.94 t ha-1 calcium
metasilicate (CaSiO3).
Rekomendasi untuk tebu ratoon 1.2 - 2.5 t ha-1 CaSiO3,
kalau kandungsn Si dalam tanah 64 - 78 kg ha-1.
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WAKTU DAN FREKUENSI APLIKASI SILIKAT
Umumnya aplikasi Si dilakukan ke tanah sebelum
penanaman bibit.
Pengalaman petani tebu di Florida, kalau respon terhadap
bahan Si dapat diperoleh pada aplikasi tahun pertama,
maka tidak perlu aplikasi Si lagi paling tidak selama empat
tahun.
Dalam sistem rotasi / pergiliran tanaman padi dengan
tebu, aplikasi terak-silikat sebelum tanaman tebu , dan
sebelum tanaman padi dalam rotasinya dengan tebu,
menunjukkan respon agronomis yang bagus.
Pengalaman menunjukkan bahwa aplikasi terak-silikat
yang lebih menguntungkan adalah sebelum tanaman padi
dalam sistem rotasi padi – tebu.
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UKURAN PARTIKEL BAHAN SILIKAT
The particle size of the Si fertilizer is important in
increasing Si content of leaves and subsequent disease
control. Particle size is associated with increased surface
area; consequently, the distribution and dissolution of
smaller Si particles mixed in the soil is enhanced and the
probability of root particle contact is increased.
Combining fine particles into pellets probably results in
less Si-soil contact, leading to reduce Si availability to the
crop, although some particle degradation could occur
during soil incorporation. The particle should be of a size
and well mixed with the soil. If very fine, Si sources create
dusty conditions and can adversely affect material
handling and application performance in the field. Special
precautions are necessary for avoiding exposure of
workers to the dust. This dust problem may limit the use
of silicate slag for sugarcane in developing countries
where it will be mainly applied manually.
Mini-granulation of fine calcium silicate materials seems
to a potential alternative for addressing the dust problem.
Small particle size increases the effectiveness of silicate
materials.
Harada (1965) called attention to the superiority of finely
ground TVA slag compared with coarsely ground, 16 mesh
(<1.6 mm) material.
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