54
cm and 20-40 cm. However, at a soil depth of 0-20 cm, the
mean pH, calcium and magnesium values were 6.13, 3.66
centimoles per cubic decimeter (cmoOc dm ) and 1.96
cmolc dm-3, respectively, whereas at a depth of 20-40 cm,
the pH value was recorded at 5.74 and the calcium content
was 2.59 cmolc dm-3 and the magnesium content was 0.82
cmolc dm-3.
The soil silicon content was recorded at an average level of
6.07 and 4.21% at depths of 0-20 and 20-40 cm, respectively,
D finding thDt PDy be e[SODined by OoZ PobiOity oI 6i in the
soiO SrofiOe D IDctor Zhich confirPs SreYioXs reseDrch thDt
sXggested thDt the ODcN oI significDnt eIIect cDn be e[SODined
by slower translocation, uantity and speed of reaction of
the silicon source applied due to what has been described
as “ soil buffer capacity”, the ability of soil to replenish the
soil solution of a particular solute as it will be removed by
plant uptake or any other process.
During the trial it was observed that the silicon was absorbed
by the root systeP YiD PDss ÁoZ in the IorP oI siOicic Dcid
(H4SiO4), with the absorption occurring at a steady pace.
It has been previously obseved that in grasses, silicon
absorption can be even more rapid than that of water, which
results in a reduction in the silicon concentration.
In the case of the ‘Palmer’ mango trees tested in this study,
it was observed that the silicon absorption occurred at a
much slower paste, at roughly the same rate to that of water,
a factor which indicate that mango trees may be potential
silicon accumulators.
Calciumandmagnesium contents were statistically equal with
averages of 29 g 230 kg-1 and 2.0 g kg-1, respectively, values
which are within acceptable standards for the cultivation of
mango trees.
Production characteristics, including the number of fruits
per plant, average fruit weight, fruit length, production and
productivity were also unaffected by the silicon quantities.
The ‘Palmer’ mango trees bore an average of 374 fruits, each
weighing an average of 439 grams and measuring 138 mm
in length. Total production was 163 Kilos per tree, averaging
around 34 tons per hectare. Within the mango cultivation
coPPXnity IrXits DYerDge Zeight oI IrXits ÁXctXDte DroXnd
426 grams and 119 mm in length, with yields of between
18.5 and 26 tons per hectare being the norm.
The ‘Palmer’ fruit diameters were also found to be
significDntOy diIIerent DPong the diIIerent siOicon DSSOicDtions
(See Fig. One).
Conclusions
The tests showed that Agro-silicon soil applications had
OittOe or no inÁXence on OeYeOs oI diseDse or Sest incidence
or the silicon, calcium and magnesium content of ‘Palmer’
mango-associated soil and leaves, indicating that Mango
trees may be potential silicon accumulators.
While silicon may take an active role in plant defense
responses, it may have a more effective passive role in
improving tolerance of stresses such as drought, because
during water uptake by the plant, silicic acid forms solid
amorphous, hydrated silica (silica gel) layers which are
thought to act as a form of physical barriers, to evaporation
and other stresses. Similar research in corn and rice have
shown that when supplemented with silicon, these plants
displayed marked increases in drought and heat tolerance
compared to unamended plants. ■
Figure One: . Fruit diameter from ‘Palmer’ mango
trees in trial
'oses of caOcium siOicate and magnesium
' Ng ha
' Ng ha ,
' Ng ha ,
' Ng ha ,
' Ng ha