silicate fertilization of sugarcane cultivated in tropical … papers - 2016...field crops research...
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Field Crops Research 167 (2014) 64–75
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Field Crops Research
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ilicate fertilization of sugarcane cultivated in tropical soils
ônica Sartori de Camargoa,∗, Gaspar Henrique Korndörferb, Patricia Wylerc
Agência Paulista de Tecnologia dos Agronegócios (APTA), Rod. SP 127, km 30, P.O. Box 28, 13412-050 Piracicaba, SP, BrazilFederal University of Uberlândia, P.O. Box 593, 38400-902 Uberlândia, MG, BrazilUniversity of São Paulo/ESALQ, P.O. Box 9, 14418-900 Piracicaba, SP, Brazil
r t i c l e i n f o
rticle history:eceived 7 November 2013eceived in revised form 17 July 2014ccepted 17 July 2014vailable online 13 August 2014
eywords:ieldultivarutritionertilizationilicon
a b s t r a c t
Although the benefits of silicon (Si) fertilization for sugarcane yields have already been demonstrated, fewstudies have examined the effects of silicate fertilization applied at less than 200 kg ha−1 Si in the furrowat planting on the soluble Si concentration in the soils, plant uptake in sugarcane (a Si-accumulatingcrop) and damage caused by the stalk borer (Diatraea saccharalis) under field conditions. The objectiveof this study was to evaluate the effects of a Ca–Mg silicate that was applied in the furrow at plantingon the available Si in the soil, sugarcane yields and stalk borer damage of two sugarcane cultivars underfield conditions. Two experiments were conducted on two soil types with a low silicon content (a TypicQuartzipsamment-Q and a Rhodic Hapludox-RH) using a completely randomized factorial scheme designwith four replicates, four Si application rates (0, 55, 110 and 165 kg ha−1 Si) and two cultivars (IAC 86-3396and SP 89 1115). Ca–Mg silicate was applied during furrow planting such that all plots received the samequantity of Ca and Mg. On both of the soil types, silicate fertilization increased the Si concentrations in thesoil and the leaves of the plants at 8 months for both the plant cane and the first ratoon, thereby showingresidual effects. Additionally, the potential for silicon fertilization applied in the furrow at planting to
reduce stalk borer (D. saccharalis) damage was confirmed for stalk Si concentrations that were greaterthan 3 g kg−1 Si as shown in the RH soil experiment. Therefore, the practice of silicate placement at lowrates (<200 kg ha−1 Si) in the furrow at planting should be considered an alternative method of nutritionalmanagement for sugarcane in sandy and loam sandy soils with additional benefits of increased solubleSi in the soil, Si uptake and sugarcane yield and may help reduce the stalk borer damage of D. saccharalis.© 2014 Elsevier B.V. All rights reserved.
. Introduction
Silicon (Si) is the second most abundant element in the Earth’srust, but low soluble Si contents are observed in highly weatheredoils in humid tropical areas, especially sandy and sandy loam soilsSavant et al., 1999). Sugarcane is an Si accumulator (Epstein, 2009),nd the Si contents in the aboveground biomass can reach between07 and 500 kg ha−1 Si (Samuels, 1969; Ross et al., 1974; Savantt al., 1999) in only one harvest, surpassing the levels of someacronutrients, such as nitrogen. Intensive management and the
lanting of monocultures for sugarcane cultivation could decreasehe Si availability in these areas (Berthelsen et al., 1999), resulting
n a need for Si fertilization (Epstein, 2009).Beneficial responses to silicon fertilization, including increasedhotosynthetic activity (Cheng, 1982; Elawad et al., 1982),
∗ Corresponding author.E-mail addresses: [email protected], [email protected] (M.S.d.
amargo), [email protected] (G.H. Korndörfer), [email protected] (P. Wyler).
ttp://dx.doi.org/10.1016/j.fcr.2014.07.009378-4290/© 2014 Elsevier B.V. All rights reserved.
increased tolerance to salinity (Ashraf et al., 2010a,b) and reducedlevels of damage by disease and insects (Savant et al., 1999;Raid et al., 1992; Keeping et al., 2009), have been demonstratedin sugarcane. Most of these effects result from increasing levelsof Si deposited in the leaves and stems (Kvedaras and Keeping,2007). Positive effects on increasing yield and sugar content havebeen observed in sugarcane crops in several countries, includingMauritius, the USA (Hawaii and Florida), Australia and Brazil. Theseeffects have been observed in crops that are grown on soils withhigh contents of oxides (Ayres, 1966; Fox et al., 1967; Ross et al.,1974; Berthelsen et al., 2001a,b; Gurgel, 1979) and organic matter(Elawad et al., 1982; McCray and Ji, 2012), as well as sandy andloamy soils (Korndörfer et al., 2000, 2002; Brassioli et al., 2009).
The most commonly used Si source in sugarcane crop is sili-cate or basic slag, which could lead to increased pH, Ca and Mgconcentrations in the soil (Alcarde, 1992). Despite a long history
of research on the silicon fertilization of sugarcane that extendsback to 1960, few studies have isolated the effects of Ca, Mgand pH when different rates of silicate are used (Ayres, 1966;Keeping and Meyer, 2006; Keeping et al., 2013; Berthelsen et al.,
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001b; McCray and Ji, 2012). In addition, it is essential to evaluatehe soluble Si in soils to predict the Si requirement for sugar-ane, as performed by Berthelsen et al. (2001b) in Australia. Theseuthors cultivated sugarcane into four groups based on the levelf soluble Si (extracted with CaCl2 0.01 mol L−1) in the soil: veryow (0–5 mg kg−1), low (5–10 mg kg−1), limited (10–20 mg kg−1)nd sufficient (20–>50 mg kg−1). Another study was conducted inlorida by McCray and Ji (2012), who observed positive responseso Si fertilization when the soil Si levels were less than 15 mg m−3
i (0.5 mol L−1 acetic acid extraction). Although the Si extractantsave been previously evaluated in soils that were cultivated withugarcane, this is the first study that compares both of the com-on (0.5 mol L−1 acetic acid and 0.01 mol L−1 CaCl2) without the
nfluence of Ca, Mg and pH in soil provided by silicate application.n analysis of the soluble Si concentration in soils, especially with
he pH, Ca and Mg concentrations being held constant, and the Siptake by sugarcane could confirm whether the yield obtained withilicate fertilization is due exclusively to increasing levels of solubleilicon in the soil.
Furthermore, most of the positive effects of the published exper-ments were observed with the application of silicate at rates thatre similar to the application of agricultural lime (>2 or 3 t ha−1)pplied across the entire cultivated area (Ayres, 1966; Berthelsent al., 2001a,b; Elawad et al., 1982; McCray and Ji, 2012; Brassiolit al., 2009). In contrast, silicate fertilization at these high rates cane costly for the sugarcane crop if Si deficiency is all that is requiredor correction rather than when used as an acidity correction ors with lime application (Anderson et al., 1991). Si fertilization inlanting furrows could be a useful method in order to provide Sio sugarcane plants at a reduced cost, as shown by Keeping et al.2013), but this method was not studied using rates that were lesshan 200 kg ha−1 Si.
Another potential advantage of the silicon fertilization of sug-rcane is a reduction in the level of damage inflicted by insects.tudies conducted in greenhouses and under field conditions haveemonstrated that Si positively affects the control of the stalk borerldana saccharina. Keeping and Meyer (2002) studied six cultivarsnd found reductions of 19 and 33% in pest damage with the appli-ation of 425 and 850 kg ha−1 Si, respectively. In pots studies, Meyernd Keeping (2005) also observed that Si application (200 kg ha−1
i) decreased the damage caused by the stalk borer by 70 and 35%hen N was applied to soils with low and high levels of Si, respec-
ively. In addition, Keeping and Meyer (2006) demonstrated that Sipplication increased the Si uptake in plant stalks and reduced stalkorer damage by 26 and 34% in the two cultivars. Recently, Keepingt al. (2013) published the first study of silicate application and E.accharina herbivory under field conditions. These authors demon-trated a decreased percentage of stalk borer damage to plant canesnd two ratoons that contained 394 and 1080 kg ha−1 Si and thatad been treated with 4 and 8 t ha−1, respectively, of applied sili-ate.
Similar damage is caused by a different stalk borer, Diatraeaaccharalis (F.) (Lepidoptera: Crambidae), in Central and Southmerica. Several studies have demonstrated that stalk borer dam-ge (or the percentage of bored internodes) of 1% can resulted inosses of 0.42% of sugar or 0.21% of alcohol and a 1.14% weight lossParra et al., 2010). This pest is controlled by biological methodsnd/or using resistant cultivars. Using silicate to increase the ratef silicon uptake in sugarcane could reduce the damage caused by D.accharalis, as demonstrated by Elawad et al. (1982) in a greenhousexperiment.
However, the association between Si availability, sugarcane
ptake of Si and beneficial effects in sandy and loam sandy soils,hich are commonly found in tropical regions, requires furthertudy. In addition, there are few studies of sugarcane that associatei uptake with the D. saccharalis damage under field conditions over
Research 167 (2014) 64–75 65
time. Most of the studies investigated on stalk borer E. saccharina insugarcane. Therefore, the objectives of this study were to evaluatethe effects of a Ca–Mg silicate applied at less than 200 kg ha−1 Si inthe furrow at planting on the soluble Si concentration in the soils,plant uptake in sugarcane and damage caused by the stalk borer (D.saccharalis) in two cultivars under field conditions.
2. Materials and methods
The experiments were conducted on the plant (March 2008 toJuly 2009) and ratoon crops (July 2009 to August 2010) that weregrown on a Typic Quartzipsamment (Q) soil and on plant cane(March 2009 to August 2010) and ratoon crops (August 2010 toAugust 2011) that were grown on a Rhodic Hapludox (RH) soil. Bothof the experiments were conducted in a commercial area in Piraci-caba (22◦42′30′′S; 47◦38′01′′W), São Paulo, Brazil. The chemicalcontent and texture were analyzed in soil samples that were col-lected in the 0–20 cm layer from both experimental areas (Table 1).These soils were selected by texture (sandy and loam sandy), whichcould provide differences in the soluble Si (Savant et al., 1999). Theminimum and maximum temperature and rainfall were monitoredmonthly (Fig. 1).
A completely randomized factorial design (4 × 2) with four repli-cations was used in the experiments. Four Si rates (0, 55, 110 and165 kg ha−1 Si) were used. Two cultivars were examined: IAC87-3396 (intermediate resistance to D. saccharalis, Sugarcane Center,Agronomic Institute-IAC) and SP89-1115 (susceptible to D. saccha-ralis, Sugarcane Technology Center-CTC). The source of silicon wasa Ca–Mg silicate (262.1 g kg−1 Ca; 56.8 g kg−1 Mg and 108.4 g kg−1
Si) applied in the furrow at planting. All of the treatments wereadjusted to receive the same quantities of Ca and Mg by applyinglime (343 g kg−1 Ca and 96 g kg−1 Mg) and/or MgCl2 (11.9% Mg) asnecessary. The cultivars were selected due to their high yield andhigh sprouting rate under sugarcane residue mulch.
During sugarcane planting (March 19, 2008, on the Q soil andMarch 21, 2009, on the RH soil), the silicate treatments and nitro-gen, phosphorus and potassium were applied in continuous bandson both sides of the furrows (0–20 cm depth) by hands. The fur-rows were covered with soil by rotavator as commonly used incommercial sugarcane areas. The soil was fertilized with nitrogen,phosphorus and potassium based on the soil analyses (Raij et al.,1997). Fertilizer was applied at rates of 40 kg ha−1 of N, 100 kg ha−1
of P2O5 and 100 kg ha−1 of K2O (10–25–25). Each plot containedfive 10-m rows. Surface nitrogen (40 kg ha−1 N; ammonium sulfate,20% N) and potassium (60 kg ha−1 of K2O; KCl, 60% K2O) fertiliza-tion occurred 30 days after planting. During the first ratoon stage,surface fertilization with N (100 kg ha−1 of N; ammonium sulfate)and K (60 kg ha−1 of K2O; KCl) was performed, according to Raijet al. (1997).
The 20 youngest fully expanded leaves (top-visible dewlap-TVD) without midribs (Anderson and Bowen, 1992) were collectedfrom each plot during the plant cane stage at 8 months after germi-nation (Q soil, December 2008; RH soil, December 2009) and duringthe first ratoon stage (Q soil, March 2010; RH soil, March 2011) forthe evaluation of Si content (Elliott and Snyder, 1991).
The yield (tons of sugarcane stalks per hectare) was determinedfor the plant cane and first ratoon by weighing the chopped caneof each plot in a truck that was equipped with a grab loader thatwas instrumented with a load cell. To determine the Si contents,before the harvest of both the plant cane and first ratoon, sugarcanesamples were taken from 1 m of each row of sugarcane per plot and
divided into straw (old and new leaves + tops) and stalks. Both thefresh and dry matters were weighed. The Si content in the straw andstalks was determined according to Elliott and Snyder (1991). Thestalk borer damage was determined by calculating the percentage
66 M.S.d. Camargo et al. / Field Crops Research 167 (2014) 64–75
Tab
le1
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emic
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ical
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rist
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ils
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the
exp
erim
ents
.
Soil
Sia1
(mg
kg−1
)Si
c2
(mg
kg−1
)p
H3
(mg
kg−1
)O
M4
(gd
m−3
)P5 (m
gd
m−3
)K
6
(mm
olc
dm
−3)
Ca6
(mm
olc
dm
−3)
Mg6
(mm
olc
dm
−3)
CE7
(mm
olc
dm
−3)
BS8
(%)
Als
atu
rati
on(%
)C
lay
(%)
Loam
(%)
San
d(%
)
Q3.
32.
44.
717
40.
418
141
479
64
88R
H6.
92.
95.
216
141
227
5555
016
282
1Si
a:Si
inac
etic
acid
0.5
mol
L−1.
2Si
c:Si
inC
aCl 2
0.01
mol
L−1.
3p
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15
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0
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300
mar
/08
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8
mai
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jun/
08
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8
ago/
08
set/0
8
out/0
8
nov/
08
dez/
08
jan/
09
fev/
09
mar
/09
abr/0
9
mai
/09
jun/
09
Tem
pera
ture
(o C)
Rai
nfal
l (m
m)
Plant cane Q soil
Rainfall - - -Average temperature
A
15
18
21
24
27
30
0
50
100
150
200
250
300
mar
/09
abr/0
9m
ai/0
9ju
n/09
jul/0
9ag
o/09
set/0
9ou
t/09
nov/
09de
z/09
jan/
10fe
v/10
mar
/10
abr/1
0m
ai/1
0ju
n/10
jul/1
0ag
o/10
Tem
pera
ture
(o C)
Rai
nfal
l (m
m)
Plant cane RH soil
Rainfall - - -Average temperature
B
15
18
21
24
27
30
0
50
100
150
200
250
300
jul/0
9
ago/
09
set/0
9
out/0
9
nov/
09
dez/
09
jan/
10
fev/
10
mar
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abr/1
0
mai
/10
jun/
10
jul/1
0
ago/
10
Tem
pera
ture
(o C)
Rai
nfal
l (m
m)
Rainfall - - -Average temperature
First ratoonQ soil C
15
18
21
24
27
30
0
50
100
150
200
250
300
ago/
09
set/0
9
out/0
9
nov/
09
dez/
09
jan/
10
fev/
10
mar
/10
abr/1
0
mai
/10
jun/
10
jul/1
0
ago/
10
Tem
pera
ture
(o C)
Rai
nfal
l (m
m)
First ratoonRH soil
Rainfall - - -Average temperature
D
Fig. 1. Rainfall and average temperatures during experiments conducted on Q andRH soils during the plant cane (A, B) and first ratoon (C, D) stages of sugarcane crops.
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M.S.d. Camargo et al. / Field
f bored internodes in a sample of 20 stalks from three central rowsf sugarcane.
After harvesting, the soil samples were obtained from 0–25 cmn depth. The soil Si concentrations were determined using aceticcid (0.5 mol L−1) and CaCl2 (0.01 mol L−1) according to Korndörfert al. (1999). The data were subjected to an analysis of variance byhe F-test. The results for the two cultivars were compared usingukey’s test, and the Si rates were analyzed by linear and polyno-ial regression using the SAS (Statistical Analysis System) program.
. Results
.1. Chemical characteristics and soluble silicon content of the soil
The application of silicon (Si) did not affect (p > 0.05) the soil pH,hosphorus (P), calcium (Ca) or magnesium (Mg) content, cationxchange capacity (CEC) or base saturation (BS%) in the sampleshat were collected from the 0–25 cm depth after the harvest ofoth the plant cane and first ratoon (Tables 2 and 3) because all ofhe nutrients, including Ca and Mg, were applied at equal rates invery experimental unit.
The levels of soil fertility (acidity, P, Ca and Mg) of the bothxperiments were evaluated according to the classification of Raijt al. (1997). The soil samples that were collected from the Typicuartzipisamment (Q) soil after the harvest of the plant cane exhib-
ted medium (5.1–5.5) to high (4.4–5.0) acidity, while the sampleshat were collected after and the first ratoon harvest exhibited highcidity. The P, Ca and Mg contents were within the range that is con-idered low (6–12 mg dm−3 of P) to medium (13–30 mg dm−3 of P)nd high (>7 mmolc dm−3 Ca; >8 mmolc dm−3 Mg) after each of thewo harvests. The soil acidity levels of the Rhodic Hapludox (RH)oil were low and medium (pH 5.6–6.0) at the plant cane and firstatoon stages, respectively. The BS of the Q soil was lower than thatf the RQ soil in both stages.
The soluble silicon concentrations in 0.5 mol L−1 acetic acid inhe soil for the plant cane (Fig. 2A and B) and first ratoon (Fig. 2C and) increased with the increasing rate of silicate application. Thereere significant interactions between the cultivar and Si rates for
he Si that was extracted by acetic acid (0.5 mol L−1) for both cropsn the Q soil (Fig. 2A and C). No differences between the cultivars
ere observed in the RH soil for either measure of soluble Si for thelant cane and first ratoon (Fig. 2B and D), therefore the average ofhe two cultivars was used.
There was also an increase in the silicon that was extracted byaCl2 (0.01 mol L−1). In the Q soil, the cultivars exhibited differ-nces only after the plant cane (Fig. 3A.) However, no differencesetween the cultivars were found for the soluble silicon in CaCl20.01 mol L−1) in the first ratoon of the Q (Fig. 3B) and RH (Fig. 3C)oils.
.2. Silicon uptake, sugarcane yield and stalk borer damage
The macronutrient concentrations in the top visible dewlapTVD) leaves that were collected at 8 months, including the Cand Mg content (data not shown), were not affected (p > 0.05) byhe treatments because the nutrients were applied at equal ratescross all of the experimental units. The leaf macronutrient con-entrations were within the range that is considered sufficientor sugarcane (Raij et al., 1997; 18–25 g kg−1 of N; 1.5–3.0 g kg−1
f P; 10–16 g kg−1 of K; 2–8 g kg−1 of Ca; 1–3 g kg−1 of Mg and.5–3.0 g kg−1 of S).
The silicon content in the TVD leaves was influenced by the Siate of application and cultivar type, with no interaction betweenhese two treatments, in the experiments that were conducted inhe Q (Table 4) and RH (Table 5) soils. The SP 89-1115 cultivar had
Research 167 (2014) 64–75 67
the highest Si content in the plant cane and the first ratoon in the Qsoil and in the plant cane in the RH soil. The Si content of the TVDleaves from the plant cane and first ratoon of the crops that weregrown in the Q (Fig. 4A and C) and RH (Fig. 4B and D) soils increasedwith increasing Si application rate.
The silicon concentrations in the sugarcane straw and stalk wereaffected by the cultivar type in both of the soils (Tables 4 and 5),except for the first ratoon in the Q soil (Table 4). Higher values of Siin the straw, soluble Si in the soil and TVD-Si concentrations wererecorded for SP89-1115 in both of the experiments. There was also asilicate fertilization effect on the Si in sugarcane straw in the RH soil(Table 5), and the regressions between the silicate application rate(X) and the Si content (Y) of sugarcane straw were significant forthe plant cane (Y = 0.003X + 0.545; R2 = 0.80, p < 0.05). For the firstratoon, the regression between silicate application rate (X) and theSi content (Y) of sugarcane straw was significant only for the SP89-1115 cultivar (Y = 0.017X + 1.980; R2 = 0.93, p < 0.05).
The sugarcane yield was influenced by the cultivar type and theSi application rate (Tables 4 and 5), but a significant interaction wasobserved only between the cultivar and Si in the first ratoon in theRH soil. Higher yields were found for SP89-1115 in all of the har-vests, except for the first ratoon in the RH soil. The sugarcane yieldshowed a linear increase in response to silicon fertilization in bothcrops for the plant cane on both soil types (Fig. 5). No differences inthe Brix values of sugarcane, which averaged 21, were observed inthis study. The linear regressions between the silicate applicationrate and sugarcane yield were significant for the plant cane andratoon in both soil types (Fig. 5).
The stalk borer damage was higher on SP 89-1115 in both of theexperiments (Tables 4 and 5), which was consistent with this cul-tivar’s high susceptibility to D. saccharalis (Dinardo-Miranda et al.,2012). The percentage of stalk borer damage on the plant cane andfirst ratoon in the RH soil (Table 5) decreased linearly with siliconfertilization (Fig. 6). The linear regressions that were applied for thefirst ratoon used the mean values of two cultivars because theseregressions were not significant when analyzed separately. How-ever, no significant effect was observed on the stalk borer damagefor the crops that were grown in the Q soil (Table 4). The percent-age of fiber in the sugarcane stalks was affected only by the cultivartype in both of the experiments (Tables 4 and 5), with SP89-1115showing lower values.
4. Discussion
The soluble Si concentration in the soils increased as a functionof silicate fertilization, which accordingly resulted in the increasedSi content of the TVD leaves and yield for the plant cane and thefirst ratoon of sugarcane crops that were grown in both soils. Thesugarcane cultivar type also had an effect in some of the analy-ses. Furthermore, silicon fertilization increased the Si in the plantstalks and decreased the stalk borer damage in both the plant caneand first ratoon of crops that were grown in the RH soil. Theseresults are associated with the release of soluble Si in the soil andSi uptake by plants because no significant effect was observed ofsilicate application on the soil pH or Ca and Mg contents, com-pared to the controls that were treated with lime and/or MgCl2.Previous studies (Berthelsen et al., 2003; Kingston et al., 2005) alsodemonstrated positive results of silicate fertilization of sugarcane,but these results cannot be related only to increases in the Si inthe soil, because the pH, Ca or Mg contents in the soil were not thesame in every treatment. Our results confirm that Si is beneficial for
sugarcane plants (Savant et al., 1999; Epstein, 2009; McCray and Ji,2012) and that Si amendments that are applied in the furrows atplanting could be useful for improving the yields and managing D.saccharalis in sugarcane cultivation in sandy and loam sandy soils.
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.S.d.Camargo
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Table 2Chemical attributes, soluble silicon in acetic acid 0.5 mol L−1 and CaCl2 0.01 mol L−1 of soil samples collected at 0–25 cm in depth following plant cane harvest of a crop grown on a Quartzipsamment soil.
Si rate (kg ha−1) Plant cane First ratoon
pH1 P2
(mg kg−1)Sia3
(mg dm−3)Sic4
(mmolc dm−3)Ca5 (%) Mg5 CEC6
(mg kg−1)BS7
(mg dm−3)pH1 P (mg kg−1) Sia3
(mg dm−3)Sic4
(mmolc dm−3)Ca5 (%) Mg5 (%) CEC6
(mg kg−1)BS7
(mg dm−3)
IAC87-33960 4.6 8.8 4.0 2.3 17.0 4.8 51.2 43.8 4.6 11 7.0 4.1 17 7.5 44 5455 5.0 8.5 7.6 3.3 27.0 8.0 54.3 57.5 4.6 8.3 9.8 5.1 15 6.3 51 44110 4.6 8.0 15.8 5.2 16.3 6.0 52.4 42.0 4.8 13 25.7 5.4 21 9.0 59 51165 5.2 14.5 20.3 4.3 31.5 8.3 75.6 59.8 4.8 20 21.2 5.4 16 8.0 47 53
SP89-11150 4.9 13.8 3.3 2.3 25.0 8.0 61.5 55.5 4.3 16 5.3 3.9 9 6.8 49 3655 5.8 16.0 11.3 3.4 29.0 14.3 81.7 72.8 4.6 7.8 7.4 5.2 18 8.8 55 49110 5.0 14.3 18.9 3.7 28.8 5.5 65.6 51.5 5.0 8.8 8.0 5.5 35 10.0 69 56165 5.1 16.0 47.8 7.4 28.0 9.3 76.3 56.8 4.4 7.5 13.8 5.0 13 8.5 50 40Cult. (C) ns ns * ns ns ns * ns ns ns * ns ns ns ns nsRate (R) ns ns * * ns ns ns ns ns ns * ns ns ns ns nsC*R ns ns * ns ns ns ns ns ns ns * ns ns ns ns nsIAC873396 4.83a 9.9a 11.9b 3.8a 22.9a 6.7a 58.3b 50.7a 4.6a 13.2a 15.9a 4.9a 17.2a 7.7a 50.1a 50.6aSP891115 5.18a 17.0a 20.3a 4.2a 35.3a 9.2a 71.2a 59.1a 4.5a 10.1a 8.6b 4.9a 18.7a 8.1a 55.7a 45.4aMSD8 0.66 1.8 4.4 1.0 13.4 3.7 10.8 16.7 0.31 5.7 3.3 0.7 11.03 2.5 12.34 9.3
1pH CaCl2.2P: anion resin exchangeable.3Sia: Si in acetic acid 0.5 mol L−1.4Sic: Si in CaCl2 0.01 mol L−1.5Ammonium acetate method.6Cation exchange capacity.7Base saturation.8MSD: minimum significant difference.*Significant at a 5% significance level.**Means followed by the same letter in the column do not differ based on a Tukey’s test (p < 0.05); ns = non-significant.
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Table 3Chemical attributes, soluble silicon in acetic acid 0.5 mol L−1 and CaCl2 0.01 mol L−1 of soil samples collected at 0–25 cm in depth following plant cane harvest of a sugarcane crop grown on a Rhodic Hapludox soil.
Si rate (kg ha−1) Plant cane First ratoon
pH1 P2 (mgkg−1)
Sia3 (mgkg−1)
Sic4 (mgdm−3)
Ca5 (mmolcdm−3)
Mg5
(mmolcdm−3)
CEC6
(mmolcdm−3)
BS7 (%) pH1 P () Sia3 (mgkg−1)
Sic4 (mgdm−3)
Ca5 (mmolcdm−3)
Mg5
(mmolcdm−3)
CEC6
(mmolcdm−3)
BS7 (%)
IAC87-33960 5.7 16.5 23.2 5.1 23.5 17.8 58.4 71.0 5.5 9.5 13.1 4.5 22.2 12.7 55.7 64.055 5.7 28.8 21.1 5.6 26.8 18.0 60.9 74.3 5.7 12.7 18.2 5.2 27.0 12.0 56.9 68.5110 5.3 24.8 17.1 5.4 23.0 16.0 59.2 66.0 5.7 12.2 17.0 5.1 25.7 12.7 56.5 68.5165 5.5 40.0 40.2 6.7 25.0 16.3 59.4 69.5 5.7 21.7 20.0 6.1 26.0 12.7 56.8 68.5
SP89-11150 5.7 50.5 15.4 4.5 35.8 19.5 72.4 76.8 5.5 35.2 11.5 3.8 24.7 9.7 56.5 6155 5.5 48.5 10.3 4.0 18.0 12.5 52.9 59.0 5.2 10.2 12.6 4.0 16.7 8.5 52.5 49.7110 5.6 55.3 31.6 5.7 31.3 16.8 65.9 71.3 5.2 22.0 19.7 4.9 23.0 10.2 59.2 57.2165 5.6 110.0 20.8 5.3 31.3 17.0 67.5 71.3 5.3 18.5 31.9 6.8 23.5 8.5 57.8 56.5Cult. (C) ns * ns * ns ns ns ns * ns Ns ns ns ns ns *Rate (R) ns ns * ns ns ns ns ns ns ns * * ns ns ns nsC*R ns ns * ns ns ns ns ns ns ns Ns ns ns ns ns nsIAC873396 5.5a 27.5b 25.4a 5.7a 24.6a 17.0a 59.5a 70.2a 5.7a 13.5a 17.2a 5.2a 25.2a 12.5a 56.5a 67.4aSP891115 5.5a 83.6a 19.5a 4.8b 29.1a 16.43a 64.7a 69.6a 5.3b 10.9a 18.9a 4.8a 22.0a 9.3a 56.5a 56.1bMSD8 0.2 32.2 6.3 0.8 8,2 2,3 8,8 7,3 0.17 4.23 7.02 0.76 4.73 3.10 4.71 4.27
1pH CaCl2.2P: anion resin exchangeable.3Sia: Si in acetic acid 0.5 mol L−1.4Sic: Si in CaCl2 0.01 mol L−1.5Ammonium acetate method.6Cation exchange capacity.7Base saturation.8MSD: minimum significant difference.*Significant at a 5% significance level.**Means followed by the same letter in the column do not differ based on a Tukey’s test (p < 0.05); ns = non-significant.
70M
.S.d.Camargo
etal./Field
CropsR
esearch167
(2014)64–75
Table 4Sugarcane yield, Si concentration in TVD leaves, stalks and straw and percentage of bored internodes and percentage fiber of stalks in the plant cane and first ratoon of two sugarcane cultivars grown on a Quartzipsamment soilwith varying rates of Si application.
Si rate (kg ha−1) Plant cane First ratoon
Yield(t ha−1)
TVD(g kg−1Si)
Straw (%) Stalk (◦) Bored(internode)
Fiber(t ha−1)
Brix (g kg−1
Si)Yield(t ha−1)
TVD(g kg−1Si)
Straw (%) Stalk (◦) Bored(internode)
Fiber(t ha−1)
Brix (g kg−1
Si)
IAC87-33960 70.94 3.7 2.3 0.35 0.73 13.52 20.1 79.73 6.4 4.0 0.5 1.10 12.63 22.455 71.87 3.9 2.0 0.35 0.07 13.34 20.2 73.98 7.2 4.1 0.4 4.04 12.57 22.5110 78.37 3.7 2.3 0.30 1.11 14.18 20.3 78.00 7.3 3.4 0.4 1.38 13.29 22.7165 82.15 3.9 2.4 0.30 0.49 13.72 20.3 98.18 7.2 4.3 0.4 1.24 12.49 22.6SP89-11150 120.32 4.2 2.8 0.35 2.95 11.18 21.4 102.80 8.6 5.1 0.1 9.66 10.70 22.555 127.75 4.7 2.9 0.50 3.47 11.09 21.7 102.30 8.6 5.3 0.1 9.69 10.91 22.4110 131.22 4.8 3.1 0.43 2.54 10.64 21.6 105.35 9.0 6.0 0.2 8.75 11.31 22.4165 126.41 5.0 3.2 0.45 4.08 10.89 21.6 116.63 8.6 4.2 0.2 9.29 10.90 22.7
Prob > FCult. (C) * * * ns * * * * * * * * * nsRate (R) * * ns ns ns ns ns * ns ns ns ns ns nsC*R ns ns ns ns ns ns ns ns ns ns ns ns ns ns
AverageIAC873396 76.5 b 3.8b 2.2b 0.4 a 0.6b 13.6a 20.2b 82.5b 7.0 b 3.9 b 0.4 a 1.9b 12.7a 22.5aSP891115 126.4a 4.6a 2.6 a 0.3 a 2.8a 10.9b 21.6a 106.9a 8.7 a 5.1 a 0.2 b 9.0a 10.9b 22.5aMSD** 4.7 0.3 0.4 0.1 1.1 0.3 0.3 7.3 0.7 2.0 0.3 1.7 0.4 0.2
*Significant at a significance level of 5%.**Means followed by the same letter in the column do not differ by Tukey test (p < 0.05); ns = non-significant.
M.S.d. Camargo et al. / Field Crops Research 167 (2014) 64–75 71
Y = 0.103X + 3.397 R = 0.97*
Y = 0.002X2 - 0.029X + 4.407 R =0.88*
0
10
20
30
40
50
60
0 55 110 165Si
-ac
etic
acid
(mg
kg-1
)
Si (kg ha-1)
IAC87-3396
SP89-1115
Plant cane Q
A
Y= 0.0855X + 18.333 R2 = 0.55*
15
20
25
30
35
40
45
0 55 110 165
Si -
acet
ic ac
id (m
g kg
-1)
Si (kg ha-1)
RHPlant Cane
B
Y = -0.001X2+0.206X+5.325 R =0.77*
Y = 0.047X + 4.68 R2 = 0.68*
05
10152025303540
0 55 110 165
Si -
acet
ic ac
id (m
g kg
- 1)
Si kg ha-1
IAC 87 3396
SP 89 1115
C
First ratoon Q
Y = 0.080X + 11.39 R = 0.89*
0
5
10
15
20
25
30
35
0 55 110 165
Si -A
cetic
Aci
d (m
g kg
-1)
Si (kg ha-1)
D
RHFirst Ratoon
F vest on. The
( gures.
efeirlop
i(
TSt
**
ig. 2. Soluble silicon in 0.5 mol L−1 acetic acid of soil samples collected after the har, and SP 89-1115, � ) grown on Q and RH soils with varying levels of silico
� ).*Significant by the F-test (p < 0.05). Standard error bars are included in all fi
Silicate applied in the furrows at planting increased thextracted Si (using two different extractants) in the soil samplesrom 0 to 25 cm in depth (Figs. 2 and 3) due to the very low Si lev-ls (0–5 mg kg−1 Si, 0.01 mol L−1 CaCl2) (Berthelsen et al., 2001b)n both of the soils. McCray and Ji (2012) also observed positiveesponses to silicate fertilization in soils with Si levels that wereower than 15 mg kg−1 Si (0.5 mol L−1 Si acetic acid). The resultsf this study confirm the positive effects of silicate application at
lanting on Si supply for cultivated sugarcane.The higher extraction capacity of 0.5 mol L−1 acetic acid resultedn higher Si concentrations compared to 0.01 mol L−1 CaCl2Tables 2 and 3) in agreement with other studies (Pereira et al.,
able 5ugarcane yield, Si concentrations in TVD leaves, stalks and straw and percentage of borewo sugarcane cultivars grown on a Rhodic Hapludox soil with varying rates of Si applica
Si rate (kg ha−1) Yield(t ha−1)
TVD Straw Stalk(g kg−1 Si)
BoredInternode(%)
Fiber Brix
IAC87-33960 155.4 5.7 4.5 0.5 5.64 12.3 20.755 157.8 6.5 4.2 0.7 7.12 12.4 21.1110 153.4 6.0 4.7 0.8 3.52 12.5 20.5165 152.8 6.4 5.3 1.0 2.52 13.0 20.6
SP89-11150 163.4 6.2 5.4 0.6 31.58 10.8 21.055 165.4 7.1 5.3 0.8 25.32 10.8 21.3110 163.4 7.0 5.9 1.0 20.88 11.0 21.4165 165.8 7.5 6.3 1.3 19.52 11.0 21.4
Prob > FCult. (C) * * * * * * nsRate (R) Ns * ns * * ns nsC*R ns ns ns ns ns ns ns
AverageIAC873396 154.8b 6.2b 4.7b 0.7a 4.7b 12.5a 20.7SP891115 164.5a 6.9a 5.7a 0.9a 24.3a 10.8b 21.2MSD** 4.26 0.3 0.9 0.3 3.9 0.5 0.6
Significant at a significance level of 5%.*Means followed by the same letter in the column do not differ by Tukey test (p < 0.05);
f the plant cane (A, B) and first ratoon (C, D) of two sugarcane cultivars (IAC 87-3396linear regressions applied for the RH soil used the mean values of two cultivars
n = 4 repetitions.
2004; Camargo et al., 2007). This result is due to the acetic acid Siextraction being performed at low pH values (1.0–2.0), which couldpotentially extract non-available Si (Pereira et al., 2007) and over-estimate the Si content, when different silicate rates were appliedand the soil pH increased. However, the lack of an effect of the soilpH in the experiments due to the balancing of lime in all of the plotsconfirms that the observed differences in Si can be attributed to theincreased Si availability resulting from silicate fertilization, which
is consistent with the results of Camargo et al. (2013). In addi-tion, the other extractant (0.01 mol L−1 CaCl2) also showed highervalues of soluble Si concentrations than those that were observedfor the control treatment with a residual effect of the release of Sid internodes and percentage fiber of stalks in the plant cane and first ratoon fromtion.
Yield(t ha−1)
TVD Straw Stalk(g kg−1 Si)
BoredInternodes(%)
Fiber Brix
137.43 6.4 2.8 1.0 17.8 12.9 17.6132.20 14.3 3.3 0.6 14.5 12.7 16.9147.73 17.5 2.7 0.7 12.2 12.5 27.2137.93 19.0 2.9 0.9 11.8 13.1 16.7
109.33 7.51 3.1 2.3 34.9 10.9 16.3111.30 10.13 3.1 2.5 30.5 11.1 16.2115.55 20.80 3.6 3.7 26.9 11.1 15.7118.10 14.30 3.4 5.0 32.5 10.8 15.6
* ns * * * * ns* * ns * * ns ns* ns ns ns * ns ns
a 136.3a 14.3a 2.9b 0.8 b 14.1b 12.8a 23.6aa 113.6b 12.8a 3.4a 3.4a 31.2a 10.9b 18.6a
3.4 5.22 0.4 0.6 1.7 0.4 7.5
ns = non-significant.
72 M.S.d. Camargo et al. / Field Crops
Y= -0.0002X2+ 0.04X + 2.14 R = 0.85*
Y = 0.028X + 1.85 R2 = 0.65*
0123456789
10
0 55 110 165
Si -
CaC
l 2(m
g kg
-1)
Si (kg ha-1)
IAC 87-3396
SP 89-1115
Q
A
Plant Cane
Y = -0.0001X2 + 0.027X + 3.977 R = 0.91*
3
4
5
6
0 55 110 165
Si -
CaC
l 2(m
g kg
-1)
Si (kg ha-1)
Q
B
First Ratoon
Y = 0.012X + 3.976 R = 0.90*
012345678
0 55 110 165
Si -
CaC
l 2(m
g kg
-1)
Si (kg ha-1)
C
RHFirst ratoon
Fig. 3. Soluble silicon in 0.01 mol L−1 CaCl2 of soil samples collected after the harvestof the plant cane (A) and first ratoon (B, C) of two sugarcane cultivars (IAC 87-3396
, and SP 89-1115, � ) grown on Q and RH soils with varying levels of silicon.The regressions applied for the first ratoon used the mean values of two cultivars(� ).*Significant by the F-test (p < 0.05). Standard error bars are included in allfigures. n = 4 repetitions.
Research 167 (2014) 64–75
through silicate application. However, the levels were not sufficient(>20 mg kg−1 Si) according to Berthelsen et al. (2001a), althoughthe Si uptake and sugarcane yield increased. These results indicatethat more studies investigating extraction techniques that are stillbeing debated are necessary, as shown by Haynes et al. (2013), whoprovide valuable discussion on this topic.
In both of the extraction procedures, the Si content was lower inthe first ratoon than in the plant cane in the Q soil (Tables 2 and 3).The possible major factors contributing to the reduced levels ofsoluble Si in the soil include Si uptake by sugarcane, Si leachingand Si conversion to insoluble Si over time (Berthelsen et al., 1999;Camargo et al., 2013; Savant et al., 1999; Keeping et al., 2013).
Differences between the cultivars were observed in the Si con-centrations in the TVD leaves that were collected under favorableclimate conditions (Fig. 1) from the plant cane and first ratoon(Tables 4 and 5). The SP89-1115 cultivar showed higher Si concen-trations in both the Q and RH soils, except in the first ratoon. Thisgenotypic variability in the Si uptake by sugarcane that was grownin different soil types is consistent with the results of other studies.Deren et al. (1993) observed values in the range of 6.4 to 10 g kg−1
Si in the TVD leaves for 52 genotypes of sugarcane that were grownin organic and sandy soils (low Si content). Korndörfer et al. (2000)also showed Si levels varying from 0.7 to 11.4 g kg−1 Si for three cul-tivars that were grown in sandy soil. Similar values were obtainedby Camargo et al. (2010). These authors verified Si levels that weregreater than 10 g kg−1 Si for nine sugarcane cultivars that weregrown in soil in which the Si levels were non-limiting. Despite thegenotypic variability, the differences in Si levels of the TVD leavesare also related to the Si content in the soil, which increased withsilicate fertilization as observed in these experiments.
The direct effect of Si fertilization on the Si concentrations inthe TVD leaves in these experiments (Fig. 4) has been previouslydemonstrated and the responses varied by cultivar, soil type andclimate. In a field experiment, Elawad et al. (1982) observed Sicontents of 8.3 and 12.3 g kg−1 Si in the leaves of the control treat-ment group (application rate of 0) and in the leaves of a group thatwas treated with silicate at a rate of 5 t ha−1, respectively. For thefirst ratoon, the Si content increased from 3.1 to 5.3 g kg−1 underthe same silicate application rate (Elawad et al., 1982). In addition,Raid et al. (1992) observed 2.7 g kg−1 Si for a control treatment and6.1 g kg−1 Si for an application of 6.7 t ha−1 Si of silicate to the soil.In the first ratoon, the Si levels increased from 2.5 g kg−1 Si for thecontrol treatment to 5.4 g kg−1 Si for the silicate fertilization treat-ment (Raid et al., 1992). In contrast to these results, lower valueswere recorded for the plant cane than for the first ratoon. Althoughthe data collection was performed at 8 months, the higher Si con-tent in the first ratoon was related to the lower yield, which couldreduce the concentration of Si in the leaves (dilution effect).
A response to silicate fertilization as a function of the soiltype has already been shown in previous studies, but few stud-ies have evaluated the Si concentrations in the TVD leaves ofcrops that were grown under field conditions. For a soil contain-ing 4 mg kg−1 Si (extracted by 0.01 mol L−1 CaCl2) (Kingston et al.,2005), the Si concentrations in the TVD leaves that were collectedat 7 months increased from 1.5 g kg−1 Si for the control treat-ment to 4.7 g kg−1 Si with the application of 6 t ha−1 silicate. Forsoils with 8 and 9 mg kg−1 Si, the Si levels in the leaves were2.9 and 4.7 g kg−1 Si, respectively, for the control treatment and5.3 and 7.4 g kg−1 Si, respectively, for 6 t ha−1 of silicate (Kingstonet al., 2005). Berthelsen et al. (2001a) also observed an increasein the Si concentrations in the TVD leaves that were collected at7 months with 3 t ha−1 calcium silicate applied to a Mossman soil
(4.2 mg kg−1 Si–CaCl2 0.01 mol L−1). The values were 1.4 g kg−1 Sifor the control treatment and 3.6 g kg−1 Si for the silicate fertil-ization treatment, and the increase in the Si was smaller in thesoils with higher levels of soluble silicon. The Si concentrations
M.S.d. Camargo et al. / Field Crops Research 167 (2014) 64–75 73
Y = 0.004X + 3.91 R 0.90*
3.83.94.04.14.24.34.44.54.64.74.84.9
0 55 110 165Si
(g k
g-1)
Si (kg ha-1)
A
Plant Cane Q
Y = 0.0073X+ 6.802 R2 = 0.97*
6.5
7.0
7.5
8.0
8.5
0 55 110 165
Si (g
kg-1
)
Si (kg ha-1)
C
First Ratoon Q
Y = 0.005X + 6.144 R2=0.51*
5.0
5.5
6.0
6.5
7.0
7.5
0 55 110 165
Si (g
kg-1
)
Si (kg ha-1)
Plant Cane RH
B
Y= -0.001X2 + 0.169X + 6.399 R =0.93*
0
5
10
15
20
25
0 55 110 165
Si (
g kg
-1)
Si (kg ha-1)
First Ratoon RH
D
F atoona (�
n
iaS0fewt
Ftr
ig. 4. Silicon content of TVD leaves of sugarcane grown to the plant cane and first rpplied for the plant cane and the first ratoon used the mean values of two cultivars= 4 repetitions.
n the leaves were 2.9 and 4.3 for the control treatment and 4.7nd 6.6 g kg−1 with Si fertilization in an Innisfail soil (8.6 mg kg−1
i–CaCl2 0.01 mol L−1) and a Bundaberg soil (9 mg kg−1 Si–CaCl2.01 mol L−1), respectively (Berthelsen et al., 2001a). The Si values
or the TVD leaves in these studies (Kingston et al., 2005; Berthelsent al., 2001a) were below the critical value (10 g kg−1 of Si) thatas proposed by Anderson and Bowen, 1992) even with Si fer-ilization. These values are similar to our results, where a value
Y = 0.047X + 97.57 R = 0.84*
94
96
98
100
102
104
106
108
0 55 110 165
Yie
ld (t
ha-1
)
Si (kg ha-1)
Plant Cane Q
A
Y = 0.094X + 86.926 R2 = 0.60*
70
80
90
100
110
120
0 55 110 165
Yie
ld (t
ha- 1
)
Si (kg ha-1)
C
First Ratoon Q
ig. 5. Sugarcane yield for the plant cane and first ratoon of crops grown on Q (A, C) anhe plant cane and the first ratoon used the mean values of two cultivars (� ).*Signiepetitions.
grown on Q (A, B) and RH (C, D) soils with varying levels of silicon. The regressions).*Significant by the F-test (p < 0.05). Standard error bars are included in all figures.
that was equal to or greater than 5 g kg−1 Si was obtained whenSi was applied. Additionally, an increase in the sugarcane yields(Berthelsen et al., 2001a) and/or a reduction in the disease sever-ity (Raid et al., 1992) were also observed with silicate fertilization,
even when the increase in the Si concentrations in the TVD leaveswas smaller than expected. Furthermore, some studies on sugar-cane that was grown in sandy (Berthelsen et al., 2003) and organicsoils (McCray and Ji, 2012) have produced best cane yield in theseY = 0.083X + 153.299 R2 =0.78*
150
155
160
165
170
0 55 110 165
Yie
ld (t
cane
ha-1
)
Si (kg ha-1)
B
RHPlant Cane
Y = 0.055X + 108.9 R = 0.91*
108
110
112
114
116
118
120
0 55 110 165
Yie
ld (t
cane
ha-1
)
Si (kg ha-1)
First ratoon RH
D
d RH (B, D) soils with varying levels of silicon. The linear regressions applied forficant by the F-test (p < 0.05). Standard error bars are included in all figures. n = 4
74 M.S.d. Camargo et al. / Field Crops
05
10152025303540
0 55 110 165
Bor
ed in
tern
odes
(%)
Si (kg ha-1)
SP 89-1115IAC 87-3396
Plant Cane Y=-0.024X + 6.645R2=0.60* Y=-0.074X + 30.42 R2=0.80*
A
Y = -0.026X + 25.23R = 0.71*
15
20
25
30
0 55 110 165
Bor
ed in
tern
odes
(%)
Si (kg ha-1)
First Ratoon
B
Fig. 6. Percentage of bored internodes in the plant cane and first ratoon of twosugarcane cultivars (IAC 87-3396 , and SP 89-1115, � ) grown on an RH soilwith varying levels of silicon. The linear regressions applied for the first ratoonuS
eTwr
bPcBtaocfsct
tsagheefiHwaa
rea
sed the mean values of two cultivars (� ). *Significant by the F-test (p < 0.05).tandard error bars are included in all figures. n = 4 repetitions.
xperiments when the levels were 5 g kg−1 Si in the TVD leaves.hese results suggest that the 10 g kg−1 Si threshold value, whichas proposed by Anderson and Bowen (1992), needs to be
eviewed.Superior yields (tons cane/ha) were observed for SP89-1115 in
oth of the soils, except for the first ratoon in the RH soil (Table 5).rior to the onset of the experiments, orange rust caused by Puc-inia kuehnii (W. Krüger) E.J. Butler was not considered a problem inrazil, and the susceptibility of SP89-1115 was unknown. However,his disease has occurred in RH soil. Although the photosyntheticctivity (Bokhtiar et al., 2012) was not evaluated in this study,range rust can significantly reduce the net photosynthetic rate,arbon fixation efficiency and cane yield (Zhao et al., 2011). There-ore, the occurrence of orange rust on SP89-1115, which is a highlyusceptible variety, could explain the lower productivity of thisultivar in the first ratoon in the RH soil even though the Si concen-ration in the TVD leaves increased with Si fertilization.
The sugarcane yield increased linearly in response to silicon fer-ilization and it was also observed with soluble Si contents in theoils and Si concentrations in the TVD leaves (Figs. 2–4). The positivend residual effects of silicate fertilization on sugarcane that wasrown in many soil types have been previously demonstrated usingigher rates of Si application (>2 t ha−1) across a total area (Elawadt al., 1982; Savant et al., 1999; Kingston et al., 2005; Berthelsent al., 2003; Korndörfer et al., 2000, 2002; Brassioli et al., 2009). Dif-erences among cultivars in response to Si fertilization, as reportedn these experiments, have already shown by Raid et al. (1992).owever, this is the first published study focusing on silicate thatas applied in the furrow at planting time using low rates of Si
pplication (<200 kg ha−1 Si) producing positive effects on the soilnd plant yields.
Although the root system of sugarcane is very deep, most of theoots (51–70%) are concentrated in the 0–20 cm depth (Vasconcelost al., 2003; Otto et al., 2009). The proximity of the roots to silicatepplied in the furrow could promote greater solubilization than
Research 167 (2014) 64–75
the application across a total area. Despite low Si application ratescompared to high Si extraction by sugarcane, the increase in thesoluble Si concentration, uptake and yield in two harvests confirmsthis method of silicate placement as an alternative for supplyingthis beneficial element to sugarcane.
The cultivar also affected the Si concentrations in straw, withhigher values for SP89-1115, in agreement with the TVD-Si con-centrations for that cultivar (Tables 4 and 5). It is very common toobserve low quantities of Si on stalks compared those found theTVD leaves and straw of sugarcane (Gallo et al., 1974; Keeping andMeyer, 2006). In addition, these low levels of Si in the soil couldbe considered enough to supply the Si concentrations in the stalks.Therefore, silicate fertilization did not affect the Si concentration ofthe stalks.
The percentage of bored internodes was not influenced by theSi fertilization of the Q soil, which could be due to the low yield,reduced percentage of bored internodes of (4 and 10% for the plantcane and first ratoon, respectively) and low Si concentrations in thestalks (Table 4). Furthermore, the Si content in the stalks of bothof the cultivars in Q soil was lower than 3 g kg−1 Si, which is theminimum value required to enhance Si-mediated resistance to thestalk borer E. saccharina (Keeping et al., 2009, 2013; Keeping andMeyer, 2006; Kvedaras and Keeping, 2007). This minimum valuecould also be true for D. saccharalis because larval penetration bystalks is similar to that of E. saccharina (Dinardo-Miranda et al.,2013).
In contrast, silicate fertilization increased the Si concentrationsin the stalks and reduced the stalk borer damage in the plantcane and first ratoon of the crops that were grown in the RH soil(Fig. 6), and the Si content of the stalks was higher than 3 g kg−1 Si(Table 5). These results agree with those of Elawad et al. (1982), whoreported reduced stalk damage by D. saccharalis with the applica-tion of Si through sodium metasilicate in greenhouse experiments.Studies from South Africa (Meyer and Keeping, 2005; Kvedaraset al., 2005; Keeping and Meyer, 2006; Keeping et al., 2013) alsoshowed a reduction in damage by the stalk borer E. saccharina.This study, however, was the first study in which Si applied atless than 200 kg ha−1 Si in the furrows at planting reduced dam-age caused by natural infestations of D. saccharalis evaluated underfield conditions.
The silicate placement in the furrows increased the Si concen-trations in the stalk, despite low application rates (<200 kg ha−1
Si) in two soil types with low soluble silicon. This result could beexplained by the close proximity of silicate and the root system,as previously cited. The increase in the total Si concentration inplants increases resistance to herbivorous insect attack in agree-ment with our results. The reduced digestibility and/or increasedhardness of sugarcane tissues due to Si deposition, mainly as opa-line phytoliths or amorphous Si reduce stalk borer E. saccharinasurvival and damages (Keeping and Meyer, 2006; Keeping et al.,2009, 2013). In addition, greater effects of Si fertilization on stalkborer damage have been reported in susceptible cultivars (Keepingand Meyer, 2006; Keeping et al., 2009). Both of the cultivars thatwere used here have already been studied regarding the resistanceof D. saccharalis in sugarcane under greenhouse (Dinardo-Mirandaet al., 2012) and field conditions (Dinardo-Miranda et al., 2013).These authors found a significantly higher (>25%) percentage ofbored internodes in SP 89-1115, which is susceptible, than in IAC87-3396.
Our results confirm that Si applied at low rates can increasethe soluble Si of the soil, increase the Si uptake and reduce stalkborer damage when silicate is applied in the furrow at plant-
ing. This method of silicate placement could be used to supplySi at a reduced cost while improving the yield and reducing theD. saccharalis in areas where broadcasting silicate is prohibitivelyexpensive.
Crops
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. Conclusions
Our results demonstrate that it is possible to increase the solublei in the soil, the sugarcane uptake of Si and the sugarcane produc-ivity by applying silicate at planting, with residual effects due to Siupply in soils with high (>80%) sand contents. Although resistantultivars and biological control are used to manage damage fromhe stalk borer D. saccharalis, silicon fertilization in the furrow atlanting may help reduce stalk damage by this pest where suchethods are not used or where silicate is expensive. Therefore, the
lacement of silicate at low rates (<200 kg ha−1 Si) in the furrow atlanting should be considered an alternative method of nutritionalanagement for sugarcane with additional benefits in sandy and
oam sandy soils.
cknowledgments
The authors thank Sao Paulo Research Foundation (FAPESP), Saoaulo (Brazil) for financial support and scholarship (third author)nd Raizen (Costa Pinto Sugar Mill, Piracicaba, Brazil) for provid-ng experimental areas and logistical support in the developmentf this project. We also thank Agronelli Agro-Industry (Uberaba,razil) for providing silicate (Harsco minerals) for these experi-ents.
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