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Agronomy
THE EFFECTS OF THE METHOD OF LAND PREPARATION
ON THE GROWTH AND YIELD OF SUGARCANE IN
FINE-TEXTURED VERTISOLS AND INCEPTISOLS IN THE
CAUCA VALLEY, COLOMBIA
Sun Jen Yang and Rafael Quintero D.
Colombia Sugar Cane Research Institute
I
ABSTRACT
The objective of this study was to find an effective but also economicalmethod of seed-bed preparation for sugarcane. The experiment was
conducted on lnceptisol (Palmeras series), and Vertisol (Galpon series) in
the Cauca Valley, Colombia. There were six treatments which involved
subsoiling, chiselling, heavy disking and light harrowing. The time required
for each operation was recorded and after the completion of the tredtment
the depth and the degree of soil disturbance achieved by the operations
were measured. Cane growth was measured periodically and the yields of
cane and sugar were determined at the time of harvest. To observe residual
effects, the trials were continued but only light cultivation was applied to
the first ratoon crops. The results indicated that subsoiling produced the
deepest soil penetration and the greatest degree of soil disturbance followed by chiselling, while disking had the least effect. The differences in the
amount of soil disturbance between the treatments were smaller six months
after the operations were carried out. No significant differences were found
between the treatments in terms of cane growth, nutrient uptake and final
yields for both plant and ratoon crops. Traditional land preparation includes
cross subsoiling, cross disking and harrowing but it is suggested that cross
chiselling plus harrowing would be more economically effective.
INTRODUCTION
In Colombia centrifugal white sugars are produced mainly in the Cauca Valley
where a total of 135,000 ha of land are cultivated to produce 1.2 million tonnes
of cane sugar annually. The soils on sugarcane plantations belong mainly to four
orders : Mollisols, Inceptisols, Vertisols and Alfisols. Most of these soils are fine
textured with 2:l clay minerals, (IGAV-CVC5).
Tillage operations are important not only to produce good soil conditions for
cane growth, but they also affect the costs of production significantly. On most
sugar estates in the Valley, the standard practices for land preparation are crossdeep subsoiling, disking, harrowing and ridging. Subsoiling is a costly operation,
needing high tractor power.
Keywords: Land preparati'on, fine textured soil, soil disturbance
SUN JEN YANG AND RAFAEL Q W R O D.
The effectiveness of this practice is dubious because the soils have good physical
characteristics. When the price of sugar reaches the low level that it has reached
today, it is essential to reduce the cost of cultural practices as much as possible whilst
affecting yields as little as possible. The purpose of this study was to compare
standard land preparation methods with other simplified methods in fine-textured
Vertisols and Inceptisols.
MATERIALS AND METHODS
The field experiments in this study were conducted on two soils, a Palmeras
clay loam (Vertic Ustropept) and a Galpon clay (Tipic Pellustert). Important physicochemical properties of these two soils are shown in Table I. The Palmeras clay loam is
an Inceptisol with a sub-angular blocky structure in the surface 50 cm of soil, and
the bulk density is relatively high. It has weak acidity and a medium level of fertility.
This soil is located extensively in the southern part of the Cauca Valley. The internal
drainage is generally poor because of a high water table. The Galpon clay is a Vertisol
with a very fine texture. The soil depth generally exceeds 80 cm and a well developed
sub-angular blocky structure can be observed in the surface 70 cm layer. The soil
is compacted, the density being relatively high before treatment. Drainage is
moderately good and the level of the water table ranges between medium and low.
It is weakly acid to neutral, has a medium organic matter content and low phosphorus
and high potassium contents in the top soil. The Galpon soil series is widely distributed in the Valley, but is concentrated mainly in the north. The two soils studied contain
high percentages of 2:l expansion clays which are mainly Montmorrilonite and
Vermiculite. The treatments used involved four operations : subsoiling, chiselling,
heavy disking and harrowing. Details of the treatments are shown in Table 11. The
experiment was arranged in a randomized complete block design with three replications. The area of each plot varied between 0.3 and 0.9 ha, depending on the site.
Old stools were eradicated and land levelling was practised before the treatments
were imposed. All the treatments were carried out during the dry season and because
the soil moisture was low, conditions were suitable for land preparation. The subsoiling was conducted with a three-shank subsoiler, the shanks being 75 cm apart. It
was drawn by a D6 Caterpillar or a Steiger tractor. Chiselling was carried out with
a 5-shank ripper drawn by a Caterpillar D5 at San Carlos sugar mill and by a wheel
TABLE II. TREATMENTS USED FOR LAND PREPARATION
Soil
Series
Palmeras
I
I
(Vertic
Ustropept)
Galpon
(Typic Pellustert)
TREATMENTS USED
+
1. subsoiling (2)
disking (1) + harrowing (2)
harrowing (2)
2. Subsoiling (2) + chiselling (1)
3. Disking (2)
harrowing (2)
4. Chiselling (2)
harrowing (2)
harrowing (2)
5. Subsoiling (1)
6. Plowing + harrowing (2)
+
+
+
+
tractor at Cauca sugar mill. The tines were 55 cm apart. Twelve disks 90 cm apart
were used for heavy disking, the implement being drawn by a D6 Caterpillar at
Cauca mill and by 250 HP Steiger at San Carlos.
All the harrowing was conducted with an implement made up of 24 disks 65
cm apart drawn by a wheel tractor. For cross subsoiling and chiselling, the two
passes were made at an angle of 15" to 20". When conducting the treatments, the
time required for and the cost of each operation were recorded and the penetration
depths achieved by the implements were observed.
After the completion of all the treatments, cane variety C P 57-603 was planted.
The methods of fertilization, weed control, irrigation and other cultural practices
were those followed conventionally by the sugar mills. Two months after land preparation was completed, soil cores were taken from each 10 cm or 20 cm layer in
the surface 60 cm of soil in each plot to determine soil bulk densities. T o evaluate
the effects of treatments on cane growth, populations were counted and stalk length
was measured when the crops were 3 and 6 months of age. Top Visible Dewlap
(TVD) leaves were sampled at 6 months to determine any effects on nutrient uptake.
The leaf samples were dried, ground and analyzed for N, P , K, Ca and Mg. Rooting
characteristics were observed by exposing the roots in the surface 80 cm of soil when
the crop was 6 months old.
The crops were harvested at 14 months of age and the number and the length of
millable stalks, and the cane and sugar yields were determined. To observe the
residual effects of land preparation practices, the experiments were continued into
the first ratoon crops. Only light cultivations were conducted after harvest of the
plant crops to avoid unnecessary disturbance of the soil. The growth nutrient uptake
and final production of the crop in each treatment of the first ratoon were measured.
EXPERIMENT RESULTS
The depth of penetration of each implement, the time required and the cost
for each operation are shown in Table 111. Because the two sugar mills had different
tractors and implements, the times required and the costs were not directly comparable. In general, subsoiling produced the deepest penetration and the largest
amount of soil disturbance, followed by chiselling, and disking or harrowing had
the least effect. Soil bulk densities measured two months after treatment showed
a similar trend (Table IV). It was apparent that when soil moisture content was
low, subsoiling produced the greatest shattering effect, loosening any compact soil
layers. However, subsoiling was an expensive operation taking more time and costing
more per unit area than the other operations. Unless the increase in cane production
due to subsoiling compensates for the cost. the operation would not be economically
justifiable.
When the plant crop was six months old, root distribution was observed and
growth measurements were conducted. The results indicate that in all the treatments
most roots were conxentrated in the surface 30 cm layer directly under the cane
stool. Only a few roots were found at depths below 30 cm or midway between two
furrows.
124
TABLE IV.
AGRONOMY
EFFECT O F DIFFERENT METHODS OF LAND PREPARATION O N
SOIL BULK DENSITY TO A DEPTH OF 50 CM TWO MONTHS
AFTER TREATMENT
Bulk density (glcm3)
TREATMENT
0-10 cm10-20 cm20-30 cm30-40 cm40-50 cm
(Table II)
Site
Hda. La Cecilia
I. Cauca
1.
2.
3.
4.
5.
6.
Hda. Campo Alegre
I. San Carlos
1.
2.
3.
4.
5.
6.
TABLE V.
EFFECTS OF DIFFERENT LAND PREPARATION METHODS O N
GROWTH AND LEAF NUTRIENT CONTENTS O F PLANT CANE 6
MONTHS OLD.
Site
TREATMENT
(Table II)
Hda. La Cecilia
I. Cauca
1.
2.
3.
4.
Hda. Campo Alegre
I. San Carlos
1.
2.
3.
4.
5.
6.
*'I
5
,
Population
(1031ha)
Stalk
length
(cm)
63
65
63
61
176
173
180
174
2.10
2.09
1.99
2.12
0.17
0.17
0.16
0.17
1.06
1.13
1.12
1.20
75
73
69
71
76
71
160
159
166
165
160
156
2.22
2.08
2.09
2.11
2.11
1.94
0.25
0.27
0.26
0.24
0.25
0.24
1.38
1.32
1.27
1.24
1.33
1.33
TVD leaf nutrient
NO/o P % K %
At both sites, the treatment involving cross subsoiling and disking caused the
amount of roots in the surface 20 cm to 30 cm soil layer of soil under the stool
to be greater than in the other treatments. There was not a consistent indication
that rooting was correlated with the depth to which an implement penetrated the soil.
I
t
I
125
SUN JEN YANG AND RAFAEL QUINTERO D.
TABLE VI.
EFFECT OF METHOD O F LAND PREPARATION ON CANE AND
SUGAR PRODUCTION IN THE PLANT CROP
Site
Hda. La Cecilia
I. Cauca
TREATMENT Millable
(Table II)
Stalks
(1031ha)
1.
2.
3.
4.
5.
6.
64.5
65.7
64.3
60.6
65.3
62.8
NS
Stalk
length
(cm)
284
29 1
286
279
291
295
NS
Cane
Sugar yield
yield
(tonslha)
(tonslh a)
142
137
139
139
135
135
NS
15.3
16.0
16.4
15.9
16.3
14.8
NS
Hda. Campo Alegre
I. San Carlos
There were no statistically significant differences in population stalk length or
leaf nutrient contents of the plant crop at both sites following the different soil
treatments (Table V). Since treatments did not affect the growth or the nutrient
uptake of the crops, it is not surprising that no significant differences in cane and
sugar yields due to land preparation were observed (Table VI). However, the
traditional method of cross subsoiling plus disking or chiselling did produce slightly
higher cane yields than the other treatments. The disk plowing treatment, on the
other hand, caised the yields to be lowest.
After the plant crops were harvested, the experiments were maintained using
light cultivation during the first ratoon in order to observe any residual effects of
land preparation. The results of growth measurements conducted when the crop
was six months old indicate that, as in the plant crop, no statistically significant
differences between treatments could be observed (Table VII). The N contents of
the leaves were a little lower than in the plant crop, but there were no statistically
significant differences in leaf nutrient contents between the treatments.
The harvest results shown in Table VIII indicate that n o significant differences
between treatments were found in number and length of millable stalks and cane
and sugar yields of ratoon crops. However, the treatments associated with subsoiling
still had a slightly higher production and disk plowing had the lowest.
DISCUSSION
In many sugarcane producing areas of the world, deep tillage, which can be
achieved by plowing, subsoiling or chiselling, is believed to be necessary to produce
126
AGRONOMY
TABLE VII.
RESIDUAL EFFECTS OF METHOD OF LAND PREPARATION ON THE
GROWTH AND LEAF NUTRIENT CONTENTS OF FIRST RATOON
CANE SIX MONTHS OLD
Site
TREATMENT Popula(Table II)
tion
(1031ha)
(Cecilia 6)
I. Cauca
N
%
P
%
K
O/O
Ca
%
Mg
%
1.
2.
3.
4.
5.
6.
I
(Campo Alegre 7)
I. San Carlos
TABLE VIII.
Stalk
length
(cm)
1.
2.
3.
4.
5.
6.
RESIDUAL EFFECTS OF LAND PREPARATION METHODS ON
THE YIELDS OF THE FIRST RATOON CROP
Site
TREATMENT
(Table II)
Millable
stalks
(1031ha)
~ta%
~e"~th
(c$)
Hda. La Cecilia
I. Cauca
I.
69.9
242
Hda. Campo Alegre
I. San Carlos
1.
2.
3.
110.3
104.0
100.8
251
239
248
Cane
yield
(tonslha)
Sugar
yield
(tonslha)
110
17.1
I
SUN E N YANG AND RAFAEL Q W R O D,
127
high crop yields. The purpose of deep tillage is to break up compact subsoil layers
or hard pans to permit deep root penetration. However, the effectiveness of deep
tillage varies from soil to soil, from place to place and from year to year. The need
for deep tillage, therefore, has been questioned for more than 50 years.
SavesonI3 reported that deep ploughing and subsoiling produced the greatest
increase in sugarcane yields on fine sandy loams and silty loams, but no responses
were obtained on silt loams and clay alluviums. Ricaud12 conducted experiments
on Commerce silt loam soils in Louisiana and found that a 19% to 40% increase
in cane yield resulted due to subsoiling. Deep tillage in a Pullman clay loam (Torrectic
Paleustrolls) in the Southern High Plains of the U.S. increased water intake and
storage in the soil profile, leading to higher yields of wheat, sorghum and corn
) ) Taiwan,
.
subsoiling to a depth of 45 cm increased
(Musick8, Musick and ~ u s e k ~In
cane yield 20% to 30% in the plant crop in comparison with the conventional shallow
tillage of 30 cm in unirrigated clay soil, but the residual effect lasted only to first
ratoon, no increase being observed thereafter (Chengl).
Subsoiling has been used widely on Hawaii sugarcane plantations. The main
purpose is to reduce surface erosion and runoff in non-irrigated areas. In irrigated
areas, subsoiling is employed prior to plowing in order to obtain better penetration
and granulating action of disk plows (Trouse and Humbert14). Plowing and subsoiling to depths up to 100 cm have been tested on 10 different soil series in the
South African sugar industry. The results obtained indicate that deep tillage did
not produce better cane yield than the conventional plowing to a depth of 20 cm
~ , ~Pearsonu).
to 25 cm ( M ~ b e r l y and
Experimental results obtained from Brazil ( ~ e r n a n d e s ~show
, ~ ) that subsoiling
was effective only on soils with compact layers. On a dark Latosol, subsoiling to
a depth of 60 cm to 70 cm actually caused cane production to decrease.
The results obtained in this study show that different methods of land preparation did not produce signfficant differences in cane and sugar yield on an Inceptisol
and a Vertisol in the Cauca Valley. Both Inceptisols and Vertisols are fine textured
soils with well-developed sub-angular blocky structure in the surface 45 cm to 70
cm soil layer. Although the bulk densities of the soils are high, cracks between
structural units are sufficient for water to enter and for the exchange of air between
soil and atmosphere. They also provide channels for root growth. Furthermore,
more than 90% of sugar cane plantations in the valley are irrigated, and the main
purposes of deep tillage fall away under such conditions.
Fine textured soils generally maintain a high moisture content, especially during
the rainy season and they have a high water table level, which is common in the
valley. Subsoiling or chiselling in a moist or wet soil has no shattering effect to
loosen the soil. On the contrary, there may be a puddling action which tends to
seal the grooves made by the shoe of an implement (Baver2). As reported by Trouse
and Humbert14 from Hawaii, shear plane development in a wet soil was obtained
to a depth of less than 15 cm and plastic flow shear extended for the rest of the
depth of subsoiling. As a result, rain or irrigation water ran into the subsoiler paths
and accumulated there, causing poor local aeration and drainage.
I
128
AGRONOMY
Cost is another important factor to be considered in deciding on the method
of land preparation. Deep tillage uses a lot of power. Nichols and Reeves1° pointed
out that the major factor in power requirement is the horizontal pressure of the
implemerlt against the soil, which increases the force required for fragmentation
or shear. When soil is dry and suitable for subsoiling, power consumption is high
because of large cohesive forces. In the Cauca Valley, subsoiling is done mostly
by high power Caterpillar crawler tractors or Steiger 250 H.P. tire tractors. The
cost of a standard land preparation which includes cross subsoiling, disking and
harrowing is 25% to 80% higher than the simplified method of cross disking or
chiselling plus harrowing. Since deep tillage did not increase yields significantly,
the extra costs are considered to be unwarranted.
CONCLUSION
The deep tillage of soils of fine texture with well-developed structure in the
Cauca Valley is considered to be unnecessary. At all events, subsoiling should not
be used universally without regard to the soil properties. The standard land preparation method of cross subsoiling, cross disking plus harrowing has not only low
efficiency as far as operating time is concerned, but it is also costly. The practice
should be used only in soils where root development and water movement are restricted by dense compact layers in the profile. For soils without restrictions, cross disking
plus harrowing can be used instead to maintain good soil tilth to a depth of 25 cm
to 35 cm. When preparing land during the dry season in some soils where the surface
layer is very hard, one pass of a subsoiler may be added in order to achieve the
desired depth of tillage by disking.
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~,
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129
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