EFFECTS OF NINE CASSAVA-BASED CROPPING SYSTEMS ON SUPERFICIAL SOIL STRUCTURAL DEGRADATION IN THE ANDEAN HILLSIDES OF COLOMBIA

ISCO 2004 - 13th International Soil Conservation Organisation Conference – Brisbane, July 2004
Conserving Soil and Water for Society: Sharing Solutions


EFFECTS OF NINE CASSAVA-BASED CROPPING SYSTEMS ON SUPERFICIAL SOIL
STRUCTURAL DEGRADATION IN THE ANDEAN HILLSIDES OF COLOMBIA

C. ThierfelderA, E. Amèzquita C.B, and K. StahrA
A University of Hohenheim, Department of Soil Science, 70593 Stuttgart, Germany.
christian.thierfelder@debitel.net
B Centro Internacional de Agricultura Tropical (CIAT), A.A. 6713 Cali, Colombia, e.amezquita@cgiar.org.

Abstract
Soil erosion is increasing in Latin America. This study was conducted to determine the influence of nine long-term
cropping systems on Andean hillside soil; specifically the degradation of soil structure. During the course of
studying each soil treatment, resulting changes in soil properties and their effects on water infiltration and crop
yield were recorded. The effects of soil crusting and sealing were investigated during the period Jan 2000 - Dec
2001 in southwest Colombia. Physical parameters such as penetration resistance, shear strength, and infiltration
capacity, as well as chemical parameters such as nutrient content, soil reaction, organic matter content and
electrical conductivity were analyzed. Two types of soil crusting were observed during the project. One occurred
due to splash impact of raindrops on barely covered soil surfaces. The second occurred due to excessive application
of chicken manure. A seasonal increase in penetration resistance and shear strength in some treatments did not
necessarily lead to restrictions in water infiltration. A nutrient-rich minimum tillage treatment, which displayed the
highest penetration resistance of up to 46.4 kg cm-2 during the dry periods, presented no restricting effects on soil
water intake (76.2 mm h-1 final infiltration in 2000) due to an optimal aggregate development during 14 years of
cultivation. Measurements of physical and chemical properties showed that conservative soil treatments, like
minimum tillage and crop rotations, improved soil structure and prevented the development of soil crusting with its
associated negative effects on infiltration and yield. In contrast, treatments with destructive soil use, including the
application of high amounts of chicken manure, were characterized by the highest reduction of infiltration due to
soil crusting.

Additional Keywords: crusting, penetration resistance, infiltration, aggregation, conservation, erosion

Introduction
Soil erosion is a major global issue because of its adverse effects on sustainability. In Latin America, the reasons
behind increasing soil erosion are twofold: climatic circumstances coupled with inappropriate land-use and
mismanagement of soils, especially on marginal hillsides (Oldeman et al., 1990). Many researchers have identified
soil crusting and sealing as a primary factors in soil erosion (Callebaut et al., 1985). However, the impact of long-
term cropping systems on the degradation of soil structure in South America have received minimal scientific
attention (Roth, 1992). Therefore the aim of this study was to acquire a basic understanding of the impact of nine
Andean cassava-based cropping systems on the development of soil crusting and sealing, and its effects on nutrient
content, water infiltration and cassava (Manihot esculenta C.) -yield.

Materials and Methods
Research site and treatments
Field research was conducted from January 2000 to December 2001 in Santander de Quilichao at the CIAT
Research Station, Department of Cauca in southwestern Colombia (3°6'N, 76°31'W, 990 m.a.s.l.). Precipitation
reached 2207 mm a-1 in 2000 and 1384 mm a-1 in 2001. Trials were installed on 27 Wischmeier- plots on a ferralic
Cambisol (WRB, 1998) developed from fluvially translocated volcanic ashes.

The treatments are summarized below:
T1 Bare fallow; continuously clean tilled, no fertilizer, and no crop
T2 Cassava (Manihot esculenta Crantz) with chicken manure; All cassava treatments consisted of variety CIAT
523-07 in 2000 and CIAT 383 in 2001; planted as a sole crop and all planted 1 by 0.8 m (12,500 plants per ha),
rototiller treatment, 4t ha-1 chicken manure
T3 Cassava; as a sole crop in monoculture, rototiller treatment, no fertilizer
T4 Cassava; as a sole crop in minimum tillage, no rototiller, 300 kg ha-1 mineral fertilizer
T5 Cassava; with chicken manure, as a sole crop, rototiller treatment, 8t ha-1 chicken manure
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ISCO 2004 - 13th International Soil Conservation Organisation Conference – Brisbane, July 2004
Conserving Soil and Water for Society: Sharing Solutions


T6 Cassava; with chicken manure, as the main crop with Vetiver grass (Vetiver zizanioides L. Nash; CIAT No.
26898) as a double row life barrier occupying 12,5% of the plot area, rototiller treatment, 4t ha-1 chicken
manure
T7 Cassava; as the main crop (1 by 0.8 m, 12,500 plants per ha) intercropped with Chamaechrista rotundifolia
Stapf, rototiller treatment, and 300 kg ha-1 mineral fertilizer
T8 Cassava; as a sole crop, in rotation with Bracchiaria decumbens Benth. and Centrosema macrocarpum Stapf,
300 kg ha-1 mineral fertilizer
T9 Cassava; as a sole crop, with intensive rototiller treatment, 300 kg ha-1 mineral fertilizer

Before planting all cultivated treatments were fertilized and limed. Dolomitic lime was applied at a rate of 500 kg
ha-1. The mineral fertilized treatments were fertilized at a rate of 300 kg ha-1 (10N-30P205-10K2O). All chicken
manure plots received 4 t (8 t) ha-1 at the beginning of each cropping season. The nutrient contents consisted of: N:
3.2 %, P: 3.4 %, K: 4.1 %, Ca: 6.1 %, Mg: 1.0 %, Fe: 0.2 %, Mn: 0.6 %, Na 0.5 % in 2000 and N: 2.5 %, P: 3.4 %,
K: 3.3 %, Ca: 11.8 %, Mg: 1.0 %, Fe: 0.4 %, Mn 0.5 %, Na 0.4% in 2001

Tools and methods
Soil crusting dynamics were investigated from both physical and chemical perspectives. Physical soil analysis
consisted of weekly measurements with a Penetrometer (Daiki Soil and Moisture Sensors, Model DIK-5560)
described by (Bradford, 1986) and shear strength measurements with a hand vane tester (Torvane, Model EL26-
3345). Infiltration was measured with a mini-rain-simulator described by (Amézquita et al., 1999) suitable for
infiltration measurements in marginal remote areas. Infiltration was measured in April/May and October/November
in 2000 and 2001 by irrigating a defined soil surface area with a distinct amount of rain (90 mm h-1). The difference
between rain amount after 50 min and total run-off was defined as infiltration. Chemical soil analysis consisted of
soil reaction, organic matter, nutrient content, and cation exchange capacity. Yield was measured by weighing fresh
cassava roots after harvest. For statistical analysis, ANOVAS were tested following the General Linear Model with
SPSS as statistical software. To separate significant means the Tuckey’s test was applied.

Results and Discussion
All nine treatments were grouped into three categories to evaluate specific aspects of investigation, such as the
impact fertilization on soil crusting, the influence of conservation systems on structural development, and the
effects of different tillage treatments on soil structure and system stability. The manure group included T2, T3, and
T5. The conservation group consisted of T6, T7 and T8. The tillage group included T1, T4, and T9. The cassava
chicken manure treatments (T5, T6, and partly T2) demonstrated seasonal structural changes in both years (Table 1
and 2). In the major rainy seasons (March-May 2000 and 2001), no penetration and shear strength restrictions were
investigated. In contrast, in both dry seasons (June-September 2000 and 2001) its superficial soil structure altered
under field conditions and changed from a well-structured soil to a superficially crusted soil.

In general, chicken manure treatments in both years revealed chemical dispersion of clays during the cropping
cycle, this was clearly observed in the field (especially in T5 and T6). It started with a dispersion phase during the
first rainy season (March-May) and ended with a strong crusting phase (June-August). Similarly, the treatments
with bare soil surfaces (T1 and T3) displayed strong slacking during the rainy seasons and consequently formed
strong soil crusts, especially in 2000. This followed the observations of various authors (Callebaut et al., 1985) and
resulted in a strong increase in soil erosion (data not presented here). A minimum tillage treatment (T4) showed the
most significant increase in penetration resistance and shear strength, which did not result in major infiltration
restrictions (Table 3). Infiltration was significantly lowest in the chicken manure treatment (T5) and in the
monoculture treatment (T3).

Chemical soil analysis (Table 4) showed the highest pH, organic matter (OM) and nutrient content in the minimum
tillage treatment which can be attributed to the beneficial effect of mulching, as also found by Derpsch et al.
(1986). Bare fallow and monoculture led to a strong decrease in pH and OM as well as the exchangeable cations.
Only Al was very high in T1 and T3.

Yield was significantly influenced by precipitation amount. Highest yield was achieved in T8, T2, and T4 in 2000
the year with increased precipitation, while T3 and T9 revealed significantly lower yields. In 2001, T4 could best
resist the dryer soil circumstances and maintain root yield at a high level, while others (i.e. T2, T6 and T7)
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ISCO 2004 - 13th International Soil Conservation Organisation Conference – Brisbane, July 2004
Conserving Soil and Water for Society: Sharing Solutions


experienced a severely reduced yield due to water scarcity and increased competition for resources between
cassava and its intercropped plants (Ruppenthal, 1995).

Table 1. Impact of climatic season on penetration resistance (in kg cm-2) in grouped treatment systems
(March-May and Juni-August 2000 and 2001), Santander de Quilichao, Colombia
Group Treatment
2000

2001


Rainy
Dry
Rainy
Dry
season
season
season
Season
Manure
Cassava 4 t ha-1 chicken manure (T2)
3.2 a1
9.2 ab

2.1 a
4.6 a
Cassava
monoculture
(T3)
3.1 a
6.7 a

2.2 a
4.3 a

Cassava 8 t ha-1 chicken manure (T5)
3.5 a
12.3 b

2.4 a
7.8 b
Conservation
Cassava 4 t ha-1 ch. manure (V) (T6)
3.6 b
11.8 a

2.1 a
5.3 a
Cassava
+
Cham. rotundifolia (T7)
3.5 ab
9.4 a

2.5 ab
4.8 a

Cassava rotation (T8)
2.6 a
9.8 a

2.6 a
7.5 b
Tillage
Bare fallow (T1)
5.2 b
9.7 a

1.7 a
3.7 a

Cassava minimum tillage (T4)
5.5 b
28.5 b

5.3 b
24.0 b

Cassava intensive tillage (T9)
2.9 a
4.2 a

1.9 a
3.7 a
1 Means followed by the same letter in column are not significantly different at p?0.05 probability level, Tuckey-Test


Table 2. Impact of climatic season on shear strength (kPa) in grouped treatment systems measured (March-
May and Juni-August 2000 and 2001), Santander de Quilichao, Colombia
Group Treatment
2000

2001

Rainy
Dry
Rainy
Dry
season
Season
season
season
Manure
Cassava 4 t ha-1 ch. manure (T2)
15.6 a1
30.4 a
15.3 a
37.2 a
Cassava
monoculture
(T3)
16.9 ab
28.5 a
15.4 ab
33.9 a

Cassava 8 t ha-1 ch. manure (T5)
17.3 b
36.0 a
16.81 b
48.6 b
Conservation
Cassava 4 t ha-1 ch. m. (V) (T6)
17.0 b
34.1 a
16.6 a
42.0 a
Cassava
+
Cham. rotundifolia (T7)
15.4 a
30.3 a
17.8 a
40.4 a

Cassava rotation (T8)
14.6 a
30.6 a
19.6 b
60.8 b
Tillage
Bare fallow (T1)
20.5 b
35.9 b
13.6 a
28.2 a

Cassava minimum tillage (T4)
22.9 c
53.2 c
41.5 b
78.1 b

Cassava intensive tillage (T9)
14.9 a
21.9 a
13.7 a
27.9 a
1 Means followed by the same letter in column are not significantly different at p?0.05 probability level, Tuckey-Test

Table 3. Impact of treatment on infiltration (mm h-1), measured in April/May and October 2000 and 2001,
Santander de Quilichao, Colombia
No Treatment
2000
2001

Infiltration
Standard
Infiltration
Standard

after 50 min
Deviation
after 50 min
deviation

(mm
h-1)

(mm h-1)
T1 Bare
fallow
52.1 a1
18.2 54.2
ab1
6.8
T2
Cassava 4 t ha-1 chicken manure
54.8 a
19.1
63.9 bcd
15.2
T3 Cassava
monoculture
42.7 a
16.2
38.8 a
6.2
T4 Cassava
minimum
tillage
76.2 a
16.2
87.4 d
6.5
T5
Cassava 8 t ha-1 chicken manure
42.2 a
11.4
36.1 a
15.2
T6
Cassava 4 t ha-1 chicken manure (V)
49.6 a
15.9
59.3 abc
11.9
T7 Cassava
+
Chamaecrista rotundifolia
56.6 a
23.2
78.0 cd
9.9
T8 Cassava
rotation
70.9 a
16.4
83.9 d
4.5
T9
Cassava intensive tillage
46.5 a
11.3
43.2 ab
12.6
1means followed by the same letter in column are not significantly different at p?0.05 probability level, Tuckey’s Test


Conclusions
The study of physical and chemical soil properties in nine cassava-based cropping systems revealed that
conservative soil treatments, like minimum tillage and crop rotations, improved soil structure and prevented the
development of soil crusting with its associated negative effects on infiltration and yield. In contrast, treatments
with destructive soil use (T1 and T3, T9), including the application of high amounts of chicken manure (T5 and
T6), were characterized by the highest reduction of water infiltration and yield due to soil crusting.

Acknowledgements
The authors want to thank the German Academic Exchange Service (DAAD), the Eiselen Foundation, and the
German Agency for Technical Cooperation (GTZ) for financial help.
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ISCO 2004 - 13th International Soil Conservation Organisation Conference – Brisbane, July 2004
Conserving Soil and Water for Society: Sharing Solutions



Table 4. Influence of treatment on exchangeable and soluble nutrients in the surface horizon, at 0–5 cm
depth, 2000 and 2001 in Santander de Quilichao
Treatments in 2000
pH
OM

N
P

K
Ca
Mg
Al

CECe



(%)
mg
kg-1
cmol
kg-1
cmol kg-1
T1 Bare
fallow
4.3 a
5.6 a
1670 a1
-

0.1 a
0.2 a
0.1 a
4.7 d

5.0 a
T2
Cassava 4 t ha-1 chicken manure
5.2 cd
6.5 ab
2320 b
-

0.3 c
4.4 c
1.5 c
0.5 a

6.7 c
T3 Cassava
monoculture
4.9 b
6.5 ab
2231 b
-

0.2 b
2.1 b
0.9 b
1.8 c

5.0 a
T4 Cassava
minimum
tillage
5.4 d
6.8 bc
2611 c
-

0.4 c
6.5 d
1.6 d
0.3 a

8.7 d
T5
Cassava 8 t ha-1 chicken manure
4.9 b
6.5 ab
2348 bc
-

0.4 bc
2.3 b
0.9 b
1.7 c

5.3 a
T8 Cassava
rotation
5.0 bc
6.4 ab
2436 bc
-

0.3 b
4.1 c
0.9 b
0.9 b

6.2 b
Treatments in 2001












T1 Bare
fallow
3.8 a
4.8 a
2275 a1
5.4 a

0.1 a
0.3 a
0.1 a
3.9 c

4.5 a
T2
Cassava 4 t ha-1 chicken manure
4.7 d
6.1 bc
2721 a
47.1 b

0.3 b
4.8 d
1.5 c
0.4 a

6.9 d
T3 Cassava
monoculture
4.3 b
5.7 b
2532 a
17.2 ab

0.2 a
2.3 b
0.8 b
1.9 b

5.1 b
T4 Cassava
minimum
tillage
5.2 e
7.1 d
2896 a
49.1 b

0.4 c
6.7 e
1.9 d
0.3 a

9.2 e
T5
Cassava 8 t ha-1 chicken manure
4.6 c
6.0 bc
2537 a
48.5 b

0.3 bc
2.7 b
0.9 b
1.8 b

5.8 c
T8
Cassava rotation
4.4 c
6.1 bc
2654 a
38.9 ab

0.2 a
3.6 c
0.8 b
1.5 b

6.1 c
1means followed by the same letter in column are not significantly different at p?0.05 probability level, Tuckey’s Test

Table 5. Influence of land use option on cassava fresh root yield in long-term cassava cropping systems,
Sanatander de Quilichao, Colombia
No
Treatment
2000

2001


Yield (t ha-1)1
S.D.

Yield (t ha-1) S.D.
c
T2
Cassava 4 t ha-1 chicken manure
30.92 c
6.23
19.94 b
4.36
T3 Cassava
monoculture
4.33 a
1.01
11.39 a
3.47
T4 Cassava
minimum
tillage
27.01 c
6.86
22.51 b
0.97
T5
Cassava 8 t ha-1 chicken manure
23.17 bc
4.30
20.20 b
1.82
T6
Cassava 4 t ha-1 chicken manure (V)
21.90 bc
0.63
7.94 a
1.43
T7 Cassava
+
Chamaecrista rotundifolia
21.05 bc
2.69
6.79 a
1.57
T8 Cassava
rotation
30.58 c
2.67
n.a.
n.a.
T9
Cassava intensive tillage
11.98 ab
3.45
19.46 b
1.07
1 Yield values followed by the same letter are not significantly different at P?0.05 (Tuckey’s HSD-test).


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