Journal of Experimental Biology and Agricultural Sciences, January - 2014; Volume – 1 (7 - Special Issue on soil and water management in agriculture)
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
ISSN No. 2320 – 8694
EFFECT OF PLANTING METHODS ON GROWTH AND YIELD OF CASSAVA
(Manihot esculenta Crantz) GROWN WITH POLYTHENE-COVERING
Abdullahi N1, Sidik J B2, Ahmed O H1* and Zakariah M H3
1
2
3
Department of Crop Science, Faculty of Agriculture and Food Sciences, Universiti Putra Malaysia Bintulu Sarawak Campus, 97008 Bintulu, Sarawak, Malaysia.
Department of Animal Science and Fishery, Universiti Putra Malaysia,Bintulu Sarawak Campus, 97008 Bintulu, Sarawak, Malaysia.
Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia.
Received – February 06, 2013; Revision – July 21, 2013; Accepted – December 15, 2013.
Available Online- January 15, 2014.
KEYWORDS
Planting methods
Yield components
Storage roots yield
Cassava (Manihot esculenta)
Polythene-covering
ABSTRACT
Cassava and Sago constitute the main sources of starch in South East Asia. The production of these
starchy plants is in declining due to the problem of low yield, high labor cost, pest and diseases damage,
and shortage of land. These production bottlenecks forced Malaysia to import cassava roots from
neighboring producer countries. One simple method to enhance cassava productivity is incorporating
polythene-covering in agriculture. Present research was carried out to reveal information on the effect of
planting methods on some yield attributes in cassava grown with polythene-covering. The involving
factors are three cassava varieties, three planting methods, and four black polythene-covering types. The
planting methods evaluated were: (і) vertical planting forming 90 0 angles with ridges, (іі) incline
planting forming 45 0 to 600 angles with ridges, and (ііі) horizontal planting forming 180 0 angles with
ridges. Significant differences among planting methods in all variables tested were observed. Horizontal
and incline plantings were the most efficient in terms of leaf longevity with leaf fall reduction of 49.17%
as compared to vertical planting. However, vertical planting recorded the maximum leaf area index of
3.73 per plant. The mean storage roots number of 17.44 per plant obtained in incline planting was the
highest. Regardless of variety, the effect of incline planting in terms of fresh storage roots yield was the
highest (yields of 20.12 to 32.99 t ha -1). This investigation suggests that storage roots yield of cassava
could be enhanced by planting cuttings in an incline position with polythene-covering. Farmers
interested in vertical planting could incorporate polythene-covering at day 1 after planting.
* Corresponding author
E-mail: [email protected] (Ahmed O H)
Peer review under responsibility of Journal of Experimental Biology and
Agricultural Sciences.
Production and Hosting by Horizon Publisher (www.my-vision.webs.com/horizon.html).
All_________________________________________________________
rights reserved.
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
Ahmed et al
481
1 Introduction
Cassava (Manihot esculenta) is a member of the family
Euphorbiaceae. It is an important crop of Africa, Asia, and
Latin-America (Ravi et al., 1996). Storage root have high
starch content (89%) (Silvestre, 1989). The leaves and tender
shoots are important sources of vitamins, minerals, and
proteins (Balagopalan, 2002; Nweke et al., 2002). Starch of
cassava has wide industrial applications. It is extensively used
in the manufacture of adhesive, dextrines, food paste and as
filler in the manufacture of paints (Godfrey et al., 2012).
Cassava crop is well known for its adaptation to poor soils
conditions, and responds well to better management practices.
It is also resistant to drought (Chantaprasan and Wanapat,
2003). The most common methods of cassava propagation is
stem cuttings and sexual seed, but propagation by stem
cuttings is mostly the commonest practice. There exists
conflicting reports about the appropriate cutting orientations.
As par Oguzor (2007) report vertical method of planting
cassava gave the best sprouting percentage of 88.8% than
horizontal and inclined planting. According to their report
there is no significant difference on the number of germinated
nodes among the planting methods. Mbah et al. (2008)
reported higher tuber yield in vertical and inclined positions
compared to horizontal method. Keating et al. (1988) reported
that planting method did not have significant effect on growth
and yield of cassava.
Cassava was first introduced into Malaysia in 1836 through
Jakarta, Indonesia (Burkill, 1936), as a possible substitute for
sago, which has a long growing period of 10 – 15 years before
it can be harvested. Problems of low yield, high labor cost,
pest, and diseases render cassava production unprofitable,
resulting in continuous but increasingly import of cassava roots
from outside Malaysia to meet the national demand. However,
due to the global demand for cassava starch, it is increasingly
difficult to secure sufficient supplies from the main regional
producers such as Thailand, Vietnam, and Indonesia to meet
the needs of the country. Besides varietal improvement
programme and fertilization, adoption of polythene-covering in
cassava agriculture is one of the ways to increase its
commercial yield (Aniekwe et al., 2004). However,
information about the selection of appropriate planting method
for cassava grown with polythene-covering is a pre-requisite
for adoption of this new cropping system. Such information to
the best of our knowledge is unknown. The objective of the
study was to compare the effect of three planting methods on
yield and yield components of three cassava varieties grown
with polythene-covering.
2 Materials and Methods
2.1 Experimental site and soil analysis
This study was carried out at the experimental field of
University Putra Malaysia Campus Bintulu, (3 0 10’N; 1130
2’E) Sarawak, Malaysia from June 2011 to November 2011.
The soil of the experimental area was classified as Bekenu
Series (Ultisols). Bekenu series is a member of the Bekenu
family which is fine loamy, siliceous, isohypherthermic, red
yellow to yellow Tipik Tualemkuts (Paramanathan, 2000). It is
yellow to brownish in colour, deep and well drained. The
rainfall data (mm), minimum and maximum temperatures (°C),
relative humidity (%), and hours of sunshine in Bintulu during
the experimental period are shown in Table 1.
Twenty soil samples were taken at 0 – 15 cm depth using an
augur for physico-chemical analysis. The samples were air
dried, sieved to pass a 2 mm sieve, and analysed for texture
(Tan, 2005), pH (Peech, 1965), total N (Tan, 2005), available P
(Murphy and Riley, 1962), and exchangeable K (Tan, 2005).
2.2 Experimental procedures
The experiment was carried out over a period of 5 months
(June to November, 2011) in a 3 × 3 × 4 factorial in
randomized complete block design with three replications. The
planting methods evaluated were: (і) vertical planting forming
900 angles with ridges, (іі) inline planting forming 45 0 to 600
angles, and (ііі) horizontal planting forming 180 0 angles with
the ridges. These planting methods were tested on three
cassava varieties: (і) Manihot Mardi 92, (іі) Sri Medan, and
(ііі) Sri Pontian in four above-ground stem polythene-covering
types at; 0, 1, 30, and 60 days after sowing.
Table 1 Selected meteorological data at Bintulu during the experimental period, June 2011 to December, 2011.
June
July
August
September
October
November
December
Maximum Temp.
(°C)
Minimum
Temp. (°C)
Rainfall (mm)
Relative Humidity
(%)
Sun Shine hours
(Ohms)
31
31
31
31
31
30
29
24
24
24
24
24
24
24
282
239
287
312
371
409
455
63.7
64.1
62.4
64.2
66.5
67.2
68.5
6.3
7.0
6.1
5.2
5.2
6.2
4.4
(Source: whether Online, 2013)
_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
Effect of Planting Methods on Growth and Yield of Cassava (Manihot esculenta Crantz) Grown with Polythene-covering.
482
Table 2 Mean ± SE of Selected physico-chemical characteristics of Bekenu series before and after planting cassava (n = 6) Mean of three
replicates; ± SE of Selected; (n = 6).
Physico-chemical properties
Before planting
After planting
Sand (%)
67.00 ± 0.87
68.50 ± 0.29
Silt (%)
16.00 ± 0.29
16.17 ± 0.72
Clay (%)
17.00 ± 0.29
15.33 ± 0.73
Soil texture
Sandy loam
Sandy loam
pH (H2O)
4.94 ± 0.12
5.13 ± 0.19
Total Nitrogen (N) (%)
0.19 ± 0.01
0.19 ± 0.02
Available Phosphorus (P) (mg L -1)
13.30 ± 0.06
14.16 ± 0.17
1686.20 ± 70.69
947.0 ± 13.32
Exchangeable Potassium (K) (mg L -1)
Stem cuttings, 20 cm in length and approximately 6 cm in
diameter selected from the tested varieties were planted on
second June 2011 in vertical, incline, and horizontal positions.
For vertical and incline plantings, cuttings were planted 5 cm
deep in the soil while cuttings horizontally planted were buried
to a depth of 2 cm from the surface.
variance (ANOVA). Means found to be significant were
compared using Duncan’s multiple range test at P≤0.05.
Statistical analysis was carried out using the Statistical
Analysis System version 9.2.
This was immediately followed by above-ground stem
polythene-covering (about 5 cm from the ground surface) with
a silver shine polythene sheets (0.03 mm × 1000 mm × 1000
mm) at 0, 1, 30, and 60 days after planting. To provide aeration
for the growing roots enclosed inside the polythene, a metal
nail (7.5 cm long with 4 mm diameter) was used to hole the
polythene (20 cm apart), resulting in 25 holes in 1 m × 1 m
polythene. The main size of the experimental area was 432 m 2.
A replicate size of 144 m2 comprising 10 ridges, each
measuring 14.4 m long and at 1 m intervals was established.
Planting distance of 1 m × 1 m was adopted. First weeding
using a hoe was done at 1 month after planting while
subsequent weeding were carried out by hand to minimize
roots injury. A commercial fertilizer ‘Blue fertilizer’
N:P:K:Mg 12:12:17:2 at the rate of 400 kg ha -1 (Mbah et al.,
2008) was applied in two equal split doses at one month and
two months of planting. The sampling unit consisted of two
central plants of each treatment of which two plants from each
treatment were excluded in data collection (guard rows).
Watering was done when necessary to complement rainfall in
period of drought. No insecticide or herbicide was applied
throughout the experimental period.
3.1 Soil analysis
2.3 Collection of data and statistical analysis
Data were collected at harvest (5 months after planting). Leaf
area index were computed using LAI 2000 canopy analyser
(LI-COR). Number of leaf fall per plant was estimated by
counting the number of leaf scars at harvest. Number of
storage roots formation per plant was counted manually and
storage roots yield (t ha -1) was measured on fresh weight basis
using a weighing balance. Data collected were analyzed and
treatment effects were detected using factorial analysis of
_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
3 Results and Discussion
The results of the soil analysis before planting and after harvest
are shown in Table 2. The observed soil acidification after
harvesting cassava could be due to the application of
nitrogenous fertilizer and subsequent leeching of ammonium in
form of nitrate and crop removal of lime-like elements (e.g.,
Ca and Mg) at harvest (Chris, 2009). Available P increased by
0.86%, whereas total exchangeable K decreased by 739.2%.
The texture of the soils remained unchanged and it was
classified as sandy loam. Howeler (1991) reported that for each
tonne of cassava root dry matter produce, 4.5 kg of N, 0.83 kg
of P and 6.6 kg of K are removed. Putthacharoen et al. (1998)
reported that with an average root yield of 11 t ha -1, cassava
removes lower N and P than those of other crops, and while K
removal was similar to those of other crops and lower than that
removed by pineapple.
3.2 Leaf longevity
Figure 1 shows leaf fall rate of the three cassava varieties
under three planting methods grown with polythene-covering.
In Manihot Mardi 92, regardless of polythene-covering type,
vertical planting had the highest number of leaf fall (57.00 to
87.67 per plant) compared to those of the remaining planting
methods whose effects were statistically similar (30.33 to
68.33 per plant). In Sri Medan, the effect of planting method
on leaf fall rate was not significant except for cuttings planted
with polythene-covering at 30 and 60 days after planting. In
cuttings planted with polythene-covering at 30 days after
planting, incline planting showed the lowest leaf fall (42.33 per
plant) compared to those of vertical planting (59.33 per plant)
and horizontal planting (49.00 per plant). However, at C3,
483
incline planting exhibited the highest leaf fall rate (80.67 per
plant) compared to those of the remaining planting methods
(leaf fall of 34.00 to 54.67 per plant). In Sri Pontian, there were
no significant differences among the planting methods tested
with respect to leaf fall rate.
This study shows that planting method influenced leaf fall rate
in cassava grown with polythene-covering, although the effect
was unstable, suggesting varietal effect. This information is
important because practices that enhance leaf longevity
positively influence leaf net photosynthetic activity and yield
in cassava. El-Sharkawy et al. (1990) and Osiru et al. (1995)
Ahmed et al
reported that selection for longer leaf life positively influenced
yield in cassava. Furthermore, the different effects exhibited by
all the planting methods examined in Sri Medan at various
polythene-covering (Figure 1), suggests the needs for
evaluating cassava genotypes under various planting
orientations when considering leaf fall rate as selection index
in breeding programme and when incorporating polythenecovering in cassava agriculture. Leigner (2002) reported that
cassava cultivar, soil characteristics, and climate together
determine whether there is an advantage to vertical, inclined or
horizontal planting, or, whether any position may be used.
Figure 1 Effect of planting method
on leaf fall rate among three cassava
varieties grown with polythenecovering. Bars denote the standard
error (SE) of the means and n=6.
Letters above columns within the
same polythene-coverings which are
different
represent
significant
differences among the planting
methods at P ≤ 0.05 according to
Duncan’s test. C0 = without
polythene-covering, C1 = polythenecovering at day 1 after planting, C2 =
polythene-covering at 30 days after
planting, and C3 = polythenecovering at 60 days after planting.
Figure 2 Effect of planting method
on leaf area index among three
cassava varieties grown with
polythene-covering. Bars denote the
standard error (SE) of the means and
n=6. Letters above columns within
the same polythene-coverings which
are different represent significant
differences among the planting
methods at P ≤ 0.05 according to
Duncan’s test. C0 = without
polythene-covering, C1 = polythenecovering at day 1 after planting, C2 =
polythene-covering at 30 days after
planting, and C3 = polythenecovering at 60 days after planting.
_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
Effect of Planting Methods on Growth and Yield of Cassava (Manihot esculenta Crantz) Grown with Polythene-covering.
484
3.3 Leaf area index (LAI)
3.4 Number of storage roots formation per plant
The leaf area index of the three cassava varieties grown with
polythene-covering is shown in Figure 2. In Manihot Mardi 92,
planting method did not have significant effect on LAI except
for when cuttings were grown with polythene-covering at 30
days after planting (C2). The vertical planting showed the
highest effect with LAI of 2.90 per plant, compared to those of
incline planting (LAI of 2.08 per plant) and horizontal planting
(LAI of 1.79 per plant). In Sri Medan, the maximum LAI was
obtained in an incline planting with polythene-covering at 1
and 30 days after planting (LAI of 3.73 per plant), whereas that
of horizontal planting had the lowest effect (LAI of 2.14 to
2.85 per plant) regardless of polythene-covering type.
However, the effect of incline planting was not significantly
different from that of vertical planting except for cuttings
planted with polythene-covering at day 1 after planting (C1)
where the effect of incline planting (LAI of 3.72 per plant) was
superior to that of vertical planting (2.12 per plant).
Planting method did not have significant effect on tuber
formation irrespective of variety or polythene-covering type
except for cuttings planted on a bare soil in Manihot Mardi 92
and Sri Pontian and when planting with polythene-covering at
day 1 after planting in Sri Medan (Figure 3). In Manihot Mardi
92, the effect of incline and horizontal planting methods were
statistically similar (14 and 15 tubers per plant, respectively),
and these were significantly different from that of vertical
planting (11.00 per plant). Similarly, in Sri Medan, vertical
planting exhibited the lowest effect (12.33 tubers per plant)
compared to those of incline planting (17.33 per plant) and
horizontal planting (17.00 per plant). In Sri Pontian, incline
planting was the most efficient in terms of tuber formation
(14.67 tubers per plant) compared to those of horizontal
planting (10.00 per plant) and vertical planting (9.67 per plant)
(Figure 3). It is not yet clear, what causes greater tuber
formation in angle planting (incline and horizontal plantings),
the gravitational force could be the driving force. The present
findings are in close agreement with those of several
investigators. Franck et al. (2008) reported higher number of
lateral roots formation when shoots were bent within 1 mm of
the root tip, followed by 3 mm away from the root tip and the
lowest when bent further away 3 mm. The reduction in tuber
formation in all the tested varieties when cuttings were planted
at vertical position could be due to low light interception in
vertically oriented foliage compared to inclined leaves.
Marcelis et al. (1998) reported higher light interception in
inclined leaves compared to vertically positioned leaves in
horticultural plants. According to Smith (1995), the quality of
light intercepted at the leaf or stem allows for rapid
reallocation of resources between roots to shoot system. The
shoots depend on the roots for nutrient and water uptake, while
the continued root growth is reliant on photosynthates fixed in
the leaves (Kramer and Boyer, 1995).
In Sri Pontian, planting method did not show significant effect
with respect to LAI across all the polythene-covering type
(Figure 2). The data showed that planting method markedly
influenced the LAI of cassava grown with polythene-covering.
The lack of significant effect among the planting methods in
Sri Pontian suggests significant varietal influence. The higher
LAI observed when cuttings were planted at vertical position
with polythene-covering at 30 days after planting in Manihot
Mardi 92 could be an adaptive strategy of this variety to
changes in soil microclimate conditions caused by polythenecovering at 30 days after planting. Gandhi and Bains (2006)
reported that mulches modify the microclimate by modifying
soil temperature, soil moisture and evaporation and the
modified microclimate affected the yield contributing
characters of the plant. This result is important because LAI
largely determined the amount of intercepted radiation and its
direct effects on storage root growth (Keutgen et al., 2002).
Figure 3 Effect of planting method
on number of tuber formation per
plant among three cassava varieties
grown with polythene-covering. Bars
denote the standard error (SE) of the
means and n=6. Letters above
columns within the same polythenecoverings which are different
represent significant differences
among the planting methods at P ≤
0.05 according to Duncan’s test. C0
= without polythene-covering, C1 =
polythene-covering at day 1 after
planting, C2 = polythene-covering at
30 days after planting, and C3 =
polythene-covering at 60 days after
planting.
_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
Ahmed et al
485
Figure 4 Effect of planting method
on fresh storage roots yield (t ha -1)
among three cassava varieties grown
with polythene-covering. Bars denote
the standard error (SE) of the means
and n=6. Letters above columns
within the same polythene-coverings
which are different represent
significant differences among the
planting methods at P ≤ 0.05
according to Duncan’s test. C0 =
without polythene-covering, C1 =
polythene-covering at day 1 after
planting, C2 = polythene-covering at
30 days after planting, and C3 =
polythene-covering at 60 days after
planting.
3.5 Fresh storage roots yield (t ha -1)
The data shows that planting method had significant effect on
fresh storage roots yield in cassava grown with polythenecovering (Figure 4). In Manihot Mardi 92, incline planting
caused the lowest yield (14.18 t ha-1) compared to that of
vertical planting (19.78 t ha-1) when cuttings were grown on a
bare soil (C0). However, at C2, incline planting showed the
greatest effect (yield of 28.39 t ha-1), and was significantly
different from those of vertical planting (24.01 t ha -1) and
horizontal planting (24.60 t ha-1). The observed increase in
storage production under incline orientation could be related to
better light interception in inclined leaves compared to
vertically positioned leaves. Research by Boote and Loomis
(1992) on light harvesting and photosynthesis by the canopy
showed that, light interception efficiency was higher for incline
arranged leaves, but lower for vertical leaf arrangements.
According to Ross et al. (2005) light regulates stem elongation
in a wide range of higher plants, and its effects are manifested
in different ways throughout the plant life cycle. In Sri Medan,
planting method did not have significant effect on storage roots
yield regardless of polythene-covering except for C1, where
the yield recorded in vertical planting (30.16 t ha-1) and incline
planting (32.99 t ha -1) were statistically similar, but different
from that of horizontal planting (18.85 t ha-1).
In Sri Pontian, planting methods did not differ significantly
with respect to storage roots yield except for C3 where, incline
planting caused the highest yield (20.12 t ha -1) compared to
those of vertical planting (11.07 t ha -1) and horizontal planting
(11.13 t ha-1) (Figure 4). In the present study, planting method
was seen to influence fresh storage roots yield of cassava
grown with polythene-covering, although the effect was
amplified by interaction between the variety and polythene_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
covering. Aina et al. (2007) reported significant effect of
genotype and environment interactions for storage root yield in
cassava.
Conclusion
The present findings indicated the possibility of polythenecovering integration with cassava agriculture using traditional
planting methods. Considering storage root yields, both
vertical and incline planting methods were effective and are
therefore recommended for farmers.
Acknowledgement
The contributions of all team members who assisted to the
success of this study are gratefully acknowledged. The study
was sponsored by the Umaru Musa Yar’Adua University
Katsina, Katsina state, Nigeria.
References
Aina OO, Dixon AGO, Akinrinde EA (2007) Effect of soil
moisture stress on growth and yield of cassava in Nigeria.
Pakistan Journal of Biological Sciences 10: 3085 – 3090.
Aniekwe NL, Okereke OU, Aniekwe MAN (2004) Modulating
effect of black plastic mulch on the environment, growth and
yield of cassava in a derived Savanna Belt of Nigeria.
Tropicultura 22: 185-190.
Balagopalan C (2002) Cassava utilization in food, feed and
industry. In Cassava Biology, Production and Utilization
Effect of Planting Methods on Growth and Yield of Cassava (Manihot esculenta Crantz) Grown with Polythene-covering.
(Hillocks RJ, Thresh JM, Bellotti AC (eds), New York: CABI
Publishing. pp. 301-318
486
Kramer PJ, Boyer JS (1995) Roots and root systems. In:
Kramer PJ, Boyer JS (eds.). Water relations of plants and soils
San Diego, Academic Press Inc. U.S.A. pp. 115-166.
Boote KJ, Loomis RS (1992) The Prediction of Canopy
Assimilation, in: Modelling Crop Photosynthesis- from
Biochemistry to Canopy, Boote, K.J. and Loomis, R.S., pp.
109.137, CSSA, No. 19, Wisconsin, USA.
Leihner D (2002) Agronomy and cropping systems. In:
Hillocks RJ, Thresh MJ, Belloti AC (Eds.). Cassava: Biology,
production and utilization. CABI International, Oxford.
Burkill JH (1936) A dictionary of economic products of the
Malay Peninsula, Government of Malaysia and Singapore,
Kuala Lumpur.
Marcelis LFM, Heuvelink E, Goudriaan J (1998) Modelling
Biomass Production and Yield of Horticultural Crops: a
Review, Scientia Horticulturae 74: 84-111.
Chantaprasarn B, Wanapat M (2003) Effects of different
harvest intervals on cassava foliage (cassava hay) and root
yield. Tropical Feed Resources Research and Development
Center (TROFREC) Department of Animal Science,Faculty of
Agriculture, Khon
Kaen University, Khon Kaen
40002,Thailand.
http://www.mekarn.org/msc200305/theses05/chan_p1.pdf,
accessed on 10 May, 2012.
Mbah EU, Muoneke CO, Okpara DA (2008) Evaluation of
cassava (Manihot esculenta Crantz) planting methods and
soybean [Glycine max (L.) Merrill] sowing dates on the yield
performance of the component species in cassava/soybean
intercrop under the humid tropical lowlands of southeastern
Nigeria. African Journal of Biotechnology 8: 42-47.
Chris G (2009) Soil Acidity Needs Your
Noteworthy Small Land Holder Series NW 16.
Attention.
El-Sharkawy MA, Cock JH, Lynam JK, Hernandez AP,
Cadavid LF (1990) Relationships between biomass, root yield
and single-leaf photosynthesis in field-grown cassava. Field
Crops Research 25: 183–201.
Franck AD, William DT, Philip K, Karl AF, Irina K, Eric VG,
Hugues N, Francesco P, Xugang L, Roland N, Thomas L,
Klaus P (2008) Mechanical induction of lateral root initiation
in
Arabidopsis
thaliana.
http://www.pnas.org/cg1/do1/10.1073/pnas.0807814105,
accessed on 07 July, 2012.
Gandhi N, Bains GS (2006) Effect of mulching and date of
transplanting on yield Contributing characters of tomato.
Journal Research Punjab Agriculture University India 43: 6-9.
Godfrey AI, Ezekiel UU, Donatus FU (2012) Selection Criteria
for Stem and Tuber Yields in Cassava (Manihot esculenta
Crantz). Journal of American Science 8: 1120 - 1124.
Murphy J, Riley JI (1962) A modified single solution method
for the determination of phosphate in natural waters. Analytical
Chemistry Acta 27: 31-36.
Nweke FI, Spencer D, Lynam JK (2002 ) Cassava
Transformation: Africa’s Best Kept Secret. East Langsing, MI:
Michigan State University Press.
Oguzor NS (2007) Effect of planting methods on growth of
cassava. Research Journals of Biological Sciences 2: 590-592.
Osiru DSO, Hahn SK, Osonubi O (1995) Mechanisms of
drought tolerance in cassava. Journal of African Crop Science
2: 233-246.
Paramanathan S (2000) Soils of Malaysia: Their characteristics
and identification. Volume 1. Akademi Sains Malaysia, Kuala
Lumpur, pp: 121-384.
Peech HM (1965) Hydrogen-ion activity. In: Method of Soil
Analysis, part 2 In: Black CA, Evants DD, Ensminger LE,
White JL, Clark FE, Dinauer RC (Eds.) American Society of
Agrnomy, Madison, Wisconsin.
Howeler RH (1991) Long-term effect of cassava cultivation on
soil productivity. Field Crops Research 26: 1-18.
Putthacharoen S, Howeler RH, Jantawat S, Vichukit V (1998)
Nutrient uptake and soil erosion losses in cassava and six other
crops in a Psamment in eastern Thailand. Field Crops Research
57: 113-126.
Keating BA, Wilson GL, Evenson JP (1988) Effects of length,
thickness, orientation, and planting density of cassava
(Manihot esculenta Crantz) planting material on subsequent
establishment, growth and yield. East African Agricultural
Journal 53: 145–149.
Ravi V, Aked J, Blagopalan C (1996) Review on tropical root
and tuber crops1. Storage methods and quality changes.
Critical Reviews in Food Science and Nutrition 36: 661 – 709.
Keutgen M, Kubota F, Saitou K (2002) Effects of exogenous
injection of sucrose solution to plant on the carbon distribution
to tuberous root production in sweet potato (Ipomoea batatas
Lam.). Japanese Journal of Crop Science 70: 575-579.
_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
Ross JJ, Reid JB, Weller JL, Symons GM (2005) Shoot
architecture. 1. Regulation of stem length. In Plant
Architecture and its Manipulation. Tumbull, C.G.N. (ed.).
Oxford, UK: Blackwell, pp. 57-91.
487
Silvester P (1989) Cassava: The tropical agriculturist.
Macmillan Publishers Ltd. London.
Smith H (1995) Physiological and ecological function within
the phytochrome family. Annual Review Plant Physiol. Plant
Molecular Biology 46: 289-315.
_________________________________________________________
Journal of Experimental Biology and Agricultural Sciences
http://www.jebas.org
Ahmed et al
Tan KH (2005) Soil sampling, preparation, and analysis (2 nd
ed.). Boca Raton, Florida, U.S.A.