ABSTRACT
Three field experiments were conducted in 2016 and 2017 cropping seasons at Umudike to study the effects of intercropping and intra-row spacing, examine the most suitable time to introduce sweet potato, and determine the effects of intercropping and integrated nutrient management on sweet potato and mungbean growth, yield and productivity in south eastern Nigeria. The experiments on intra-row spacing and integrated nutrient management on sweet potato / mungbean were laid out as factorial fitted in a randomized complete block design (RCBD), while the experiment on time of introducing sweet potato on sweet potato / mungbean mixture was a randomized complete block design (RCBD) with three replicates. Treatments on intra- row spacing, consisted of all combinations of two cropping systems (sole and intercrop), four intra-row spacings of sweet potato (15, 30, 45 and 60cm) and four intra-row spacing of mungbean (5, 10, 15 and 20cm). The experiment on time of introducing sweet potato in mixture, treatments comprised two cropping systems (sole and intercrop) and five times of introduction (sweet potato planted 6 weeks before, 3 weeks before, same day as, 3 weeks after and 6 weeks after mungbean planting). Treatments in the experiment on integrated nutrient management comprised two cropping systems (sole and intercrop) and four levels of nutrient management (0, 4kg/ha agrolyser, 10t/ha organomineral fertilizer and 10t/ha organomineral fertilizer + 4kg agrolyser). Generally, intercropping significantly reduced sweet potato vine length and leaf area index at 9WAP and storage root yield in 2017. Intercropping also reduced mungbean leaf area index in both years and seed yield in 2016. In both sweet potato and mungbean, the closest intra-row spacings resulted in highest leaf area index, but the closer spacings of 100 x 30cm or 100 x 15cm gave significantly higher root yield in sweet potato than the wider spacing 100 x 60cm in 2017. However, the spacing of 100 x 15cm produced higher seed yield in mungbean than the spacing of 100 x 10cm in 2016. Land equivalent ratio (LER) and land equivalent coefficient (LEC) showed yield advantages but economic analysis indicated monetary yield disadvantages due to intercropping. The most profitable systems were obtained from sole sweet potato at the narrowest intra-row spacing of 15cm, followed by 30cm. In both years, sole sweet potato had statistically similar root yields with sweet potato introduced 6 weeks before mungbean but higher yields than other planting schedules except when sweet potato was planted 3 weeks before mungbean in 2016. Root yield reductions when sweet potato was introduced before and after mungbean plantings were 9.8 – 39.6% and 60.0 – 65.2% respectively. Seed yield reductions in mungbean when sweet potato was planted before and after mungbean were 39.8 – 54.4% and 13.6 – 28.2% respectively. Except for when sweet potato was introduced 3 weeks after mungbean and simultaneous planting in 2016, sole mungbean had significantly higher seed yield than intercropping at different times of introduction of sweet potato in mixture in both years. Although LER and LEC showed yield advantages due to intercropping, the highest profit was obtained from sole sweet potato, followed by planting sweet potato 6 weeks before the introduction of mungbean. Intercropping reduced sweet potato root yield and mungbean seed yield while 10t/ha organo mineral fertilizer + 4kg agrolyser or 10t/ha organo mineral fertilizer alone produced significantly higher root yield than 4kg/ha agrolyser or the control on average. LER and LEC indicated yield advantages accrued to intercropping but the highest profit was achieved in sole sweet potato with combined use of 10t/ha organo mineral fertilizer + 4kg agrolyser, followed by application of 10t/ha organo mineral fertilizer alone.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of Contents vii
List of Tables
xii
Abstract xv
CHAPTER
1: INTRODUCTION
1.1 Background of the Study 1
CHAPTER
2: LITERATURE REVIEW
2.1 Origin, distribution, botany and evolution of sweet potato 5
2.1.1 Origin 5
2.1.2 Distribution 6
2.1.3 Botany 6
2.1.4 Evolution 8
2.2 Biology and morphology of sweet potato 9
2.2.1 Growth habit 9
2.2.2 The stem 9
2.2.3 The leaves and petiole 10
2.2.4 The flowers 10
2.2.5 The storage roots 11
2.3 Agronomy of sweet potato 11
2.3.1 Climatic and soil requirements 11
2.3.2 Propagation 12
2.3.3 Weeding and earthing up 12
2.3.4 Mulching 12
2.3.5 Manure and fertilizer application 13
2.3.6 Harvesting 13
2.3.7 Yield 14
2.4 Uses and Health Benefits of Sweet Potato 14
2.4.1 Human food 14
2.4.2 Animal feed 15
2.4.3 Industrial uses 16
2.4.4 Health benefits 16
2.4.5 Sweet potato varieties 17
2.5 Origin and Distribution of Mungbean 18
2.6 Taxonomic Status of Mungbean 18
2.7 Botany of Mungbean 18
2.8 Morphological Characteristics 19
2.9 Varieties of Mungbean
20
2.10 Ecological Requirements of Mungbean 22
2.10.1 Climate 22
2.10.2 Soil requirements 23
2.11 Agronomic Practices that are carried out in Mungbean Production 23
2.11.1 Harvesting 27
2.11.2 Threshing, drying and storage 27
2.12 Uses of Mungbean 28
2.13 The Health Benefits of Mungbean 28
2.14 Intercropping Systems 29
2.14.1 Advantages of intercropping 30
2.14.2 Disadvantages of intercropping 32
2.14.3 Sweet potato cultivation under intercropping
systems
32
2.14.4 Sweet potato legume intercropping systems 33
2.14.5 Assessment of intercropping system 36
2.15 Intra-row Spacing and Sequential Planting on Performance of
Sweet
Potato and Mungbean 39
2.16 Fertilizer Rates on Performance of Sweet Potato and Mungbean 41
CHAPTER
3: MATERIALS AND METHODS
3.1 Location of the Study Area 43
3.2 Planting Materials 43
3.3 Experiment 1: Effect of Plant Population on Growth, Yield and
Productivity of
Component Crops
in Orange-fleshed Sweet Potato (Ipomea
batatas) and
Mungbean (Vigna radiata) Intercrop 44
3.3.1 Field preparation and soil sampling
44
3.3.2 Experimental design, treatment and treatment allocation 44
3.3.3 Planting and field maintenance 46
3.3.4 Records of agronomic measurement 46
3.3.5 Assessment of intercropping system
48
3.5 Experiment 3: Effect of Integrated Nutrient Management on
Orange-Fleshed
Sweet Potato and
Mungbean Intercrops 51
3.5.1 Field preparation and soil sampling
51
3.5.2 Experimental design, treatments and treatment allocation 51
3.5.3 Planting and field maintenance 53
3.5.4 Statistical model and analysis 53
3.5.5 Statistical analysis 53
CHAPTER
4: RESULTS AND DISCUSSION
4.1 Soil and Meteorological Data 54
4.2 Experiment 1: Effect of Plant Population on Growth and
Productivity
of Component Crops in Orange-Fleshed Sweet Potato
(Ipomea batatas)
and Mungbean (Vigna radiata)
Intercrop
57
4.2.1 Sweet potato growth characteristics
57
4.2.2 Mungbean growth and yield 63
4.2.3 Mungbean yield
63
4.2.4 Land use efficiency and economic returns 69
4.2.5 Discussion 74
4.3 Experiment Two 77
4.3.1 Sweet potato growth and yield 77
4.3.3 Mungbean and yield 82
4.3.4 Land use efficiency and economic returns 86
4.3.5 Discussion 90
4.4 Experiment Three 93
4.4.1 Sweet potato growth and yield 93
4.4.2 Mungbean growth and yield 99
4.4.3 Productivity indices and economic returns 106
4.4.4 Discussion 110
CHAPTER
5: CONCLUSION AND RECOMMENDATIONS
References
117
Appendices 141
LIST
OF TABLES
4.1 Soil physical and chemical properties
of Umudike in 2016 and 2017 55
4.2 Meteorological data of Umudike in 2016
and 2017 56
4.3 Effect of cropping system on vine
length (cm) of sweet potato
at different
weeks after planting 58
4.4 Effect of sweet potato intra-row
spacing (cm) on vine length (cm) of
sweet potato at different weeks
after planting 59
4.5 Effect of cropping system on leaf area
index of sweet potato at
different weeks after planting 60
4.6 Effect of sweet potato intra-row
spacing on leaf area index of sweet
potato at
different weeks after planting 61
4.7 Effect of intercropping and intra-row
spacing on sweet potato storage
root yield (t/ha) 62
4.8 Effect of cropping system on plant
height (cm) of mungbean at
different weeks after planting 64
4.9 Effect of mungbean intra-row spacing on
plant height (cm) of
mungbean at different weeks after
planting 65
4.10 Effect of cropping system on leaf area
index of mungbean at
different weeks after planting 66
4.11 Effect of mungbean intra-row spacing on
leaf area index of mungbean at
different weeks
after planting 67
4.12 Effect of intercropping and intra-row
spacing on mungbean seed
yield (t/ha) 68
4.13 Effect of intercropping and intra-row spacing on land equivalent
ratio (LER and land equivalent coefficient (LEC) 70
4.14 Effect of intercropping and intra-row spacing on gross monetary
returns in 2016 different weeks after planting 71
4.15 Effect of intercropping and intra-row spacing on gross monetary
in 2017 72
4.16 Effect of intercropping and intra-row spacing on net monetary
returns in 2016 and 2017 73
4.17 Effect of time of introducing sweet potato on vine length (cm)
of Umuspo 3 sweet potato 79
4.18 Effect of time of introducing sweet potato on leaf area index
of Umuspo 3 sweet potato 80
4.19 Effect of time of introducing Umuspo 3 sweet potato on storage
root yield (t/ha) of sweet potato 81
4.20 Effect of time of introducing sweet potato on plant height (cm)
of
mungbean 83
4.21 Effect of time of introducing sweet potato on leaf area index
of mungbean
84
4.22 Effect of time of introducing sweet potato on seed yield (t/ha)
and yield of mungbean 85
4.23 Effect of time of introducing sweet potato on land equivalent
ratio
(LER) and land equivalent coefficient (LEC) of sweet
potato/mungbean
intercrop 87
4.24 Effect of time of introducing sweet potato in mungbean on gross
monetary
returns (GMR) 88
4.25 Effect of time of introducing sweet potato in mungbean on net
returns 89
4.26 Effect of intercropping on vine length (cm) of sweet potato at
different weeks after planting 94
4.27 Effect of integrated nutrient management on vine length (cm) of
sweet potato at different weeks after planting 95
4.28 Effect of intercropping on leaf area index of sweet potato at
different weeks after planting 96
4.29 Effect of integrated nutrient management on leaf area index of
sweet potato at different weeks after planting 97
4.30 Effect of intercropping and integrated nutrient management
on sweet potato storage root yield (t/ha) 98
4.31 Effect of intercropping on plant height (cm) of mungbean
at different weeks after planting 101
4.32 Effect of integrated nutrient management on plant height (cm) of
mungbean at different weeks after planting 102
4.33 Effect of intercropping on leaf area index of mungbean at
different weeks after planting 103
4.34 Effect of integrated nutrient management on leaf area index of
mungbean at different weeks after planting 104
4.35 Effect of intercropping and integrated nutrient management in
mungbean seed yield (t/ha) and yield components 105
4.36 Effect of intercropping and integrated nutrient management on
land
equivalent ratio (LER) and land equivalent coefficient
(LEC) 107
4.37 Effect of intercropping and integrated nutrient management
on gross monetary returns (GMR) 108
4.38 Effect of intercropping and integrated nutrient management
on net monetary returns (NMR) 109
CHAPTER 1
INTRODUCTION
1.1 BACKGROUND OF STUDY
Sweet potato is an
important root crop in tropical and sub-tropical countries like China, USA, India, Japan, Indonesia, Philippines,
Thailand, Vietnam and Nigeria (Maniyam et
al., 2012). Among the root and
tuber crops grown in the world, sweet potato ranked second after cassava (Ray and Ravi, 2005). Sweet
potato is one of the most important root and tuber crops in sub-Saharan Africa with both domestic and industrial
uses, and its nutritional value far
exceeds yam, cassava and cocoyam (Motsa et
al., 2015). Within sub-Saharan Africa, it is regarded as the third most important root and tuber crop after
cassava and yam (Allemann et al.,
2004). Sweet potato yields high amount of energy per unit area per unit time
and is expected to bridge the gap in food shortages and malnutrition. The
orange-fleshed sweet potato (OFSP) is
believed to be the least expensive source of dietary vitamin A available to
poor families (Laurie et al., 2013). This is due to its high
nutritive value of B – carotene content which is a precursor of vitamin A synthesis (Ukpabi
et al., 2012).
Mungbean (Vigna radiata) is a fast growing
and maturing annual herbaceous legume
which has been recently introduced in South-eastern Nigeria (Agugo,
2003). It is an annual erect or semi-erect plant with a deep tap root system that facilitates the utilization of nutrients
and
enhances nitrogen economy
(Lambrides and Godwin, 2006). Mungbean
is consumed as a
seed sprout or in processed forms that
include cold, jellies, noodles, cakes and brew. It could be eaten
roasted, fried or boiled (AVRDC, 2003). Other uses of mungbean other than food include increased cash income,
enrichment of the soil through nitrogen fixation and formation of a good ecological environment on land (Edah, 2001).
Mungbean has a special importance in intensive crop production system of the country due to its short growing period.
The Seeds contain about 24-26% protein, 51% carbohydrate, 4% mineral and 3% vitamins (Afzal et al., 2008) and is rich.in dietary
iron (Gopalan et al., 2000). Mungbean
seeds are fat-free and rich in protein. As a
result, they can be used to replace meat in many dishes especially for
vegetarians (Rachwa- Rosiak et al., 2015). Its biomass in fresh or
dry form is good and valuable for animal feed
(Zahera and Permana, 2015).
Intercropping is the
predominant cropping system in the humid tropics (Okigbo, 1978). According to
Babatunde et al. (2012), it is the
growing of two or more crops in proximity to promote interaction between them. Ikeorgu (1983) explained that intercropping is the growing
of two or more crops simultaneously
on the same field such that the period of overlap is long enough to include the vegetative stage. Intercropping increases
total productivity per unit area through maximum utilization of land, labour and
growth resources (Craufurd 2000). The Philosophy of intercropping lies in the improvement of resource utilization
efficiency and increase in production
per unit area (Zhang et al., 2007).
Root crop-legume intercropping plays a significant
role in the utilization of limited resources. This is because legumes transfer
fixed nitrogen to intercropped root crops during their joint growing period
and this nitrogen
is an important resource to the crops (Bassey, 2015). Small holder farmers practice intercropping to ensure
risk minimization, profit maximization, flexibility, improvement of soil fertility and soil conservation, pest and
disease control, and balanced nutrition (Matusso
et al., 2014).
Maximum productivity in
intercropping could be achieved when inter and intra-row
crop competitions are minimal for growth limiting factors and the density of
each crop adjusted to minimize competition between them (Ogologwung et al., 2016; Akpaninyang et al., 2013). Maximization of yields in crop mixtures
will always be on the basis of high species
compatibility, optimum plant population and the minimization of above and below ground competition for growth
(Trenbath, 1976). Generally, increasing plant density is one of the ways
of increasing the capture of sunlight within the crop canopy. Nevertheless, the
efficiency of the capture of solar radiation may decrease at high plant density
due to mutual shading in the plants (Zhang et
al., 2006). Optimum plant population not only ensures high yields but
varies depending on environmental factors such as soil fertility, moisture
supply and genotype or plant size (Gonzalo et
al., 2006) as well as cropping system.
The increasing land use
intensity without adequate or balanced use of fertilizers and with little or no use of micronutrients have
caused severe fertility deterioration of soils resulting in stagnation or absolute decline
of crop productivity, though inorganic fertilizers have been the conventional method of soil mineral input in
sweet potato production, these fertilizers
may pose danger to the environment especially if inappropriately applied (Yeng et al.,
2012). Also, due to high energy costs, inorganic fertilizers have become very expensive and also scarce (Yeng et al., 2012). Therefore, environmental
concerns point to the need for evolving
more ecologically friendly
methods of sustaining soil fertility (Okpara
et al., 2004), necessitating the use
of organo-minerals and agrolyzers.
Several hypotheses have
been formulated concerning possible positive
interaction between inorganic and organic inputs when applied simultaneously resulting in added benefits in terms of
improved crop yields, soil fertility
or both, and lower cost of production (Opara et al., 2012). The use of
organo- minerals and agrolyzers as
fertilizers for producing crops have not received a lot of attention for more sustainable crop productivity
(Tejada et al., 2009). These
organo-minerals are excellent source of different
nutrients and have the ability
to improve soil characteristics (Moller,
2009) and crop productivity. Agrolyzers are low cost micronutrients, non-bulky
agricultural inputs that mostly supply the micro nutrients required for high crop yields.
Investigations conducted on the nutrient requirements of sweet potato in South eastern
Nigeria have been generally on inorganic fertilizers (Njoku, 2000; Okwuowulu and
Asiegbu, 2000), and organic
fertilizers (Okpara et al., 2004),
while there is limited information on
the use of organo mineral fertilizers and agrolyzers solely or in combination
on sweet potato/mungbean intercrop. There is limited information on mungbean and sweet potato
intercropping in respect of population density of component crops, time of introducing sweet potato in
mixture and nutrient management in South Eastern Nigeria.
The main objectives of this
study was to evaluate the effects of
plant population, time of introduction of component crops and integrated
nutrient management on sweet potato/mungbean intercrop in South Eastern
Nigeria, while
The specific objectives of this study
were to:-
i. To determine the effects of plant population on the
growth, yield and yield components of sweet potato/mungbean intercrop.
ii. To examine the effects
of time of introducing sweet potato on growth and performances of sweet potato/mungbean intercrop.
iii. To evaluate the effects
of integrated nutrient
management on the growth, yield and yield components of sweet potato/mungbean intercrop.
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