ABSTRACT
Two field trials were conducted in 2019 and 2020 cropping seasonsat National Root Crops Research Institute, Umudike, Nigeria to determine sweetpotato response to integrated nutrient management. The experiments were laid out ina randonzied complete block design and replicated three times. The treatments comprisedof eight (8) different combinations of organic and inorganic manures[Integtared nutrient management (INM)] with zeroapplication as control. The results indicated that the application of INM in the form of NPK + poultry manure significantly increased growth and fresh storage root yield of sweetpotato compared to other INM treatments studied.In 2019 and 2020 cropping seasons,the application of NPK+PM compared to the other treatments gave the highest fresh storage root yield (19.44 t/ha) and (22.52t/ha) in 2019 and 2020, respectively.Proximate analysis of the sweetpotato roots indicated strong variations amongst the INM treatments studied. The resultsfrom the combined analysis indicated that NPK+PM x year 2020 significantly gave the highest fresh storage root yield. The economic productivity showed that highest gross monetary returns, net retruns and benefit-cost-ratio were recorded under NPK+PM application compared to other treatments. The findingsof the study can be appliedin the management of nutrient status and fertility of the soil for sustainable production of sweetpotato in Umudike and related agro-ecosytems in Nigeria.
TABLE
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Table of contents vi
List of Tables ix
Abstract x
CHAPTER 1: INTRODUCTION 1
CHAPTER 2: LITERATURE REVIEW 4
2.1 Sweetpotato 4
2.2 Economic
and Nutritional Values of Sweetpotatoes 6
2.2.2 Constraints
of sweetpotato production in Nigeria 9
2.2.3 Inadequate
supply of good quality seeds/planting material 9
2.2.4 Inadequate storage facilities 9
2.2.5 Effects
of soil amendments in crop production 11
2.2.6 Soil nutrient requirements of sweetpotato 12
2.2.7 Sources
and types of organic amendments 13
2.2.8 NPK
use efficiency of sweetpotato 15
2.2.9
The influence of inorganic fertilizer on soil
biological life 16
2.2.10. The contributionsof organic and inorganic fertilizer on
soil biological life 17
2.2.11 Dry matter production in sweetpotato 18
2.2.12The
contributions of soil nutrient elements in the carotene build up or yield of orange fleshed sweetpotato 21
CHAPTER 3:
MATERIALS AND METHODS 23
3.1 Site
Description 23
3.2 Field
Preparation and Soil Sampling 23
3.3 Experimental
Design and Treatment Allocation 24
3.3.1 Planting and field maintenance 24
3.4
Data Collection 25
3.4.1 Vine length 25
3.4.2
Number of branches 25
3.4.3
Length of internodes 25
3.4.4
Freshplantbiomas 25
4.3.5
Dry weight of plant 25
3.4.6
Fresh root yield per plot 25
3.4.7
Number of fresh roots per net plot 25
3.4.8
Weight of fresh roots per net plot 26
3.4.8 Moisture
content 26
3.4.10 Ash
content 27
3.4.11 Fat
content 27
3.4.12 Crude
fibre 28
3.4.13 Crude protein 28
3.4.14 Carbohydrate
content 29
3.4.15 Starch 29
3.4.16 Energy
value 30
3.5 Mineral
Analysis of Sweetpotato Samples 30
3.5.1 Calciumand magnesium 30
3.5.2 Phosphorus 32
3.5.3 Potassium 32
3.5.4 Zinc 33
3.5.5
Sodium 33
3.5.6 Iron 34
3.5.7 β-carotene 34
3.6 Crop Productivity Analysis 35
3.6.1 Gross monetary return (GMR) (N·ha−1):
35
3.6.2 Variable cost of production (N·ha−1) 35
3.6.3 Net return (NR) (N·ha−1) 36
3.6.4 Benefit-cost ratio (BCR) 36
3.7 Statistical Analysis 36
CHAPTER
4:
RESULTS 37
Discussion 69
Conclusion 73
References 74
LIST OF
TABLES
Table
4.1: Physico-chemical properties of the soil of the experimental sites in 2019
and
2020 cropping seasons 38
Table 4.2: Meteorological data of the
study area in 2019 and 2020 cropping seasons 39
Table 4.3: Chemical analysis of the
poultry manure and rice husk dust 40
Table 4.4: Effect
of integrated nutrient management on vine length (cm) of
sweetpotato at
sampled ages in 2019 and 2020 cropping seasons 41
Table 4.5: Effect
of integrated nutrient management on length
of internodes (cm)
of sweetpotatoat sampled ages in 2019
and 2020
cropping seasons 42
Table 4.6: Effects
of integrated nutrient management on number
of branches of
sweetpotato at sampled ages in 2019 and
2020
cropping seasons 44
Table 4.7: Effects of integrated nutrient management on number of
leaves of
sweetpotato at sampled ages in 2019 and 2020 cropping seasons 45
Table 4.8: Effect
of integrated nutrient management on plant biomass and
above ground dry
matter (AGDM) (g) of sweetpotato in 2019
and 2020
cropping seasons 46
Table 4.9: Effect
of integrated nutrient management on crop growth rate (CGR),
relative growth
rate (RGR) and absolute growth rate (AGR) of sweetpotato in 2019
and 2020 cropping
Seasons 48
Table: 4.10 Effect
of integrated nutrient management on fresh root yield
and yield
components of sweetpotato in 2019 and 2020 cropping seasons 49
Table 4.11: Effect
of integrated nutrient management on mineral uptake of
sweet potato vine
in 2019 and 2020 cropping seasons 50
Table 4.12: Effect
of integrated nutrient management on mineral uptake of
Sweetpotato leaves in 2019 and 2020 cropping seasons 51
Table: 4.13:
Effect of integrated nutrient management on mineral uptake of
Sweet potato roots
in 2019 and 2020
Cropping seasons 54
Table 4.14: Effect
of integrated nutrient management on proximate composition of
sweetpotato roots
in 2019 and 2020 cropping seasons. 55
Table 4.15: Effect
of integrated nutrient management on carotene and starch
content of
sweetpotato in 2019 and 2020 cropping seasons 56
Table: 4.16:
Combined analysis of variance on number of leaves of sweetpotato
at the sampled
ages 57
Table 4.17:
Combined analysis of variance on number of branches of sweetpotato
at sampled ages 59
Table 4.18:
Combined analysis of variance on shoot dry matter of
sweetpotato at
sampled ages 61
Table 4.19:
Combined analysis of variance on crop growth rate (CGR), relative
growth rate (RGR)
and absolute growth rate (AGR) ofsweetpotato 62
Table 4.20:
Combined analysis of variance on yield and yield attributes of
Sweetpotato 63
Table 4.21:
Correlation matrix of growth, yield and mineral composition of
sweetpotato in
2019 cropping season 66
Table 4.22:
Correlation matrix of growth, yield and mineral composition of
sweetpotato in
2020 cropping season 67
Table 4.23: Effect of integrated nutrient management on
productivity of
sweetpotato in 2019 and 2020 cropping season
CHAPTER 1
1.1 INTRODUCTION
Sweetpotato
(Ipomoea batatas L.) is the seventh
most important food crop Worldwide (FAO, 2002).Sweetpotato is a root crop that is
cultivated as an annual crop, though it is regarded as perennial, it is a crop
which reliably provides food on marginal and degraded soils with little labour
and few or no inputs from the outside farm . In Nigeria, it is often harvested
as at four months making it possible to crop it twice in a year with or without
irrigation .The crop is efficient in the production of carbohydrate, proteins,
vitamins and cash per unit of land and time (Magagula et al., 2010), Its nutritional content
provides enormous potential for preventing malnutrition and enhancing food
security in the developing world. Sweetpotato is regarded as an important crop
because of it nutritional and industrial utilization.
Sweetpotato
cultivars have varied flesh (orange, yellow white, cream and purple) and skin
colors due to natural pigments. These pigments include carotenoid compounds
which have numerous health benefits like ß carotene, a precursor of vitamin A
which is found in higher amounts in sweet potato with orange flesh (Kays 2002
and Burri 2011). The maintenance of the
nutritional status of tropical soils has not been adequate and FAO (1994) identified
soil degradation caused by erosion, compaction and crusting associated with nutrient
mining, acidification, loss of organic matter and detoriation of drainage
conditions causing water logging and salinization to be the main culprits.
Continuous cultivation of crop like sweet potato (Ipomea batatas Lin) on the same land will lead to soil nutrient
exhaustion and low yield. Moreover, sweet potato like any other tuber crop is a
heavy feeder exploiting greater volume of soil for nutrient and water. FAO (2016)
reported that sweetpotato is one of the most important food security crops in
the world with an approximate production of 106 million tons from 8 million
hectares.
According
to FAO (2016), Asia is the largest sweetpotato producing continent in the world
with the production of 79 million tons (about 75% isfrom China alone) followed
by Africa. In East Africa, Low et al.,
(2009), reported that it is the second most important crop after cassava.Niringiye
et al.,(2014), reported that it can be grown in several environmental conditions.The
storage roots are prefered for its rich source of dietry energy (Oduola et
al., 2018;Olaitan, 2012).Olatunji and Ayuba (2011) reported that agricultural
productivity of tropical soils is hindered by soil fertility constraints and
deteriorating nutrient status. Many interrelated factors both natural and
managerial cause soil fertility decline. The decline in soil fertility may
occur through leaching, crop removal and soil erosion. Mbah and Onweremadu (2009)
submitted that unless those lost nutrients are replenished through the use of
organic or mineral fertilizers or partially returned through crop
reconstitution of organic matter, soil nutrients will decline continuously. Soil
organic matter can be increased by adding plant residues such as rice husk
dust, compost and also by adding biochar to the soil.
Rice
husk dust is the dusty particles from milled rice husk usually produced during
the milling process and it is a bye-product of rice production (Lu et al., 2014).
Application of rice husk dust or rice husk to crop field not only improves the
physical or chemical properties of soil but also resolves the waste disposal
problem. Kookana et al., (2013),
reported that nowadays rice husk dust is receiving more interest because of the
potential for carbon sesquestration and its ability for improving soil fertility
and increasing crop yield. Lu et al., (2014)
pointed out that application of rice husk dust or biochar to soil not only
improves soil fertility but also increases water and nutrient retention. The
addition of RHD to the soil was found to increase the soil pH available P, soil
porosity, plant available water (PAW) and also increase the exchangeable
Potassium (K) and Magnesium (Mg). Similarly, RHD contains high content of
silicon and Potassium nutrients. Varela et al.,(2013), submitted that these properties indicate that RHD has
great potential to be used as a soil amendment material. In spite of the need
of sweetpotato in the nutritional well-being of Nigerians, especially the
orange fleshed sweetpotato, low yield has been
obtained in farmers´fields because of declining soil fertitity due to
continuous cropping and disregard for soil amendment measures (Mahamod et al.,1999). Hence the overall aim of
the study is to acertain the effects of soil amendment materials on the growth
and yield of of sweetpotato. Hence, this study was conducted with the following
specific objectives:
- to determine the effects of integrated nutrient
management on the growth and fresh root yield of sweetpotato,
- to determine the effects of integrated nutrient
management on the biomass, fresh root yield and nutritional quality of
sweetpotato,
- to determine the effects of integrated nutrient
management on the economic productivity of sweetpotato.
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