ABSTRACT
A two-year field experiment was conducted at the National Root Crops Research Institute, Umudike situated in a rain forest agro-ecology in 2020 and 2021 cropping seasons to evaluate the effect of NPK-enriched rice mill waste forms for commercial root production of orange-fleshed sweet potato. Studies in both years were factorial and laid out in a Randomized Complete Block Design (RCBD) with three replications. The experiment involved the application of four levels of NPK 15:15:15 fertilizer at 0 kg/ha, 200 kg/ha, 400 kg/ha and 600 kg/ha, respectively. Rice mill waste involved its carbonized form at 0 t/ha and 5 t/ha and un-carbonized form at 0 t/ha and 10 t/ha respectively. On the average, rice mill waste forms increased the vine length, number of leaves per plant, number of branches per plant, stem girth, but had no significant effects on root yield components. The use of combined application of NPK 15:15:15 fertilizer at 400 kg/ha + 5 t/ha CRMW + 10 t/ha URMW proved satisfactory as total root yield (t/ha) seemed best in both 2020 and 2021 cropping seasons and therefore is recommended for orange-fleshed sweet potato production in Umudike, Abia State, Nigeria.
TABLE OF CONTENTS
Title page i
Declaration ii
Certification iii
Dedication iv
Acknowledgments v
Table of Contents vi
List of Tables
Abstract
CHAPTER 1
INTRODUCTION
1.1 Background of the Study 1
1.2 Statement of Problem 2
1.3 Objectives of the Study 4
1.4 Justification of the Study 5
CHAPTER 2
LITERATURE REVIEW
2.1 Origin and Distribution of Sweet Potato 6
2.2 Botany of Sweet Potato 6
2.2.1 Production and production
regions 8
2.2.2 Soil and climatic requirement 9
2.2.3
Propagation 10
2.3 Economic Importance of Sweet
Potato 11
2.4 Concept of Integrated Nutrient
Management 12
2.5 Effects of Integrated Nutrient
Management on Soil Properties. 14
2.6 Effects of Integrated Nutrient
Management on Crop Yield 16
2.7 Effects of Integrated Nutrient
Management on Yield of Sweet Potato 17
2.8 Effects of Mineral Fertilizer on
Soil Chemical Properties 18
2.9 Effects of Mineral Fertilizer on
Growth and Yield of Sweet Potato 18
2.10 Effects of Organic Manure on
Soil Chemical Properties 21
2.11 Effects of Organic Manure on Growth
and Yield of Sweet Potato 22
2.12 Nutrient Requirements of Sweet
Potato 24
CHAPTER 3
MATERIALS AND METHODS
3.1 Description of the Experimental
Site 25
3.1.1 Location of the experiment 25
3.1.2 Rainfall 25
3.1.3 Temperature 26
3.1.4 Relative humidity 26
3.1.5 Sunshine 26
3.1.6 Soils of the study area 26
3.2 Field Experiment 29
3.2.1 Land preparation 29
3.2.2 Experimental design/treatment 29
3.2.3 Planting
material 29
3.2.4 Field maintenance 30
3.3 Data Collection 30
3.4 Yield Parameters 30
3.5 Soil Analysis 31
3.6 Statistical Analysis 32
CHAPTER 4
RESULTS AND DISCUSSION
4.1 Physical and
Chemical Properties of the Soil at the Experimental Site 34
4.2 Effect of
NPK-enriched Rice Mill Waste Forms on the Growth and Yield of 38
Orange-fleshed
Sweet Potato
4.2.1 Vine length 38
4.2.2 Number of
leaves 44
4.2.3 Number of
branches 49
4.2.4 Stem girth 54
4.3 Effect of
NPK-enriched Rice Mill Waste Forms on the Root Yield of Orange- 59
fleshed Sweet
Potato
4.3.1 Total roots
yield weight 59
4.3.2 Marketable
roots yield 60
4.3.3 Unmarketable
roots yield 60
4.3.4 Number of
marketable roots 61
4.3.5 Number of
unmarketable roots 61
4.4 Discussion 75
CHAPTER 5
CONCLUSION AND
RECOMMENDATIONS
5.1 Conclusion 78
5.2 Recommendations 78
REFERENCES 80
APPENDICES 91
LIST
OF TABLES
3.1
Agro-meteorological data of the study area in 2020 and 2021 28
4.1 Physical
and chemical properties of soils of the experiment area 36
4.2 Chemical
properties of the rice mill waste used in the experiment 37
4.3 Effect
of NPK-enriched rice mill waste forms on the vine length 40
of orange-fleshed
sweet potato in 2020 and 2021 cropping seasons
4.4 Interaction
of NPK fertilizer × carbonized
rice mill waste × un-carbonized 43
rice
mill waste effect on vine length of orange-fleshed sweet potato in
2020
and 2021 cropping seasons
4.5 Effect
of NPK-enriched rice mill waste forms on the number of leaves per 45
plant
of orange-fleshed sweet potato in 2020 and 2021 cropping seasons
4.6 Interaction
of NPK fertilizer × carbonized
rice mill waste × un-carbonized 48
rice
mill waste effect on number of leaves
per plant of orange-fleshed
sweet
potato in 2020 and 2021 cropping seasons
4.7 Effect
of NPK-enriched rice mill waste forms on number of branches of 50
orange-fleshed
sweet potato in 2020 and 2021 cropping seasons
4.8 Interaction
of NPK fertilizer × carbonized
rice mill waste × un-carbonized 53
rice
mill waste effect on number of branches of orange-fleshed sweet potato
in
2020 and 2021 cropping seasons
4.9 Effect
of NPK-enriched rice mill waste forms on stem girth of orange- 55
fleshed sweet potato in 2020 and
2021 cropping seasons
4.10 Interaction
of NPK fertilizer × carbonized
rice mill waste × un-carbonized 58
rice
mill waste effect on stem girth of orange-fleshed sweet potato in
2020
and 2021 cropping seasons
4.11 Effect
of NPK-enriched rice mill waste forms on root yield attributes 62
of
orange-fleshed sweet potato in 2020 and 2021 cropping seasons
4.12 Interaction
of NPK fertilizer × carbonized rice mill waste × un-carbonized 65
rice mill waste effects on yield and yield components
of orange-fleshed
sweet potato in 2020 and 2021 cropping seasons
4.13 Combined
analysis of variance of yield and yield attributes of orange-fleshed 68
sweet
potato across the two years
4.14 Combined
analysis of variance of interaction of NPK fertilizer × carbonized 71
rice mill waste × un-carbonized rice
mill waste effects on yield and yield components of orange-fleshed sweet potato
across the two years
4.15 Correlation matrix of growth
and yield components of sweet potato in 2020 74
and 2021
cropping seasons
CHAPTER 1
INTRODUCTION
1:1 BACKGROUND OF THE STUDY
Root
and tuber crops are important sources of carbohydrate for millions of people
throughout the tropics. Sweetpotato (Ipomoea
batatas (L) Lam), a trailing perennial plant of the family Convolvulaceae
(morning glory family), and the only member of the genus Ipomoea whose roots are edible, is undeniably one of the world’s
most important food crops due to its high nutritive value (Data and Eronico,
1987). It is believed to have originated from either Central America or within
the tropical region of North Western parts of Central America (Onwueme, 1978;
Hahn and Hozyo, 1984). It is one of the major root crops that had suffered
neglect in the past but now appears to be gaining a prime position as a source
of food and industrial raw materials. Globally, sweet potato ranks third among
root and tuber crops after potato (281 million tonnes) and cassava (164 million
tonnes), with a production of about 122 million tonnes (FAO, 1996). China
accounts for the highest production of sweet potato (2,883,408 tonnes) making
Asia the world’s leading producer of sweet potato (FAO, 2012), followed by Uganda and
then Nigeria in that order (FAO, 2004). In
Nigeria, it is one of the four major root and tuber crops coming after cassava,
yam and cocoyam (APMEU, 1996). These crops play important roles in both social
and economic development of the country.
Sweet
potato is widely adapted to most agro-ecological regions of Nigeria with low
input requirements and shorter growing periods of 3-6 months, depending on the
altitude. High root yield can be obtained in sweet potato, especially under
fertile soil conditions than other root crops (Kozai et al, 1996). Sweetpotato produces more edible energy, protein and
dry matter on a per hectare per day basis than any other crop. The root of
sweet potato is rich in vitamins A, B2, B5, B6, B9 and C, and as well as copper
(Abd El-Baky et al., 2009). The roots possess great food qualities and are
excellent source of antioxidants and carotenes (Woolfe, 1992). The roots and
shoots are consumed as fresh or processed food and also serve as animal feed.
The potentials of this crop as a major source of raw material for industrial
uses and medicinal purposes; use for treating diabetes, hookworms, ulcer and
internal bleeding (Kozai et al, 1991;
Woolfe, 1992; Berberich et al., 2005)
have increased its importance. The Food and Agriculture Organization (1991,
1998 and 2004) indicated that the production increased from 260,000 to 2.2
million tonnes in Nigeria under a period of 15 years.
1.2 STATEMENT OF PROBLEM
The
potential contribution of this crop towards food security in Nigeria is
underestimated as a huge gap exists between its potential yield of 20 - 40t/ha
and actual yield of 3 - 5t/ha in farmers’ fields (Akoroda and Egeonu, 2008).
Unamma et al (1984), reported that
the constraints responsible for farmer’s low yields could be as a result of
weed competition, poor soil management and very little attention given to its
research.
Apart
from diseases and other biotic stresses which affect the plant (Terry and Oyekan,
1976), the soil environment is an important yield determinant. Unfortunately,
research into the soil nutrient conditions for sweet potato production has not
been extensive. This may have been due to the notion that sweet potato is
adapted to soil acidity and it is deep-rooting, with the ability to produce
fairly good yield from poor soils. While the bulk of reported findings on soil
nutrient studies dwelt largely on the type, time and methods of application of
chemical fertilizers, studies on soil nutrient amendment through the use of
organic fertilizer sources under the weathered soils of the high rainforest
belt of the South-east Nigeria have been very scanty.
As
sweet potato breeding focus has shifted from only yield improvement to include
nutrient bio-fortification, a sweet potato type called the orange-fleshed sweet
potato (OFSP) has been developed and released to farmers. The OFSP is a
pro-vitamin A fortified sweet potato that is rich in Beta-carotene, the
precursor of vitamin A. These newly bred sweet potato types have been developed
under high nutrient environment (Afuape, S.O., personal communication). To
maximize the yield potential of these newly developed varieties, there is the
need to formulate nutrient composition to enhance the OFSP root and nutrient
production.
The
soils of the South-east geopolitical region of Nigeria are characterized by low
organic matter content, low nutrient status, low cation exchange capacity and
low clay content (Lal and Kang, 1986). The soils are strongly weathered and
highly acidic (FAO, 1989), causing low crop response to fertilizer application
unless the soil is substituted with organic manure (Asiegbu, 1989). The high
rainfall of South east Nigeria causes leaching and reduces the soil nutrient
content (Onunka and Ugbaja, 1995).
Sweet
potato plant has been shown to require relatively large amounts of soil
nutrients (IITA, 1995). In the past decades, intensive use of inorganic
fertilizers was advocated for crop production in the tropics in order to
alleviate these nutrient deficiencies (Anonymous, 2000). Presently, the use of
inorganic fertilizers as soil amendment has become cost-intensive and beyond
the reach of peasant farmers. Isola (1998), reported that application of chemicals
or inorganic fertilizers on highly weathered, low organic matter and nutrient-poor
soil without compensating organic fertilizer under intensive farming system and
shortened fallow periods, could lead to nutrient imbalance and soil acidity
with an attendant poor crop yield.
In
view of these problems, there is a surge of interest in exploring organic
residues alone or in combination with inorganic fertilizer as a means of
enhancing soil fertility. These organic materials have been observed to contain
plant nutrients such as calcium, phosphorus, potassium, magnesium, copper, zinc,
manganese and iron (Adebowale, 1985), are high in pH and in improving water and
nutrient-holding capacity of soils (Nyobe, 1998). Hundreds of tons of rice mill waste
are produced daily in Nigeria, especially in the South-east. The current
revolution in the production of rice by the Federal government which has led to
a sporadic rise in rice production in South-east Nigeria has made rice mill
waste abundant. In fact, in many areas, rice mill wastes could constitute a
very serious environmental problem if not handled and adequately removed as it
stands to pollute the environment. Though presently considered as an
environmental nuisance, interestingly, this organic material can be carbonized
through the use of a carbonator machine. Carbonize rice mill waste has the
potential of being used to improve soil pH and fertility especially when
complemented with NPK fertilizer. It is also an energy source for bacteria,
fungi and earthworm in the soil. The integrated application of organic and
inorganic nutrient sources rather than total dependence on any of the sources
is expected to ensure reduction in expenditure on chemical fertilizer, a more
balanced plant nutrition and control of soil acidity.
Therefore,
an attempt to study the Response of Orange-fleshed sweet potato to NPK-enriched
rice mill waste (bran) forms on South-eastern soils of Nigeria is to be made as
there is lack of information in this regard.
1.3 OBJECTIVES OF THE
STUDY
The
main objective of the study is to determine the response of orange-fleshed
sweet potato to NPK-enriched rice mill waste (bran) forms for commercial sweet
potato production.
The
specific objectives of the study are to:
I.
To determine the optimum
level of NPK 15:15:15 fertilizer for the commercial production of
orange-fleshed sweet potato (OFSP) varieties;
II.
To determine the best
level of soil nutrient amendment combination for commercial root yield of OFSP.
1.4 JUSTIFICATION OF THE
STUDY
Yield
stands to be the most desirable trait by sweet potato farmers. Despite its high
agronomic and food security potentials of sweet potato, being a short duration
crop (3-4 months) that could be cropped more than once in the year, its
production is limited due to a number of production factors (Laurie et al., 1999) chief of which is poor
soil management (Unamma, 1984). Poor soil nutrient and condition could be
addressed through the application of inorganic and organic fertilizers.
Determining the optimum levels of combination of both organic and inorganic
fertilizers in sweet potato storage root production will be a critical step in
the ploy to enhance the yield of the crop and increase farmers’ income. The
quest to identify the optimum rate at which both NPK fertilizer and rice mill
waste can be combined to enhance the productivity of the new OFSP varieties and
improve the soil nutrient condition justifies this study.
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