ABSTRACT
A two year field experiment was conducted during the growing seasons of 2015 and 2016 at National Root Crops Research Institute, (NRCRI) Umudike, South eastern Nigeria to evaluate the response of sweetpotato variety (UMUSPO 1kj) to four rates (0 ,200, 400 and 600kgha-1) of NPK 15:15:15 fertilizer and four levels of plant spacing (15,20,25 and 30cm). The experiment was laid out as a factorial in randomized complete block design (RCBD) with three replications. Result showed that fertilizer significantly (P < 0.05) increased vine length at 4 and 16 weeks after planting in 2015 when 400kgha-1 of fertilizer was applied with the longest vine length observed at 30cm plant spacing at 8 and 12 WAP in 2015 while in 2016, it ranged from 43.6 to 59.2 respectively with 15cm that gave the longest vine length. Fertilizer had no significant (P>0.05) effect on yield of sweetpotato in both years but the yield obtained in wet season was higher than that of dry season when 400kgha-1 of fertilizer was applied across the both years.
TABLE
OF CONTENTS
Title
Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgement v
Table
of Contents vi
List
of Tables vii
Abstract viii
CHAPTER 1:
INTRODUCTION
1.1
Introduction 1
1.2 Justification of Study 4
1.3 Objectives of the work 5
CHAPTER 2: LITERATURE
REVIEW
2.1 Importance
of sweetpotato 6
2.2 Distribution of SweetPotato 7
2.3.
Spacing and Optimum Population 8
2.4
Nutrient Requirements of SweetPotato 9
2.5
Nitrogen 9
2.6
Phosphorous 10
2.7
Potassium 10
2.8
Responses of Sweetpotato to NPK Fertilizer 10
2.9
Effect of Planting Density on root Production in sweetpotato 11
CHAPTER
THREE:
MATERIALS AND METHODS
3.1 Experimental site 14
3.2 Soil sampling 14
3.3 Land preparation 14
3.4 Planting Materials 15
3.5 Experimental Design 15
3.6 Agronomic practices 15
3.7 Data Collection 15
3.8 Statistical Analysis 17
CHAPTER 4: RESULTS
AND DISCUSSION
4.1 Result
18
4.2 Discussion 42
CHAPTER 5: CONCLUSION AND RECOMMENDATION
5.1 Conclusion 44
5.2 Recommendation
44
REFERENCES 45
LIST
OF TABLES
4.1. Meteorological
data of the experimental site 19
4.2: Soil Physico-chemical
properties of the experimental site in 2015
and 2016 cropping
season 20
4.3:
Effect of fertilizer and
plant spacing on vine length (cm) of
sweet
potato at different ages in 2015 and 2016 cropping
seasons 21
4.4: Effect of fertilizer and plant
spacing on number of leaves/plant
Of sweet
potato at different ages in 2015 and2016 cropping
seasons. 23
4.5: Effect of fertilizer and plant
spacing on shoot dry weight (g)/
Plants of sweet
potato at different ages in 2015 and 2016 cropping
season 27
4.6: Effect
of fertilizer and plant spacing on leaf dry weight/plant (g) of
sweetpotato
at different ages in 2015 and 2016 cropping seasons 28
4.7: Effect
of fertilizer and plant spacing on crop growth rate (CGR) of
sweetpotato at different ages in 2015 and 2016 cropping
seasons 29
4.8: Effect of
fertilizer and plant spacing on relative growth rate (RGR) of
sweet
potato at different ages in 2015 and 2016 cropping seasons 30
4.9:
Effect of
fertilizer and plant spacing on Absolute growth rate (AGR) of
sweetpotato
at different ages in 2015 and 2016 cropping seasons 31
4.10: Effect of fertilizer and plant
spacing and leave weight
ratio
of sweetpotato at different ages in 2015 and 2016 cropping
seasons 32
4.11: Effect of fertilizer and plant
spacing on bulking rate (BR) of
sweetpotato
at different ages in 2015 and 2016 cropping seasons 33
4.12: Effect of fertilizer and plant
spacing on number of fresh roots/ha
of sweetpotato at
different ages in 2015 and 2016 cropping
season 35
4.13 Effect
of fertilizer and plant spacing on fresh root yield (t/ha) of
sweet potato at different ages 36
4.14 Analysis
of variance of the combined analysis of fresh root yield
across two cropping seasons (wet and dry)
indicating the least
significant difference 37
4.15 Analysis
of variance of the combined analysis of fresh root yield
across two cropping seasons (wet and dry)
indicating the least
significant difference 38
4.16: Effect of season on root yield
of sweetpotato 38
4.17 Correlation matrix of growth
and yield attributes of sweet potato
as influenced by fertilizer rate and plant
spacing in 2015
cropping season 40
4.18: Correlation matrix of growth and
yield attributes of sweet potato as
influenced by fertilizer rate and plant spacing
in 2016 cropping
season 41
CHAPTER
1
INTRODUCTION
Sweetpotato (Ipomoea batatas (L.) Lam), which is of the family Convolvulaceae is
a perennial crop commonly cultivated as yearly and a starchy staple food crop
in the hot, sub-tropical and frost-free temperate climatic zones of the world
(Onwueme & Sinha, 1991). It is
thought to have originated in Central America but also has a secondary centre
of range in the Southwest pacific Islands (Loebesian et al., 2009). According to Som (2007), sweetpotato grades fifth as
the greatest and vital food crop next to rice, wheat, maize and cassava in most
growing countries whereas by worlds standard in line with CIP (2000) it grades
seventh next after wheat, rice, maize, potato, barley and cassava. It is grown
on about 8.2 million hectares worldwide, with an annual yield of about 102
million tons, with a normal yield of about 12.1 tha-1. (FAOSTAT,
2010).The crop is famous as extremely tolerant tuberous root crop to great
temperatures, low quality soils, floods and shows certain opposition to pests
and infections (Uwah et al., 2013). Sweetpotato is commonly cultivated alone or
mix-cultivated with other staples such as maize, cassava, yam or okra in West
African countries where it is active in overpowering weed growing in such
fields (Eneji et al., 1995). In
Africa, most of sweetpotato cultivars have white or cream-fleshed storage roots
but those with orange flesh are now being upgraded for their high ß- carotene
content, a precussor of vitamin A (Sreekanth, 2008). The prospective of sweetpotato to assure food
security is under-estimated as its use is frequently restricted to alternative
food in African countries. Sweetpotato is appreciated for its roots, vines and
leaves. The roots are boiled, fried, baked or roasted for humans or boiled and
fed to livestock for vigor. They can also be made into flour for bread making,
starch for noodles as well as used as raw material for industrial starch and
alcohol (Ukom et al., 2009).
The flour is used also in sweetening
native beverages like Kunu-zaki, burukutu, and for invigorating baby foods and
foo-foo/pounded yam in Nigeria (Tewe et
al., 2003). The leaves are used as vegetables in yam and cocoyam porridge
and are great source of protein, vitamins and several minerals. The vines and
leaves of sweetpotato are greatly used as livestock feed. Sweetpotato roots are rich in vitamins A, B,
and C; and minerals such as K, Na, Cl, P and Ca (Onwueme & Sinha, 1991). It
can hence be a great value-added food mainly for children and expectant women
who are more frequently prone to vitamin A shortage in Sub-Saharan Africa
(Degras, 2003). Food and Agricultural Organization (2012) reported that 115
countries produced 108,274,685 tons of sweetpotato in 2010 with China producing
the largest, (82,474,410 tons), followed by Indonesia, (2,083,623 tons). Far
behind, is Africa with its contribution of about 14% of global production put
at 14,441,099 tons in 2010 but ranked second in the world after Asia. Nigeria
grades second in Africa after Uganda with the production figure of 2,883,408
tons which has shown a growing trend over the years (FAOSTAT, 2012). However sweetpotato
crop can be cultivated easily, it has certain production and economic
restrictions. The cost of labour are exorbitant in some areas; harvests are
poor resulting from low fertility standard of the over-cropped soils, while
post-harvest shortages and low purchase values have abridged production and
discouraged investment. Onunka et al. (2012)
established that produces of sweetpotato is currently limited by several causes
amongst which are unfertile soils, choice of variety, date of planting, weather
condition, soil type, weed, insect and infection pressure and crop control
measures among others. The crop flourishes in marginal soils but enhanced soil
fertility intensifies its development and yield performance.
In Nigeria, very little information exist
on the appropriate combination rates of inorganic fertilizers for sweetpotato
production. However, it has been reported that the response of the crop to
varying regimes of nitrogen, phosphorus and potassium fertilizers has been
positive (Dapaah et al., 2004).
Several hypotheses have been formulated concerning possible positive
interaction between inorganic and organic inputs when applied simultaneously
(Giller et al., 1995) resulting in
added benefits in terms of improved crop yields, soil fertility or both, and
lower cost of production (Palm et al.,
1990). There is need to explore the huge and rich potential of sweetpotato for
commercial and industrial utilization. The identification and selection of an
appropriate combination rate of inorganic and inorganic fertilizers will
increase the production level of sweetpotato in the country to improve food
security, reduce poverty, improve nutrition as well as contribute significantly
to reduce the importation of wheat flour and other products meant for the food
industry. Sweetpotato, sugarcane, Irish potato and cassava are crops that need
high quantity of potassium (K) because leaves, vines, stems and tubers
frequently take up considerable amount of (K) from the soil. Potassium is shown
to be the most vital nutrient in the production of sweetpotato as it
application increases yield by the creation of bigger sized tubers. Potassium also affects the amount, size,
value and the unit weight of tuberous roots produced, while the lowest levels
of K proposed for healthy development and yield are twice those suggested for
N, though three times as much may be applied and rarely even more (Degras,
2003). In Japan, it was estimated that a tuber yield of 13 t/ha, removes about
70kg N/ha, 20kg P2O5/ha and 110kg K2O/ha from the soil reliant on the
diversity, crop period and agro-climatic area (Degras, 2003). Comparisons of
this kind are occasional for tropical zones but figures given by IFA (1991)
portrayed the specific significance of both K particularly in the root and N in
the leaves. Common approval in most countries is 35-65kg N, 50-100kg P2O5 and
80-170kg K2O per hectare (IFA, 1991). Mohammed (1982), reported that most
farmers usually do not apply any fertilizer or just apply a small measure of
urea or organic manure of indefinite degree.
This may be one of the purpose why yields
gotten by local farmers are lower than yields found elsewhere. Patricia
and Bansal (1999) stated that potato crop has strict necessity for a
balanced fertilization management, without which development and expansion of
the crop are poor and both yield and value of tubers are reduced. Plant
populace is one of the most vital elements to great yield of sweetpotato (Sarkar,
1985). Farooque et al.
(1983) and Tallyrand (1981) reported that increase in sweetpotato
plant populace augmented total yield per unit area.
Nevertheless, Baker
(1981) stated that intra-row gapping had no consequence on entire root
yield or yield of marketable tuber. Thus, proper inervals in sweetpotato is
still a contentious issue amongst the growers. There are a number of
restrictions that hamper the production and productivity of sweet potato under
farmers' circumstances. Among these, lack of appropriate agronomic practices
has been a limiting factor and farmers are complaining of difficulty in
management activities for different varieties (like those having long vine and
horizontal root growth system and the other short vine and roots developing
vertically downward). Therefore, evaluation and selection of different inter
and intra row spacing by participating farmers will improve production and
productivity of the crop, which has great contribution for increment of the
national average yield.
1.2 JUSTIFICATION OF STUDY
To contribute towards the solution of low
root and vine yield obtained by farmers in Nigeria, studies must be conducted
on improved varieties of sweetpotato crops which normally do require higher
quantities of fertilizer with appropriate plant spacing thereby leading to
higher yield likened to the local varieties. Fertilizer application and plant
spacing information on the newly released sweetpotato varieties for the south
eastern zone of Nigeria by the National Root Crops Research Institute (NRCRI),
Umudike is infrequent and not well documented requiring this field trial.
1.3
OBJECTIVE OF THE STUDY
The
objectives of the study were to determine:
i.
the effect of compound
fertilizer rates on growth and root yield of sweetpotato,
ii.
the effect of plant spacing
on growth and root yield of sweetpotato,
iii.
the interactive effects
of compound fertilizer rates and plant intervals on growth and root yield of
sweetpotato,
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