ABSTRACT
This research was designed to evaluate on-farm orange-fleshed sweet potato variety response to time of planting and NPK (15:15:15) compound fertilizer; and the effect of sweet potato variety and pro-vitamin A maize spatial arrangement on productivity and economic returns of the intercropping systems. The planting time experiment was a split-split plot laid out in a randomized complete block design with three replications. The main plot treatments were two mid season planting dates of mid May or early July and late season plantings of mid or late August. The sub plot treatments were three NPK (15:15:15) fertilizer rates (0,200 and 400kg/ha), while the sub-sub plot treatments were three orange-fleshed sweetpotato varieties (Umuspo1, Umuspo3 and Umuspo4). The experimental design for sweetpotato and maize intercrop studies was a randomized complete block design (RCBD) with three replications. The treatments were fifteen and comprised sole Umuspo1, sole Umuspo3 and sole Umuspo4, sole maize at spatial arrangements of 1x1m,4 plants/stand,1x0.5m 2plants/stand and 1x0.25m 1 plant/stand, and Umuspo1, Umuspo3 and Umuspo4 mixed with maize at the three spatial arrangements. Results indicated that planting in mid May or early July resulted in significantly more branches, greater leaf area index, higher number of storage roots per plant, root weight per plant and higher storage root yield than planting in August. NPK fertilizer application at 400kg/ha significantly increased storage root yield while Umuspo1 and Umuspo3 had comparable shoot and storage root yields but significantly higher values than Umuspo4 in 2020. Maize seed yield was not significantly influenced by intercropping, sweetpotato variety and maize spatial arrangement, while sole Umuspo3 sweetpotato had comparable root yield with Umuspo3 intercropped Umuspo3 and sole Umuspo1 but significantly higher yield than Umuspo4 in both cropping systems and Umuspo1 intercrop irrespective of maize spatial arrangement. The highest LER, ATER and LEC were obtained from all the sweetpotato varieties intercropped with maize at 1x1m, 4 plants/stand spacing pattern, but the highest profit (net monetary returns) was from Umuspo3 orange-fleshed sweetpotato mixed with maize at 1x0.5m spacing 2 plants/stand spatial arrangement. Based on the results, it is recommended that Umuspo1 and Umuspo3 orange-fleshed sweetpotato be planted in mid-May to early July and NPK fertilizer applied at 400kg/ha for high root yield. Intercropping Umuspo3 variety with maize at 1x0.5m spacing 2 plants/ stand arrangement resulted in good use of land and the highest profit, and is recommended to give farmers meaningful yield gains and profit from the two nutritious crops, having diets rich in vitamin A.
TABLES
OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgments v
Table of Contents vi
List of Tables ix
Abstract xii
CHAPTER
1: INTRODUCTION 1
CHAPTER
2: LITERATURE REVIEW 5
2.1 Effect
of Time of Planting 5
2.2 Effect
of NPK Fertilizer on Crop Growth and Yield 6
2.3 Effect
of Variety 8
2.4 Intercropping 10
2.5 Types
of Intercropping 12
2.5.1 Row
intercropping 12
2.5.2 Mixed
intercropping 12
2.5.3 Strip
intercropping 12
2.5.4 Relay
intercropping 12
2.5.5 Patch
intercropping 13
2.6 Advantages
of Intercropping 13
2.6.1 Increase
in yield (production) 13
2.6.2 Improvement
in soil fertility or soil nitrogen 13
2.6.3 Stability
and uniform yield 14
2.6.4 Increase
in income per unit area 14
2.7 Disadvantages
of Intercropping 14
2.8 Assessment
of Intercropping System 15
2.8.1 Competition
indices in intercropping 15
2.8.2 Land
equivalent ratio (LER) 15
2.8.3 Land
equivalent coefficient (LEC) 16
2.8.4 Area
time equivalent ratio (ATER) 16
2.8.5 Competition
ratio (CR) 17
2.8.6 Monetary
equivalent ratio (MER) 17
2.9 Spatial
Arrangement in Intercropping System 18
CHAPTER
3: MATERIALS AND METHODS 20
3.1 The
Study Location 20
3.2 Planting
Materials 20
3.3 Experiment
1- On Farm Evaluation of Sweetpotato Varieties
Response to Planting Date and NPK Fertilizer
Application 22
3.3.1 Field preparation and soil sampling 22
3.3.2 Experimental design and treatments 22
3.3.3 Planting and field maintenance 23
3.3.4 Data collection 23
3.3.5 Harvest 24
3.3.6 Statistical analysis 24
3.4 Experiment
2- Effect of Interaction of Pro Vitamin A Maize
Spatial Arrangement and Orange-fleshed Sweetpotato
Variety
on
Productivity of Component Crops 25
3.4.1 Field preparation and soil sampling 25
3.4.2 Experimental design and treatments 25
3.4.3 Planting and field maintenance 26
3.4.4 Data
collection 27
3.4.5 Sweetpotato 27
3.4.6 Maize 28
3.4.7 Statistical
analysis 28
CHAPTER
4: RESULTS AND DISCUSSION 30
4.1 Results 30
4.1.1 Soil
and meteorological data 30
4.1.2 Experiment
1: Effect of planting time, NPK fertilizer and variety on
orange-fleshed
Sweetpotato 33
4.1.2.1
Crop growth 33
4.1.2.2 Yield and yield components 38
4.2 Discussion 54
4.2.1 Experiment
2: Effect of intercropping sweetpotato varieties and maize
spatial
arrangement on component crops. 56
4.2.1.1 Sweetpotato growth and yield 56
4.2.1.2 Maize growth and yield 63
4.2.3 Land
use efficiency and economic returns 67
CHAPTER
5: CONCLUSION AND RECOMMENDATIONS 75
5.1 Conclusion 75
5.2 Recommendations 76
References 77
Appendix 89
LIST
OF TABLES
PAGE
3.1 Description
of sweet potato varieties 21
3.2 Description
of maize variety 21
4.1: Soil
physical and chemical properties of the experimental sites in
2019 and 2020 31
4.2: Meteorological
of the experimental site (Umuahia) in 2019 and 2020 32
4.3: Effect
of planting time, NPK fertilizer and variety on number of
branches at different
weeks after planting in 2019 34
4.4: Effect
of planting time, NPK fertilizer and variety on number of
branches at different
weeks after planting in 2020 35
4.5: Effect
of planting time, NPK fertilizer and variety on leaf area
index at different weeks
after planting in 2019 36
4.6: Effect
of planting time, NPK fertilizer and variety on leaf area
index at different weeks
after planting in 2020 37
4.7: Main
effects of planting time, NPK fertilizer and variety on
biomass (t/ha) 40
4.8: Effect
of interaction of planting time, NPK fertilizer and variety
on shoot biomass (t/ha) 41
4.9: Effect
of interaction of planting time, and variety on shoot
biomass
(t/ha) 42
4.10: Main
effect of planting time, NPK fertilizer and variety on number
of storage roots/plant 43
4.11: Effect
of interaction of planting time, NPK fertilizer and variety on
number of storage
roots/plant 44
4.12: Effect
of interaction of planting time and variety on number of
storage root/plant 45
4.13: Main
effects of planting time, NPK fertilizer and variety on storage
root weight (kg) 46
4.14: Effect
of interaction of planting time fertilizer and variety on
storage root weight (kg) 47
4.15: Effect
of interaction of planting time and NPK fertilizer on storage
root weight (kg) 48
4.16: Effect
of interaction of planting time and variety on storage root
weight (kg) 49
4.17: Main
effect of planting time, NPK fertilizer and variety on storage
root yield (t/ha) 50
4.18: Effect
of interaction of planting time, NPK fertilizer and variety on
storage root yield (t/ha)
51
4.19: Effect
of interaction of planting time, NPK fertilizer on storage
root yield (t/ha) 52
4.20: Effect
of interaction of planting time and variety on storage root
yield
(t/ha) 53
4.21: Effect
of intercropping with sweetpotato varieties and maize spatial
arrangement on number of
branches of sweetpotato at different
sampling dates in
2019 59
4.22: Effect
of intercropping with sweetpotato varieties and maize spatial
arrangement on leaf area
index of sweetpotato at different sampling
dates in 2019 60
4.23: Effect
of intercropping and maize spatial arrangement on shoot
biomass (t/ha) of three
sweetpotato varieties 61
4.24: Effect
of intercropping and maize spatial arrangement on root yield
and
yield component of three sweetpotato varieties 62
4.25: Effect
of intercropping with sweetpotato varieties and maize spatial
arrangement on maize
plant height (cm) at different sampling
dates in 2019 64
4.26: Effect
of intercropping with sweetpotato varieties and maize spatial
arrangement on maize leaf
area index at different sampling
dates in 2019 65
4.27: Effect
of intercropping with sweetpotato varieties and maize spatial
arrangement on maize seed
yield and yield components 66
4.28: Effect
of intercropping and maize spatial arrangement on land
equivalent ratio in 2019
and 2020 68
4.29: Effect
of intercropping with sweetpotato varieties and maize spatial
arrangement on LEC and
ATER 69
4.30: Effect
of intercropping and maize spatial arrangement on gross
monetary returns of sweet
potato/maize intercropping 70
4.31: Effect
of intercropping and maize spatial arrangement on net
returns of
sweetpotato/maize intercropping 71
CHAPTER
1
INTRODUCTION
Sweetpotato (Ipomoea batatas L.) originated from South America and is a
perennial plant grown as an annual crop for its swollen storage roots (Gibson
and Kreuze, 2015). It is an important crop in many parts of the world being
cultivated in more than 100 countries (Woolfe, 1992). Within sub-Saharan
Africa, it is regarded as the third most important root and tuber crop after
cassava and yam (Hahn and Hozyo, 1998). Sweetpotato serves as a staple food
crop and feed to livestock while the leaves serve as protein-rich vegetables
(Nwinyi, 1992). Sweetpotato roots may be boiled or fried and eaten or
reconstituted into fufu or blended with other carbohydrate flour sources such
as wheat, and used for baking bread and biscuits or used industrially for
production of starch, adhesives, textiles, paper and alcohol (Woolfe, 1992).
Cultivars grown in Nigeria have white or cream-fleshed roots, but those with
orange-fleshed roots especially the recently released varieties are being
promoted because of their high
-carotene content, a precursor of
vitamin A (Sreekanth, 2008). The strategy of increasing orange-fleshed
sweetpotato consumption is particularly important because it helps to alleviate
vitamin A deficiency or night blindness especially in children and pregnant or
nursing mothers who are more prone to vitamin A deficiency in sub-Saharan
Africa (Degras, 2003).
Sweetpotato
is a vegetatively propagated crop where vine cuttings from previous crops or
volunteer plants are usually used as planting material by farmers in Nigeria.
This practice can lead to the accumulation of systemic pathogens, especially
viruses and degeneration of sweetpotato cultivars in Nigeria (Nwadinobi et al., 2018). Although a drought
tolerant crop, sweetpotato is grown in the drier savanna and humid forest zones
of Nigeria. However, degeneration of sweetpotato planting materials due to
virus infection also depends on the prevailing weather conditions, as high rainfall
and high humidity favour buildup of external virus inoculums which can lead to
high infection rate and rapid deterioration (Sreekanth, 2008). Depending on the
rainfall pattern, planting dates have been shown to have tremendous influence
not only on disease infection but also on sweetpotato growth, yield and
chemical composition of crops (Nedunchezhiyan and Byju, 2005; Munkvold and
Yang, 1999; Olori-Great, 2015). Anioke (1996) reported the need to review the
production technologies including time of planting in south eastern Nigeria
following the release of new sweetpotato varieties by National Root Crops
Research Institute, Umudike. Generally, rainfall patterns have been erratic in
recent time due to prevailing climate change, such that rains may not stabilize
until May or June compared with March or April previously reported (Van
Rheenen, 1973). For a photoperiod sensitive crop like sweetpotato, a change in
planting date could have considerable effect on plant development and growth (Marcos
et al, 2011).
Maize,
is also a staple food crop in Nigeria. but unlike sweetpotato, it is sensitive
to water deficit and hence, is prone to crop failure and low yields, if rains
are not timely and regular during the cropping season (Ossom, 2010). In South-eastern
Nigeria, maize is usually sown early in the cropping season to reduce pests and
disease problems and avoid cloud cover which are prevalent late in the season.
Farmers plant white and yellow maize varieties, but the conventional white
maize is unfortunately deficient in vitamins and protein because of the
limiting quantities of essential amino acids lysine and tryptophan (Vasal,
2001). The Bende white variety is particularly popular in the region, where it
is consumed because of its soft starch, after boiling and roasting as fresh
maize. Consequently, the large percentage of the population who depend on the
conventional white maize are exposed to deficiencies of protein or vitamins and
associated ailments (Krivanek et al., 2007).
In contrast to the conventional white maize cultivar, pro-vitamin A maize (PVA)
is yellow in colour and rich in beta-carotene (Krivanek et al., 2007), and are being promoted to combat vitamin A
deficiency in developing countries including Nigeria.
High
human population in South-eastern Nigeria has resulted in small farm holdings
or sizes of less than one hectare to two hectares (Okigbo and Greenland, 1976;
Okigbo, 2000). In such a situation, intercropping is the predominant cropping
system and biofortified crops such as orange-fleshed sweetpotato and pro
vitamin A maize are required in the system to improve food and nutritional
security. Both crops have been shown to be compatible as they possess different
photosynthetic pathways, different growth habits and requirement of different
growth resources (Islam et al., 2007).
As a cropping strategy that farmers are encouraged to adopt and increase
productivity, intercropping is more productive and profitable when it is done
properly by selecting compatible crops (Begum et al., 2010), spatial arrangements and population density of
component crops (Islam et al., 2006)
and judicious application of chemical fertilizers (Basak, 2008).Whether with
monocrops or intercrops, yields obtained in southeastern Nigeria are generally
low because farmers in the region rarely use fertilizers, despite the rising
population pressure which has resulted in shortened fallow periods. The poor
yields obtained from farmers field suggest the need for fertilizer application
if high yields are to be sustained. Apart from fertilizer application, the
arrangement of the components, is particularly important when both crops are of
different height and canopy architecture (Chiezey et al, 2005). The taller crop will likely intercept more light to
the detriment of the shorter one due to shading. Spatial arrangement in
traditional farming is haphazard, without any attempt to arrange the crops in a
way that the components intercept adequate solar energy.
This study was conducted with the
following objectives:
1) To evaluate on-farm orange-fleshed sweetpotato
variety response to planting date and NPK fertilizer in Umuahia, south eastern Nigeria.
2) To determine the effect of
provitamin A (PVA) maize spatial arrangement and orange-fleshed sweetpotato
variety on sweetpotato/maize intercropping in Umuahia, South-eastern Nigeria.
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