INVESTIGATIONS OF AGRONOMIC PRACTICES TO IMPROVE
THE ESTABLISHMENT AND YIELDS OF
AMARANTHUS HYBRJ.DUS
f,
AND
CLEOME GYNANDRA
BY
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0600433190North-West University Mafikeng Campus Library
'MARAFOLATSANE THAKANE SEEISO
DISSERTATION SUBMITTED IN FULFILMENT OF THE REQUIREMENTS FOR THE
DEGREE OF MASTER OF SCIENCE IN AGRICULTURE (CROP SCIENCE), IN THE
DEPARTMENT OF CROP SCIENCE, FACULTY OF AGRICULTURE, SCIENCE AND
TECHNOLOGY, NORTH-WEST UNIVERSITY (MAFIKENG CAMPUS)
SUPERVISOR: PROFESSOR. S.A. MATERECHERA
ABSTRACT
Many people are becoming increasingly aware of the importance of indigenous African leafy vegetables in meeting their household food security, and are therefore producing them in their home gardens and farms. There is however not enough information regarding agronomic practices for their optimum productivity. In an effort to investigate viable techniques of producing indigenous leafy vegetables among local communities, this study was carried out to test agronomic practices that can be used to improve the establishment, growth, productivity and quality of two dominant indigenous African leafy vegetables (IAL V s) namely, Amaranth us hybridus and Cleome gynandra.
The effects of seed sowing depth on emergence and early seedling development of Amaranthus hybridus and Cleome gynandra, was investigated in a glasshouse study.
Eight sowing depths (1.5, 3.5, 7, 10, 15, 20, 25 and 30 mm) were imposed on seeds of two African indigenous (Amaranthus hybridus and Cleome gynandra) and exotic (Spinacia oleracea and Brassica napus) leafy vegetable species using a split plot design with four replicates. Exotic vegetables had significantly higher (p<0.05) seedling emergence (95%) than the indigenous ones (60%). Among the indigenous species, Cleome gynandra had a higher emergence (70%) than Amaranthus hybridus (61 %). However, there were no significant differences on emergence amongst the exotic vegetables. Exotic vegetables also had significantly higher (p<0.05) mean plant height (8.6 em) than indigenous vegetables (1.01 em). In all the vegetable species, both emergence and plant height decreased with deeper sowing due to higher soil strength. The biomass yields of the seedlings were reduced with deeper sowing although the differences were not significant. There were however significant differences (p<0.05) among the biomass yields of the vegetable species at different sowing depths. Generally, significantly higher biomass yields (6.4 g/plant) were obtained in exotic species compared with indigenous ones (0.2 g/plant). The results suggest that seeds of indigenous African leafy vegetables were more sensitive than the exotic ones to deeper (> 1 0 mm) sowing and their emergence was more adversely affected by soil strength at this depth. Both deep (15-20mm)
and shallow ( <1 Omm) sowing depths reduced the emergence of seedlings of both species of IAL V s studied. It was thus concluded that an optimum stand of IAL V s can be obtained if the seeds are sown at optimum depth of 10 mm.
The effects of applying kraal manure (cattle, goat and control) and leaf cutting management (cutting edible tender tips only, cutting all leaves and cut all the leaves only at the end) on leaf biomass yield of indigenous African leafy vegetables Cleome gynandra and A. hybridus were studied. The plants were grown in large PVC pots laid in a randomized complete block design and leaves were cut five times before the final harvest. Applications of kraal manure improved leaf biomass yield of both vegetables and the yield was increased with successive cutting where kraal manure was applied. Plants that were grown in soil amended with goat manure produced significantly higher total fresh leaf biomass yield (470.86 g pof1) than those under cattle manure (328.42 g pof1) in C. gynandra. A similar observation
was made in A. hybridus plants.
The results showed that fresh leaf biomass of C. gynandra and A. hybridus were increased when kraal manure was added. The yield was higher in goat manure when all the leaves were cut than in cattle manure for both vegetables. It was observed that in all the cutting techniques, plants that were not amended with kraal manure produced the lowest crude protein content while the highest CP content was obtained from the plants that were amended with kraal manure across all the cutting techniques. The biomass yields of both vegetable species in the treatments with manure increased progressively with each harvesting while those in the control declined. Plants where all the leaves were cut produced significantly higher total yields (371 g por1) compared with cutting only edible tender leaves (342.83 g pof1)
and cutting all the leaves at the end (165.35 g pof1). A combination of goat manure and cutting all leaves gave the highest fresh leaf biomass yield (571.99 g pof1) while the corresponding yield for cattle manure was (439.69 g pof1). The results revealed variations among the two manure types with goat manure being superior to cattle manure. It was concluded that the yields of Cleome gynandra and Amaranthus hybridus could be increased by adopting an appropriate manure and leaf cutting technique.
In order to determine the influence of phosphorus fertilizer and leaf cutting techniques on biomass yield and quality of leaves of amaranthus (Amaranthus hybridus) and cleome (Cleome gynandra), an experiment was conducted in pots where single super phosphate (SSP) fertilizer was applied at rates equivalent to 0, 20, 40 and 60 kg ha-1. Phosphorus application significantly (P<0.05) increased leaf biomass yields compared with the control. The biomass yields of both species increased with increasing P level with plants that received 60 kg P ha-1 producing significantly (P<0.05) higher total fresh leaf yield (266.7 g pof1) than in 20 and 40
kg ha-1. Application of P fertilizer also contributed to increased fresh stem and root biomass of both C. gynandra and A. hybridus. In both vegetable species, highest fresh leaf yield was obtained from the plants whose leaves were all cut leaving mature leaves and stems while lowest yields were obtained when plants were cut once at final cut. There was a high moisture content in plants whose leaves were cut throughout while the lowest moisture content was obtained from plants that were cut once at the end. The biomass yields increased with increasing P rates across all cutting techniques in both vegetable species. A combination of fertilizer at 60 kg P ha-l and cutting all leaves throughout produced highest fresh leaf yield. The results indicated that crude protein was decreased when leaves were cut once at end of the study across all the phosphorus rates. Highest crude protein content was obtained when all leaves were cut at all P rates in both vegetable species. It was concluded that leaf cuttings with high rates of P fertilizer can contribute to improved biomass yield production of the two indigenous African leafy vegetables.
In both C. gynandra and A. hybridus, the crude protein in leaves was enhanced by application of kraal manure with goat manure producing higher crude protein than cattle (14.2% vs 13.4%, respectively) and (12.2% vs 11.44%, respectively). Application of phosphorus significantly (P<0.05) increased the crude protein content of vegetable leaves. Frequent cut of leaves enhanced crude protein production while cutting leaves once at final cut produced lowest crude protein. It was concluded that the crude protein content of IAL V s can be improved by P fertilizer and frequent cut of leaves of IAL V s.
Not withstanding the limitation of practical application of pot growth experiments, the significance of this study is that, the findings can help to promote the production of IAL V s by providing the necessary agronomic information for their cultivation. The results of this study indicate that planting depth and fertility management are important for improving productivity and should however be confirmed under different field conditions and for longer experimental duration to provide recommendations for farmers.
\
DEDICATION
To my family, husband and kids, with much love, admiration and appreciation.
DECLARATION
I, Seeiso Thakane 'Marafolatsane declare that this dissertation submitted for the degree of Master of Science in Agriculture (Crop Science), at North-West University (Mafikeng Campus) has been composed by myself and has not been accepted in any previous application for a degree. The work of which this is a record has been done by myself and sources of information have been acknowledged by means of references.
Signature
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(~·
Date
6
·~ U -14:
ACKNOWLEDGEMENTS
First and foremost, I would like to express my deep sense of gratitude to my supervisor Professor S.A. Materechera for his valuable time, patience, guidance and straight talk. I have learnt a lot throughout the entire period. I would like to extend my sincere thanks to the late Professor S.M. Funnah for his great contribution in compiling this project, the support and encouragement he offered me. I also thank him for helping in the statistics part of the project. May his soul rest in peace on the glory of God. My thanks and appreciations also go to Professor S.D. Mulugeta for his assistance in data analysis. I would not have done any thing without his help.
Grateful thanks are passed on to Mr J.B.K. Kasirivu who was always helpful on the practical side of the research and for supplying the seeds of the AIV s. I am also greatly indebted to the Crop-Science laboratory technician, Mr K.S. Gareseitse for his assistance in the preparation of chemicals used for soil and manure analyses. I do not forget the help offered by the field technician, Mr R. Mashile, mostly on the practical aspects of the project. I am deeply indebted to Dr H. Mokoboki and Dr C. Lebopa for providing me with the procedure for plant crude protein analysis. Deepest gratitude are also due to Ms M. Hae for being supportive throughout the entire study. Special thanks to my colleagues and friends at the North-West university (Mafikeng Campus), for their support and acceptance of an international student. I wish to thank Mr E. Varkey, the Principal of Maseribane High School, my work place, for being so lenient and supportive by allowing me some time to complete my project while I was supposed to be at work.
I would like to extend my heartfelt gratitude to my husband, Mr L.E. Seeiso for his understanding, encouragement and moral support during the difficult times I faced while studying. To my children, Rafolatsane and Palesa, I say "thank you for being so patient". To Mr and Mrs Nkhabutlane, I say "thank you so much for your support and taking care of my children", I wish you all the best. Above all, I thank the Lord who provided me strength and made all things possible.
TABLE OF CONTENTS CHAPTER PAGE ABSTRACT ... ! DEDICATION ... V DECLARATION ... VI ACKNOWLEDGEMENTS ... VII
TABLE OF CONTENTS ... VIII
LIST OF TABLES ... XI
LIST OF FIGURES ... XIV
LIST OF APPENDICES ... XV
LIST OF ABBREVIATIONS AND ACRONYMS ... XVI
PUBLICATIONS FROM THE DISSERTATION ... XVII
CHAPTER 1: GENERAL INTRODUCTION AND OBJECTIVES OF THE
STUDY ... 1
CHAPTER 2: SIGNIFICANCE OF AFRICAN INDIGENOUS LEAFY VEGETABLES IN FOOD AND NUTRITIONAL SECURITY OF SMALLHOLDER HOUSEHOLDS 2.1 Introduction ... 7
2.2 The status of African indigenous leafy vegetables in South Africa ... 9
2.3 Uses of African indigenous vegetables ... 10
2.3.1 The role of AILVs in household food and nutritional security ... 10
2.3.2 Medicinal value of AILVs ... 16
2.3 .3 The socio-economic importance of indigenous vegetables ... 18
2.4. Factors affecting the utilization of African indigenous leafy vegetables ... 18
2.5. Integrating indigenous knowledge in the production and utilization of African indigenous leafy vegetables ... .20
2.6. The need for research in AILVs in South Africa ... 22
CHAPTER 3: EFFECTS OF SEED SOWING DEPTH ON EMERGENCE AND EARLY SEEDLING DEVELOPMENT OF TWO SELECTED AFRICAN INDIGENOUS LEAFY VEGETABLES 3 .1. Introduction ... 24
3.2. Literature Review ... 26
3.3. Material and Methods ... 29 VIII
3.3.1 Soil sampling and analysis ... 29
3.3 .2 Experimental treatments and design ... 31
3.3.3 Source of seed and seed weight determination ... 33
3.3 .4 Seed viability test ... 34
3.3.5 Sowing of seeds ... 35 3.3.6 Data collection ... 33 3.3.7 Data analysis ... 35 3.4 Results ... 36 3.5 Discussion ... 45 3.6 Conclusions ... 48
CHAPTER 4: BIOMASS YIELD OF AMARANTHUS hybridus AND CLEOME gynandra IN RESPONSE TO KRAAL MANURE TYPES AND LEAF CUTTING TECHNIQUES 4.1 Introduction ... 49
4.2 Literature Review ... 51
4.3 Materials and Methods ... 63
4.3.1 Soil sampling and analysis ... 63
4.3.2 Manure collection and analysis ... 65
4.3.3 Treatments and Experimental design ... 68
4.3.4 Raising of seedlings ... 71
4.3.5 Transplanting and growing of seedlings in pots ... 71
4.3.6 Data Collection ... 72
4.3.7 Data analysis ... 74
4.4 Results ... 75
4.4.1 Properties of soil used in the study ... 75
4.4.2 Properties of manure used in the study ... 76
4.4.3 Results ofthe analysis ofvariance ... 76
4.4.4 Effect of kraal manure application on biomass yield and moisture content of C. gynandra and A. hybridus ... 81
4.4.5 Effects of cutting techniques on biomass yield, moisture content and crude protein of C. gynandra and A. hybridus ... 81
4.4.6 The interactive effects of kraal manure application and cutting techniques on biomass yield, moisture content and crude protein of C. gynandra and A. hybridus ... 84
4.4.7 Trends in the leafbiomass yield of C. gynandra and A. hybridus as influenced by kraal manure ... 86
4.4.8 Trends in the leaf biomass yield of C. gynandra and A. hybridus as influenced by leaf cutting techniques ... 88
4.5 Discussion ... 89
4.6 Conclusions ... 93
CHAPTER 5: THE RESPONSE OF AMARANTHUS hybridus AND CLEOME gynandra TO PHOSPHORUS FERTILIZER AND LEAF CUTTING TECHNIQUES 5.1 Introduction ... 94
5.2 Literature Review ... 96
5.3 Materials and Methods ... 102
5.3.1 Site location, soil sampling and analysis ... 102
5.3.2 Treatments and experimental design ... .l02 5.3.3 Raising seedlings of C. gynandra and A. hybridus ... 103
5.3.4 Transplanting and growing of seedlings in pots ... 103
5.3.5 Collection of data ... 1 05 5.3.6 Data analysis ... 106
5.4 Results ... 1 06 5.4.1 Properties of soil used in the study ... 106
5 .4.2 Results of the analysis of variance ... 1 06 5.4.3 Effect of phosphorus application on biomass yield ... 108
and moisture content of C. gynandra and A. hybridus 5 .4.4 Effect of cutting techniques on biomass yield and moisture content of C. gynandra and A. hybridus ... 111
5.4.5 The interactive effect of phosphorus application and cutting techniques on biomass yield, moisture content, plant height and crude protein of C. gynandra and A. hybridus ... . 114
5.4.6 Trends in the leaf biomass yield of C. gynandra and A. hybridus as influenced by phosphorus application rate ... 118
5.4.7 Trends in the leaf biomass yield of C. gynandra and A. hybridus as influenced by cutting techniques ... 118
5. 5 Discussion ... 119
5.6 Conclusions ... 122
CHAPTER 6: GENERAL DISCUSSION, CONCLUSIONS AND RECOMMENDATIONS 6.1 General Discussion ... 123
6.2 Conclusions ... 130
6. 3 Recommendations for future research ... 131
REFERENCES ... 133
APPENDICES ... 151 X
Table Table 2.1 Table 2.2 Table 2.3 Table 2.4 Table 2.5 Table 3.1 Table 3.2 Table 3.3 Table 3.4 Table 3.5 Table 3.6 Table 3.7 Table 3.8 Table 3.9 Table 3.10 Table 3.11 Table 3.12 Table 4.1 Table 4.2 Table 4.3 Table 4.4 LIST OF TABLES Title Page
Composition per 1 OOg of edible portion of A. hybridus,
C. gynandra, S. nigrum and C. olitorus compared to B. oleraciae ... l3 Nutritive value of Amaranth us leaves ... 14
Nutritive value of African Indigenous Vegetables as compared to
some exotic vegetables ... 15 The ~-carotene contents of fresh, boiled and fried amaranth leaves ... 16 Antioxidant activity of selected AIL V s (values per 1 OOg edible portion,
fresh weight basis) ... 17 Maximum soils strength per depth as affected by soil preparation method .... .28 Treatment combinations of sowing depths (D) and vegetable varieties
(V) for the first experiment. ... 32 The weight of 100 seeds for the four vegetable species used in this study ... 33 Analysis of variance (F values) of plant-height, shoot-biomass and
seedling etnergence ... 3 7 General trend effects of sowing depth on plant height, shoot-biomass
and seedling emergence of vegetable species at the first experiment.. ... 38 Effects of vegetable species on seedling height, seedling shoot-biomass and seedling emergence of seedlings sown at different depth ... 3 9 The interactive effects of sowing depth and vegetable species on
seedling emergence percent, seedling height (em) and seedling
shoot-biomass (g) of vegetable species ... .40 Analysis ofvariance for F values of plant-height, shoot-biomass and
seedling emergence for the second experiment ... 41 General trend effects of sowing depth on seedling height, seedling shoot-biomass and seedling emergence of seedlings ... 42 Effects of vegetable species on seedling height, seedling shoot-biomass and seedling emergence of seedlings sown at different depths ... .42 The interactive effects of sowing depth and vegetable species on seedling emergence percent, seedling height (em) and seedling shoot-biomass (g) of vegetable species ... 43 Pearson correlation coefficients (r) between soil penetrometer resistance (PR), soil water content (SW), seed sowing depth (SD), seedling
emergence (SE) and seed weight (SS) ... .45 Effects of different sources of manure on growth of cassava ... 54 Effect of different sources of manure on yield of cassava ... 55 Effects of sheep kraal manure rate on nutrient amounts
in amaranthus leaves at 30 days after transplanting (DAT) ... 57 Nutrient content of leafy traditional vegetables in South Africa (per 1 OOg fresh weight) ... 59
Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9 Table 4.10 Table 4.11 Table 4.12 Table 4.13 Table 4.14 Table 4.15 Table 4.16 Table 4.17 Table 5.1 Table 5.2 Table 5.3 Table 5.4 Table 5.5 Table 5.6 Table 5.7 Table 5.8 Table 5.9
Effects of manure on percent leaf nutrient content of cassava ... 60 Amount of nutrients equivalent to one hectare ... 67 Treatment combinations of types of manure (M) and cutting techniques (C) for C. gynandra and A. gynandra ... 68 Dates of cutting the leaves of A. hybridus and C. gynandra ... ... 72 Properties of the soil used in the study ... 7 4 Properties of manure used in the study ... 75 Analysis of variance showing the F values for total fresh leaf mass, total dry leaf mass, leaf moisture content, fresh stem mass, dry stem mass,
fresh root mass and dry root mass of C. gynandra and A. hybridus ... 7 6 Analysis ofvariance showing the F values for fresh leaf mass at
different cutting times for C. gynandra and A. hybridus plants ... 78 Analysis of variance showing the F values for dry leafbiomass at
different cutting times for C. gynandra and A. hybridus ... 79 Effect of kraal manure application on biomass yields and moisture
content of C. gynandra and A. hybridus ... 81 Effect of leaf cutting technique on biomass yields and moisture
content of C. gynandra and A. hybridus ... 82 The interactive effects of manure and cutting techniques on total fresh leaf yield, total dry leaf yield and leaf moisture content of C. gynandra and hybridus ... 84 The interactive effects of manure and cutting techniques on fresh
stem yield, dry stem yield, fresh root yield and dry root yield of
C. gynandra and A. hybrid us ... 85 Effects of different rates of phosphorus fertilizer on fruit production ... 96 Effects of different P levels and sources on grain yield of wheat crop ... 97 Effects ofP rates on vegetative growth and photosynthetic
pigments chlorophyll and carotenoids ... 98 Interaction between phosphorus rates and cutting height on initial
dry herbage yield (t ha-1) in lablab in the 2007 wet season at
Samaru, Nigeria ... 1 00 Root length density and P uptake in groundnut as influenced by seed size and phosphorus fertilization ... 1 02 Treatment combinations of phosphorus fertilizer rates (P) and
cutting techniques (C) on C. gynandra and A. hybridus ... .. 1 04 Dates and time frames of cutting the leaves of A. hybridus and
C. gynandra ... 1 06 Analysis of variance showing the F values for total fresh leaf mass,
total dry leaf mass, leaf moisture content, fresh stem mass, dry stem mass, fresh root mass, dry root mass and stem height of C. gynandra
and A. hybridus ... .. 1 08 Analysis of variance (F values) for fresh leaf mass at different cutting
times for C. gynandra and A. hybridus plants ... 11 0 XII
Table 5.10 Analysis of variance showing the F values for dry leaf mass at
different cutting times for C. gynandra and A. hybridus plants ... 111 Table 5.11 Effect of phosphorus application on biomass yield
and moisture content of Cleome gynandra and A. hybridus ... . 113 Table 5.12 Effect of cutting techniques on biomass yield and moisture content
of C. gynandra and A. hybrid us ... 114 Table 5.13 The interactive effects of phosphorus fertiliser and cutting techniques
on total fresh leaf yield, total dry leaf yield, leaf moisture content and
stem height of C. gynandra ... .. 116 Table 5.14 The interactive effects of phosphorus fertiliser and cutting techniques
on fresh stem yield, dry stem yield, fresh root yield and dry root yield
of C. gynandra ... . 117 Table 5.15 The interactive effects of single super phosphate and cutting techniques
on crude protein content of C. gynandra and A. hybridus ... 118
Figure Figure 3.1 Figure 3.2 Figure 3.3 Figure 4.1 Figure 4.2 Figure 4.3 Figure 4.4 Figure 4.5 Figure 5.1 Figure 5.2 Figure 5.3 LIST OF FIGURES Title Page
Seeds of the leafy vegetables used in the experiment and their seed
weights ... 34 Soil penetrometer resistance and water content at different sowing depths during the experilnent. ... 44 Visual signs of soil crusting in the soil when dry ... .4 7
The floors of goat kraal (a) and cattle kraal (b) where manure samples were collected ... 65 Layout of treatments in the net screen house ... 69 C. gynandra plant attacked by aphids (a) and A. hybridus cut by
locust (b) ... 71 Trends in the leaf biomass yields of C. gynandra and A. hybridus
during the experimental period as influenced by manure types ... 86
Trends in the leaf biomass yields of C. gynandra and A. hybridus during the experimental period as influenced by cutting techniques ... 87 Layout of treatments ... 1 05 Trends in the leaf biomass yields of C. gynandra and
A. hybrid us as influenced by phosphorus application rate ... 119 Trends in the leaf biomass yields of C. gynandra and
A. hybridus as influenced by cutting techniques ... 120
LIST OF APPENDICES
Appendix Title Page
Appendix 1 Calculation of application rates of kraal manure 151
Appendix2 Calculation of phosphorus fertilizer rates 154
Appendix 3 Calculation of Ammonium Sulphate rates 155
Appendix 4 ANOV A tables for seedling-height, shoot biomass and
and seedling emergence in sowing depth experiment 156 Appendix 5 ANOV A tables for biomass yield, moisture content and
crude protein of C. gynandra in kraal manure experiment 157 Appendix 6 ANOV A tables for biomass yield, moisture content and
crude protein of A. hybridus in kraal manure experiment 159 Appendix 7 ANOV A tables for biomass yield, plant height and crude
protein of C. gynandra in phosphorus experiment 161 Appendix 8 ANOV A tables for biomass yield, plant height and crude
protein of A. hybridus in phosphorus experiment 164
AIDS ANOVA
c
DF EP FAO FW GLM IALV IK IPGRI MC NRF SAS SE SEMDLIST OF ABBREVIATIONS AND ACRONYMS Acquired Immune Deficiency Syndrome Analysis of variance
Carbon
Degrees of freedom Emergence percent
Food and Agricultural Organization ofthe United Nations Fresh weight
General Linear Model
Indigenous African Leafy vegetables Indigenous knowledge
International Plant Genetic Resources Institute Moisture content
National Research Foundation Statistical Analysis System Seeds emerged
Standard error mean difference
PUBLICATIONS FROM THE DISSERTATION
A. Published
1. SEEISO, T.M. AND MATERECHERA, S.A., 2011. Effects of seed sowing Depth on Emergence and Early seedling Development of two African Indigenous Leafy Vegetables. Life Science JournalS, 12-12. http://www.lifesciencesite.com
2. SEEISO, T.M. AND MATERECHERA, S.A., 2012. Yield response of the African indigenous leafy vegetable Cleome gynandra to application of cattle and goat kraal manure and harvesting techniques. Journal of Food, Agriculture and Environment 10, 789-784.
B. Submitted
1. SEEISO, T.M. AND MATERECHERA, S.A., 2011. Is the Effect of Sowing Depth on Emergence and Early Seedling Development Similar in African Indigenous and Exotic Leafy Vegetables? Acta Horticulturae (in press).
C. Conference presentations
1. SEEISO, T.M., 2010. Is the Effect of Sowing Depth on Emergence and Early Seedling Development Similar in African Indigenous and Exotic Leafy Vegetables? North-West University presented at the Faculty of Agriculture, Science and Technology at research day on September, 2010.
2. SEEISO, T.M., 2011. Yield response of the African indigenous leafy vegetable Cleome gynandra to application of cattle and goat kraal manure and harvesting techniques. North-West University presented at the Faculty of Agriculture, Science and Technology at research day on October, 2011.
CHAPTER 1
GENERAL INTRODUCTION AND OBJECTIVES OF THE STUDY
The food and nutritional insecurity that most African countries face today can be mitigated and sustainably reversed if a manifest change can be realised through the appreciation of African indigenous foods (Oniang'o et al., 2004). Africa is endowed with a large variety of fruits and vegetables which have been accepted by communities through habit and tradition and are appropriate as well as desirable food sources. However, most of these food crops are underexploited and receive insufficient attention within the mainstream of food security development and management interventions. Indigenous African leafy vegetables (IAL V s) are plants whose leaves are consumed as relish and have originated in Africa or have been cultivated in Africa over a long period of time (Schippers, 2000; Gockowski et al., 2003; Van Rensburg et al., 2007). They include crops that are wild, semi-wild, or domesticated. In South Africa, Van Rensburg et al. (2007) identified more than 100 different species of plants that were being used as indigenous African leafy vegetables. South African people refer to these plant species collectively using the terms moraga (Sesotho, Sepedi), or imifino (isiZulu, isiXhosa), which loosely translated, means leafy vegetables.
Indigenous African leafy vegetables (IALVs) are an important part of farming and consumption systems throughout Africa (Aphane et al., 2002). They are important sources of micronutrients including vitamins A and C, iron, and others (Aphane et al., 2002). Indigenous African leafy vegetables are crucial to food security particularly during famine and natural disasters. There is an increasing awareness of the health protecting properties of non-nutrient bio-active compounds found m indigenous African leafy vegetables (Smith and Eyzaguirre, 2007). Indigenous African leafy vegetables are increasingly being recognized as possible contributors of both micronutrients and bio-active phytochemicals that have been linked to protection against cardiovascular and other degenerative diseases (Smith and Eyzaguirre, 2007).
Malnutrition is a senous problem facing Africa and research suggests that indigenous African leafy vegetables could help undercut food insecurity at the household level (Van Resburg et al., 2004). This is because IALVs are cheap,
highly nutritious, reliable and culturally appropriate food in times of scarcity. They are often better suited to the rigours of marginal environments and they can tolerate drought, poor soil fertility, diseases and pests, and require little in the way of management and inputs (Van Resburg et al., 2004; Guarino, 1997).
The United Nations Food and Agriculture Organization (F AO) has widely noted that most widespread and debilitating nutritional disorders, including birth defects, mental and physical retardation, weakened immune systems, blindness and even death has resulted from poor consumption of vegetables (Roy et al., 2006). Indigenous African Leafy Vegetables, though rich in vitamins, minerals and trace elements, have over the decades been recording an ever-diminishing consumption and production trend (Mwangi and Kimathi, 2006). However, the reawakening of demands for nutrition and health by modem communities has gradually created an enormous consumer demand for traditional food crops and IAL V s are on the spotlight due to their superior nutritive value (Mwangi and Kimathi, 2006). Indeed there is an increasing consensus that wild and cultivated IAL V s could significantly contribute to alleviating hunger and malnutrition (Burlingame, 2000).
The formal cultivation of IAL V s is more common in East and West Africa than in Southern Africa where it is often harvested from the wild (Kgaphola and Viljoen, 2004; Modi et al., 2006; Abukutsa-Onyango, 2007). Collecting and cultivating indigenous African leafy vegetables continues to be widespread among African people in South Africa (Bhat and Rubuluza, 2002; Van Rensburg et al., 2004; Modi et al., 2006). Indigenous African leafy vegetables are often intercropped with grain crops, particularly maize or other vegetables though monocropping also occurs (Hart and Vorster, 2006; Maundu et al., 1999). A recent study has shown that IAL V s are well known and play an important role among African communities in the rural villages surrounding Mafikeng town (Mooketsi and Gestring, 2011). In all these cultivation practices, there is dearth of information on the agronomic practices to be applied on IAL V s.
Furthermore, the harvesting practices for the IAL V s are not well studied nor documented. The cutting techniques have also been shown to influence productivity of crops. Yield response depends on the growth at which defoliation occurs and cutting frequencies (Rahman et al., 2008). Indigenous African leafy vegetables are
harvested at different stages of their growth cycle, since some are only palatable for short periods (seedling till plant starts to flower) (Vorster, 2007). In some communities, the high demand for vegetables leads to frequent leaf harvesting which decreases plant vigour and cause stunted and bushy growth (Okong'o, 2005). In cases of crop loss or food insecurity, frequent leaf harvesting will however continue. There are also other techniques of harvesting IAL V s that have been practiced based on culture and tradition (Hart and Vorster, 2006). The influence which all these practices have on growth and yields of IAL V s have not been systematically investigated and documented.
Throughout the ages, the establishment of food crops on agricultural lands has been recognised as risky, yet high productivity depends on it (Tisdall, 1996). Poor crop establishment can result from poor contact between seed and soil, or from dry and waterlogged soil. Evidence is also accumulating that seedlings whose emergence is delayeq have a reduced relative growth rate after emergence (Tisdall, 1996). Seedling emergence is also influenced by the depth of sowing as small seeded crops like amaranthus have limited food reserves to support gennination and seedling emergence (Odeleye and Olufolaji, 2010). Seedlings often fail to reach the surface when seeds are placed at uneven depth (Tisdall, 1996).
It is known that kraal manure, for example can supply significant quantities of major plant nutrients hence promote growth and yields of vegetables (Edmeades, 2003). Animal manure also Improves the chemical, physical and biological properties of soils (Wijewardena, 2000). In the South African smallholder sector, which is largely responsible for the production of most crops, animal manures have long been the primary way in which plant nutrients are returned to cultivated soils (Van A verb eke, 2008). In general vegetables differ from most perennial crops since they have a short growing period of 2 to 4 months and generate a high quantity of bimass rapidly to remove large quantities of plant nutrients (FAO, 1984). This suggests that the vegetables should receive a relatively large supply of plant nutrients m a short time from the soil for adequate growth and satisfactory vegetable crop yields. Animal manure can supply significant quantities of major plant nutrients hence they promote crop growth and yields. Animal manures also improve the chemical, physical and biological properties of soil (Wijewardena, 2000).
Azeez et al. (2010) showed that there was an increase in biomass yield of pumpkin and nightshade in response to application of three types of animal manures. They suggested that the microorganisms that are present in the stomach of ruminant animals contribute to differences in response observed in crops supplied with different manures. Kipkosgei et al. (2003) reported that for cattle and goat manure, biomass production of Solanum villoswn increased as the rate of application was increased to 68.25 tons ha-1 in the case of goat manure and 85.28 tons in the case of cattle manure. Animal manure at the tested levels contained higher levels of N, P and K and suggested that the results could be attributable to this concentration level of nutrients in animal manure.
It is of concern that the leafy vegetables of Africa are being displaced in many areas, leading to a decline in production, use and the diversity of vegetables being grown (Aphane et al., 2002). This trend will clearly have a detrimental impact on the nutritional status of households, and the incomes of, especially, women farmers. The availability of indigenous vegetables has declined drastically because of excessive cultivation of field crops and land degradation which affects their habitat (Aphane et al., 2002). The degradation of the natural environment puts the existence of wild indigenous vegetables at stake. This problem can be overcome by domestication of indigenous leafy vegetables and integrating them into existing production systems on farms where their agronomic practices can be improved by such practices as fertilization and harvesting techniques.
Cleome gynandra, locally known as lerotho (seTswana) and Amaranthus hybridus locally known as theepe (Sesotho) are among the group of indigenous African leafy vegetables that have a high potential for development as cultivated crops in South Africa. They grow best during summer and requires full exposure to sunlight. Cleome gynandra is a high nutritious food. The young plants of cleome species are edible and are cultivated by several communities. Fresh leaves and tender shoots are boiled whole and mixed with other ingredients to produce a tasty relish. The leaves of cleome are rich in vitamin A and C and contain moderate levels of calcium and 1ron. Amaranthus is also more widely used as a pot-herb and supplies a substantial portion of the protein, minerals, vitamins (especially A and C) and iron in the diet. Leaves may be dried and stored for use in deficit periods. It is a readily available vegetable in the rainy season when exotic vegetables become scarce. Cleome and
amaranthus are some of the most dominant and frequently used indigenous African leafy vegetables in villages around Mafikeng (Mooketsi and Gestring, 2011). However, there is very little information available regarding their production and management techniques.
Many people are becoming increasingly aware of the importance of IAL V s in meeting their household food security, and are therefore producing them in their home gardens and farms (Vorster, 2007). There is however not enough information regarding their optimum agronomic practices including such aspects as fertilizer application rate, harvesting techniques and sowing depths. There is, therefore, a need to investigate viable techniques of producing indigenous African leafy vegetables so that they can be promoted among local communities.
The aim of this study was to investigate agronomic strategies that can be used to improve growth, productivity and quality of two dominant indigenous African leafy vegetables (IAL V s) in villages surrounding Mafikeng town namely, Amaranthus hybridus and Cleome gynandra. The specific objectives of the study were to:
1. Investigate the effects of sowing depth on emergence and early seedling development of Amaranthus hybridus and Cleome gynandra
2. Determine the response of Amaranthus hybridus and Cleome gynandra to different types of animal manures and cutting techniques.
3. Determine the influence of phosphorus fertilization and cutting techniques on yield and quality of Amaranth us hybridus and Cleome gynandra leaves
The following hypotheses were tested for each of the above objectives:
1. Sowing depth can improve emergence and early seedling development of Amaranthus hybridus and Cleome gynandra
2. Different types of animal manure when combined with harvesting techniques can affect the yield and quality of Amaranthus hybridus and Cleome gynandra leaves differently
3. Different levels of phosphorus fertilization combined with harvesting techniques affect the yield and quality of Amaranthus hybridus and Cleome gynandra leaves differently
Dissertation outline
The dissertation has been organized into six chapters. Chapter one gives a general outline of the problem associated with the utilization and production of the indigenous African leafY vegetables and identifies the research gaps. The objectives of the study are also given in this chapter. The significance of indigenous African leafY vegetables and their role in the food and nutritional security of households among smallholder farmers in sub-Saharan Africa and South Africa in particular are examined in chapter two. Chapter three reports the results of a glasshouse study which investigated the effects of seed sowing depth on emergence and early seedling development of two indigenous African leafY vegetables (Cleo me gynandra and Amaranthus hybridus). Their performance was also compared with two exotic vegetables (Brassica napus and Spinacia oleraceae). In chapter four the influence of two types of kraal manure and leaf cutting techniques on the biomass yields of the two indigenous African leafY vegetables were investigated. Chapter five reports the results of another experiment conducted to quantity the effect of applying phosphorus from fertilizer in combination with leaf cutting techniques on the response of the two IAL V s in terms of growth yield and quality of the leaf biomass. Chapter six provides a general discussions and practical implications of the results from the study and draws some conclusions and recommendations for future studies.
CHAPTER2
SIGNIFICANCE OF AFRICAN INDIGENOUS LEAFY VEGETABLES IN FOOD AND NUTRITIONAL SECURITY OF SMALLHOLDER HOUSEHOLD 2.1 Introduction
According to F AO (2005), South Africa has an average annual rainfall of less than 500 mm. More than 80 % of its land surface is classified as semi-arid to arid. Only 18 % is classified as dry sub-humid and sub-humid. Rain fed crop production is concentrated in these mentioned zones as well as in the central and eastern reaches of the semi-arid zone where favourable soil characteristics occur. The total land area of South Africa is 127 million hectares of which 82 % IS agricultural land
while 14 percent of the land receives sufficient rainfall for arable land crop production. The remainder is used for extensive grazing, forestry and nature conservation. Only 1.35 million hectares are under irrigation and produce a significant proportion of the country's total agricultural output, especially in horticultural and vegetable production. In the year 2003-2004, South Africa's total gross value of agricultural output was estimated at R 72 000 million and it contributed 3.8% to the economy (National Agricultural Marketing Council, 2009).
South Africa's total population in the year 2000 was estimated at 44.7 million and 40 % of the population is classified as living with poverty (Population Unit, 2000). While the country is self-sufficient in food production, 43 % of households are vulnerable to food insecurity (Population Unit, 2000). Poverty 1s wide-spread in rural areas of South Africa. When attention is put towards subsistence farming and development of smallholder agriculture, it will help to alleviate food insecurity in South Africa, particularly in the rural areas. Machete et al. (2004) reported that fertilizer application in these sectors can have a significant impact on raising smallholder agricultural productivity particularly considering the decline in soil fertility levels which have become prevalent throughout Africa.
African indigenous leafy vegetables (AILVs), also referred to as traditional leafy vegetables, are crops that grow wild or are cultivated and are gathered or harvested for food within a particular African ecosystem (Vorster, 2007; Aphane et al.,
which the leafy parts, which may include young succulent stems, flowers and very young fruits are used as vegetables. Most indigenous African leafy vegetables grow naturally in the bush and do not have to be tended for them to produce the edible parts. Traditional vegetables are sources of food in the form of leaves, seed, berries, fruit, roots, tubers, stems and rhizomes (Vorster, 2007; Vorster et al., 2007; Guarino, 1997). According to the F AO (1988), traditional vegetables are all plants whose leaves, roots or fruits are acceptable and used as vegetables by rural and urban communities.
Smith and Eyzaguirre, (2007) defined leafy vegetables as those plants whose leaves are edible, usually succulent portion of plants which are consumed as a side dish with a starchy staple. The definition of leafy vegetables noted that vegetables are 70-95 % water and are generally low in dry matter and nutrients, often contain minerals and vitamins. Indigenous African leafy vegetables have the potential to fill a valuable niche in the production of food in rural areas especially where the climate is not conducive to the production of exotic vegetables (Flyman and Afolayan, 2006). This is because such vegetables are efficient sources of important micronutrients, in respect to unit cost of production and per unit area. Indigenous African leafy vegetables are important sources of micronutrients including vitamins A and C, iron, and others (Aphane et al., 2002; Vorster and Van Rensburg, 2005). Thus, IAL V s can play a significant role in improving the quality of life among resource-poor households and help reduce malnutrition and poor health (Gockowski
et al., 2003). Indigenous African leafy vegetables are an important component of
farming and consumption systems throughout Africa (Odhav et al., 2007). Indigenous African leafy vegetables are therefore crucial to food security particularly during famine and natural disasters. Indigenous African leafy vegetables are increasingly being recognized as possible contributors of bio-active phytochemicals that have been linked to protection against cardiovascular and other degenerative diseases (Smith and Eyzaguirre, 2007).
In the past, traditional societies have exploited edible indigenous plant resources to obtain their nutritional requirements (Chweya and Mnzava, 1997). Studies on the agro-pastoral societies of Africa indicated that these plant resources still play a significant role in nutrition, food security and income generation (Chweya and Mnzava, 1997). It is therefore worthwhile to note that the incorporation of IALVs
or maintenance of IAL V s vegetables could be beneficial to nutritionally marginal populations, or to specific vulnerable groups within populations, especially in developing countries. Domestication and cultivation of IAL V s 1s, therefore, essential in broadening the food base of developing countries and will lead to diversification of vegetables which will ensure a dietary balance and intake of micronutrients.
About 13000 indigenous vegetable spec1es are found in different parts of the world (Mwangi and Kimathi, 2006) such as America, Europe, Asia and Oceania (Chweya and Mnzava, 1997) of which 3000 are found in African countries (Mwangi and Kimathi, 2006). Reports on the diversity of traditional leafy vegetables in sub-Saharan Africa by Biodiversity International showed that there are more than 20 leafy vegetable species specific to Africa that are used in daily diets and are of nutritional importance (Smith and Eyzaguirre, 2007).
These plants together with exotic crops that were introduced between the eighth and mid-twentieth century formed part of the daily diet of Africans. These crops were adapted where they fitted well with the local environment. In Africa as a whole, production, trade and consumption of African indigenous leafy vegetables are expanding (Van Rensburg et al., 2007).
2.2. The status of African indigenous leafy vegetables in South Africa
Agriculture is one of the major contributors to the economy of South Africa, however, the biodiversity of the country has not benefited the majority of its population. Indigenous African leafy vegetables have been substituted by western foods that are highly processed and less nutritive (Van Rensburg et al., 2007; Aphane et al., 2003). In South-Africa 100 species of plants that were used as indigenous African leafy vegetables have been identified and African people refer to these plant species collectively, using the term moraga (Sesotho, Sepedi) or imfino (isiZulu, isiXhosa) (Van Rensburg et al., 2007).
Indigenous African leafy vegetables are an important part of farming and food consumption patterns throughout South-Africa. Many such plants grow in the wild or as weeds in cultivated areas but have also been domesticated through semi-cultivation or semi-cultivation. When domesticated, IAL V s require few inputs and tend to
grow in areas unsuitable to grow exotic vegetables (Aphane et al., 2003). Collecting and cultivating green leafy vegetables continues to be widespread among African people in South Africa even though western influences have considerably modified their food consumption patterns.
There are many different species of leafy vegetables used in South-Africa many of which are fairly localized. Many of these vegetables are not readily amenable to conventional agronomic studies as they are often grown in small patches in home gardens. The indigenous African leafy vegetables are being displaced in many areas leading to a decline in production, use and diversity of vegetables being grown.
The role of African indigenous leafy vegetables in the food consumption patterns of South-African households is highly variable and depends on factors such as poverty status, degree of urbanisation, distance to fresh produce markets and time of year (Van Rensburg et al., 2007).
2.3. Uses of African indigenous vegetables
2.3.1. The role of AILVs in household food and nutritional security
According to F AO (1988), food security exists when all people at all times have physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life. Household food security is the application of this concept to the family level, with individuals within households as the focus of concern.
The main food security challenge in South Africa is to increase the ability of historically disadvantaged groups to meet their minimum daily requirements for proper nutrition. This malnutrition of the majority population stems from the insufficiency and instability of food supply, inability to purchase food, weak institutional support networks, poor nutrition, inadequate safety nets, and weak disaster management systems (Aphane et al., 2002). Food insecurity and malnutrition are highest in some provinces m South Africa with large rural populations such as KwaZulu-Natal, Northern Cape, Eastern Cape and the Free State (Aphane et al., 2002) .
Due to multiple uses and plant parts that can be eaten, traditional vegetables play an important role in food security. Indigenous African leafy vegetables are crucial to food security particularly during famine and natural disasters, two problems that are currently prevalent m South Africa (Chweya and Mnzava, 1997; Aphane et al., 2002; Gockowski et al., 2003). The importance of indigenous African leafy vegetables in food security was evidenced by the findings of Modi et al. (2006) in their study on potential role for indigenous vegetables in household food security. The study was conducted in Kwazulu-Natal South Africa. The aim of the study was to assess the general knowledge and availability of indigenous vegetables at Ezigeni location. Nineteen subsistence farmers participated in a focus group discussion. From the results, the farmers indicated no availability of exotic leafy vegetables, an indication that indigenous African leafy vegetables may be the major source of micronutrients for the majority of resource-poor people at Ezigeni. The study showed that the scarcity of food crops generally coincided with the time of the year when indigenous African leafy vegetables were becoming more abundant, for example end of August to October.
It was concluded that indigenous African leafy vegetables could contribute significantly to the dietary requirements of rural household at Ezigeni. These results are in agreement with the findings of Vorster, (2007) on the role and production of traditional leafy vegetables in rural communities in South Africa based in Limpopo and KwaZulu-Natal provinces. A questionnaire was used to collect relevant data from the villagers. Across the three villages studied, the results indicated that there is an availability of IAL V s at longer periods of the year, at this time, that is when they process the excess bulk of IAL V s by drying them so that they can be used during winter period to supplement the diet when the amount of fresh IAL V s is relatively low. It is, therefore, important to include IALVs into the agricultural production systems since many people depend on them, especially in the rural areas of South Africa.
Indigenous African leafy vegetables play multiple roles in the diet, beside providing certain nutrients, they add flavour, colour and texture that relieve the monotony of bland starch diet. As a group, they provide improved nutrition for people of all economic levels. Indigenous vegetables have been reported to contain comparatively high amounts of Vitamins A and C (Flyman and Afolayan, 2006;
Aphane et al., 2002). IALVs are usually inexpensive or free and are a rich source of nutrients especially vitamins A and C, and minerals (calcium and iron). The high nutritive value of IAL V s was confirmed in a study on the role of indigenous leafy vegetables in combating hunger and malnutrition (Van Rensburg et a!., 2004). The results of their study are presented in Table 2.1 which shows the nutrient composition of IALVs when compared to cabbage which is an exotic leafy vegetable. It is observed from the table that IALVs have high nutritive values when compared to exotic leafy vegetable, cabbage. Indigenous African leafy vegetable, amaranth us is nutritionally more valuable than any of the other AIL V s. It provides about 4500 units of vitamins per 100 g edible portion compared with 600 g for swiss chard and 280 g for cabbage. It also provides more energy, protein, minerals and vitamins especially vitamin C than the other indigenous African leafy vegetables (Table 2.2). Amaranthus is a good supplement for diets based on cereals and tubers as it is rich in lysine (Schippers, 2000).
Cleome is known for its nutritional and medicinal value (Table 2.1 ). It is used to help mothers recuperate after giving birth and during breast-feeding, as well as for stomach ailments (Chweya and Mnzava, 1997). Increased soil fertility results in increased crude protein of the leaves. Corchorus is rich in vitamins A and C, protein, calcium and folic acid (Table 2.1 ). In some species, the protein content of the young leaves can be as high as 25 %. This vegetable eases indigestion and is also used as a laxative. Much of the healthy nutrients are lost due to overcooking especially when the water in which it was boiled is discarded (Schippers, 2000). S.
nigram is a good source of calcium when compared to other IALVs (Table 2.1). It was concluded that Indigenous African leafy vegetables will benefit farmers across Africa and help to improve the nutritional status ofthe vulnerable groups.
Indigenous African leafy vegetables especially the dark green leafy ones, are known to contain oxalates, phytates, nitrates, tannins and saponins, all of which are known to reduce the absorption of certain micronutrients in the body (Guil et al., 1997). Table 2.3 shows the nutritive value of a few indigenous African leafy vegetables as compared to some popularly grown exotic vegetables consumed and marketed m many parts of Africa. The table shows that indigenous vegetables have relatively high micronutrient content as compared to exotic vegetable species. Indigenous vegetables have high protein percentages, calcium,
p -
Carotene and vitamin C asTable 2.1 Composition per 100g of edible portion of A. hybridus, C. gynandra, S. nigrum and C. olitorus compared to B. oleraciae
A. hybridus C. gynandra S. nigrum C. olitorus B. oleraciae
Iron (mg) 8.9 6 1.0 7.7 0.7 Protein (g) 4.6 4.8 4.3 5.6 1.7 Moisture (%) 84 86.6 87.2 Calories 42 34 38 43 26 Carbohydrates (g) 8.2 5.2 5.7 7.6 6 Fiber (g) 1.8 - 1.3 1.7 1.2 Ascorbic acid (mg) 64 13 20 53 54 Caicium (mg) 410 288 442 266 47
Phosphoros (micrograms) 103 Ill 75 122 40
~-Carotene (milligrams) 5716 - 75 7850 100
Thiamine 0.05 - - 0.13 0.04
Riboflavin 0.42 - 0.59 0.26 0.10
Source: F AO (1988); Schippers (2000)
Table 2.2 Nutritive value of Amaranthus leaves
Variety Protein(%) Fat(%) Fiber(%) Fe Ca Vitamin A Vitamin C
A. hypochondriachus 27.6 2.2 7.6 24.3 3.8 41.9 13.6
A. tricolor 27.4 1.8 6.6 10.4 3.4 33.7 11
A. cruentus 26 2 9.1 61.3 3.3 43.8 6.3
A. hybridus 30.3 1.5 8.3 99 2.4 34.4 11.2
A. hybridus (mayfords) 26.8 2.3 6.2 84.5 2.9 45.8 9.2
Source: Van der Reever and Coertze (1996)
compared to exotic vegetable species. Exotic vegetable species are an excellent source of iron, for example, kale has 32 mg and spinach has 32 mg per plant. The only exception which is higher than the exotic vegetables is the cowpea with 39 mg. It can therefore be concluded that indigenous African leafy vegetables have the highest micronutrient content as compared to exotic vegetable species.
Table 2.3 Nutritive value of Indigenous African leafy Vegetables as compared to some exotic vegetables
Indigenous vegetables Protein Calcium Fe Bcarotene Vitamin C Species (%/plant) (mg/plant) (mg/plant) (mg/plant) (mg/plant)
Amaranthus 4.0 480 10 10.7 135
Spider plant 5.1 262 19 8.7 144
Cowpea 4.7 152 39 5.7 87
Nightshade 4.6 442 12 8.8 131
Jute Mallow 4.5 360 7.7 6.4 187
Exotic Vegetable Species
Kales 2.5 187 32 7.3 93
Cabbage 1.4 44 0.8 1.2 33
Spinach 2.3 93 32 5.1 28
Source: FAO (1988)
The potential effect of IALVs on th~ nutritional status was confirmed by Faber et al. (2010) in a study conducted in Limpopo and Kwazulu-Natal provinces. The study was conducted to determine the availability and nutrition related uses of indigenous African leafy vegetables in rural and urban households and to determine the ~-carotene content of the dominant indigenous African leafy vegetables. Amaranth emerged as the indigenous African leafy vegetable that was popular in both provinces. The ~-carotene content of fried, boiled and fresh amaranth (per 100 g edible portion) from the study is presented in Table 2.4. The mean vitamin A value (!l retinol activity equivalents; RAE) of fresh, boiled and fried amaranth was 421 ll RAE/1 00 g, 429 ll RAE/1 00 g and 627 ll RAE/1 00 g respectively. The ~
carotene content of fried amaranth was higher than that of boiled amaranth. This may be caused by higher temperature generated during frying, resulting in greater moisture loss from fried leaves compared to boiled leaves (Faber et al., 2010). Amaranth can potentially contribute significantly to vitamin A requirements of
nutritionally vulnerable communities. The conclusion made in this study was that indigenous African leafy vegetables were commonly consumed in the study areas, mostly because they are a free source of nutritious food that can be
easily accessed and regularly harvested during the growing season and they are generally rich sources of various micronutrient.
Table 2.4 The P-carotene contents of fresh, boiled and fried amaranth leaves
Preparation Method Fresh leaves Boiled leaves Fried leaves Total ~-carotene fl/lOOg mean (SD) 6156 6472 930 Trans-~-carotene Vitamin A fl/lOOg flgRAE/lOOg mean (SD) mean (SD) 5047 421 5151 429 7526 627
SD = standard deviation; vitamin A value calculated from all-trans-p-carotene = 1 J..Lg retinol
activity equivalents
Source: Faber et al. (2010) 2.3.2. Medicinal value of AILVs
A large number of indigenous African leafy vegetables have long been known and reported to have health protecting properties and uses (Okeno et al., 2003; Ayodele, 2005). Several of these indigenous African leafy vegetables continue to be used for prophylactic and therapeutic purposes by rural communities (Okeno et al., 2003; Ayodele, 2005). The indigenous knowledge of the health promoting and protecting attributes of indigenous African leafy vegetables is clearly linked to their nutritional and non-nutrient bioactive properties (Smith and Eyzaguirre, 2007). The major class of phytochemicals is the polyphenols. Polyphenols are quantitatively the mam dietary antioxidants and possess higher in vitro antioxidants. Plant phenolics include phenolic acids, coumarins, flavonoids, stilbenas, hydrolysable and condensed tannins, lignins and ligneous. These and other antioxidants present in fresh vegetables, promote good health by assisting in preventing cancer and high blood pressure, stimulating the immune system, improving drug metabolism and tissue regeneration (Szeto et al., 2002).
Indigenous African leafy vegetables thus have the potential to be exploited as sources of antioxidants. This was proven by the work of Uusiku et al. (20 1 0) on nutritional value of leafy vegetables of sub-Saharan Africa and their potential contribution to human health. The aim of their work was to determine whether indigenous African leafy vegetables can potentially contribute to the alleviation of protein energy malnutrition and micronutrient deficiencies while taking into account the effect of antinutrient and the role of antioxidants found in IAL V s in the prevention of diseases. Table 2.5 shows the antioxidant activity of the vegetables analysed.
Table 2.5 Antioxidant activity of selected IALVs (values per 100g edible portion, fresh weight basis).
African leafy vegetables
Amaranthus sp. B. pilosa B. alba C. agentia C. album C. monophylla C. olitorius Crassocephalum sp. G. parviflora H esculenta Jfava M utilissima M. balsamina N aquatica 0. gratissimum 0. sinuatum P. oleracea S. thellungii Solanum sp.
Source: Uusiku et al. (20 1 0)
Antioxidant activity (%) 45 54 89 90 42 84 45 89 76 56 96 90 94 100 11 92 96 99 78
From Table 2.5, it is indicated that the leaves of C. argentea, J Flava, M utssima, M balsamina, N aquatic, 0. sinnatum, P, oleracia, S. thellungi, U dioica and X mafaffa have good antioxidant activity with 90, 96, 90, 94, 100, 92, 96, 99, 100 and 99 % respectively. The conclusion made out of these findings was that, raw IAL V s have been shown to possess antioxidant activity and thus have the potential to be
used as cheap natural sources for reducing cellular oxidative damage and consequently reducing degenerative conditions such as cardiovascular diseases and cancer.
2.3.3. The socio-economic importance of indigenous vegetables
Indigenous African leafy vegetables play an important role m mcome generation and subsistence. For example, Adebooye and Opabode (2004) reported that Solanecio biofrae and Amaranthus cruentus, indigenous leafy vegetables in South-West Nigeria are several times more expensive than the routinely cultivated species especially during the dry season. Surveys carried out by the Natural Resources Institute in Cameroon and Uganda provided evidence that indigenous vegetables offer a significant opportunity for the poorest people to earn a living, as producers and traders without requiring large capital investments (Schippers, 2000). A direct effect of this is that the vegetables provide employment opportunities for those that are outside the formal sector in peri-urban areas of many African cities because of their short, labour-intensive production systems (Schippers, 2000; Adebooye and Opabode, 2004). Madisa and Tshamekang (1997) stated that indigenous vegetables of equal or better nutritional status could perform better under cultivation with relatively low input levels in Botswana. Currently, people are getting vegetables from the wild to meet their dietary requirements. This exploitation of wild resources is an important source of income and food, especially for the rural poor, who are also under employed. These vegetables are cheaper than exotic ones and thus affordable by an average Motswana (Madisa and Tshamekang 1997).
2.4. Factors affecting the utilization of indigenous African leafy vegetables
Most indigenous vegetables are underutilized, few of them are popularly used by small groups of people in very limited geographical areas. This condition of underutilization of indigenous vegetables puts their survival at stake. A number of factors currently constrain the cultivation and use of the IAL V s. The decline in use of traditional leafy vegetables by many rural communities has been observed. This was evident from the study conducted in some villages in Limpopo and KwaZulu-Natal Provinces by Vorster (2007). The study focused on the role and production of traditional leafy vegetables in three rural communities in South Africa.
