Chapters 5.38
5.38 -Adopting Watermelon to Combat Drought
Devon Dempster, University of Guelph, Canada
Suggested citation for this chapter.
Dempster,D. (2022) Adopting Watermelon to Combat Drought, In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Background
Drought throughout Africa and the subtropics is a common problem and is worsening due to the effects of climate change (Verschuren, 2000). Watermelon (Citrullus lanatus) originates in Africa (Paris, 2015) and its wider adoption is a possible solution for smallholder farmers, as watermelon plants have deep root systems that can exploit soil moisture, making them ideal for drought conditions (Mtumtum, 2012). The crop has both nutritional and income benefits
Cultivation requirements
Target crops and country
China is the world's largest producer of watermelon; producing as much as two-thirds of the world’s watermelon (National Research Council, 2008). Despite this, watermelon has been concluded to originate from northeastern Africa (Paris, 2015) (National Research Council, 2008).When considering genetics, cultivated watermelon are most similar to crops from West Africa (Chomicki, 2015). African Citrullus is genetically diverse, with plenty of potential to improve crop yield and tolerance (National Research Council, 2008).
Steps to cultivate watermelon from its seed
When planting on dry sites, sowing of seeds is executed when rainfall begins; the opposite is done for moist crop sites, in which planting is executed when rainfall ends (National Research Council, 2008). Ideally, planting is done when the soil temperature has reached at least 20°C (National Research Council, 2008). Seeds are sown in 2-4 cm deep soil, in groups of 1-3 at a time (National Research Council, 2008). Later on, seedlings are thinned to 1 per site; in the meantime, transplants may be planted during the appearance of leaves (Mtumtum, 2012). The World Vegetable Center in Taiwan, a CGIAR Institute, has a seedbank of the world’s watermelon seeds and makes available seeds of different watermelon varieties to the public sector (see link below).
Environmental/external factors
Dry and upland areas are good prospects for watermelon crops. Dry areas are ideal for wild watermelons deep root systems, in which they exploit moisture from the soil. Upland areas are also ideal (depending on latitude and elevation) as watermelon crops call for extended growing periods and high temperatures (National Research Council, 2008). Humid areas are less ideal as they increase the risk of a variety of diseases, though many are bred to resist them (National Research Council, 2008). An annual rainfall of 600 mm-1200 mm is needed for wild watermelon (Mtumtum, 2012). However, watermelon can survive on as little as 250-500 mm of rainfall (National Research Council, 2008). Watermelon can generally grow on any soil type, but it does best on sandy or well drained soils, soils with good moisture retention capacity, and plenty of organic matter (National Research Council, 2008). The depth of soil should be approximately 10 cm, with a pH of 5.0 - 8.0 (ideally pH 5.5 - 7.0) (National Research Council, 2008). The ideal temperature range for watermelon is 23-27°C (growth stops below 18°C), however some grow where the temperature is 36°C (southern regions) (National Research Council, 2008). Control of weeds can be done through the use of herbicides (if affordable), or through manual labour (Ayinde, 2013). Weeding performed manually demands 2-3 weeding prior to harvesting; weeding is most affected by factors such as damage of flowersunintentional cutting of vines, as well as stepping on immature fruits as they are still developing (Ayinde, 2013). Watermelon flowers are staminate, and they normally begin to develop 4-8 weeks following seeding (Wehner, 2008). The growing season for watermelon crops typically spans approximately four months and reaches maturity about 45 days after blooming (National Research Council, 2008).
Constraints to Adopting Watermelon
Watermelon market economic relationships
In Africa, there is a high demand for watermelon (Balogun, 2019). Some marketers are motivated by the profitability, while others are interested in its livelihood benefits (Balogun 2019). Ninety percent of marketers are constrained by credit accessibility (Balogun, 2019). Cost of marketing counts for nearly 50% of marketing expenditure: cost of transportation, cost of handling, market fees, and cost of storage (Balogun, 2019). When stored in direct sunlight/high temperatures, the physiological damage to the watermelon accelerates and decreases shelf life, making them less profitable (Balogun, 2019). However, watermelon seed has economic value for marketers, as they are high in good properties such as fats and protein, and have a variety of uses (Mtumtum, 2012). In West Africa, melon seed, called Egusi, is a staple food crop.
Economic value for local markets
Watermelon offers the prospect for development of rural areas as it is easy to grow, store, and eat (National Research Council, 2008). The majority of marketers are married and have a moderate sized family, meaning they have labour available to them (Balogun, 2019). As well, the majority of marketers have an education beyond primary school, thus indicating literacy to a degree (Balogun, 2019). This may in turn translate to profit and ability to innovate, adopt new technologies and skills that could improve their overall profit (Balogun, 2019). However, the low cost of watermelon and general unstable market prices develop challenges within local markets (Ayinde 2013). These problems arise as an aftermath of inadequate transportation and pricing systems (Balogun, 2019). Up to 30% loss of product occurs during the transportation process (Balogun, 2019). Furthermore, prices may double during off season, making it difficult to benefit from price increases (Balogun, 2019).
Nutritional value and other uses
Watermelon provide a fair amount of nutrition. It is a source of provitamin A (300 RE/100 g for some red types) and vitamin C (100 mg/100 g) (National Research Council, 2008). Its vitamins help lesson night blindness, prevent eye problems, dry skin conditions, and psoriasis (Ayinde, 2013). Watermelon also contains potassium, about 4% of daily nutritional value per 1 cup (USDA, n.d.), which can aid in controlling blood pressure and perhaps prevent stroke (Ayinde, 2013). It is also high in fibre, providing 2% of daily nutritional value per 1 cup (USDA, n.d.). Watermelon seeds contain between 20-40% protein, and fair amounts of minerals and B vitamins (National Research Council, 2008, p. 174). Watermelon has a wide variety of uses as well, predominantly for food consumption. It can be cooked as vegetables (vegetable watermelons), seeded (for income or consumption), pickled, emergency food security, eaten fresh, used for rinds, oil, leaves, and flowers (National Research Council, 2008). In some cases, seed cake can be used as animal feed, and watermelon may be used to provide water for animals (National Research Council, 2008).
Achievability of Wider Adoption
Steps that farmers can take to adopt new crops
Intercropping is a powerful tool that farmers can use to produce higher yields. Intercropping is characterized as concurrent growing of more than one crop on the same area of land (Mtumtum, 2012). As an example, pumpkin and melon can often be intercropped with maize (corn) as they complement one another (Mtumtum, 2012). Additionally, intercropping functions as live mulch as it represses weeds without the need to apply an organic or inorganic component (Mtumtum 2012). Mulching in itself can be used as a crop production technique to provide a better environment for crop growth (Mtumtum, 2012). In addition to suppressing weeds, it aids the soil in retaining moisture and temperature regulation (Mtumtum, 2012).
Retail and labour cost
In one study in Nigeria, the gross return per 1 hectare for melon was ₦12, 638.61 ($34.82 USD) in 2008; on average the total cost was ₦8, 838.74 ($24.35 USD) providing a net income of ₦3, 799.87/Ha ($10.47 USD) for a farm (Ayinde, 2013). In Kwara State, the contrast between the sum of the return and total cost of crop production provided a total margin of ₦1, 263.81/Ha ($3.48) (Ayinde, 2013). Most farmers could not sell their product as a result of this (Ayinde, 2013). Therefore, before promoting adoption of watermelon as a cash crop, the local market potential of the crop versus input costs, needs to be carefully assessed. In other parts of the world, watermelon is considered a good source of income for women farmers.
Required labour/technologies for improved crop yield
Cultivation of watermelon is highly labour intensive (especially due to its weight) (Ayinde, 2013). The process of cultivation includes many steps including splitting the pod, fermentation, collecting seeds from these pods, and washing and drying them by sun (Ayinde, 2013). Storage of watermelon is dependent on the overall size of the harvest, and the available labour. In some cases, watermelon is left in the fields, or they are assembled in a pile at the homesteads (Mtumtum, 2012). Piling the cultivated fruit acts as a suitable storage for food/water for up to a year’s duration without the watermelon going bad or decreasing in quality (Mtumtum, 2012). Thus, the fruit has remarkable post-harvest stability.
Critical Analysis
Pests that target watermelon plants
The most significant watermelon pest in Africa is the Melon Fly (Bactrocera Cucurbitae) (National Research Council, 2008). Less significant are root knot nematodes (National Research Council, 2008). Wild collections of watermelon are well known to resist pests, and usually remain unaffected (Mtumtum, 2012). Pests (and diseases) can be exterminated through use of pesticides (chemically), or with non-chemical methods. To lessen risks, farmers can use disease free fruit (seeds), plant earlier in the crop season, and/or rotate crops annually (Mtumtum, 2012).
Various diseases
There are a number of diseases that watermelon crops are susceptible to. These include bacterial fruit blotch, damping off, anthracnose, powdery mildew and downy mildew, Fusarium wilt, gummy stem blight, and an assortment of viruses such as Watermelon Mosaic Virus (National Research Council, 2008). Downy mildew is caused by Pseudoperonospora cubensis; and damping off, caused by Macrophomina phaseolina, is most frequent during the seedling stage (Mtumtum, 2012). Humidity and excess rainfall encourage the occurrences of these diseases (Mtumtum, 2012). Viruses, on the other hand, are transmitted to crops through aphids and cucumber beetles (though some may occur through humidity/soil health) (National Research Council, 2008). Further, this is why dry conditions are most ideal for watermelon crops (Mtumtum, 2012). Chemical control of these issues is most needed, preferably on a weekly basis (Ayinde, 2013). However, this is rarely the case as it is expensive for small scale farmers to afford such chemicals.
Helpful online resources to get started
Obtaining Seeds: AVRDC - World Vegetable Center, Taiwan: Search using the Latin name Citrullus lanatus: http://seed.worldveg.org/search/passport https://avrdc.org/seed/seeds/
https://www.seedsavers.org/grow-watermelon Purchasing seeds from Seed Savers
https://www.youtube.com/watch?v=-NKyehOeaJQ Market for watermelon in Uganda
https://www.youtube.com/watch?v=vZRYBtBXb2s Watermelon growing
https://www.youtube.com/watch?v=apgo4I_RP0U Video on how to plant, grow and harvest watermelon
file:///Users/devondempster/Downloads/ExtensionFolderNo-64-watermelon.pdf Watermelon cultivation PDF
https://www.ecofog.gf/giec/doc_num.php?explnum_id=995 Watermelon cultivation and postharvest handling
https://www.agmrc.org/commodities-products/vegetables/watermelon Watermeon marketing
https://shareok.org/handle/11244/6583 https://www-cabdirect-org.subzero.lib.uoguelph.ca/cabdirect/FullTextPDF/2016/20163395041.pdf Both of the above links provide articles that touch on different methods of food preparation
ovidsp.dc2.ovid.com/ additional (overlooked) benefits of watermelon on human health, specifically on vascular function and exercise performance
References
1. Ayinde, I., Lategan, F., Yusuf, S. (2013). Profitability and adoption of watermelon technologies by farmers in moro local government of Kwara State, Nigeria. Journal of Agricultural Science, 5, 91-99. http://www.ccsenet.org/journal/index.php/jas/article/view/22613
2. Balogun, O. L., Akinboro, O. S., Akinwole, O. T., & Osuji, E. E. (2019). An economic analysis of watermelon marketing. International Journal of Vegetable Science, 25(4), 355-361. https://journals-scholarsportal-info.subzero.lib.uoguelph.ca/details/19315260/v25i0004/355_aeaowm.xml
3. Chomicki, G. and Renner, S. S. (2015). Watermelon origin solved with molecular phylogenetics including Linnaean material: another example of museomics. New Phytologist, 205, 526-532. https://nph-onlinelibrary-wiley-com.subzero.lib.uoguelph.ca/doi/full/10.1111/nph.13163
4. Mtumtum, N. P. (2012). Performance of wild watermelon (citrullus lanatus L.) in response to population density and mulch. MSc Thesis, University of Kwazulu-Natal, South Africa.
6. National Research Council. (2008). Lost Crops of Africa: Volume III: Fruits. The National Academies Press, 3, 165-182. https://www.nap.edu/read/11879/chapter/12#168
7. Paris, H.S. (2015). Origin and emergence of the sweet dessert watermelon, Citrullus lanatus. Ann. Bot., 116(2), 133-148 https://apps.webofknowledge.com/full_record.do?product=WOS&search_mode=GeneralSearch&qid=1&SID=5DT33wjcYfMAyRNzaVV&page=2&doc=14
8. Spindell Berck, C., Berck, P., Di Falco, S. (2018). Agricultural Adaptation to Climate Change in Africa. London, UK: Taylor & Francis Group. https://www-taylorfrancis-com.subzero.lib.uoguelph.ca/books/e/9781315149776
9.Suits, D. (1955). An Econometric Model of the Watermelon Market. Journal of Farm Economics, 37(2), 237-251. http://www.jstor.org/stable/1233923
10. Verschuren, D., Laird, K. & Cumming, B. (2000). Rainfall and drought in equatorial east Africa during the past 1,100 years. Nature, 403, 410–414
11. Wehner, T.D. (2008). Watermelon. Handbook of Plant Breeding Vegetables, 1, 381-418. Springer, New York. https://link.springer.com/chapter/10.1007/978-0-387-30443-4_12#citeas
12. USDA. (n.d.). Watermelon. United States Department of Agriculture. Retrieved from https://snaped.fns.usda.gov/seasonal-produce-guide/watermelon