Template:Chapters 3.1

3.1 - Yam in sacks on terrace walls

Emma Desilets, University of Guelph, Canada

Related video(s): Yam sac (English subtitles) (Source: Access Agriculture)

https://www.youtube.com/watch?v=NMtyPhQHrJQ

Suggested citation for this chapter.

Desilets,E. (2022) Yam in sacks on terrace walls. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Introduction

A staple crop in many parts of Africa and Southeast Asia (Opara, 2003), yams (Dioscorea sp. not to be confused with sweet potato) are an important source of carbohydrates, contain good amounts of fibre and vitamin C (Wanasundera & Ravindran, 1994), and can provide a family with a new source of income and nutrition. Unfortunately, many smallholder farmers in hilly regions lack enough cultivated land area to grow more crops and support their families (Chapagain et al., 2019). To overcome this, farmers utilize terrace farming, which creates step-like patterns on sloping hillsides, where the flat surfaces are cultivated; however the vertical walls are typically unused (Chapagain et al., 2019). For smallholder farmers, every inch of land counts - so taking advantage of these unused walls by vertically growing yam in sacks is an option to consider as shown in Figure 1. Yams can also be grown in sacks on flatlands, to save labour at harvest, fertilizer/manure and conserve water.

Figure 1. Practice of growing yam in sacks (Ghimire et al., 2016).

It is important to note that this practice is not reserved for hillsides, but yams can be grown in sacks against any wall, such as the side of a house or even leaning against one another. Growing yams in sacks not only utilizes unused space and provide yams with adequate sunlight, but it prevents leaching of critical fertilizers and water, and critically the practice also helps cut down on labour especially at harvest time – the bag can simply be opened rather than having to dig out a large and very heavy tuber (Chapagain et al., 2019). The practice appears to have started in Nepal in 2014 (Chapagain et al., 2019), but has now spread to West Africa where some farmers grow up to 5000 yams in sacks.

Implementation of Yam in Sacks

This section will explain how to grow yam in sacks. According to the Food and Agriculture Association (FAO), yams are not typically grown from seeds and are instead grown by planting cut pieces of adult yam (Henderson, 1977).

How to Plant:

While seeds can produce yam, propagation is preferred to maintain high yields and similar traits of the parent tuber. To start, cuttings from the tuber are taken, preferably from the crown, which is the top section containing stems, or with a small whole tuber, weighing 250-400 grams each (Henderson, 1977). A sack or bag to grow the yam in is also needed. Appropriate sacks should be long enough to contain the average fully grown tuber, and a great option would be to use an empty seed sack or an empty fertilizer bag. The sack is filled up halfway, or enough so that it can be lifted, and then transported to rest against a wall or terrace or other bags, where it will remain for the duration. The bag should not contain any large stones, as this will impede the growth of the yam. In addition, the area should be exposed to the sun, as yams are light-loving, shade-sensitive plants which require warm temperatures after planting (Lebot, 2020). The remainder of the sack should then be filled with soil, leaving some space at the top for fertilizer or manure. The soil must be light, sandy, well-drained, and crumbly, as the tuber penetrates the soil while expanding during growth (Lebot, 2020). Subsequently, about five inches (12 cm) of soil near the back of the sack as opposed to the center should be dug to plant the yam. According to a video entitled “How to Plant Yam in Bags” which documented this process, the yam should be placed horizontally, so that the crown is in the centre of the soil, but the cut end of the yam is against the side of the sack. This is done because the growth of the yam will come from the crown; if it were not central, the yam could break through the bag (1/3 TV, 2021). The tuber should then be covered with soil. To protect the yam, dry, dead leaves and grass should be placed over top of the soil.

How to Fertilize:

The last step to planting the yams is to fertilize the soil. Fertilizing could be the key to healthy yams and a good harvest. One option is to simply scatter compost, manure or fertilizer on top of each bag in addition to the dry leaves. Fertilizing yams in sacks is different than in the ground, as the yam roots cannot travel when confined to the sack. When growing yams in a sack, the roots are planted near the top of the bag. Referencing the above video again, it was found that spreading fertilizer over top of the soil, or at the bottom of the bag, is an ineffective method. The concentration of the fertilizer is simply too strong if directly applied, which is why it is suggested to fertilize in batches (1/3 TV, 2021). Five to six weeks after planting, only seven or eight balls of fertilizer should be scatter on top of the dry leaves. Rain should dissolve the fertilize, or the sacks can be watered at least three times a week. This fertilizing process should be repeated weekly, for 1 month (1/3 TV, 2021).

How to Harvest:

Mature yams are distinguishable by the yellowing of leaves, and most edible yams reach maturity in 8-11 months after planting (Opara, 2003). To harvest, the sacks should be torn down the side. A shovel can be used to remove some of the soil but then the actual yam should be dug by hand as it is possible to damage the tuber. The stem of the yam should then be cut and removed. It is possible to recycle the sacks by lying them on their sides and emptying the contents. The soil can be reused again. The yams should be stored in a cool, dark area until ready for use. It is important to note that yams contain toxic substances when raw and must be sliced and soaked in water or cooked before consumption (Opara, 2003).

Critical Analysis

While harvesting yams in sacks requires much less labour than harvesting on land, planting is slightly more difficult and requires more resources. Growing yams is typically a highly laborious and tiresome process. Yams grown in the ground require standing, bending, and squatting for long amounts of time, which is very intensive considering some yams can grow to weigh larger than 100 lbs or 45 kg (Opara, 2003). Planting in sacks cuts down on intensive labour, but it is more time-consuming as each individual sack must be prepared. As each tuber requires one sack, many sacks and pieces of the tuber will need to be acquired. A farmer may already have some empty sacks or fertilizer bags, or they can be acquired at the market, but accessing these materials may also be difficult. Acquiring sacks large enough to accommodate the size of the growing yam may also be difficult, as smaller bags will limit the size of the tuber. In addition, the disposal of the unusable sacks will create plastic waste, so consideration should be given to biodegradable bags. If materials needed to grow yam in sacks are accessible, some benefits are that it cuts down on hard labour, especially at harvest time, utilizes unused space, and mitigates weeds, soil fertility decline via reduced leaching, soilborne and leaf pests and diseases -- all of which comprise the highest constraints to yam production (Wanasundera & Ravindran, 1994). It also permits yams to be grown in regions with otherwise heavier (clay soil). Another aspect to consider when growing yams is their storage ability. Storage losses can be detrimental, as a yam can lose 10-20 percent of its weight after three months of regular storage in a cool, dry area. These figures include an element of moisture loss, and a decrease in the food value of the yam tubers also occurs (Coursey, 1967). Yams cannot be stored in cold storage, as they will suffer chilling damage, and yams are susceptible to insects and plant pathogens (Coursey, 1967). There are also added costs for materials, purchasing yam tubers, sacks, and fertilizer, but these items may already be common-place, or easy to acquire from the market. The range cost of yams per plant is $2 USD. This added source of income can make a dramatic difference to a smallholder farm if this technique is successfully adapted.

Picture Based Lesson to Train Farmers

Click on the image to access a higher resolution image as well as lessons adapted for different geographic regions.

Sub-Saharan, Africa/Caribbean version: http://www.sakbooks.com/uploads/8/1/5/7/81574912/4.1subsaharan_africa_carribean.pdf

South Asian version: http://www.sakbooks.com/uploads/8/1/5/7/81574912/4.1_south_asian.pdf

East/Southeast Asian version: http://www.sakbooks.com/uploads/8/1/5/7/81574912/4.1e.s.a.pdf

Latin American version: http://www.sakbooks.com/uploads/8/1/5/7/81574912/4.1latin_america.p

df

Source:

MN Raizada and L Smith (2016) A Picture Book of Best Practices for Subsistence Farmers: Edition (note geographic region). eBook, University of Guelph Sustainable Agriculture Kit (SAK) Project, June 2016, Guelph, Canada. Available online at: www.SAKBooks.com

Links to Useful Resources

https://www.youtube.com/watch?v=dV_D99fow4M - Step by step process on planting yam in sacks

https://www.youtube.com/watch?v=PPJ-LBuVCzY&t=1431s - Harvesting yam in sacks

https://www.youtube.com/watch?v=yTbG3GmavCU - Benefits to planting yam in sacks

https://www.youtube.com/watch?v=bOtpdL8KFJo - Alternate video showing the process of planting yam in sacks

https://www.youtube.com/watch?v=_m95fQ6rCOs - Growing yam in sacks in Nigeria

https://www.youtube.com/watch?v=oHzV2DI0EEg - Commercial yam farming

References

1. Chapagain, T., & Raizada, M. N. (2017). Agronomic Challenges and Opportunities for Smallholder Terrace Agriculture in Developing Countries. Frontiers in Plant Science, 8, 331. https://doi.org/10.3389/fpls.2017.00331

2. Chapagain, T., Ghimire, B., Pudasaini, R., Gurung, K., Choi, K., Rai, L., Magar, S., Bishnu, B. K., & Raizada, M. N. (2019). The Underutilized Terrace Wall can be Intensified to Improve Farmer Livelihoods. Agronomy for Sustainable Development, 39(3), 2–11. https://doi.org/10.1007/s13593-019-0574-2

3. Coursey, D. G. (1967). Yam Storage—I: A Review of Yam Storage Practices and of Information on Storage Losses. Journal of Stored Products Research, 2(3), 229–244. https://doi.org/10.1016/0022-474x(67)90070-7

4. Henderson, A. (1977). How to Propagate Yams. In Roots and Tubers (pp. 30–38). Food and Agriculture Organization of the United Nations, Rome, Italy.

5. Ghimire, B., Dhakal, R., Pudasaini, R., Devkota, R., & Chaudhary, P. (2016). Demonstration of yam cultivation in sacks at Laitak village [Photograph]. Leisa India. https://leisaindia.org/wp-content/uploads/2016/06/Demonstration-of-yam-cultivation-in-sacks-at-Laitak-village-300x169.jpg

6. Lebot, V. (2020). Yams: Agronomy. In Lebot, V, Tropical Root and Tuber Crops: Cassava, Sweet Potato, Yams and Aroids, (pp. 273–292). CABI. https://doi.org/10.1079/9781789243369.0273

7. Opara, L. U. (2003). Yams - Food and Agriculture Organization. Food and Agriculture Organization of the United Nations. Retrieved November 8, 2022, from https://www.fao.org/fileadmin/user_upload/inpho/docs/Post_Harvest_Compendium_-_Yams.pdf

8. 1/3 TV. (2021, May 17). Step by Step Process How to Plant Yam in Bags [Video]. YouTube. https://www.youtube.com/watch?v=dV_D99fow4M

9. Wanasundera, J. P., & Ravindran, G. (1994). Nutritional Assessment of Yam (Dioscorea alata) Tubers. Plant Foods for Human Nutrition, 46(1), 33–39. https://doi.org/10.1007/bf01088459