Yams Flashcards
What are Yams plants?
Genus Dioscorea, 644 species, family: Dioscoreaceae
dioecious twining climbers, occasionally both male and female flowers can be found on same plant
all species of economic importance are tuberous
main tropical food yam species are D.alata, D.rotundata … p. 3
produce a tuber as an annual underground storage organ, which shrivels away when regrowth commences, and a new tuber can be formed simultaneously
Yams has been neglected by research, 13’000 references for 644 species whereas maize has 1 species and 300’000 references
Domestication and distribution of tropical yams
D. alata was domesticated after arrival of the Australoids, 60’000 years ago in the present New Guinea or Melanesia
D.esculenta is an ancient crop in the Pacific. THe species wa most likely introduced onto Fiji / Melanesia / New Guinea between 3500 and 3000 BP
D. rotundata started to be domesticated in West Africa 7000 yr ago
Yam yield in Africa and Asia
High tuber yields reported for Eastern Asia and Melanesia
Tuber yields remain low (around 10 t/ha) in Africa
Surfaces under yam increased in West Africa from 0.8 M ha in 1961 to 7 M ha in 2016
High yields can be obtained on limited surfaces
Yams in Europe
France, Germany and Switzerland have Yams production
Why do you grow yams?
For food:
Staple food, famine food, “healthy” food, processed food: puree, frites, fufu, boiled, cake, bread
For cash:
In Côte d’Ivoire, depending ont he tome ant the yam species / variety, you will get between less than 100 CFA/kg tuber to more than 500 CFA/kg
For medicinal / dermatological use:
Dioscorea spp. can contain allantoin and steroidal saponins, Products currently derived from wild yam species
For culture:
new yam festival in west Africa and Melanesia
Stories regarding Yam
How do you grow Yam? (West Africa)
Almost no external input
Yam cropping possible only 2 yrs after each other
On farm yields <10t fresh tuber/ha
(potential yield around 50t/ha)
trees are burned and the Yam is planted in ashes
Challanges in yam production
Low yielding varieties
“seed” quantity: 1/3 of harvest is traditionally used as “seed” for new plantation
“seed” sanitary quality: nematodes, viruses, fungi, mealybugs
Pests and diseases on foliage
weeds
Staking/needs for wood
Soil fertility decline
Losses during tuber conservation
too much work
markets are not transparent
no agricultural extension
no high added value products
not interesting for policy makers
negative impact on biodiversity/forest
YAMSYS case study
p. 15 - 21
Innvations developed in the YAMSYS project
Increase planting density of yam from 1 plant on several m2 to 1 plant/m2
- reduces cropped surface
- reduces labor
- allow for water harvesting
Healthy “seeds”
- improves crop establishment
- better quality of harvested tubers
- less storage losses
Use improved germplasm and crop rotation
- use of legumes (for nitrogen fixation)
- decrease the pressure of pests and diseases
- reduce the rate of deforestation for yam cultivation
Improved staking
- requires less wood, hence decrease in deforestation
- reduces weed pressure
- maintains soil moisture
- exposes foliage better to sunlight hence increased yields
Balanced fertilizer application (mineral and organic)
- improve plant growth
- improve tuber quality
- increase yields
Improve seed storage
- maintain seed quality until the next planting season
- reduce storage losses
- improve crop establishment and productivity
Impact of fertilization and rotation on tuber yield of D. alata
High yield variability, but very good yields
Large differences between sites
generally higher yields in year 3 than year 1
See slides for more information on the YAMSYS
slides
