Agronomy and Propagation of Yam Basic information

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Agronomy and Propagation of Yam
Basic information

• Introduction
• What is yam Agronomy?
• Climatic requirements for yam
• Land preparation for yam
• Planting materials
• Planting time
• Plant growth maintenance
• Herbicides application in yam
• Farming systems and Yam
• Vine cutting propagation
Outlines

Classification
kingdom: Plantae
Order : Dioscoreales
Family: Dioscoreaceae
Genus: Dioscorea
Species: Dioscorea spp
Introduction
3

What is yam agronomy?
• This is the application of a broad base
scientific knowledge in yam cultivation or
production
• It involves the application of knowledge from
breeding, farming systems, physiology, soil
fertility management among others for yam
cultivation
• It is the overall study of sustainable
management of the yam crop in terms of crop
health, soil fertility and production
profitability.

Climatic Requirement for Yam
• Yams grow better under rainfall distribution of 1000-1500
mm over a period of 6-7 months of the cropping season.
• Yam requires moisture throughout its active growth period for
vine and leaf development and most critically during tuber
initiation and bulking.
• The optimum temperature range for yam is between 25oC and
30oC
• Yams require well pulverized, loose soil with high organic
matter levels, for the easy penetration and expansion of the
tubers.

Land Preparation for Yam
• Appropriate land preparation is an indispensable
prerequisite for yam cultivation
• Under traditional cultivation different forms of
land preparation can be utilized in yam
production, depending on the ecology, cultivar,
and length of fallow period.
• These include mounds, ridges and holes when
planting on flats.
• Mounds are the most common and their sizes vary
depending on the ecology, production zone, and
yam cultivar production purpose, and sett size.

Land preparation(cont.)
• In areas with very high water table, very large
mounds are made, with each taking about three
seed yams.
• For mechanical land preparation, ridges are made
at 1m apart.
• Yam requires at least a depth of 40cm which can
be achieved through appropriate calibration.
• Adequate depth is important for yam in order to
enhance good tuber shape and yield

Planting Materials
• Planting materials are healthy cut yam pieces (setts),
or whole tubers, prepared for planting for any of the
various purposes under breeding activities.
• The size depends on the purpose of the planting.
• For multiplication, the materials are cut into 30-50 g
sett sizes
• For yield trials, the sett size ranges between 150-250 g
• For crossing blocks, the setts size will be 250-400 g

Planting Materials (Cont.)
• Apart from tubers other planting materials for yam
include botanical seeds and vine cuttings
• Botanical seeds are the true yam seeds originating
from sexual reproduction.
• Sexual seeds are only used for breeding purpose
because tubers emanating from them are usually
limited in size.
• Vine cuttings are nodal cuttings prepared from yam
vines used for the production of minitubers.

Planting Time
• Traditionally, the planting time for yam depends on
the onset of rains.
• The planting time is determined by the ecology,
edaphic properties and the purpose of production.
• In the forest zone, planting is done from March to
April with the early rains.
• In the southern Guinea savanna, planting is done
early in the dry season from November to December
and sprouting takes place in the dry season in
readiness for the approach of rains.

Planting Time (Cont.)
• Technically yam is perennial that is planted
as annual crop.
• Hence yam can be planted once dormancy
has been broken and favorable temperature
and moisture condition provided.
• The yam tuber has tendency of self-
regeneration or re-sprouting in the soil if not
harvested

Plant Growth Maintenance
• To obtain maximum yield adequate crop
maintenance must be provided for planted
yam in form of:
• Weeding
• Staking and trailing
• Fertilizing soil (where the soil is
malnourished)
• Remounding or earthening up

Herbicide Application for Yam
• After planting the yams there is need to ensure
minimum weed growth within the field for optimum
growth and yield of the yam.
• The first step is to apply suitable herbicides. For yam,
combination of Diuron (a systemic pre-emergent) and
glyphosate (a contact) herbicides has been effective.
• Diuron and glyphosate should be mixed at 2.3L and
1.8L respectively per hectare.
• Application should be done not later than 7 days after
planting (DAP) of the yam.
• Subsequently, manual weeding is used for further
weed control, and this should not be less than 2 time
before harvesting.

Vine cutting propagation in yam
• The major constraint in yam production is
the high cost of planting materials.
• This is attributed to the low multiplication
rate in yam and the fact that yam tuber
serves both as food and planting material.
• Vine cutting propagation involves the
production of small tubers from direct
planting of yam vines in soil medium.

Procedures in vine cutting propagation
• Establish the mother plant (plant from which vine will be
collected) or screen house.
• At about 2 months after establishment of mother plant
prepare a place for vine cuttings which could be a screen
house or constructed makeshift shade.
• Arrange nursery bags filled with mixture of carbonized
rice husk and top soil or river sand top soil in the screen
house of shade
• The medium should be mixed in a ratio of 2 parts of CRH
or river sand to 1 part of top soil.

Procedures in vine cuttings (Cont.)
• Nursery bags should be arranged in batches of 20
bags per batch for easy management.
• Collect vines from mother plants between 60 and
90 days after planting.
• Collection should be done with a sharp scissors
and each clone well tagged with ribbons.
• Vines must be collected very early in the morning
or late in the evening to minimize stress on the
vine and enhance vine cuttings survival

• The collected vine should be taken to screen house
or constructed shade for preparation
• Prepare the vines into cuttings with one node
• The vine length above the node should not be
more 1cm while length below node should be
about 2.5cm to allow for firm attachment into the
soil
• Plant the cuttings by inserting the longer end of
the cutting into the medium with the nodes well
submerged and the leaves above the soil.

• Water the planted cutting and keep moist
regularly
• A well planted vine cutting should start
rooting and shooting by 21 days after
planting.

Plate 1. Stages in vine cuttings establishment: (A) Mother Plants Field, (B)
Collected Yam vine, (C) Prepared one-nodal cuttings in water ready for
planting, (D) Vine cuttings planted in nursery bags containing carbonized
rice husk and top soil
A
D
CB
19

A
Plate 2. Vine cuttings field nursery stages. A: Bamboo
framework for nursery shade, B: established vine
cuttings in the nursery, C: Vine cuttings development at
60 DAC showing roots and a young shoot, D: matured
shoot at 90 DAC stretched out
DC
B
20

BA
DC
Plate 3. Tuber development in yam vine cutting; A: tuber at 60 DAC, B:
multiple tuberization in vine cuttings, C: Tuber with senescened shoot,
D: tubers at 120 DAC
21

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Agronomy and Propagation of Yam Basic information

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Agronomy and Propagation of Yam Basic information