A blog maintained by Tevita Kete, PGR Officer
Secretariat of the Pacific Community (SPC), Suva, Fiji Islands
This weblog documents the activities of Pacific Agricultural Genetic Resources Network (PAPGREN), along with other information on plant genetic resources (PGR) in the Pacific.
The myriad varieties found within cultivated plants are fundamental to the present and future productivity of agriculture. PAPGREN, which is coordinated by the Land Resources Division of the Secretariat of the Pacific Community (SPC), helps Pacific countries and territories to conserve their crop genetic diversity sustainably, with technical assistance from the Bioversity International (BI) and support from NZAID and ACIAR.
SPC also hosts the Centre of Pacific Crops and Trees (CEPaCT). The CEPaCT maintains regional in vitro collections of crops important to the Pacific and carries out research on tissue culture technology. The CEPaCT Adviser is Dr Mary Taylor (MaryT@spc.int), the CEPaCT Curator is Ms Valerie Tuia (ValerieT@spc.int).
PAPGREN coordination and support
Mr William Wigmore
Mr Adelino S. Lorens
Dr Lois Englberger
Mr Apisai Ucuboi
Dr Maurice Wong
Mr Tianeti Beenna Ioane
Mr Frederick Muller
Mr Herman Francisco
Ms Rosa Kambuou
Ms Laisene Samuelu
Mr Jimi Saelea
Mr Tony Jansen
Mr Finao Pole
Mr Frazer Bule Lehi
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Wednesday, May 30, 2007
Posted 5:38 PM by Tevita
Discovered: New technique to boost yam production
From: Businessday ( Courtesy of Luigi)
Nigeria is the centre of origin of the white yam (Dioscorea rotundata) because of the immense genetic diversity of this species in Nigeria. It therefore behoves Nigeria to have a pride of place in spearheading the development of yam production and processing technologies in the world like Brazil is doing in cassava.
It is in this vein that note is taken of the Minisett Technique of seed-yam multiplication developed by the National Root Crops Research Institute (NRCRI), Umudike, which has reached mass adoption stage within and without the frontiers of Nigeria.
Recently, the Dry- season Yam Production Technique was also developed in Nigeria, which is discussed hereunder.
Yam is a sun-loving crop and the tuber yield is increased by the amount of sunshine to which the crop is exposed. The bottleneck in achieving this increase is that yam tubers have only one month of the year when most of them sprout, irrespective of method of storage- that is the month of February. A few precocious tubers sprout in January and some laggards in March. When the tubers sprout in February, they remain vining in the barn of the upland farmers until the rainfall resumes in March/April in the Rain-Forest and Guinea Savanna zones of Nigeria.
But the onset of the rainy-season marks the beginning of increase in atmospheric cloudiness. In the months preceeding the rainy season is the dry-season with abundant sunshine.
It then becomes logical that the best time to plant yam tubers is at the beginning of the dry-season in order to increase yam tuber yield by combining the sunshine of the dry season with that of the early phase of the rainy season. White yam takes 7-8 months from sprouting to tuber maturity when the yam vines dry up.
Scientists at the Institute of Agricultural Research and Development (IAR&D), University of Port Harcourt, have developed a technique for changing the sprouting time of yam tubers to any month desired, instead of the month of February only.
When the seasonal growth cycle of yam is changed, it remains permanent because there is a natural mechanism in the yam plant to sustain the perpetuity of this change. When the yam tuber is changed to sprout towards the end of September and the sprouted tubers are planted about the middle of October, which is towards the end of the rainy season, the sprouts emerge early in November and begin to grow under maximum possible sunshine and mature in May. The young yam plant makes use of the residual soil moisture left by the rainfall. Watering, 2-3times a week, starts in December and ends in February. Mulching with dry grass reduces the frequency of watering .
In locations like Port Harcourt near large bodies of water, occasional convectional rains occur in the dry season to re-charge the soil. Planting on beds is better than planting on mounds in the dry season, suggesting that yams can now be grown at the backyard watered from the tap with hose, watering can or bucket like vegetable gardens.
The rains take over in the month of March till maturity in May. By the month of May, some of the upland yam farmers may still be planting. Thus Nigeria can now have two crops of yam in a year- the dry season crop (October -May) and the rainy season crop (March-October), ensuring availability of fresh tubers in the market all the year round.
By changing the seasonal growth cycle of yam, every part of Nigeria can now grow yams by irrigation or watering. Yams planted in the dry season do not require stakes to support the yam vines. Previous research results at NRCRI, Umudike, had shown that the reason why yams are staked is to remove the yam vines from the physiological damage which flood water causes unstaked yams during the rainy season in the Rain-forest zone of Nigeria. Yams are grown without stakes in the Guinea Savanna zone. Hence staking of yams in the dry season does not increase the tuber yield of yams.
It has been estimated that staking constitutes 25 per cent of the total outlay in yam production and cutting stakes from the bushes and secondary forests impacts negatively on the ecosystem. Planting yams without stakes in the dry-season therefore eliminates a major cost item in yam production and saves the ecosystem. Yield of dry season crop is also double the yield of the rainy season crop because of exposure to brighter and longer duration of sunshine, contributing to make the farming effort more profitable.
In the seasonally- flooded locations along the River Niger such as Otuocha/Aguleri in Anambra state, farmers plant their yams around December/January. These tubers continue to remain dormant in the ground until the obligate sprouting time of February. The sprouts then emerge and begin to grow and develop because there is adequate residual moisture in their soils to sustain yam growth throughout the dry- season.
The yam plants are exposed to the sunny period of February to May/June and that explains why Otuocha/Aguleri farmers produce large, ceremonial tubers. This location and their neighbours contribute the bulk of the yams sold in the Nigerian markets between the end of July and November.
These yams which sprouted in February should mature in September/ October but they are usually harvested prematurely early in July 2-3months before full maturity. A close look at the tail of these tubers will show that they are light-yellow in colour, suggesting that they were still growing when they were harvested.
The premature harvesting is caused by the fear of the River Niger overflowing its banks in July, August and September, causing flooding. It requires only 3-4 days of flooding for yam tubers to get rotten in the ground.
Therefore, if the farmers of Otuocha/Aguleri adopt this technology and plant sprouted yams in October/November, they will harvest mature tubers in May/June, long before the River Niger overflows its banks from the end of July.
To catch the early market, the farmers may still harvest their yams prematurely in March/April. The farmers will also grow their yams without stakes and harvest increased tuber yield because of exposure to more insolation, making the farming exercise more profitable. These yams harvested in May/June will sprout in October/November to continue the cycle.
In all the seasonally- flooded plains along the major rivers of Nigeria- the fadamas- yams can be grown with this new technology. Indeed, it has been estimated that the fresh -water zone of the Niger Delta has the potential of producing 30 million metric tonnes of yam tubers in the dry-season annually.
This potential exists not only in the flooded pains of the River Niger but also of River Benue and other rivers. Infact the dry- season yam production activity can exist conveniently in relay with swamp rice in these seasonally inundated areas.
Some dams exist in Nigeria especially in the north and yams should be included in the dry- season crop production programme of these irrigated areas.Water supply through the boreholes is rapidly increasing in Nigeria and farmers in the upland locations can grow yams in the dry-season by watering.
In Nigeria, yams are grown traditionally during the rainy-season in upland and lowland areas. When this production is added to that produced in the dry-season by irrigation, Nigeria will be harvesting a basket full of yams for domestic food self- sufficiency and surpluses for processing and export.
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