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Research Programme on Food Security

(Mohammed Umar and L.G. Yapa)



IRETA's mission is to contribute to sustainable growth and development of the South Pacific countries by appropriately responding to their expressed needs for research, training, information, education and extension programmes, and consultancies in the broad fields of agriculture and rural development.

To achieve this mission IRETA has developed the following objectives:

Training: provide high quality training programmes that are relevant and respond to identified regional needs.

Research: implement a relevant applied research programme in agriculture and rural development that is responsive to expressed national and regional needs.

Extension: further develop and maintain an efficient and cost effective service to disseminate and share information on agriculture and rural development to new and established users in the Region.

Consultancy: coordinate and conduct relevant consultancy services for the Region Service: where requests are adequately funded.

Management: mount a continuous effort to improve and finetune IRETA's capacity to manage the affairs of the Institute.

Promotion: distribute information about IRETA's activities and capabilities within and outside the Region.

To achieve the above-mentioned objectives IRETA staff jointly work with the senior academic staff of the School of Agriculture (SOA) to serve the needs of South Pacific Islands in their development programmes. The Heads of Agriculture in the Region, comprising of Directors and Permanent Secretaries, review the activities of IRETA annually in a Regional Board of Management (RBM) and give broad recommendations for regional work.


The overall objectives of IRETA/SOA research programme are to carry out applied agricultural research relevant to the Region and to increase food production and productivity of agricultural lands, while ensuring sustainability and protection of the environment.

The research activities have been supported mainly by the United States Agency for International Development (USAID), under the Commercial Agricultural Development Project (CAD), and the European Union (EU) funded Pacific Regional Agricultural Programme (PRAP) under LOME III and IV. Small grants are provided by the USP (USP Research Committee Grants), Australian Center for International Agricultural Research (ACIAR), International Board for Research and Management (IBSRAM) and the Governments of Australia and New Zealand. Negotiations are underway for technical assistance and a Ph.D. programme on plant protection and other related areas under CIRAD of the French Government and FAO Farming Systems Development (FSD) Project.


 Root crop improvement (taro breeding)

Due to the arrival of taro leaf blight in Samoa in 1993, and the shortage of staff, the breeding (field) programme was severely hampered and the improvement work was limited to the tissue culture laboratory. Laboratory experiments were conducted to improve the multiplication system that had been in use in the Unit for several years, that is, the use of 6-benzylaminopurine, (BAP), and -napthalenacetic acid, (NAA), in the culture medium.

The initial results showed promise, but a repeat of the experiment indicated a high level of variability and unpredictability. At this stage it was decided to evaluate the diphenyl urea thidiazuron, (TDZ). TDZ was first reported to have cytokinin activity in 1982. Since then, it has been used successfully in vitro to induce adventitious shoot formation and to promote axillary shoot proliferation, being especially effective with recalcitrant woody species. Experiments on taro have confirmed the promoting effect of TDZ on sucker production with multiplication rates varying from 7 to 30 suckers per week per plant.

Taro and vegetable production

Taro production experiments were not carried out in 1994 by the staff of the Discipline of Crop Science staff due to leaf blight epidemic. However, one of the staff members carried out two experiments at the University of Hawaii. One experiment on the response of taro Colocasia esculenta L. Schott) to shading in intercrops, indicated that sole cropping is more appropriate than inter-cropping if taro is the most important crop. The other experiment on the size of planting material on leaf emergence and dry matter production revealed no significant differences among the three different sizes used.

Vegetables are becoming important in Samoa because of the taro blight epidemic. An experiment was conducted to study the growth of seedlings of lettuce and tomato in petepots. It was concluded that local soil could provide a satisfactory potting mix for growing vegetable seedlings in petepots provided the local mix is fertile enough.

Asparagus possibly has a great potential as a vegetable crop in Samoa. The asparagus experiments focused on the age of plants when harvesting begins and the length of harvest period in each harvest cycle. It was reported that about 75 percent of the yield in most harvest cycles is obtained in the first half of the cycle. The observation suggested that lengths of harvest cycles and lengths of rest period for Samoan asparagus needed more study.

Atoll agriculture development

The overall goal of the Atoll Farming System project is improved diet through higher self-sufficiency of food production. During its two-year phase, the project will complete the identification of sustainable farming systems and effective extension services operating in pilot areas. This project is no longer with IRETA's preview.

Agroforestry based cropping systems

In Samoa, agroforestry is being tested as an alternative land-use practice to rotational natural fallows with the objective of reducing pressure for land clearance on the more fragile steep lands. The main objective of these studies is to assess the long-term benefits of hedgerow intercropping leguminous trees with taro and other crops on crop productivity, weed control and firewood production.

The Alafua alley cropping trial is in the seventh year of cropping. The trees continue to produce large quantities of foliage biomass. Compared to the 1993 season, Calliandra produced almost the same amount of prunings throughout the cropping period, whilst the production of prunings from the Gliricidia trees was reduced by 56 percent, 44 percent and 30 percent in the 4 m, 5 m and 6 m alleys respectively. Calliandra biomass production significantly outyielded Gliricidia during the drier months of the fallow period, but Gliricidia outyielded Calliandra in the wetter months. The test crop was changed to cassava in the seventh year due to taro leaf blight and no significant differences were shown in cassava yield between "tree" and "no-tree" treatments, also between tree species and alley widths.

The Moamoa alley farming trial is being continued and the main objective of this trial is to determine if the yields of food crops within an alley cropping system can be sustained by the addition of prunings from the coppiced alley trees. In the fourth cropping year, the alley trial was mix cropped with taro, Xanthosoma and banana. This change in the cropping pattern of the trial was due to the outbreak of taro leaf blight. Taro yield was greatly reduced compared to the yield of previous seasons because of leaf blight. The taro corn yield was reduced by 56 percent in 1994 compared to the 1993 yield.

Work is continuing on-station and on-farm using Erythrina subumbrans intercropped with taro and Xanthosoma. Studies involve weed control and fertility maintenance. Erythrina is also being investigated for fallow enrichment. Many farmers in Samoa consider Erythrina subumbrans as a valuable tree for sustaining taro yields. Preliminary data from soils collected under Erythrina trees indicate possible beneficial effects of the tree on soil chemical properties and several farms in Samoa have been identified where farmers are systematically using Erythrina in their taro cropping system.

A series of studies (conducted 4-5 years ago but not reported previously due to the study-leave of the researcher) aimed at evaluating five species (Cedrella, Eucalyptus, Flemingia, pigeon pea and Sesbania) that could be intercropped with taro in an agroforestry system. Experiments on firewood quality indicated that Sesbania has the highest heat generating capacity, while investigations on regrowth ability after coppicing indicated that Flemingia was the best and pigeon pea was the worst. Taro intercropping with these five tree species did not show any significant effect on taro performance. Soil pH was significantly higher under Flamingia. Investigations on weed growth revealed that the largest amount and type of weeks were collected under pigeon pea.

Conservation farming systems

Various box experiments were carried out to examine the nature of interactions between the component crops in intercropping systems; the main experimental variables were with and without root interaction, with and without shoot interaction. Preliminary results indicated that pure stand yields of components did not differ significantly from their yields in mixtures. Relative yield totals were greater than 1.0 in all treatments indicating that the components competed only partially for resources.

The field experiments were concerned with growing the beans and maize crops using various planting patterns, various tillage and minimum tillage techniques, various densities of the components, different times of planting and at various fertilizer levels. The experiment indicated that the two crops may complement each other since the beans used maize as support to obtain light, and growth of the two components was excellent.

Survey on the traditional farming systems in the South Pacific indicated that some of the traditional practices are used or known by the older farmers only. Some of the younger farmers and student interviewers are not even aware of these practices. This shows that some of the traditional practices are dying out. However, with the renewed interest in organic agriculture, there is a need to investigate the traditional systems in greater detail with the hope that they might provide some clues on how we might solve some of our current or future agricultural problems.

Crop protection

In an earlier study, it was demonstrated that honeybees, Apis mellifera L. foraging on Jatropha integerima in Samoa showed a marked preference for male flowers compared with the female flowers of this monoecious Cuban ornamental. The visual influence of the anthers on honeybees was sought by asking whether bees would change their foraging behaviour if (i) the anthers were partially or completely destroyed, (ii) the petal configuration was altered and (iii) the leaves on flowering twigs were partially or completely removed. The results of the present study add a new parameter which in the past was seldom considered, namely that of the influence of the leaves associated with flowers. Currently, it is not easy to tell whether it is the colour, shape or number of leaves which is important to the bees. Results from observing foraging responses to partially defoliated twigs seem to bear out that the number of leaves was important. Even then, one cannot at this stage rule out a possibility that all the three parameters of the flowering twigs co-actively influence the bees.

Viruses pose the greatest threat to a viable commercial cucurbit industry in Samoa. Survey results indicated that Zucchini Yellow Mosaic Virus (ZYMV) and Papaya Ring Spot Virus (PRSV) were the most predominant viruses that were found in both Upolu and Savaii. An integrated approach to manage viruses is recommended because one method of controlling viruses would only satisfy the farmer up to a certain degree. The cheapest and most effective method so far of combating viruses for Samoa is through the use of resistant varieties. Cross protection also offers a low tech and cheaper, but effective alternative.

Determination of the time and temperature effects of heat on the egg and larval stages of two fruit fly species of quarantine importance to Tonga was carried out. The two species were Bactrocera facialls (Coqullett) and B. xanthodes (Broun). Data from the Preliminary test showed that Bactrocera facialls is more tolerant to heat than Bactrocera xanthodes. Similar results were obtained for early- and late-aged egg survival/mortality tests. For both species, late-aged eggs (46 to 49 hours old) showed a higher tolerance to heat than early-aged eggs (1 to 3 hours old). Similar results were also obtained from the Hawaiian fruit fly species.

The aim of the Fijian project was to determine the relative thermal tolerances and susceptibilities of the egg and larval stages of fruit fly species of the genus Bactrocera of quarantine importance that adversely affect economically important exports from Fiji to overseas markets. Completed heat tolerance studies on early and late eggs of Bactrocera passiflorae and Bactrocera xanthodes showed that late-aged eggs are more heat tolerant than early-aged eggs for both species. Late-aged eggs of B. passiflorae are more heat tolerant than late-aged eggs of B. xanthodes.

Soil science

The discipline of soil science continued its wide coverage of research programme on organic matter management supported by (USAID), soil test crop response studies for fertilizer recommendation (URC), diagnosis of nutrient disorders of the root crops of the South Pacific Asian Centre for International Agricultural Research (ACIAR), management of sloping land (IBSRAM), and the studies on patterns of soil moisture depletion (URC). Most of these studies were carried out at the Alafua and Laloanea research fields of the Alafua Campus and some were on farmers’ fields.

The objective of the organic matter management study was to compare the effects of lime and green manure on dry matter yield and nutrient content of two consecutive 28-day cropping of maize seedlings, and on selected soil chemical properties of an acid Oxisol in Samoa. The growth responses of maize in this experiment demonstrated that soil acidity of an acid Oxisol can be alleviated by either lime or green manure additions. Furthermore, the data clearly demonstrated that green manure applications can be a good substitute for lime, especially in Samoa, where commercial liming materials are costly and scarce.

Using ACIAR and URC funds, nutrient omission pot trials were completed for nine sites. In the omission trials, several deficiencies (N, P, K, Mg, Fe; P being most deficient) were recorded in a number of sites, and rate trials were conducted. Since Tapatapao and Laloanea soils showed essentially identical physical and chemical properties, and similar nutrient deficiencies, it was decided that the information gathered for the Laloanea soils would be applicable to Tapatapao soils and thus no rate trials were conducted for the latter site. Field experiments were conducted using P-fertilizers and Erythrina mulch at Laloanea, Afiamalu and Alafua sites.

The overall objective of the IBSRAM coordinated project are to: (i) determine the extent of soil loss and runoff on sloping land and (ii) to develop viable soil management techniques and cropping systems to sustain and improve agricultural production on sloping land. Four treatments were evaluated. After the outbreak of taro leaf blight (Phytopthora colocasiae), taro (Colocasia esculenta) was replaced with taro palagi (Xanthosoma sagittifolium) from the (1994) cropping season. Soil loss and the runoff values observed were very low. Cut and carry Erythrina mulching showed the highest economic returns. Moisture depletion study at Alafua clearly indicated significant moisture stress during the first two weeks of September in 1994. The moisture stress effect of the short drought spell was noted even at the 30 cm layer. There were no marked differences between the 15 t/ha and 30 t/ha mulch treatments.

Soil fertility evaluation experiments conducted on Aranuka Island soils of Kiribati showed potassium and phosphate deficiencies in that order. The rate trials indicated a very high response to phosphate application.

Field experiments, using various rates of lime and potassium, carried out at Lomaivuna and Koronivia on the island of Viti Levu in Fiji, at Vaini on the island of Tongatapu in Tonga, and at Togitogiga in the island of Upolu in Samoa, indicated that liming had no significant effect on maize yields as measured by the weight of grain (dry), ears (fresh and dry), and above-ground biomass (fresh and dry). This may have been due to the relatively high initial pH of the soils at the four sites and the fact that, due to time constraint, the applied lime was not given time to react with the soil before maize was planted.

Study on the effect of lime and organic matter on the capacity of the Togitogiga soil to retain added water and potassium showed that high lime rates resulted in greater K absorption compared to no or low lime. Low lime resulted in more K absorption than no lime only when a small amount of K was added (1.0 g/kg). The soils studied differed greatly in their capacity to release non-exchangeable K as exemplified by the Koronivia, Togitogiga and Vaini soils. Soils that release large amounts of non-exchangeable K may be considered more fertile but they require special management if exhausting the supply of non-exchangeable potassium is to be avoided.

Animal science

The main focus behind the research programme of the discipline was the assessment of some locally available feedstuffs, such as Desiccated Coconut Waste Meal (DCWM), that have the potential to (economically) displace, fully or partially, some of the imported ingredients used in broiler feeding. Carcass analysis indicated that the 20 percent level of DCWM produced leaner (P=0.05) meat, (lesser amount of abdominal fat deposition) compared to the control diet. With its economical advantage, DCWM could be used as a feeding ingredient in commercial broiler farming.

Agricultural engineering

Investigations revealed that no mechanized cleaning systems are currently in use for taro in the Pacific Region export packhouses. No commercially manufactured machines designed specifically for export taro have been identified. One of the objectives of the USAID funded project was to specify, assemble, modify and test an improved post-harvest handling system for export taro incorporating an appropriate mechanized cleaning module. Based on findings, the conclusion is made that there is no one machine currently available that can clean taro to the quality and rate required by commercial operations, particularly those involved in the export industry. However, the carrot barrel washer gives the best results when used together with some manual finishing. Evaluation tests are continuing.

Agricultural education

In this field efforts were made to develop guidelines for agricultural programmes on Television Samoa as perceived by small farmers in Samoa. The respondents constituted 61 randomly selected small growers from districts covered by TV Samoa. Eleven districts from Upolu and six districts from Savaii received telecasts from TV Samoa during the data collection period.

The analysis showed that 24 percent of 61 respondents selected 7.45 to 8.15 pm as the best time for broadcasting Agriculture TV Programmes. Monday (66 percent), Wednesday (53 percent) and Friday (56 percent) were the selected days. Concerning the length of agricultural TV Programmes, 44 percent selected 30 minutes. With regard to the language to be used for the broadcast, 92 percent of the 61 respondents selected Samoan.

Agricultural extension

A situational analysis study was conducted at the Papaela community in Samoa as a basis for the Development of an Agricultural Extension Programme. The main aims of the study were to: (i) identify the priority needs (farm problems) of farmers of Papaela community for agricultural extension programmes; (ii) identify the farmers’ status and its relationship with farming practices; (iii) determine the viability of linkages between farmers, extension agents and researchers.

The results showed that about 75 percent of the farmers are 'matais' and 68 percent of them are above 45 years of age. Major problems for farmers that emerged from the study included: land shortage (63 percent); banana leaf streak (31 percent); lack of fertilizer and taro leaf blight (24 percent). With such problems there was a general feeling that the majority of farmers (about 88 percent) would like to make improvements on their farms. It was emphasized that one of the contributing factors to the farm problems is the need for stronger linkages between farmers, extension agents and researchers.

The objectives of the "new on-farm research activities" of the EU-PRAP programme are to: improve linkages between farmers, extension and research; foster a participatory approach to technology development and testing; provide a focus for an in-depth study of farming systems over time in order to better identify farmers' needs, opportunities and motivation; evaluate agroforestry technologies under farm conditions and monitor farmers' impressions, and from this develop farmer augmented treatments; and evaluate management and environment interactions with the selected treatments. Three locations on Upolu, Samoa have been selected to represent distinct rainfall zones with some differences in soils.

Agricultural economics

A USAID funded project is carrying out a research on marketing of ngalinut (Canarium) in the Solomon Islands. It was found that the most important products of ngalinuts with potential markets are its kernel and oil.

The main objective of this research is to examine and compare the two production/marketing systems for these products (kernel and oil) operating in the country. The specific objectives are to: examine and compare the per unit cost and profitability of producing oil in the two systems; compare the quality of the oil produced by each system; determine the returns to producers both in the short and long run; and make recommendations for the improvement of oil production and marketing of oil.

Rural development

The FAO-funded Farming Systems Development (FSD) Project was developed to address the slow rate of agricultural development despite 11 rural development interventions over the last 30 years. In the previous approaches, technology was developed by researchers in research stations then passed to extension officers to transfer to farmers. The farmer was never involved in technology development and his views and situation never considered. The FSD is a new approach to development of rural communities in the Pacific Region. It involves development with partners such as government, environmentalists, farmers, exporters, processors and others who are included in this approach. The primary concern of the FSD approach is the farmer and his socio-economic environment. FSD aims to develop rural households and communities on a sustainable and participatory basis. FSD promotes ecological sustainability and economic and social compatibility with the local culture.

FSD does not produce a product but facilitates the process of agricultural development by bringing together stakeholders in the process. The primary beneficiaries of the FSD approach are small farmers. Funding also goes to: researchers for designing relevant and appropriate studies; extension workers for developing better and well targeted messages; and planners for developing more effective policies to improve farmers' lifestyles.

A draft manual on FSD in the Pacific has been prepared and other extension materials will be published in 1996. Six national workshops and a regional workshop have been scheduled between November 1995 and August 1996.


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