By Halavatau, S.M.; Geoff Dean; Fereti Atumurirava; Mike Smith

In 2008, a problem was reported in the cassava crop in Fiji's Taveuni island, the symptom being a brown, hard wooden growth in the tuber. A visit by the Land Resources Division (LRD) of the Secretariat of the Pacific Community (SPC) to Taveuni to diagnose the problem, identified boron deficiency as the cause. The visit led to a highly productive relationship between SPC-LRD and the Tei Tei Taveuni (TTT) Farmers Association.

This relationship strengthened with the launch in 2011 of the Soil Health Project "Improving Soil Health in support of sustainable development in the Pacific" by the Australian Centre for International Agricultural Research (ACIAR).

Soil health project
'Soil health' refers to the ability of soil to perform a given function, in this case to support crop growth, and includes the chemical, physical and biological processes necessary for this. The degradation in the ability of soil to carry out any of these processes impacts the economic viability and environmental sustainability of agriculture and, in turn, agriculture's ability to support food security and livelihoods. The project aimed to address the problems of 'cropping systems in crisis' - where incautious intensification has led to crop production problems associated with declining soil fertility and a loss of the 'ecosystem functions' provided by soil, especially the suppression of soil-borne pests and diseases.

The project uses a participatory approach where scientists from SPC-LRD, the Queensland Department of Agriculture, Forestry and Fisheries (DAFF), and the Fiji Ministry of Primary Industries (MPI) Research and Extension department work with TTT farmers to identify soil-related problems in the production of taro for export and devise soil improvement methods for trial. The evaluation of soil improvement tactics is an iterative and evolving process. The results of the trials in each growing season feed into the design of the next season's trials, resulting in a refining of 'best bet' tactics and the modification or abandoning of those that are ineffective. The recommended results will finally be fed into the education/ extension effort.

Involvement of Tei Tei Taveuni farmers
The TTT farmers were involved in the problem diagnosis stage as well as in the actual field experiments to evaluate potential solutions. In 2011, based on the findings of a diagnostic survey, it was proposed that field trials be conducted on farmers' fields at nine sites (Vunivasa, Qeleni, Matei, Lamini, Welagi, Qila, Waimaqera, Delaivuna and Vuna) using eight soil treatments. The choice of treatment was based on the different soil amendments used in Taveuni as well as improved treatment methods such as use of the cover crop Mucuna pruriens. The following treatments were used:

  • A -- NPK 13-13-21 (40 g applied at planting) plus 10 g urea applied 5 and 10 weeks after planting (WAP)
  • B -- NPK 15-15-15 (34 g applied at planting) plus 10 g urea applied 5 and 10 WAP
  • C -- untreated
  • D -- Mucuna pruriens without recommended application rate for biobrew soil
  • E -- Mucuna pruriens with recommended rate for biobrew soil
  • F -- 74 g Phoscarb applied at planting plus 10 g urea applied 5 and 10 WAP
  • G -- recommended application of Rock P at planting plus 10 g urea applied 5 and 10 WAP (Extraphos and potash 300 kg/ha)
  • H -- recommended application rate for calcite lime at planting plus 10 g urea applied 5 and 10 WAP (900 kg/ha)

The results showed some trend across the nine sites. Lime was effective in reducing acidity and mproving calcium availability while Mucuna pruriens improved the vegetative and corm sizes of taro, suppressed weeds, increased earthworm numbers, improved soil structure and was likely to suppress plant parasitic nematodes.

A participatory workshop with farmers to discuss the 2011-2012 trial results agreed that the findings were good but needed further refining and decided that the following four treatments would be applied for the 2012-2013 season:

  • Lime + Mucuna pruriens + Fertilizer (soil test) + Lime (soil test)
  • Lime + Mucuna pruriens + Fish manure + Rock P
  • Mucuna pruriens + NPK 13:13:21 + Urea (conventional)
  • Mucuna pruriens + (Farmer's practice)

These were conducted in the Matei and Mua Research Station in the northern part of Taveuni, Vione in central Taveuni and Delaivuna in the south.

The results of these trials showed that the treatment with lime, Mucuna pruriens, fish manure and rock phosphate was the most effective treatment across the four sites. However, the scientists and farmers were still not convinced and decided that for the 2013-2014 growing season, the trials should assess not only fertilizer combinations but also the effects of biochar on soils fallowed with Mucuna pruriens and grass (without Mucuna). The following treatments were applied:

A1. With Mucuna pruriens + Fish manure + Rock P + Biochar
A2. With Mucuna pruriens + Fish manure + Rock P -- Biochar
B1. With Mucuna pruriens + Fertilizer -- NPK (13:13:21) + Urea + Biochar
B2. With Mucuna pruriens + Fertilizer -- NPK (13:13:21) + Urea -- Biochar
C1. With Mucuna pruriens + (Farmer's choice) -- Adjusted amendments according to Soil Test (site specific) + Biochar
C2. With Mucuna pruriens + (Farmer's choice) -- Adjusted amendments according to Soil Test (site specific) -- Biochar

D1. Without Mucuna pruriens + Fish manure + Rock P + Biochar
D2. Without Mucuna pruriens + Fish manure + Rock P -- Biochar
E1. Without Mucuna pruriens + Fertilizer -- NPK (13:13:21) + Urea + Biochar E2. Without Mucuna pruriens + Fertilizer -- NPK (13:13:21) + Urea -- Biochar F1. Without Mucuna pruriens + (Farmer's choice) -- Adjusted amendments according to Soil Test (site specific) + Biochar F2. Without Mucuna pruriens + (Farmer's choice) -- Adjusted amendments according to Soil Test (site specific) -- Biochar


Figure 1 shows the effects of different fertilizer combinations and biochar on yields of taro grown in plots fallowed with Mucuna or grass (non-Mucuna) for six months. The yields are of 16 data plants measured in kg. The results from two of the sites showed that the fish manure plus rock phosphate (D2) and farmer's choice (F2) treatments produced higher yields than the application of inorganic NPK fertilizers at all sites. Biochar did increase the yields of some treatments in both with- and without-Mucuna blocks. The effects of the use of biochar, however, need to be further investigated.

The scientists and the TTT farmers decided that, although the fish manure and rock phosphate combination seemed the 'best bet', there was need for one more season of testing to find answers to some of the questions still unanswered by the research programme. It would be good to have a second season of testing where organic amendments and inorganic amendments are compared again in fully replicated trials and to conduct paired treatment on-farm trials on more TTT Farmers Association members' farms. In order to ensure more precision, it was decided that, based on soil tests, the organic and NPK treatments could be adjusted. The adjusted treatments formed two other treatments. It was decided that the treatments for the next season would be:

  1. Fish manure and rock phosphate + biobrew
  2. NPK + Urea
  3. Fish manure and rock phosphate + Biobrew + Fertilizer amendments based on soil tests
  4. NPK + Urea + Fertilizer amendments based on soil tests.

It was also decided that the effects of biochar would be looked at separately in a set of field trials as well as in glasshouse pot experiments.

The involvement of the TTT farming community in this project from the stage of diagnosing soil health problems to the development of strategies to solve these as well as their active participation in the fieldwork is a model that SPC-LRD wants to promote in community participatory technology development.

The project was supported by ACIAR working with AusAID, with the latter funding the purchase of necessary material such as charcoal kilns and portable soil test kits. AusAID also financed the establishment of a resource centre for Tei Tei Taveuni that will provide information in print or electronic form as well as access to the Internet. In an innovative approach, the resource centre will also sell agricultural inputs to all farmers on the island. The project has thus also demonstrated the important role of funding agencies in co-financing such endeavours.

The unique combination of active partners in the Taveuni part of the Soil Health Project -- the farmers, MPI Extension & Research teams, and SPC and ACIAR researchers -- offers the best chance for maximum impact.

The research has looked into real problems identified by participants, the trial results have been discussed by researchers, farmers and the MPI extension team on the ground, and the TTT Resource Centre has been equipped to provide the recommended agricultural inputs to the farmers to apply the results. All the knowledge and 'nuts & bolts' necessary to implement the knowledge acquired from the project have been put in place and covered by this unique stakeholder partnership.

t is clear that the success of the project stemmed from the involvement of the Tei Tei Taveuni farmers in all its phases, from the diagnosis of the problem to the screening of potential on-farm solutions and monitoring and evaluation of its progress.

The success of participatory technology development depends on the engagement and integration of, and communication among key stakeholders, both public and private. All stakeholders need to know their respective roles and responsibilities to ensure success.