Soil Surveys and Soil Maps
- Gibbs, H. (1976a). Soils of Tongatapu, Tonga. NZ Soil Survey Report 35. Wellington, New Zealand Soil Bureau, Department of Scientific and Industrial Research.
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Gibbs, H.S. (1976b). Soil map of Tongatapu Island, Tonga. Scale 1:100,000. NZ Soil Bureau Map 81.
- Orbell, G.E.; Rijkse, W.C.; Laffan, M.D. (1981). Soil map of part Vava’u Group, Kingdom of Tonga. Scale 1:25,000, NZ Soil Bureau Map 197.
- Wilson, A.D.; Beecroft, F.G. (1981). Soil map of part Ha’apai Group, Kingdom of Tonga. Scale 1:25,000. NZ Soil Bureau Map 198.
- Wilde, R.H. (1981). Soil Map of ‘Eua Island, Kingdom of Tonga. Scale 1:25,000. NZ Soil Bureau Map 199.
- Orbell, G. E. (1983). Soils of the Kingdom of Tonga: an introduction. New Zealand Soil Bureau, Department of Scientific and Industrial Research, Wellington, New Zealand, 47p.
- Wilson, A.D.; Beecroft, F.G. (1983). Soils of the Ha’apai Group, Kingdom of Tonga. NZ Soil Survey Report 67. 32 p.
- Wilde, R.H.; Hewitt, A.E. (1983). Soils of ‘Eua Island, Kingdom of Tonga. NZ Soil Survey Report 68. 42 p.
- Orbell, G.E.; Rijkse, W.C.; Laffan, M.D.; Blakemore, L.C. (1985). Soils of part Vava’u Group, Kingdom of Tonga. NZ Soil Survey Report 66. 47 p.
- Cowie, J.D., Brophy, P.J. (1975). Soil map of Vaini Experimental Farm, Tongatapu Island, Kingdom of Tonga (unpublished).
- Cowie, J. D., Searle, P.L.; Widdowson, J.P.; Orbell, G.E. (1991). Soils of Tongatapu, Kingdom of Tonga. DSIR Land Resources Scientific Report 21. Lower Hutt, DSIR Land Resources. Report | Map.
- Halavatau, S. M. (1998). The effects of soil fertility factors on root crop production in Tonga. School of Land and Food. Brisbane, University of Queensland. PhD thesis. 256p.
