The importance of the agricultural sector and its reliance on the fertility of the soil was recognised by the Tongan government in the 1960's, when it requested the New Zealand government to conduct a reconnaissance soil survey of the country, including assessment of the fertility of the major soils.
Tonga Soil and Land Use Programme (1975-78)
- Gibbs. H.S. (1976): Soils of Tongatapu, Tonga, New Zealand Soil Bureau Report 35, 15p.
- Wilde, R. H. Hewitt., A.E. (1983). Soils of 'Eua Island, Kingdom of Tonga. NZ Soil Survey Report. Lower Hutt, New Zealand Soil Bureau, DSIR. 68.
- Wilson, A.D. Beecroft, F.G. (1983), Souils of the Ha'apai Group, Kingdom of Tonga, NZ Soil Survey Report, DSIR. 67.
- Orbell, G.E., et al. (1985), Soils of Part of the Vava'u Group, Kingdom of Tonga, NZ Soil Survey Report, DSIR. 66.
- Cowie, J. D., et al. (1991). Soils of Tongatapu, Kingdom of Tonga DSIR Land Resources Scientific Report. Lower Hutt, DSIR Land Resources. 21.
Soil Fertility Factors on Root Crop Production in Tonga