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Soil fertility under shifting and semi-continuous cultivation in the Southern Highlands of Papua New Guinea

Lookup NU author(s): Dr Robert Shiel

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Abstract

People in the Southern Highlands of Papua New Guinea cultivate some land semi-continuously within a regime of shifting cultivation; the staple crop is sweet potato (Ipomoea batatas). The fertility of Tropepts, variably affected by falls of volcanic ash, was investigated to give further understanding of how subsistence farmers avoid the soil constraints that commonly prompt abandonment. While organic matter, N and K all decrease significantly with time under cultivation, they do not reach critical levels. Phosphorus also decreases significantly ol;er time, although contents are small throughout. Other nutrients show no significant variation with period of use or abandonment. These findings comply with the diversity of crops cultivated early in the life of 'gardens': followed by sweet potato, cultivated as a virtual monocrop in long established 'gardens'. If continues yielding adequately regardless of decrease in nutrient availabilities, notably because nutrient ratios remain favourable for tuberisation and because of sweet potato's tolerance of small phosphorus concentrations. It appears that burning of vegetation significantly increases available minerals and helps maintain a supply which is adequate for longterm sweet potato monoculture. Similar situations are postulated for other areas of less-weathered soils within the tropics.


Publication metadata

Author(s): Sillitoe P, Shiel RS

Publication type: Article

Publication status: Published

Journal: Soil Use and Management

Year: 1999

Volume: 15

Issue: 1

Pages: 49-55

Print publication date: 01/03/1999

ISSN (print): 0266-0032

ISSN (electronic): 1475-2743

Publisher: Wiley-Blackwell Publishing Ltd.

URL: http://dx.doi.org/10.1111/j.1475-2743.1999.tb00063.x

DOI: 10.1111/j.1475-2743.1999.tb00063.x


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