Intensified sweetpotato production in Papua New Guinea drives plant nutrient decline over the last decade

Fujinuma, Ryosuke, Kirchhof, Gunnar, Ramakrishna, Akkinapally, Sirabis, William, Yapo, Jeffery, Woruba, Deane, Gurr, Geoff and Menzies, Neal (2018) Intensified sweetpotato production in Papua New Guinea drives plant nutrient decline over the last decade. Agriculture, Ecosystems & Environment, 254 10-19. doi:10.1016/j.agee.2017.11.012

Author Fujinuma, Ryosuke
Kirchhof, Gunnar
Ramakrishna, Akkinapally
Sirabis, William
Yapo, Jeffery
Woruba, Deane
Gurr, Geoff
Menzies, Neal
Title Intensified sweetpotato production in Papua New Guinea drives plant nutrient decline over the last decade
Journal name Agriculture, Ecosystems & Environment   Check publisher's open access policy
ISSN 0167-8809
Publication date 2018-02-15
Year available 2018
Sub-type Article (original research)
DOI 10.1016/j.agee.2017.11.012
Open Access Status Not yet assessed
Volume 254
Start page 10
End page 19
Total pages 10
Place of publication Amsterdam, Netherlands
Publisher Elsevier BV
Language eng
Abstract Sweetpotato (Ipomoea batatas) is the staple food of the Papua New Guinea Highlands and is primarily grown in swidden-type production systems. Because of high population growth and limited available land to expand agricultural production, land use must be intensified to ensure food security. In this study, changes in sweet potato production systems were assessed by comparing field surveys conducted in 2005 and 2014. During the nine years between surveys, the length of fallow period decreased by 48%, from an average length of 12.1 in 2005 to 6.3 years in 2014. This reduction coincided with a reduced growth period for sweetpotato production gardens from 13.1 to 9.6 month (27%). The time required to reach gardens from the family home increased by 60% from 2005 to 2014. This surrogate measure shows that increasing land pressure has forced farmers to use more remote sweetpotato gardens. The clear driver for increased production was increased demand for sweet potato as a cash crop; 83% more sweetpotato was sold, rather than consumed by the producer. Despite the increase in production, the management of soil fertility remained unchanged, and farmers continued not to use mineral fertilisers for sweetpotato production. The intensification of land use reduced the occurrence of traditional bush/tree fallow species, such as Casuarina oligodon, which were traditionally used as fallow species in the sweetpotato system, but have been replaced by food legumes, e.g., beans and peanuts. As a consequence of land use intensification, there was a dear decline in soil fertility, particularly for soil N, P, Fe, and Zn, and plant tissue concentrations of N, S, Ca, Fe and B. Given the present rate of population growth and limited land area available to expand, land use intensification will continue. Comparison of the two surveys reported here, indicated that nutrient rundown of the system is occurring. To prevent further depletion of soil nutrients, especially as further intensification of the system is anticipated, nutrient inputs to the sweetpotato production system will need to be increased. In the short to medium-term, this may be through landscape nutrient redistribution strategies such as mulching with organic matter from outside the garden area in a cut and carry or cut and place method, but in the longer-term we anticipate that high levels of production can only be sustained through the addition of mineral fertilisers.
Keyword Field survey
Land use intensification
Soil fertility
Swidden cultivation
Temporal dynamics
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID SMCN/2012/016
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: HERDC Pre-Audit
School of Agriculture and Food Sciences
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Created: Tue, 02 Jan 2018, 14:07:20 EST by Ryosuke Fujinuma on behalf of Learning and Research Services (UQ Library)