TY - JOUR
T1 - Intensified sweetpotato production in Papua New Guinea drives plant nutrient decline over the last decade
AU - Fujinuma, Ryosuke
AU - Kirchhof, Gunnar
AU - Ramakrishna, Akkinapally
AU - Sirabis, William
AU - Yapo, Jeffery
AU - Woruba, Deane
AU - Gurr, Geoff
AU - Menzies, Neal
N1 - Includes bibliographical references.
PY - 2018/2/15
Y1 - 2018/2/15
N2 - 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 sweetpotato 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 sweetpotato 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such as Casuarina oligodon, which were traditionally used as fallow species in the sweetpotato system, but have been replaced by food legumes, e.g., beans and peanuts.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 clear 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.
AB - 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 sweetpotato 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 sweetpotato 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 clear 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.
KW - Field survey
KW - Land use intensification
KW - Soil fertility
KW - Swidden cultivation
KW - Temporal dynamics
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U2 - 10.1016/j.agee.2017.11.012
DO - 10.1016/j.agee.2017.11.012
M3 - Article
AN - SCOPUS:85034598416
SN - 0167-8809
VL - 254
SP - 10
EP - 19
JO - Agriculture, Ecosystems and Environment
JF - Agriculture, Ecosystems and Environment
ER -