Food and Agriculture in PNG

magnesium may have a potassium deficiency because Bourke, R.M. (1983). Crop micronutrient deficiencies
the calcium holds the potassium in the soil and in Papua New Guinea. Technical Report 83/3.
makes it unavailable to plants. This is common, for Department of Primary Industry, Kainantu.
example, in New Ireland Province.
Dearden, P.N., Freyne, D.F. and Humphreys, G.S.
Research on nutrient deficiencies of agricultural (1986). Soil and land resource surveys in Papua New
crops started in the 1950s, but little active research Guinea. Soil Survey and Land Evaluation 6(2):43–50.
is being carried out now on soil nutrient deficiencies
or on soil nutrient management strategies in PNG. Hartemink, A.E. and Bourke, R.M. (2001). Nutrient
Soil nutrient problems exist in parts of the country. deficiencies in export tree and food crops: literature
Further intensification of land use will affect soil review and field observations. In Bourke, R.M.,
fertility, and nutrient deficiencies are therefore Allen, M.G. and Salisbury, J.G. (eds). Food Security
likely to increase, particularly in food crops where for Papua New Guinea. Proceedings of the Papua
inorganic fertilisers are not being used.2 There is a New Guinea Food and Nutrition 2000 Conference.
need to monitor the development of nutrient defi- ACIAR Proceedings No. 99. Australian Centre for
ciencies as well as to properly identify them through International Agricultural Research, Canberra.
trials and soil and foliar (leaf) analyses. pp. 316–327.

Sources Humphreys, G.S. (1991). Soil maps of Papua
New Guinea: a review. Science in New Guinea
Bellamy, J.A. (1986). Papua New Guinea Inventory 17(2):77–102.
of Natural Resources, Population Distribution and
Land Use Handbook. Natural Resources Series NSO (National Statistical Office of Papua New Guinea)
No. 6. Division of Water and Land Resources, (2002). Papua New Guinea 2000 Census: Final
Commonwealth Scientific and Industrial Research Figures. National Statistical Office of Papua New
Organisation, Canberra. Guinea, Port Moresby.

Bleeker, P. (1983). Soils of Papua New Guinea. Wood, A.W. (1982). The soils of New Guinea. In
Commonwealth Scientific and Industrial Research Gressitt, J.L. (ed). Biogeography and Ecology of
Organisation and Australian National University New Guinea. Monographiae Biologicae. Volume 42.
Press, Canberra. Dr W. Junk Publishers, The Hague. pp. 73–83.

2 Organic fertilisers include animal manure, compost
and mulch made from leaves (see Section 3.11).
Inorganic fertilisers are usually manufactured, for
example, urea, potassium chloride or mixed nitrogen,
phosphate and potash fertiliser. Most organic fertiliser
is not purchased in PNG, whereas most inorganic
fertiliser is purchased. Most of the inorganic fertiliser
used in PNG is applied to export tree crops or to
commercial crops grown for the domestic market, such
as sugar cane (see Section 5.19).

86 1.9 Soils

1.10 Landforms and altitude

Landforms The provinces with the greatest proportion of
total land area comprising mountains and hills
Landforms are the structural features of the are Enga (91%), Eastern Highlands (90%), East
landscape. Landforms have a direct relationship New Britain (83%), Simbu (79%), Central (78%)
to relief and slope and, in turn, determine rates and Morobe (77%).
of erosion, runoff and whether land is flooded.
Landforms influence agricultural land use. Almost two-thirds (63%) of the land used
for agriculture in PNG (see Section 1.2) is
The PNG landscape can be divided into five basic on mountains and hills; 12% is on volcanic
landforms (Figure 1.10.1): landforms; 11% is on plains and plateaus; and
9% is on floodplains (Table 1.10.1, Figure 1.10.2,
Mountains and hills (not of volcanic origin). Table A1.10.2).

Landforms of volcanic origin (including volcanic The provinces with the greatest proportion of
foot slopes and plains). land used for agriculture on mountains and hills
are Eastern Highlands (91% of land used for
Plains and plateaus. agriculture), Enga (90%), Simbu (86%), Madang
(76%), Sandaun (76%), Morobe (76%) and
Floodplains. Gulf (75%).

Raised coral reefs and littoral areas (beach Volcanic landforms used for agriculture are most
ridges, tidal flats, mangrove swamps and other important in Bougainville Province, where 61%
coastal features). of land used for agriculture is of volcanic origin.
This is also a significant landform for agriculture
The following summary points can be made about in Oro (46%) and Southern Highlands
these landforms in PNG: provinces (32%).

Around half (52%) of the total land area of PNG Although 59% of the land used for agriculture
is mountains and hills; almost 19% is plains or on plains and plateaus is in Western Province,
plateaus; 18% is floodplains; and a considerably much of this land is used at very low intensity
smaller proportion is volcanic landforms or (see Section 1.2).
raised coral reefs and littoral areas (Table 1.10.1,
Table A1.10.1). Provinces where a high proportion of land
used for agriculture is floodplain are East Sepik
(22%), Central (22%), Oro (16%), Gulf (16%)
and Sandaun (14%).

1.10 Landforms and altitude 87

50 0 100 200 300 400
kilometres

Mountains and hills (non-volcanic)
Volcanic landforms
Plains and plateaus
Floodplains
Raised coral reefs and littoral areas

Figure 1.10.1 The five basic landforms of the PNG landscape . Sources: McAlpine and Quigley (c . 1995); PNGRIS .

Land used for agriculture (km2) 18,000 Landform
16,000
14,000 Raised coral reefs
12,000 and littoral areas
10,000 Floodplains
8,000 Plains and plateaus
6,000 Volcanic landforms
4,000 Mountains and hills
2,000

0

SMEWSEMMESMNWEBionaaaaomenioaaeesssugulwtttnndssdrabtgettoSNheuaaueraIbNenrnuesirBeenpenrgnewalHnvaiwykHinilHBgldieBrghiigrhtliahatlnaialnanidnndsdss
WOCGeurenolsfttrearln

Figure 1.10.2 Land area used for agriculture by landform and province . Sources: McAlpine and Quigley (c . 1995); PNGRIS .
88 1.10 Landforms and altitude

Coastal landforms used for agriculture are most Lowlands (sea level to 600 m), 32–30 °C to
important in the Islands Region and in Milne 23–19 °C.
Bay Province.
Intermediate (600–1200 m), 30–27 °C to
Approximately half of the population of PNG 19–16 °C.
live on mountains and hills; 17% live on volcanic
landforms; 13% on plains and plateaus; and 9% Highlands (1200–1800 m), 27–23 °C to
on floodplains. Raised coral reefs and littoral 16–12 °C.
areas – the landform that makes up the smallest
area of PNG (only 4%) – support 11% of the High altitude (1800–2400 m), 23–19 °C to
population (Table 1.10.1, Figure 1.10.3, Table 12–9 °C.
A1.10.3).
Very high altitude (2400–2800 m), 19–16 °C to
PNG landforms with the highest population 9–7 °C.
densities on land used for agriculture are raised
coral reefs and littoral areas (70 persons/km2) Uninhabited (>2800 m), <16 °C to <7 °C.
(Table 1.10.1; see also Table 1.3.1). Population
densities on volcanic landforms average 50 These altitude/temperature classes are used because
persons/km2 and on plains and plateaus are of the crops that grow in them (see Figure 1.13.3).
around 40 persons/km2. Population densities are Some crops only grow well up to around 600 m,
lowest on mountains and hills. for example, Polynesian chestnut, pao nut and
kangkong, so 600 m is a convenient place to separate
Altitude ‘lowlands’ from the ‘intermediate’ class. Many tree
crops in PNG, such as coconut, betel nut, tulip and
In PNG, people live and practise agriculture from breadfruit, grow to about 1000–1200 m above sea
sea level to around 2800 m above sea level. Above level, so 1200 m is used to separate the intermediate
2800 m, people maintain Pandanus orchards and class from the ‘highlands’. Many food and cash crops
hunt, but they do not cultivate land or maintain do not grow well above 1800–2000 m, so 1800 m is
settlements. Because PNG is located close to the a convenient break between the highlands and ‘high
equator, there is little variation in temperature in altitude’ classes. Above 2800 m there is no permanent
most places from month to month during the year settlement or agriculture. This class is ‘uninhabited’.
(see Table 1.13.1). However, average temperature
declines with increasing height above sea level The following summarise the main points about
at a rate of 5 °C for every 1000 m of altitude (see altitude and agriculture, and altitude and population
Section 1.7), so altitude is an alternative measure for in PNG:
temperature in PNG.
Two-thirds of PNG’s total land area lies below
Temperature is a critical determinant of plant 600 m altitude and falls into the lowlands
growth (see Section 1.13). It also determines the environment. The intermediate altitude class
survival range of some insect pests, for example, the is 15% of the total land area and the highlands
Anopheles mosquito that transmits malaria. There altitude class 9%. Less than 10% of the total
is evidence that average temperatures are slowly land area is above 1800 m and only 2.5% is
increasing in PNG as a result of climate change (see above 2800 m (Table 1.10.2, Figure 1.10.4, Table
Section 1.8). A1.10.4). Above 2200 m, temperatures may fall
below freezing on cloud-free nights (see Sections
Six altitude classes from PNGRIS, and the maximum 1.6 and 1.7). The highest point in PNG is Mt
and minimum temperatures associated with them, Wilhelm (4509 m), on the border of Western
are used here: Highlands, Simbu and Madang provinces.

The greatest proportion of land used for
agriculture lies between sea level and 600 m
(62%) (Figure 1.10.5, Table A1.10.5). The lowest
proportion of land used for agriculture is in the
very high altitude class, 2400–2800 m (1.4%).

1.10 Landforms and altitude 89

















































Where a plant species flowers or fruits at about the Soil fertility
same time every year, we can infer that it is changes
in daylength that induce flowering. This is the case Soil is vitally important for crop growth. It provides
for a number of crops in PNG, including sis nut, support, nutrients, water and aeration for plants.
marita pandanus, purple passionfruit and okari nut Soil fertility depends on rainfall, the nature of the
(Terminalia kaernbachii). Some species, including underlying rock and natural erosion on steep slopes
breadfruit and Polynesian chestnut (aila), appear to (see Sections 1.9 and 3.7). Soil fertility is commonly
produce in a regular seasonal manner from about 8° reduced by more intensive cropping. As a general
south of the equator and further south, but fruit in rule, soil fertility is reduced faster by intensive
an irregular manner at locations nearer the equator. cropping in the lowlands than it is in the highlands.
It is likely that changes in daylength are too small This is because higher temperatures in the lowlands
near the equator to induce flowering in a regular way. cause natural processes to occur at a faster rate than
in the cooler highlands environments. Rainfall in
Inundation (flooding) the highlands tends to be less intensive than in the
lowlands. This means that leaching of elements from
Some locations in PNG are flooded for part of soils exposed by cultivation occurs more slowly in
the year (see Section 1.11). This has an important the highlands.
influence on agricultural production in those
locations, as many crops cannot grow under Two aspects of soil fertility, the structure and
flooded conditions. One notable exception is sago nutrient content, have an important influence on
palm, which thrives in flooded locations. Sago is a crop growth and yield. For example, under high
very important food in many places in East Sepik, nitrogen conditions plants tend to grow larger,
Sandaun, Western and Gulf provinces. It is notable take longer to mature and yield more. There are
that sweet potato is a minor crop in those locations, exceptions to this, for example, if there is too much
as it only produces where the soil is well drained. nitrogen in the soil, sweet potato will produce
Other crops that can tolerate inundation for short or a lot of top growth, but the tuber yield may be
long periods include oil palm, swamp taro, kangkong, reduced. Some crops, such as taro, corn, tobacco
taro and oenanthe. and common bean, are very sensitive to low levels of
plant nutrients. In contrast, some crops, for example
A striking feature of PNG agriculture, especially in cassava, highland pitpit and some types of banana
the highlands, is the use of steep, sloping land for (such as Yava, Kalapua or Tukuru), bear reasonably
agricultural production. The absence of mechanical well even when the levels of nutrients are low. The
or animal-drawn cultivation and the generally low soil structure is more important for some crops
rates of erosion allow the use of steep slopes for than for others. Sweet potato grows best in soils that
agriculture in the highlands. But the most important have a good structure, that is, one that is crumbly
reason for use of steep land is the desire of villagers and allows water, air and roots to penetrate. If such
to plant sweet potato on well-drained sites. Land soils are not available, because they are a heavy clay
that floods seasonally, such as alluvial plains in the for example, villagers will improve the structure by
wetter season, is often used intensively when it is tillage (see Section 3.11).
not flooded and abandoned when it is. In many
places along the levee banks of the Sepik and Ramu People can influence soil fertility in a number of
rivers, villagers plant food gardens as flood levels are ways. The first is selecting sites for planting food
falling and harvest before waters rise again around or cash crops. The second is by deciding when to
six months later. Villagers favour crops that mature move from the fallow phase to the garden phase.
faster, for example, Dioscorea alata yam rather The third is by modifying the environment in which
than D. esculenta yam, because D. alata produces plants grow.
tubers faster (see Section 3.12).

114 1.13 Crops, people and the environment

Villagers select sites for gardens and cash crops Sources
on a number of criteria. Sites on flatter land are
more likely to be more fertile, but perhaps have Bourke, R.M. (1989). Altitudinal limits of 230 economic
poorer drainage than those on sloping land. In the crop species in Papua New Guinea. Unpublished
highlands, mixed vegetable food gardens are typically paper. Department of Human Geography, Research
planted on flatter and more fertile land, while sweet School of Pacific and Asian Studies, The Australian
potato is commonly planted on better-drained sites, National University, Canberra.
which are often on a gentle to steep slope. These
factors are influenced by the nature of the soil, for Bourke, R.M. (2005). Sweet potato in Papua New
example, some sites on flat land are well drained. The Guinea: the plant and people. In Ballard, C., Brown,
fallow period is an important determinant of soil P., Bourke, R.M. and Harwood, T. (eds). The Sweet
fertility (see Section 3.8). Villagers judge how well Potato in Oceania: A Reappraisal. Ethnology
soil fertility has been restored after the fallow phase Monographs 19 / Oceania Monograph 56. Oceania
by the growth of natural vegetation on the site and Publications, University of Sydney and Ethnology,
not by the period of time the land has been in fallow, Department of Anthropology, University of
although the two factors are related. Pittsburgh, Sydney and Pittsburgh. pp. 15–24.

Villagers in PNG use a range of methods to improve Bourke, R.M., Camarotto, C., D’Souza, E.J., Nema, K.,
soil fertility. These include tilling the soil, which Tarepe, T.N. and Woodhouse, S. (2004). Production
is common where the fallow vegetation is grass
(Section 3.11); transferring organic matter as Patterns of 180 Economic Crops in Papua New
green manure (termed ‘compost’ in PNG) to the Guinea. Coombs Academic Publishing, Canberra.
soil surface or into a large mound (Section 3.11);
planting certain tree species, especially casuarina Bourke, R.M., Allen, M.G. and Salisbury, J.G. (eds)
in the highlands, into food gardens to hasten soil (2001). Food Security for Papua New Guinea.
fertility restoration (Section 3.10); and planting
a leguminous food, such as peanut, in a rotation Proceedings of the Papua New Guinea Food and
with a root crop, especially sweet potato (Section Nutrition 2000 Conference. ACIAR Proceedings No.
3.10). People also reduce soil erosion by erecting 99. Australian Centre for International Agricultural
soil retention barriers or, less commonly, building Research, Canberra. (There are 17 papers in the section
small terraces to plant crops (Section 3.9). Within ‘Food shortages and the 1997 drought and frosts’,
a garden plot, people commonly plant those crops pp.153–274, that include discussion of the impact of
that have the highest requirement for fertile soil in the drought and frosts on crop performance).
sites where fallow vegetation has been burnt and ash
has accumulated. In a few locations in the highlands, Hanson, L.W., Bourke, R.M. and Yinil, D.S. (1998).
people burn twigs and leaves of casuarina trees in
a pile and plant the crops that demand high soil Cocoa and Coconut Growing Environments in Papua
fertility in those sites, particularly some of the leafy
green vegetables. New Guinea. A Guide for Research and Extension
Activities. Australian Agency for International
Development, Canberra.

McAlpine, J.R., Keig, G. and Short, K. (1975). Climatic
tables for Papua New Guinea. Division of Land Use
Research Technical Paper No. 37. Commonwealth
Scientific and Industrial Research Organisation,
Melbourne.

Mogina, J. (2002). Changing knowledge of plants in
transitional societies at Milne Bay, Papua New
Guinea. PhD thesis. The Australian National
University, Canberra.

Smith, J.M.B. (1977). Man’s impact upon some New
Guinea mountain ecosystems. In Bayliss-Smith, T.P.
and Feacham, R.G. (eds). Subsistence and Survival:
Rural Ecology in the Pacific. Academic Press,
London. pp. 185–214.

1.13 Crops, people and the environment 115

1.14 Access to markets and services

A measure of how easy it is to travel from a village in the services were offered, or where the commodities
PNG to a service centre or market is defined here as or labour were in demand. For them, these places
‘accessibility’. It is measured by how long it takes to were more accessible.
travel from a village to the nearest service centre or
market, and by the level of services available at the Because some people had better access to markets
service centre. and services, in a relatively short span of time they
became better educated, healthier and wealthier
Before the establishment of a colonial administra- than other people. Where these differences in access
tion in PNG, rural communities grew their own to markets or services remain in place, differences
food, built their own houses, manufactured their in levels of health, education and cash incomes can
own clothing, educated their children, used local be expected.
medicinal plants and magic to treat illnesses and
injuries, defended their territory and administered Accessibility classes
their ‘laws’. Although groups of people had trade,
ritual and marriage relationships with nearby groups, Access can be measured in a number of ways, but
many individuals did not travel more than a few kilo- here accessibility is divided into the following classes:
metres from where they were born for the whole of
their lives. Their village was the centre of their world. Very poor access – more than one day’s travel to
reach any level of service centre.
The colonial state established administrative centres
that were places where education and health services Poor access – between 4 and 8 hours travel to
and forces of law and order were located. Other reach a minor service centre.
places of wealth and employment, plantations and
mines, also appeared. The colonial administration Moderate access – between 4 and 8 hours travel
made it possible to travel longer distances in safety to reach a major service centre.
and to buy and sell commodities, including labour.
Good access – between 1 and 4 hours travel to a
When people, commodities and services began to major service centre.
move longer distances in PNG, some places were
advantaged over other places. It was easier for some Very good access – less than one hour’s travel to
people to receive education and health services, or to a major regional centre.
sell commodities or labour, because they were closer,
in terms of distance, time or effort, to places where This classification of accessibility is based on the
personal experiences of the authors in every district
of PNG and takes into consideration terrain, road

116 1.14 Access to markets and services

coverage, road quality, the presence of public road The greatest number of people with very poor access
transport and shipping in the late 1990s and the to services live in Sandaun Province, where almost
services offered at various centres. Travel is defined 37 000 people (22% of the provincial population)
as surface travel by a person on foot, in a vehicle or live more than a day’s travel from a minor service
in a boat. Air travel is excluded because most people centre. More than 20 000 people in each of Southern
cannot afford it on a regular basis. Highlands and East New Britain provinces are
similarly isolated.
The unit for which accessibility is estimated is the
MASP Agricultural System (for more information Larger numbers of people have poor access to
on MASP see Section 1.15). Accessibility is measured services. In Madang Province 106 000 people live
from the centre of the system. Because agricultural more than four hours from a minor service centre.
systems were defined using attributes that did not In each of Southern Highlands, Milne Bay, Western
include accessibility, some minor anomalies exist. Highlands and Morobe provinces, over 40 000 people
In these cases, which occur close to Lae, Tabubil have poor access to services.
and Wewak, although it looks on the map as though
accessibility to these main centres is poor, it is in fact Summary of access to markets and
moderate to very good (Figure 1.14.1). services

The estimate of accessibility is based on time to A number of points can be made about access to
travel and not on the different costs of fuel. Per hour markets and services in PNG:
motorboat travel is considerably more expensive
than motor vehicle travel. Slightly less than half of the total population of
PNG have good or very good access to services.
Accessibility and population
Around 16% have poor or very poor access to
Many people in PNG have good or very good access services.
to service centres. An estimated 46% of the rural
population live within four hours travel to a major In the same province, large numbers of people
service centre. A further 38% live within eight hours in one part of the province can have very poor
travel to a major centre (Figure 1.14.2). This situation or poor accessibility, and in another part of the
is the outcome of the colonial administration province large numbers can have good or very
establishing service centres and building roads in the good accessibility. East New Britain Province is
most populated places. an example of this.

The greatest numbers of people who have very good Areas of very poor access to services are located
access to services live in East New Britain Province in the Sepik Valley and the highlands of Sandaun
and Western Highlands Province. In each of Eastern Province, along the northern edge of the
Highlands, Southern Highlands, Western Highlands highlands, in inland Gulf and Central provinces,
and Simbu provinces, more than 200 000 people have in south-east Oro Province and in inland East
good accessibility to a major service centre (Figure New Britain Province.
1.14.3, Table A1.14.1). A further 148 000 people in
each of East Sepik and Enga provinces live within Although the populations of small islands often
four hours travel of a major service centre. have moderate access to services because boat
travel takes them directly to major service
Around 16% of the PNG population has poor or very centres, the cost of outboard motor fuel is a
poor access to services. These people live further severe constraint on their ability to travel. Small
than four hours travel from any service. boat travel is also dangerous during parts of the
year because of weather conditions.

1.14 Access to markets and services 117