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Pacific Island Country

Paper Number 13

Sustainable land resources management for
plant nutrition management in Fiji*

* This country report has not been formally edited and the designations and terminology used are those of the author.

Atish Prasad
Land Use Planning Section, Department of Land Resources Planning & Development,
Ministry of Agriculture, Sugar & Land Resettlement, Fiji


Soil degradation due to soil erosion and nutrient depletion is an increasingly serious problem in Fiji. Even more alarming is the added problem of declining availability of arable lands, agricultural land use has expanded over 200 percent over the last four decades. Demands from other land uses have also shown similar increases and they often take over the good agricultural lands, thus moving agriculture onto marginal lands. Among the primary rural land use issues in Fiji, the relatively more significant are land quality, population density, proper understanding on land use, crop type and land availability and including the widespread culture of burning and poor land husbandry practices. On a positive note, Fiji has committed itself to the Declaration made at the United Nations Millennium Summit on September 2000 on Millennium Development Goals, particularly ensuring environment sustainability through the integration of the principles of sustainable development into the country’s policies and programmes to reverse or minimize the loss of environmental resources.

1. Introduction

Land resource base is finite but still it has to support a growing world population. Life depends on land and what it can support, therefore, it is important to maintain and improve its productivity. Every living organism on earth requires a good diet/food for growth and sustenance. Humans and animals are mobile and can select their diet/food from different sources and locations but plants are stationary in the soil. They are dependent on what the environment can supply them as nutrients.

In order to achieve sustainable food security, land and water resources management has been identified as one of the priority areas. Better use and management of natural resources by raising land productivity, controlling and minimizing land degradation, increasing bio-diversity and improving the quality of environment has become an issue for developing countries like Fiji.

Soil degradation is a worldwide phenomenon but in most developing countries the phenomenon is being hastened by land use mismanagement. It has been given various definitions and interpretations in different environmental situations such as the loss of land productivity, qualitatively or quantitatively, through many processes, such as, soil erosion, overgrazing, cultivation, leaching, water, logging and pollution of the land. It is also the gradual or complete reduction in soil fertility, either through the physical removal of the soil by erosion or through a gradual decline in soil fertility without loss of soil or both.

Soil degradation due to soil erosion and nutrient depletion is an increasingly serious problem in Fiji. This has adverse effects on food production and the environment. The loss of topsoil reduces the nutrient supply of the soil as well as rooting volume of the plants leading in time to lower crops yields.

Sustainable development is an imperative choice that must be made. Perhaps a precondition to sustainable development is development itself i.e. economic growth must be taken first in order to satisfy national desires for higher living standards. While Fiji’s economy develops, rational utilization of natural resources and protection of the environment has to be addressed as well.

  1. Demands on the land resources are increasing. Fiji will experience further land degradation, lower yields and increase in poverty if the ongoing expansion of commercial cropping onto marginal lands, cropping on fragile soils without conservaton practices, deforestation and burning of grasslands continue.

Implementation of the land use policy for sustainable development supported by technical teams who provide sound information to farmers and other stakeholders is urgently needed.

2. Country background

2.1 Location

The Fiji group lies in the southern hemisphere ranging from 1 800 to 2 500 km from the equator. It is situated between latitudes 15 degrees to 22 degrees south and longitudes 174 degrees east and 178 degrees west.

Fiji lies in a strategic location amongst other Pacific Islands and is 3 155 km from Sydney and 2 120 km from Auckland.

2.2 Land area

The Fiji Island group consists of approximately 300 islands with the total land area of about 18 378 km2 (1 837 789 ha) scattered over 230 000 km2 of ocean. Approximately 100 of these islands are permanently inhabited. The two main islands is Viti Levu (10 544 km2) and Vanua Levu (5 535 km2) which comprise 88 percent of the total area.

2.3 Climate and vegetation

Fiji enjoys a mild tropical climate with heavy rain under prevailing conditions, although there are definite “hot & wet” (Oct-Apr) and “cool & dry” (May-Sept) seasons. There is a difference between the windward (wet zone) and leeward (dry zone) coasts of the larger islands. Average annual rainfalls for the wet zone range from 2 800 to 3 600 mm and for the dry zone from 1 300 to 1 600 mm. Mean temperatures range from 23°C - 27°C with humidity of 75 percent - 88 percent.

Fiji was virtually covered with forest. The present plant cover comprises of fern land, open grassland, shrub land, savannah and tall forest. On all major islands, dense tropical forest covers the wet zone while the drier zones have mostly savanna grassland cover. Repeated burning of the grass cover had reduced some areas to bare ground (‘talasiga’ areas) where subsoils are often exposed. Economic planting of exotic pine and tropical hardwood species are on going in the areas.

2.4 Population

Fiji has a total population of 775 077 for 1996 at a density of 42 persons/km2 but the population had increased 810 421 by 2000. The population density figures can be considered misleading since it takes into consideration the unsuitable, inhabitable lands. The density on the populated arable lands was in excess of 373 persons/km2 (Bureau of Statistics 1996) and has drastically increased in the last five years. Over 60 percent of the population resides in rural areas, but migration to urban areas has a significant increase. The low population growth rate in the last decade of 0.8 percent per year is largely a result of emigration that has increased markedly after the 1987 & 2000 political upheavals, particularly of the Indian component of the population.

The figures for the census of population over the last century are tabulated below





1881 127 486 1946

259 638

1981 121 180 1956

345 737

1901 120 124 1966

476 727

1911 139 541 1976

599 068

1921 157 255 1986

715 375

1936 198 379 1996

775 077

Over the last four decades the population has more than doubled.

2.5 Topography

Fiji’s larger volcanic islands are dominated by steeply dissected, mountainous country with deep incisions of rivers and streams. The highest peak is Tomaniivi (mt Victoria) with a height of 1 323 metres at the summit.

There is a sharp contrast between the steep mountainous terrain and the flat land of the narrow valleys, coastal plains and river deltas, are the main areas of settlement and production.

Twyford and Wright (1965) described Fiji’s slopes for land use capability classification for the two largest islands are as follows:

Slopes and land use capability classes

Slope Group

LUC Class

Viti Levu

Vanua Levu

Flat (0-3°)

I 16%


Undulating to Rolling (4-15°)

II – IV 17%


Steepland (16°+)

V – VIII 67%


Review of Rural Land Use Policy, 2002.

3. Land utilization classes

Fiji’s land capability classification system is based on the suitability of land in its natural state for agriculture and if not, how much modification is necessary to render it suitable.

Below are the eight land classes grouped into four major classes:


Viti Levu

Vanua Levu

Total Fiji

I 21.46% 14.66% 19.36% 355 902
II 7.67% 12.61% 10.51% 193 277
III 29.01% 41.67% 31.93% 587 002
IV 41.86% 31.06% 38.20% 702 391

Land class I – first class arable lands without much improvements. Land class II – good arable lands with fairly minor improvements. Land class III – marginal lands with great attention needed for utilization. Land class IV – unsuitable for agricultural development.

4. Soils

The local classification used in Fiji is based on Twyford and Wright (1965) that splits the Fiji soils into 12 major groups called the Great Groups.

A. Recent soils

  1. Coastal Sand – occurring on the coastline
  2. Alluvial Soil – of the river valleys
  3. Colluvial Soil – of the foot slope

B. Wetland soils

  1. Gley Soil – of poorly drained low lying area
  2. Saline Soil – of the mangrove swamp

C. Black hill soils

  1. Nigrescent – in soapstone areas, boulder/rock outcrops

D. Red hill soils

  1. Latosolic Soil – stony soil of volcanic ash etc.
  2. Humic Latosols – deeply weathered and highly leached red soils
  3. Ferruginous Latosols – Talasiga soils, degraded humic latosols – highly erodible, infertile, dusky red soils

E. Yellow hill soils

  1. Red Yellow Podsolic – yellowish brown deeply weathered soils.

F. Organic soils

  1. Peat – decomposing plant matter developed under anaerobic conditions in waterlogged areas.

G. Steepland soils

  1. Steepland equivalent of all hill soils in C, D and E.

Under the USDA Classification System these soils fall into nine soil orders, namely:

  1. Entisol
  2. Inceptisol
  3. Mollisls
  4. Alfisols
  5. Andisols
  6. Ultisols
  7. Oxisols
  8. Vertisols
  9. Histosols

Fiji had a comprehensive soil survey, characterization, classification & correlation completed in 1997. This report has detailed typical profile morphological, physical and chemical information on the 227 soil series identified in Fiji. Parameters included for all soils are as follows:

5. Land use

Predominant land uses in Fiji are agriculture, tourism, forestry, urban/commercial/industrial/ residential and institutional. Agriculture includes crops and livestock grazing. The farming systems in Fiji are largely influenced by weather, thus, tailored to suite the different climatic patterns or zones (wet or dry) of the country. In the dry zones of the main islands, monocropping of sugarcane is planted extensively on the arable flats and up and down slopes greater than 15 degrees and pine (Pinus carribea) in the uplands.

The wet zone is where most subsistence semi-commercial and commercial planting of immature and mature ginger, taro and other root crops are primarily concentrated. With the recent interest in mahogany, (Sweetenia macrophylla), plantations have been set-up in the upland system known in agroforestry circle as the Taungya system. In this system, trees and crops are planted together and when the tree canopies closed, crops are withdrawn to let the trees grow mature. Mahogany is mainly concentrated in the wet zone.

Vegetables are intensively cultivated in Sigatoka valley in the intermediate zone and on scattered areas in the wet zone.

Agricultural land use has expanded over 200 percent over the last four decades. The figures for the three agricultural census are 1968 – 242 000 hectares, 1978 – 320 000 hectares and 1991 – 591 000 hectares. Demands from other land uses have also shown similar increases and they often take over the good agricultural lands, thus moving agriculture onto marginal lands.

6. Land use issues    

The primary rural land use issues are summarized as follows:

7. Addressing sound land husbandry practices

Clearly, Agricultural Landlord and Tenant Act and related legislations provide the legal mandate to enforce and improve appropriate land husbandry practices. Some of the relevant provisions are as follows:

Crown Agricultural Leases (CAL) specifies this in provisos (10). ALTA 13 (2b & 2c) specifies cultivation to maintain fertility and avoidance of measures reducing fertility.

CAL provisos 11 & 17 ban cultivation, over grazing, burning and tree felling on areas steeper than 25°. ALTA schedule 3 proviso 8 states that limit.

ALTA Schedule 3 proviso 7 provides instructions to tenants to apply measures to check soil erosion. CAL proviso 29 implements.

ALTA is not specific on slopes below 25°, however the provisions in the maintenance of soil fertility above can be applied to control burning.

ALTA schedule 3 proviso 7 can be applied to control erosion. Land Conservation & Improvement Act, Order 21 (1959) instructs all sugarcane to be grown along the contour.

Research results show the value of this technique.

This is a desirable practice to incorporate into the farming system for soil fertility and soil erosion.

Uncontrolled cattle damage crops. There is need for protection under the Land Conservation & Improvement Act and ALTA.

There is a hint of responsibility with the Committee of Valuers under ALTA 1985 revision Section 21. This clause could be used to clarify definitions related to overgrazing.

This satisfies the improvements provisions of the LCIA 1953 Cap 141– a broad little component used.

Importance of waterway maintenance is often ignored by logging, housing, farming, pasturalism and manufacturing. Blocked waterways overload systems with pollutants and sediment. (Rivers and Streams Act, Public Health Act & Environment Management Act).

Land and water are complimentary resources and have detrimental acting impact on each other. (EMA).

These provide filter zones for land-sourced sediments and have a key role in keeping creeks clean and also maintaining bank erosion.

CAL proviso 11 addresses this for steep areas but can be expanded to accommodate mass movement and improved soil cover purposes.

Environment Management Act &Anti Litter Decree addressed this but LCIA land improvement under Cap 144 must always be viewed as enhancing land values. When rubbish dumps develop unabated land values fall.

Values of mangrove areas need to be assessed and fully recognized. Building roads through these and reclaiming them should never have been done without careful analysis and results.

Should imply protection and rehabilitation together for meaningful proclamations. The Land Conservation Board is already empowered to do this.

8. Conclusion

Although the Fijians have been used to extensive cultivation, the scarcity of land availability for almost half the population will lead to a more intensive cultivation of existing available lands and the opening up of more marginal lands.

It is recognized that depletion of soil fertility also means degradation of the environment. Plant nutrient management should not be addressed in isolation. In the Fijian context environmental sustainability and farmer affordability and agricultural sustainability has to be taken into consideration as well. Nonetheless, it is recognized that the progress of increased agricultural production cannot be achieved without improving and increasing the external sources of plant nutrition. Productivity is dependent on efficient and effective supply for plants to use.

Soil is a nutrient bank, holding nutrients until plants require them, but it must not be construed as having adequate supplies of this at all times in all places. Different soils have different value for food production. As Fiji moves from subsistence agriculture to a more commercialized one the need for mineral fertilizers will increase to minimize land degradation and fertility depletion.

The capability of a soil to produce quality crops sustainably over time depends on the site fertility, which includes the inputs of climate, location and management. Thus sustainable land management technologies and land use planning play a more important role. Sources of plant nutrients other than mineral fertilizers although rarely enough must occupy an important place in the conservation of the natural resource base. The increasing demand for organically grown crops and sustainability of mineral fertilizers renders it increasingly important to look for biological solutions.

Fiji has also committed itself to the Declaration made at the United Nations Millennium Summit on September 2000 on Millennium Development Goals. One of the 8 Goals is to ensure environment sustainability through the integration of the principles of sustainable development into the country’s polices and programmes to reverse or minimize the loss of environmental resources. Those that have been published in development plans and economic summits do not appear to have been adopted following careful cross-sectoral appraisal, which had resulted in minimal implementation. However, such policies and legislations, which could be used to good effect, are constrained by a lack of enforcement through inadequate staffing, lack of technical resources and funding.


D. Leslie & I. Ratukalou (2002), Review of the rural land use in Fiji.

I.T. Twyford & A.C.S. Wright (1965), Soil resources of the Fiji Islands.

Fiji Islands Bureau of Statistics (July 2004), Key statistics.

D.M. Leslie (1997), An introduction to the soils of Fiji.

ESCAP/FAO/UN (1993), Proceedings of the regional fadinap seminar on fertilization and the environment.

Ministry of Agriculture, Fisheries & Forests (1999), Fiji National Agricultural Survey.

Paper Number 14

Status of plant nutrient management in Papua New Guinea*

* This country report has not been formally edited and the designations and terminology used are those of the author.

Kud Sitango
National Agricultural Research Institute,
P.O. Box 120 Mt. Hagen
Western Highlands Province
, Papua New Guinea


Over the last three decades there was a rapid increase in population and pressure on land for food production. The trend during the last three decades has been towards greater intensity of land use. That is, the ratio of cropping to fallow period is increasing. This is putting strain on the subsistence based shifting cultivation system system used in Papua New Guinea. The other development that put strain on the flexibility of the future development for agriculture is that more lands are being tied up to permanent cash crops especially coffee, cocoa and coconut, which unfortunately result into more land scarcity. This trend is common in high population density areas and may in the long run lead to a high rate of soil degradation and plant nutrient deletion. Mixed cropping, pigs foraging, legume rotation of sweet potato and application of ash are not capable of maintaining soil fertility. Currently, farmers in high population density areas in PNG have gone into the adopting plant nutrient application technique as alternative technology to subsistence base shifting cultivation systems to cope with the growing needs for improving food supplies. The adopted food production techniques likewise consider the introduction of improved staple crop varieties and permanent cash crop, crop rotation, integrated farming, application of natural fertilizers like coffee pulp, animal manures and application of inorganic fertilizers. However, this shift in production technology is associated with social and institutional problems that need to be immediately addressed. Among other things, these include general attitude of people towards accepting and adopting new technologies, lack of basic and appropriate information and general environmental constraints that needed proper research.

1. Introduction

In Papua New Guinea (PNG), people live and practice subsistence agriculture over a wide range of altitude (sea level to 2 850 m), rainfall (1 000 to over 7 000 mm per year), soil type and topography for over centuries. There are major differences in cultural traditions between various groups of people and subsistence food production and plant nutrient management system are very diverse. In pre-contact Papua New Guinea, people were dependent on horticultural products, hunting and fishing. The common food crops were high-starch staple foods including sweet potato, taro, yams, sago and bananas.

Rapid change in Papua New Guinea agriculture is not new. Spate (1953) wrote about the change in cash cropping, forest clearing and soil erosion. Lea (1972) reviewed recent changes in subsistence agriculture in Melanesia, concentrating on the Abelam people in western province. Ward (1982) reviewed recent changes on the loss of diversity on subsistence agriculture in Melanesia. Changes have also occurred in the soil fertility and plant nutrient management techniques over the past three decades as a result of rapid increase in population. Much of the information is extracted from literature and my observation of subsistence and semi-subsistence agriculture systems practiced in main parts of the lowland, highlands and the high altitude agro-ecological zones of Papua New Guinea.

2. Geography

Papua New Guinea includes the eastern half of the island of New Guinea, island of New Britain, New Ireland, Bougainville and hundreds of small islands. The total population of PNG is 5.2 million, which has doubled over the last 30 years. Present projections indicate a population of around eight million by 2020 (Department of National Planning and Monitoring, 1999). Growth rates in the main cities and towns are higher than in rural areas due to urban migration.

The land area is approximately 463 000 km2 and is divided into the five-agro-ecological zones. This includes the wet lowland island, the wet lowland mainland and the dry lowland (0-1 200 m), the main highlands (1 200-1 800 m) and the high altitude (1 800-2 800 m) lands. People live from sea level to approximately 2 800 m above sea level. Approximately 85 percent of people live in the rural areas of which 40 percent live in the highlands agro-ecological zone region. The population density ranges from one person/km2 in the remotest inhabited areas to over 500 people/km2 on some small islands. The average population growth rate between 1980 and 2000 was 2.7 percent.

Average annual rainfall varies extremely from more than 8 000 mm in some mountainous areas to 1 000 mm in other areas. Average temperature varies with altitude with tropical temperature in the lowlands and milder temperatures in the highlands. Frosts occur above 1 500 m and cause periodic problems for agriculture above 2 200 metres. Forest cover over 70 percent of PNG’s land area. Two common languages spoken are Melanesian Pidgin, which is spoken by a majority of people and the Hiri Motu, which is spoken in Papua (Hanson, Allen, Bourke and McCarthy, 2001). English is the language of administration and international communication. There are 800 distinct local cultures and languages. Customary land accounts for about 97 percent of the total land area where most people live and the land is under their title.

3. Population and land use

PNG is thought to have been occupied by humans for at least 40 000 years and agriculture in PNG has been practiced for at least 6 000 years (Golson and Gardner, 1990). Humans may have adopted agricultural practices to enable them to exploit their environments. Low intensity shifting cultivation operates on cycle of one or two years of cropping, followed by 5-15 years of fallowing. This is the main indigenous gardening system practiced throughout the country. Many of the rural people are semi-subsistence farmers who produce food and cash crops from their own gardens. Locally grown food provides 80 percent of calories consumed by the rural population (Gibson, 2001).

Most of the unoccupied land in PNG has very low potential. Approximately 40 percent of the rural population lives in this environment. These people are constrained by some combination of poor soil, high rainfall, steep slopes, excessive cloud cover, frequent flooding and low temperatures. On the otherhand, approximately 25 percent of the rural population, most of whom live in the highlands is vulnerable to the effect of agricultural pressure. This includes land degradation, declining crop yields and food shortage. About 20 percent of the rural population use land very intensively to the point that land is cultivated continuously (Allen, Bourke and Hanson, 2000).

4. Traditional subsistence plant nutrient application and management techniques

Traditional subsistence plant nutrient management techniques in PNG are based on shifting cultivation system that has been passed from generation to generation. These techniques mainly aim at either directly or indirectly conserving soil fertility and maintaining ecosystem stability and allowing more frequent cultivation of the soil for food production. Some of the more common practices in both the lowlands and the highlands are mentioned below.

4.1 Shifting cultivation

Shifting cultivation is the basis of the traditional subsistence agriculture in PNG for food crop production and a natural way of restoring soil fertility. Under this system the forest is cleared, a garden is planted and after period of cultivation, when the soil is exhausted, the land is abandoned for forest/grassland to grow back again for one or two years and then fallowed again for 10 years or more. During the time of fallowing the natural vegetation is allowed to regenerate and restore soil fertility. In PNG large segment of population is engaged in this farming system to satisfy food requirement at subsistence level. There are advantages of this system but it uses a lot of land and with the current population increases, cash cropping and land alienation reduced the amount of land available for gardening and the system can no longer be used.

4.2 Large mound cultivation

The use of large mounds associated with composting is the sweet potato cultivation technique used in the high altitude agro-ecological zones. Weeds, green grass and old sweet potato vines are placed in the mound crater or in a heap on the soil surface and allowed to rot for 6 to 8 weeks and then covered. Then sweet potato vines and supplementary crops are planted. People believe that by doing that, they: a) fertilize the soils prolonging its productive life, b) provide protection on shallow soil from soil erosion by channeling run off water into the spaces between mounds, c) improve soil drainage and aeration by raising sweet potato above the water table in swampy and flood prone environment and d) allow dense air to sink to ground level on cold frosty nights in high altitude agro-ecological zones (Waddell, 1972). Large mound is common in much of the Enga and Southern Highlands provinces and Tambon in Western Highlands province.

4.3 Burning

This practice involves clearing the forest or grassland and allowing the cut vegetation to dry then burn them and thereafter plant crops in the ashes. The people believe that ash from burnt vegetation is one of the main fertilizers added to the soil and large range of crops can be grown the in new gardens. The ash provides large amount of potassium, calcium and magnesium to the soil and improvements in soil fertility have been measured. The application of vegetation ash and household refuse occurs mainly in kitchen gardens, occupying small areas near houses (Humphrey, 1994). It was also observed that soil in kitchen gardens is also much less acid, and higher with phosphorous, calcium, magnesium and phosphorous (Humphrey, 1994).

4.4 Planted tree fallows

Many tree species have been planted in gardens to improve soil fertility. Tree species such as Casuarina oligodon and Parasponia species are planted into final year gardens fallows or around the edges of grdens to increase soil fertility during cultivation. Wildlings of Casuarina are transplanted into sweet potato gardens or are protected within the garden as the garden approaches the fallow phase. Dense stands of casuarinas thus replace a grass or scrub fallow. At the end of the fallow period, the side branches are trimmed and the sweet potato is planted among the standing live trees. This species has root nodules, which fix nitrogen, and has a leaf litter high in nitrogen (Parfitts 1976). Substantial increases in soil nitrogen have been found beneath Casuarina oligodon trees in Elimbari area in Simbu Province in the highlands agro-ecological (Parfitts, 1976). Planting of common fruit tree species in gardens or fallow is not commonly practiced, but trees for timber and firewood are planted. Casuarina oligodon is one of the most widely planted trees and is regarded as beneficial for the soil. The technique is commonly used between Lufa in Eastern Highlands province and the western end of Porol range, in Simbu province, in Oksapmin in Sandaun province, in Lagaip valley in Enga province and in Lamari valley in Eastern Highlands province (Bourke, 1990).

4.5 Pigs foraging

Pig is one of the important animals kept by people in Papua New Guinea. The pigs are allowed to graze freely in forest, swamps and tall grasslands and are kept out of gardens by means of fences and ditches. After most of the sweet potato has been harvested from a garden, pigs are often tethered to a stake in the garden and the pigs eat small sweet potato tubers remaining in the soil together with worms, grubs and insects. This process turns the soil over, remove weeds and improve of the fertility soil with their dung and urine. Tethering of pigs in gardens is common practice in the highlands agro-ecological zone region.

4.6 Contribution of silt from flooding

Silt is deposited by flood either regularly or sporadically in gardens, which increases soil fertility. In some areas, the stream is dug and channeled in order to enhance and control the floodwaters in the delivery of silt into the garden. This practice is common in Waghi valley in Western Highlands province and Laigap and Kandep valleys in Enga province and in areas where there is a high water table and experience regular flooding (Bourke, 1990).

4.7 Soil retention barriers

Soil erosion is one of the main problems faced by farmers in gardens on steep hill. People are well aware of the effects of erosion relating removing of soil fertility and decline of crop yield. Particularly in Simbu province in the highlands agro-ecological zone, people construct barriers such as pegged logs, fences or hurdles and stonewall along the contour or below individual plants in order to prevent or reduce the down movement of soil.

4.8 Soil tillage

Tillage includes breaking up or turning over of the whole or the major part of the soil on the garden surface. The measure includes tillage in either the first planting or subsequent plantings. The formation of soil mounds and beds involves working the soil into tilt. In most areas of PNG the tillage is generally minimal.

4.9 Use of drains

In some wet areas heavy drainage and ditches are dug around and within gardens to remove excess surface water or to lower the groundwater table. After the drainage is done, the soil is dug and prepared into fine tilt before the crops are planted. People have experienced good crop growth and yield under good drainage and soil tillage system. This is common in Waghi valley in Western Highlands province, Laigap and Kandep districts in Enga provinces.

4.10 Mix cropping

Mix cropping is typically a garden subsidiary that contain the main staple. It is planted with a wide range of either sub-dominant staples and/or other vegetables. It may or may not be distinguished from the main garden types by different fallow and agronomic techniques. This is the traditional cropping pattern common in lowlands, highlands and high altitude agro-ecological zones where large mound is practiced (Bourke, 1990).

4.11 Mounding and beds

In many parts of Papua New Guinea the soil is formed into circular mounds of varying dimensions and crops are planted on them. The mound is extensively disturbed similar to complete tillage and re-formed into mounds at each new planting. This mounding system may or may not contain compost and is common in both lowland and highlands agro-ecological zones. In some locations, the soil is also raised into elevated beds within gardens and crops planted. There are two shapes of beds distinguishable, the square and the long beds. Long beds are common in the highlands agro-ecological zones where commercial vegetable and sweet potato production is practiced (Bourke, 1990). People understand that mounds and beds are done to improve soil structure, drainage and aeration.

5. Improved plant nutrient application and management techniques currently used in Papua New Guinea

The trend during the last three decades has been towards greater intensity of land use. That is, the ratio of cropping to fallow period is increasing. This is because of large-scale migration of people towards roads, government settlements and fertile valleys. At the same, time population is increasing rapidly and the land is being tied up to permanent cash crops especially coffee, cocoa and coconut and the land became scarcer. The fallow period is reduced to less than three to five years leading to rapid soil degradation and soil nutrient depletion putting pressure on food security. Overall, sweet potato and taro yields were reported to have declined markedly over 19 years and none of the rotations tried proved a satisfactory alternative to shifting cultivation system (Bourke, 1990). In response to this, people have identified and used a number of improved plant nutrient application and management techniques in the lowland, highlands and the high altitude agro-ecological zones of the country to sustain food supply. The commonly used ones are described below.

5.1 Improved staple and cash crops

Many subsistence farmers claim that yield of sweet potato, taro yam are not as great as when they were children or in their grandparent’s time (Bourke, 1990). There was a change of staple crops from lower yielding traditional crops such as Colocasia esculenta and diploid bananas to high yielding ones such as Ipomea batatas, triploid banana, Xanthosoma sagittifolium and Manihot esculenta (Bourke, 1979). The introduction of new staple crops in both the low and highland agro-ecological zone has extended cropping period, reduced fallow period and improved food supply. There was an increase in smallholder cash cropping since 1950 that the land for food production was removed from the fallow cycle and planted with permanent cash crops like coffee, cocoa and coconut. This led to increased pressure on the land for food production and plant nutrient management systems. This is noticeable on Bougainvillea, Gazelle Peninsula in New Britain and Karkar Island in Madang province (Bourke, 1990). On the other hand, this system has prevented shifting cultivation and people settled, minimized frequent removal of vegetation and soil nutrient depletion. The coffee crop in Eastern Highlands, Simbu, Western Highlands provinces have clearly demonstrated this scheme is workable (Bourke, 1990).

5.2 Use of natural fertilizers

Most areas throughout the lowlands and highland agro-ecoogical zones in the country are using natural fertilizer in their gardens to increase soil fertility. This includes ash from fires, kitchen scraps, other plant wastes and animal manure. People realize that if a lot of these fertilizers are applied to soil, gardens can use a short fallow or even no fallow at all (Humphery, 1994).

Coffee pulp is applied to the soil either fresh or rotted. It is dug into the soil to improve fertility and it is commonly used in coffee growing areas and immediate areas where coffee is grown and pulp is available. Coffee pulp used in Nembi Plateau in Southern Highland province gave large increase in sweet potato yield (D’Souza and Bourke, 1986). However, it is very difficult and expensive to transport to other areas and its availability seasonal, thus unavailable in most areas in PNG.

People also have been placing animal manures in their gardens to increase soil fertility. The animal manure used includes that of pigs, chicken, rabbit and sheep. Pig manures are collected and applied to the gardens or the pig is tethered in gardens and the in process of foraging the dung and urine are dropped to the soil. People observed that manure gave large increase in sweet potato yields. Pig manure contains more nitrogen and less potassium than coffee pulp of the same weight. Pig is an important animal raised in PNG and recently there have been reports of increase in its population in the highlands but the amounts of manure are inadequate and unavailable for use.

Chicken manure is also used in the gardens. Chicken production for meat and cash has increased throughout the country. The manure is used in their garden for vegetable and food crop production mostly in backyard gardening. Since people can make more money in a short time, they tend to maintain continuous production. This makes available and continuous supply of manures for use in garden. Nevertheless, the keeping of livestock and use of animal manure still plays a minimum role in subsistence food crop production.

5.3 Legume rotation

The garden of harvested sweet potato is replanted with a legume crop species between plantings of main food crops. People claim that Ipomea batatas and Psophocarpus tetragonolobus rotation was a traditional crop rotation system for maintaining soil fertility prior to 1950. Peanut only became a significant crop in the highlands in 1950 and since then it was adopted into the cropping system and is used widely. Use of an Arachis hypogea/Ipomea batatas and Psophocarpus tetragonolobus rotation is widespread in the Nebilyer, Waghi and Baiyer valleys of the Western Highlands provinces and the main valleys of northern half of Eastern Highlands including Ramu, Dunantina, Benabena and Asaro. The rotation is confined to flatter land, altitudes below 1 900 m, deeper soils and is usually associated with grass fallows. Village people in the Eastern and Western Highlands provinces in the Highlands agro-ecological zone have found that a rotation of Ipomea batatas with Arachis hypogea or Psophocarpus tetragonolobus helps to maintain sweet potato yields for several years before Ipomea batatas yields decline too much (Bourke, 1978). Villages are adamant that the technique resulted in higher Ipomea batatas yields than an Ipomea batatas monoculture in Southern Highlands province (D’Souza and Bourke, 1986).

However, in current rotation, the land area cultivated with legume crops such as beans and peanut is small compared to area planted with sweet potato. People do not rotate food crops with pasture legumes.

5.4 Inorganic fertilizer application

Inorganic fertilizers are man-made ones such as Urea or muriate of potash. Already many semi-commercial farmers throughout the highlands agro-ecological zones in the country are uing inorganic fertilizers on food crops that sold. The crops include potato, broccoli, sweet potato, sugarcane and cabbage. The inorganic fertilizers are placed in gardens by basal application or side dressing to increase soil fertility.

The Irish potato-growing farmers in the highlands agro-ecological zone observed a high yield of Irish potato, variety Sequoia, with the use of inorganic fertilizers, Potato Mix (12:12:17). The average marketable yield without use of inorganic fertilizer was 9 t/ha while with the use of inorganic fertilizer the yields was 19 t/ha. So now farmers prefer planting this sequoia variety using Potato Mix rather than growing without it. The recommended application rate for Potato Mix application is 1 200 kg/ha. However, people in most area are using it in excess in expectation of higher yield. With the current problem of Potato Late Blight, there is an additional cost in production affecting most potato farmers since 2003. Broccoli is planted using a ratio of 1:1 NPK + Triplesuperphosphate, an the inorganic fertilizer, at an application rate of 40 g/plant that gave the highest yield (Kanua and Liripu, 1988).

Many village people throughout the highlands agro-ecological region are growing sweet potato for sale. The farmers who grow sweet potato range from full commercial ones to those who use their traditional subsistence techniques (Bourke, 1990). People are using Urea and Muriate of Potash and mixed in a 2:3 ratio and apply at the rate of 25 grams per square metre (Bourke, 1979). However, the result of inorganic trials on sweet potato in the highlands has not been very consistent. For this reason it was suggested that inorganic fertilizers should be used carefully (Bourke, 1979). In this area, inorganic fertilizers are also used in plantation to increase production of export crops like coffee, coconut and cocoa as a result of declining soil fertility.

The increase yield in inorganic fertilizer application is encouraging more farmers to use the inorganic fertilizers. However, the high cost and the availability of specific types of fertilizers are the main constraints that farmers experience. People are also not using the recommended rates, either applying too much or too little and not at the right time either.

5.5 Integrated farming system

In this farming system, all plant nutrient application techniques are integrated including food cropping system, animal rearing, agroforestry and soil management techniques. There is recycling of wastes to improve soil fertility and food production. Three or four of the plant nutrient management techniques commonly used are crop rotation, tilling soil and making drains, introducing new crops and use of animal manures and plant residues. This is a new system practiced in schools throughout the highlands and the lowland agro-ecological zones of the country.

6. Projections in plant nutrient consumption in subsistence and improved cropping and farming system in PNG

PNG traditional subsistence agriculture is based on shifting cultivation. Plant nutrient use by farmers in PNG is generally low by world standard. The input and output are minimum in terms of fertilizer, insecticides, animal power or machinery excluding manpower.

It appears likely that the present trend of population movement and growth in Papua New Guinea will continue in the future with low soil fertility, a more rapid soil degradation and fertility depletion

in the high populated and intensified agricultural areas. The improved and intensified agricultural techniques will be gradually employed to improve food production. Currently, the people do not have a well adopted and developed location specific cultivation techniques to counter declining crop yields and soil fertility in place.

7. Technical/policy measures being taken on Improved Plant Nutrient Management and how these are implemented

There were a number of strategies implemented in recent years to address these problems. Firstly, there was restructuring of the National Department of Agriculture and Livestock. The mandated research body for the country, National Agricultural Research Institute (NARI) emerged in 1997.

NARI then adopted the National Government Food Security Policy. Based on this, NARI developed its research and development strategy, identified research areas and conducted prioritizing exercise. One of the priorities was on development of sustainable agriculture system for PNG. The studies aimed at development of sustainable crop production technology alternative to shifting cultivation. The system should be more appropriate to farmers under PNG condition considering input cost, availability of materials and environment safety. The agronomists and soil scientists have put considerable effort in determining crop response to major and trace elements to prescribe fertilizer rates. A bibliography of soil fertility and plant nutrition in PNG is given by Bourke (1993). A treatise on soils of PNG is given by Bleeker (1983).

There was a review on conservation farming trials in composting and cropping, long-term soil exhaustion and cropping cycle trials, green manuring, improved fallow and alley cropping trials, agro forestry and soil fertility research programme initiated in 1990 (Humphrey, 1990). A livestock programme was also established with aim of improving family protein intake and farmer income. The programme also aims to integrate animals in the current cropping system to improve and maintain soil fertility. An outreach and liaison component was also established to disseminate released technologies and information to farmers. Through this the institute identified potential farmers to further disseminate information.

8. Constraints which the country is facing in implementing these activities

These are some of the constraints the country is facing in implementing the above activities. The indigenous knowledge and skills is well established in the subsistence farmers in PNG. People understand it as the best available method and they can not easily accept and adopt new ideas.

More research in developing technologies that are practical to farmers and more on cost benefit analysis of available plant nutrient application technique must be available to assist the farmers to make decision. Also, involve farmer in the research process so that farmers will be in a better position to make decision (Humphrey, 1994).

Up-to-date and appropriate information are lacking. Basic up-to-date information generated through research under PNG condition are available but they do not reach the farmers in problem areas, hence people are lacking the basic knowledge and skills they need to progress. There are mandated offices within the government structure to disseminate information but are constrained by funding. Finally, there is no policy in place to address the rapid increase in population of the country.

9. Conclusion

Shifting cultivation is the basis of agricultural system practiced in PNG throughout the centuries. This system is low in intensity and integrates various appropriate plant nutrient application and management techniques including tree planting, soil tillage and drainage, crop rotation, mix cropping and application of ash. These techniques are aimed toward conserving soil fertility, maintaining ecosystem stability and allowing continuous cultivation of the soil and food production.

Over the last three decades the trend has been towards greater intensity of land use as there has been rapid population increase and migration towards roads and government settlements, fertile valleys and urban centers. At the same time, land is being tied up by permanent cash crops especially coffee, cocoa and coconut (Bourke, 1990). This ha resulted in scarcer agricultural land hence putting pressure on food security. Observing this trend, people are gradually gravitating toward improved alternate cropping and gardening system. The improved techniques used included application of animal manures, inorganic fertilizers, crop rotation and integrated farming.

The current trend will still continue and the appropriate and available plant nutrient application and management techniques should be adopted further developed and used. However, there are constraints including lack of improved knowledge, attitudes towards accepting and adopting new innovations and further research on cost benefit analysis of the available techniques suitable to farmer need.


The United Nation Food and Agriculture Organization, Improve Plant Nutrient Management Workshop Organizers is hereby acknowledged for funding the trip for the workshop. Scientific staff of NARI Main Highlands and High Altitude Highlands Programme assisted and contributed information for this paper: Ms Debbie Kapal, Isaac Tiraken, Passingan Igua, Selwin Hariki, Mr Martin Gunther and Mr Alai Simin for technical advice and assisting in putting together this paper.


Allen, J.B., Bourke, R.M. and Hanson L. (2000). Food Security for Papua New Guinea, Proceedings of the Papua New Guinea food and nutrition 2000 Conference, PNG University of Technology Lae Morobe province.

Bleeker, P. 1983. Soils of Papua New Guinea. ANU Press, Canberra.

Bourke, R.M. 1990. Subsistence food production systems in Papua New Guinea: Old Changes and New Changes, Department of Human Geography, research School of Pacific Studies, Australian National University, Canberra, Australia.

Bourke, R.M. 1993. Bibliography of soil fertility and plant nutrition in Papua New Guinea. Papua New Guinea. DAL Technical Report 93/1.

Bourke, R.M. 1976. Food Crop farming system used on gazelle peninsula of New Britain, In K. Wilson and R.M. Bourke (eds.) Proceedings of the 1975 Papua New Guinea Food Crops Conference pp. 81-100. Department of Primary Industry: Port Moresby.

Bourke, R.M. 1979. Suggested farming system for lowland forest areas where land is Scarce, LAES Information Bulletin No. 22, Kerevat, East New Britain Province, PNG.

Bourke, R.M Allen, B.J., Hobsbawn, P. and Conway, J. 1998. Agriculture Systems of Papua New Guinea working Paper No. 1, Department of Human Geography, Australian National University, ACT 0200, Australia.

Department of National Planning and Monitoring 1999. Papua New Guinea National Population Policy 2000-2010. Port Moresby, Department of National Planning and Monitoring.

D’Souza, E. and Bourke, R.M. 1986. Intensification of subsistence agriculture on the Nembi Plateau, Papua New Guinea 2. General Information and Inorganic fertilizer trials. Papua New Guinea Journal of Agriculture, Forestry and Fisheries. Vol. 34. Pp. 29-39.

Golson, J. and Gardner, D.S. 1990. Agriculture and socio-political organization in New Guinea Highlands prehistory. Annual review of Anthropology, 19, 395-417.

Hanson, L.W, Allen, B.J, Bourke, R.M. and McCarthy, T.J. (2001). Papua New Guinea Rural Development Handbook, Australian National University, Land Management Group, Canberra, Australia.

Humphrey, W. (1994). Current Initiative in Sustainable Agriculture Research, Discussion Paper, Huon Seminar, PNG University of Technology, Lae. June 21-23.

Humphrey, W. (1990). Current Initiative In Sustainable Agriculture Research, Discussion Paper, Huon Seminar, PNG University of Technology, Lae. June 21-23.

Kanua, M.B. and Liripu, G. 1988. On-farm fertilizer trials in the highlands In: 1984-1988 Annual Research Report. Agriculture Research Division. DAL. PNG. Pp. 39.

Lea, D.D.A.M. 1972. Indigenous Horticulture in Melanesia. Some recent changes in eastern New Guinea Island, pp. 252-79. Clarendon Press: Oxford.

Parfitt, R.L. (1976). Shifting cultivation – how it affects the soil environment. Harvest 3, 63-66.

Spate, O.H.K. 1953. Changing native agriculture in New Guinea. The: Geographical Review 43(2): 151-72.

Waddell, E.W. (1972). The mound Builders: Agricultural Practices, Environment and Society in the Central Highlands of New Guinea. Monographs of the American Ethnological Society. University of Washington Press, Seattle.

Ward, R.G. 1982. Changes in subsistence cropping. In R.J. May and H. Nelson (ed.) Melanesia: beyond diversity, pp. 327-38. Australian National University.

Paper Number 15

Status of integrated plant nutrient management in Tonga*

* This country report has not been formally edited and the designations and terminology used are those of the author.

Vunivesi Minoneti
Ministry of Agriculture and Food, Fisheries and Forestry Department of Agriculture
& Food, Research and Extension Division, Nuku’alofa, Tonga


The limited arable land in Tonga poses a pressing problem on food production for its growing population, which eventually led to higher use of farm inputs such as fertilizers and pesticides to increase agricultural production. Central to sustainability of traditional farming systems in Tonga is the practice of fallow or ‘rest’ period which allow natural regeneration of soil fertility. However, the current demand for more food supply commercial planting of crops like squash has taken toll of the islands fragile soil resources. With the assistance from various international organizations, some mitigation measures and aspects of integrated farming systems employing safe use of agrichemicals are introduced along with the use of traditional plants like mucuna, a nitrogen-fixing traditional plant. There are now initial efforts to implement integrated nutrient management. On the whole, efforts of implementing strategies to conserve soil productivity in Tonga are evident. However, a large number of concerns such as scarcity of resources, large population, and even land tenure regulations, are yet to be properly addressed.

1. Introduction

The agriculture industry, which contributes more than 60 percent of the country’s total export, is the second main industry in the island of Tonga next to Tourism.

Tonga is categorized as having MIRAB economy (Migration, Aid, Remittances and Bureaucracy) consisting of a large public sector and dependency on aids and remittances.

Population growth demands an increase in food production as well as in other agricultural products. The ability to use new arable land is generally limited. Therefore, the use of fertilizers and pesticides is often the first means adopted to achieve an improvement in agricultural production.

Tongan agriculture is basically a shifting cultivation, although with various modified forms evolving and with different combinations of crops and fallow species. The production of food and cash crops of indigenous species is done mainly with shifting cultivation. On the other hand, the production of major crop for export is done with all the green revolution technologies of mechanical tillage, the use of fertilizer and pesticide on a monocrop base. The spin-off has resulted in increased use of mechanical tillage, fertilizers and pesticides for production of other vegetables and watermelon for the local market.

2. Current progress on nutrient balance and/or nutrient flow analysis at national/regional/on-farm levels

As a consequence of the current trend of increasing length of the cropping phase with very short fallow periods, soil nutrients decline. The decline is reduced by the combined use of organic and/or inorganic fertilizer compounds. There are various forms of both organic and inorganic fertilizers utilized by farmers. The most common organic fertilizer is chicken manure which is produced locally and it costs about USD2.50 per 40 kg bag. However, its nutrient content is not determined.

N, P, K, Urea and foliar fertilizer are the most common available forms of inorganic fertilizer. Their costs are USD2.00 per 40 kg bag N-P-K mixture, USD22.00 per 40 kg bag Urea, and USD9.00 per 1 kg or 1L foliar fertilizer. All these inorganic fertilizers are imported mainly from Australia and New Zealand. These and other imported fertilizers and agricultural inputs are exempted from government taxes.

The annual fertilizer consumption had increased enormously since 1987 and the consumed amount for 1998 was 1 500 mt (FAO, 1999). This was evident by the advent of the production of squash for export in 1987 which resulted in a three-fold increase in the cropped area in Tongatapu (the main island). Notably, plant nutrient consumption will keep increasing due to limited arable land and exacerbated by continuous cultivation and increased demand for agricultural products.

The current rates of fertilizers recommended for most crops and also the current recommended cultivation practices which conserve soil organic matter and prevent soil erosion on slope land were produced by the ministry of agriculture through field trials. The ministry also provides soil and plant nutrient analysis service to determine the nutrient content in the soil and plant. Based on the results, recommendations are drawn to balance nutrient decline, if necessary. This service costs about USD10.00 per sample. However, only a few squash companies avail of this service.

3.  Soil fertility/integrated nutrient management viz-à-viz crop production/ productivity, nutrient balance, farmer livelihood and environment

As a consequence of more intensified way of cultivation of the land, the intensive use of mechanical tillage generally has reduced the soil fertility at a much faster rate as compared to the traditional no tillage cropping system. The tillage preparation of land for the squash season occurs within the main rainfall season. Due to the high clay content of the Tongan soil, its structure is very fragile when wet and prone to damage when tilled. As soil structure is degraded, in combination with increased mixing of top soil with the inferior subsoil and exposure to air, there is an increased mineralization of soil organic matter. This is exacerbated by the current trend of longer cropping phase with very short fallow periods, to almost continuous cropping. Consequently, soil organic matter has declined resulting to concomitant reductions of soil’s biological, physical and chemical fertility in the agricultural lands of Tonga.

The intensive use of chemical fertilizers and pesticides has led to the Ministry of Agriculture’s call for sustainable prosperity from agriculture. This is consistent with the call from the United Nations summit on Sustainable Development in Johannesburg in September 2002 for the protection of the marine environment from land-based activities to reduce, prevent and control waste and pollution and their health-related impacts in small island developing states. It also aimed to use and produce chemicals in ways that do not lead to significant adverse effects on human health and the environment.

This has led to the initiation of some projects concerning sustainable agriculture.

A. “CROP-PRO” project

This is a project sponsored by the European Union which aims to provide assistance to the Pacific Islandcountries through the development of integrated farming approaches for sustainable crop production in environmentally-constrained systems. The objectives for the “Crop-pro” component in Tonga are:

use of surface mulch

application methods for pesticides and fertilizer

timing of applications of pesticides and fertilizer according to need

comparison of economic benefits and environment risks associated with squash production, relative to other crops

Matching sites for sustainable squash production with soil characteristics and groundwater dynamics and especially identifying ‘at risk’ regions in Tongatapu

B. “DSAP” project

This is funded by the Secretariat of South Pacific Commission and aims to develop sustainable agricultural practices in the Pacific region. So far, “mucuna” bean has been incorporated in the cultivation practices between crops. Short duration fallows with “mucuna” beans were shown to increase crop yields. The positive effect of “mucuna” is certainly related to its ability to fix atmospheric N. In addition, Bucket irrigation system has also been incorporated in the cultivation practices.

C. “PASA” project

This project is also sponsored by the Secretariat of the South Pacific Commission and aims at promoting pesticide awareness in sustainable agriculture.

4. Technical/policy measures being taken on INM and how these are implemented

It is the responsibility of the Research and Extension Division of the Ministry of Agriculture to carry out technical researches on Integrated Nutrient Management (INM) and disseminate to farmers. These technical researches were executed through funded projects. Based on the results, recommendations were formulated and provided to farmers as mentioned above.

5. Implementation constraints

Since land in Tonga is a scarce/finite resource, and there are more people than land available, there is stiff competition for the resource. Those who obtain control of this resource are entitled by `Tongan land tenure regulations to do whatever they want to do with the resource. As a consequence, the land is cropped continuously to get as much as possible before the agreed period ended. This is a major problem concerning land management which is addressed adequately by the principles and frameworks of Integrated Nutrient Management (INM).

Some farmers have their own experience and it is very hard convincing them to adopt new practices. Some INM practices are very labour intensive and this prevents their adoption.

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