Geografisk Tidsskrift, Bind 87 (1987)
Conditions for agricultural development in Central Kalimantan, Indonesia
Conditions for agricultural development in Central
The Indonesian province of Central Kalimantan is planned to receive a substantial number of settlers from Java. The settlers will be occupied in agriculture. In some areas the suitability of the land for agriculture is limited due to steep slopes, shallow soils, sandy soil texture or poor soil drainage. In the central parts of the province these limitations are less serious, but the soils are acid and low in most plant nutrients.
associate professor, Kemisk Institut, Den Kgl. Vet.
Indonesia, Kalimantan, Transmigration, Ultisols, Soil
The population of Indonesia is extremely unevenly distributed among different regions (Table 1). In the heavily populated regions, i.e. Java and the islands nearby, there is a serious overpopulation. This leads to a number of problems such a high rate of unemployment and pressure on agricultural land. The high demand for agricultural land has forced people to cultivate land which is marginally suitable for agriculture, e.g. steep upland areas. Cultivation of such areas usually results in poor yields and often causes severe soil erosion. This is described f.ex. by Repetto (1986) for regions in West Java.
On the other hand, the thinly populated regions, in particular Irian Jaya (the Western part of New Guinea) and Kalimantan (Borneo), are characterized by a low stage of development with a weak infrastructure and few service facilities.
In ordrer to relieve the problems due to population pressure in the central region around Java and to promote development in the thinly populated islands and provinces,the Indonesian Government encourages and sponsors the moving of people from densely to thinly populated regions through the so-called transmigration program. From 1969 through 1983 a total of about 2.3 million people have moved from Java and nearby islands to Sumatera,Kalimantan,
matera,Kalimantan,Sulawesi, Irian Jaya and some smallerislands (Table 2). To the figures in Table 2 a total of about 400,000 people, moved from 1950 to 1969, should be added. Hence the total number of transmigrants until the end of 1983 is about 2.7 million. The number of transmigrantsis increasing rapidly, in 1983 it was almost 0.6 million, i.e. more than 20% of the total number of transmigrantsin the period 1950-1983.
In the settlement areas the transmigrants are usually occupied in agriculture. However, various development models are used. Some transmigration settlements are established in connection with an existing or newly established production unit, e.g. a rubber factory. In these settlements the transmigrants earn their living mainly from production of the commodity processed by the factory. In areas where suitable production or marketing facilities are not available the transmigration settlements are based primarily on food crop production. The main objective of these settlements is to enable the transmigrants to achieve self sufficiency in food production and to obtain a sufficient cash income by producing and marketing a surplus of food or other crop products, often from tree crops. Typically the settlements consist of villages with about 500 families. The villages are normally developed in recently cleared forest areas. Prior to the arrival of the transmigrants, houses and service facilities such as schools, medical centers etc. are established. Each transmigrant family is allocated an area for arable agriculture. In addition an uncleared area intended for future development, usually with tree crops, is allocated to each family.
The selection of the areas to be used for transmigration is based on the availability and suitability of land. Available land is that which is not required by the indigeneous population or reserved for other purposes such as forestry. Suitability is determined by natural factors such as climate, slope and soil properties. The suitability of the land in combination with the agricultural techniques adopted must facilitate a sufficiently large and stable production in a system of permanent agriculture.
One of the main obstacles to agricultural production in many transmigration areas is low soil fertility. In fact, the main reason for the huge difference in population density between Java and the nearby islands on the one hand, and the other islands (the so-called outer islands) on the other hand, is a higher soil fertility in the Java region. The soils in Java are mainly developed on young volcanic rocks with a high content of easily weatherable minerals, which will provide a constant supply of plant nutrients. In the outer islands most soils are developed on older rocks which at present are highly weathered. Hence, the supply of plant nutrients will be low in these soils.
In the following these and other constraints to permanent agriculture in the province of Central Kalimantan will be discussed. This province has up to 1983 received some 100,000 transmigrants and it is also planned to receive a substantial number of future transmigrants.
Geographical Situation and Population
The location of Central Kalimantan is shown on the map in Fig. 2. Its area and population are shown i Table 3. The province covers about 28% of the land area of Kalimantan. Its population density is almost similar to that of East Kalimantan while South and West Kalimantan have densities of 60 and 18 inhabitants per km2 respectively. In Indonesia only Irian Jaya has a population density lower than those of East and Central Kalimantan. It is probably justified to characterize the province as being among the least developed areas in Indonesia. The infrastructure is very weak. The total length of public roads is about 4000 km, only 10% of which are hard surface roads. The road system is interconnected only to a small extent, and the main means of communication and transportation are the rivers.
The majority of the population lives in remote villages, usually situated along the rivers. The main occupation is agriculture based on shifting cultivation. The crops grown are rice, cassava, vegetables, various fruits etc., which are to a large extent consumed by the people themselves. Small amounts of food products as well as various forest products are marketed and provide for a modest cash income.
The province extends from slightly North of Equator to about 3° 30' South. Climatic data for Pangkalanbun which is situated in the Soutwestern part of the province are given in Table 4. The temperature fluctuations over the year are small, the difference between the means of the hottest and coldest months being less than 2 °C. The diurnal variation is 10-15 °C.
Fig. 3. shows average, maximum and minimum precipitation as well as potential evapotranspiration for each month. These values are, of course, not representative for the entire province. With increasing distance from the coast there is some increase in the precipitation.
It is evident from Fig. 3. that the precipitation is subject to considerable fluctuations. For all months the differences between the highest and the lowest precipitation ever recorded are very large. This unreliability of the precipitation is very important when considering rainfed agriculture. Although the mean precipitation in all months is higher than the potential evapotranspiration there is a serious risk of drought, particularly from July through October. The precipitation mostly occurs with a high intensity, usually during thunder storms. The high precipitation intensity causes a great risk of erosion on bare, sloping land.
Geology and Geomorphology
A geological sketch map is shown in Fig. 4. The Northern part of the province consists to a lajge extent of hills and mountains. The dominating rocks are pretertiary igneous, metamorphic and sedimentary rocks. Towards South the land changes into a rolling to undulating plain consisting mainly of tertiary sand- and siltstone. In some areas volcanic rocks, also of tertiary age, occur.
The Southern part of the province is a level plain at a low altitude consisting of alluvial deposits of late tertiary and quaternary age. Along the coast the plain is mainly a peat swamp. The eastern part of the province has been subject to a considerable subsidence and have thick tertiary and quaternary sediments. In this area the peat swamp extends several hundred km inland. North and West of the swamp the plain consists of rather coarse sandy terrace deposits of late tertiary and quaternary age.
The mountains and the hilly, rolling and undulating areas in the Northern and central parts of the province are covered with tropical rain forest. The vegetation in the Southern peat areas is swamp forest. On some of the coarse sandy terrace deposits a poor forest known locally as keranggas is found. This forest is characterized by a rather open stand of small trees and a fairly high frequency of conifers.
The swamp areas in the Southern and Southeastern parts of the province are dominated by poorly drained peat soils and slightly developed mineral soils. According to Soil Taxonomy (SMSS, 1985) the peat soils are classified as Histosols and most of the mineral soils will be Entisols (Fluvents). In coastal areas the peat and mineral materials are to a large extent deposited in brackish water and contain pyrites. If these soils are drained, the pyrites will oxidize to sulfuric acid and cause the soils to become strongly acid.
North and West of the swamp areas highly weathered and strongly leached soils dominate. The high degree of weathering and leaching is due to the fact that the soils have been exposed to a hot, humic climate during an extensive period of time. The soils are low in weatherable minerals and they have a low content of most plant nutrients. Furthermore, they are rather acid. The surface
1. Alluvial deposits, quaternary. /. Alluviale aflejringer, kvartære. 2. Sedimentary rocks, tertiary. 2. Sedimentære bjergarter, tertiære. 3. Sedimentary rocks, pretertiary. 3. Sedimentære bjerganer, prætertiære. 4. Igneous rocks. 4. Dybbjergarter. 5. Volcanic rocks, tertiary. 5. Vulkanske bjergarter, tertiære. 6. Phyllitic metamorphic rocks. 6. Phyllitiske metamorphe bjergarter. 1. Metamorphic rocks, undifferentiated. 7. Metamorphe bjerganer, udifferentierede.
layers of these
soils usually have a lower clay content than
The properties of the soils vary according to geology and topography. Shallow soils are found on steep slopes in the Northern mountain and hilly areas. The soils are shallow because soil material is being continuously eroded. On level and undulating plains the soils are usually deep.
Coarse textured soils are found on the sandy terrace deposits and to some extent in areas where the parent material is sandstone. On the coarsest materials the dominant soils are Spodosols according to the Soil Taxonomy classification (SMSS, 1985). In some soils the spodic horizon is found below a depth of 2 m and such soils are formally classified as Entisols.
The dominant soils of the undulating and rolling plains are deep clayey soils. Since they have been subject to clay translocation as mentioned above, they are classified as Ultisols according to Soil Taxonomy (SMSS, 1985).
A specimen Ultisol profile is described in Table 5 and analytical data are presented in Table 6. The soil has rather high contents of silt and clay, and the clay content increases with depth. The contents of organic carbon and nitrogen in the surface horizons are fairly high. From the profile description it appears that the surface horizons are friable and have granular to subangular blocky structure indicating fairly good physical properties.
properties are not very satisfactory, however.
The surface horizon has a reasonably high content of some plant nutrients such as potassium and phosphorus. However, since this horizon is very thin, and since the deeper horizons have only low contents of these elements, the total amounts in the soil profile are low. The amounts of exchangeable calcium and magnesium are also substantially higher in the surface horizon than in the underlying horizons. However, even the contents found in the surface horizons must be considered to be very low.
Despite the low content of plant nutrients in the soil it supports a vigorous growth of tropical rainforest. This is possible because considerable amounts of plant nutrients are present in the vegetation. These nutrients are recycled at a high rate. Plant residues falling on the soil surface are rapidly decomposed in the hot humid environment, and the nutrients liberated by the decomposition are rapidly absorbed by plant roots. This implies that the majority of the plant nutrients are taken up from a shallow soil layer near the soil surface. This is in accordance with the higher contents of plant nutrients in this layer (Table 6) and with the fact that the root density is very high in the surface layer.
of the rapid recycling of plant nutrients
in the ecosystem is present in the vegetation, and only a small fraction is found in the soil. The rapid uptake of plant nutrients from the soil counteracts losses of plant nutrients by leaching. Hence, the nutrient cycle in the rainforest ecosystem is an almost closed cycle with minimumlosses.
Potential for Agricultural Development
The physical environment described in the preceding sections imposes a number of constraints as to agricultural use of the land. In the Northern part of the province steep slopes and shallow soils make the majority of the land unsuited for arable agriculture without expensive soil conservation measures. Some areas could be used for cultivation of tree crops. However, this requires factories for treatment of the products and marketing facilities. At present neither are available, and an almost complete lack of roads and other means of communication makes transport of large amounts of commodities virtually impossible.
In the Southern part of the province the soils are poorly drained and will require expensive artificial drainage systems if they are to be used for dryland agriculture. Certain crops such as lowland rice may be grown on poorly drained soils. Peat soils are, however, poorly suited for cultivation of rice, partly because they become very soft when flooded. Since peat soils cover large areas in the Southern and Southeastern parts of the province, the potential for rice production is limited. It is further reduced by a low soil fertility and by the presence of pyrites in some soils.
The level plains on the terraces North of the swamp areas have coarse textured soils with a low water holding capacity. These soils are not well suited for rainfed agriculture due to a high risk of crop failure during dry spells. Due to the rainfall being being rather unreliable, several consecutive days may be without rain, even in the wet season. Since the evapotranspiration is high because of a high temperature, the soil must contain a rather high amount of plant available water to avoid water stress to the crops.
The undulating to rolling plains, located between the hilly land in the North and the swamps and sandy terraces in the South and Southeast, definitely offer the highest potential for dryland rainfed agriculture. Some areas, admittedly, have slopes so steep that risk of erosion makes the land unsuitable for arable agriculture. However, considerable areas with sufficiently low slopes do occur. In these areas the dominant soils are the deep clayey Ultisols discussed above. These soils are considered to have a water holding capacity which is high enough to reduce the drought risk to an acceptable level.
However, the acidity and the low level of available plant nutrients precludes permanent cultivation without suitable appliciations of lime and fertilizers. At present, the soils are used by the local population for shifting cultivation. In this system the nutrients present in the vegetation are made available by burning the vegetation after clearing the land. The ashes produced by the burning is alkaline and reduces the soil acidity. However, the amounts of plant nutrients and alkalinity produced are sufficient for production of only 1-2 arable crops. In order to accumulate plant nutrients for another 1 or 2 crops, the land must be left for 15-20 years.
The amounts of lime and fertilizers required to keep the acidity sufficiently low and the nutrient status sufficiently high to facilitate permanent cultivation of arable crops depend on soil properties and on the plant species and cultivars to be grown.
Plants seem to be little affected directly by soil acidity, but rather by a number of factors which depend on the acidity. At high levels of acidity some plant nutrients are present in the soil in too low amounts, e.g. calcium and magnesium, while others may become fixed in forms unavailable to plants, e.g. phosphorus. On the other hand, certain elements may be present in excessesive amounts which are toxic to plants, e.g. aluminium and manganese. Aluminium, which is a common constituent of most soil minerals, becomes soluble in acid soils and a high content of soluble and exchangeable aluminium is considered to be a principal reason for poor plant growth on acid soils. Hence, a reduction of the amount of exchangeable aluminium is considered to be the main beneficial effect of liming.
The amount of aluminium that must be removed by liming depends on the total content of exchangeable aluminiumin the soil and the amount that can be tolerated by the crops to be cultivated. The tolerance towards exchangeablealuminium differs among different crops and among different varieties of the individual plant species. Tolerant varieties of some crops will grow at an aluminiumsaturation percentage of about 40% of the cation exchange capacity (CEC) at soil pH. Hence, the aluminiumsaturation percentage must at least be reduced to this level to facilitate crop production. In the soil shown in Tables 5 and 6 the weighted average content of exchangeablealuminium in the top 20 cm is 5.0 meq/100 g and the weighted average CEC at soil pH in this soil layer is 5.8 meq/1000 g. To reduce the content of exchangeable aluminium to 40% of the CEC at soil pH, about 2.7 meq/ 100 g aluminium must be removed. According to Sanchez (1986) 1.65 t CaCO3 is required per ha for every meq/100 g aluminium that must be removed. Hence, about 4.5 t CaCO3 is required pr ha to reduce the content of exchangeablealuminium to a level that can be tolerated by the least sensitive crop plants. It should be mentioned that this is a rough calculation which disregards changes in CEC which will occur following the pH increase caused by the liming. The fact that the soil in question has a considerablecontent
siderablecontentof organic matter, which will increase the amount of lime required, has also been disregarded. Effects of removing the present rainforest vegetation has also been neglected.
An amount of 4.5 t CaCO3 per ha is not very large compared with normal liming rates, e.g. for intensively cultivated soils in Northern Europe. The reason for the moderate lime requirement is that the clay minerals in the soil in question are mainly kaolinite and iron and aluminium oxyhydroxides which have low cation exchange capacities compared with the clay minerals which are found in soils in temperate regions.
The amount of lime calculated above is necessary in order to initiate cultivation. However, during cultivation the soils will be subject to leaching and acidification which will require liming at frequent intervals. In an experiment carried out under similar climatic conditions and on a similar, but slightly coarser textured, soil in Peru, Sanchez at al. (1982) applied 3 t CaCO3 every three years.
Although these amounts are not large, again compared with common liming rates in intensive agriculture in temperate regions, it is difficult and very costly to transport them to remote areas in Central Kalimantan, due to the absence of a road system. Lime is available at some locations in Kalimantan, and it may be possible to transport the lime to some areas by river transport, but it may prove cheaper to ship the lime from other islands in Indonesia. In either case the transport will involve large costs.
In addition to lime the areas will require regular input of fertilizers. The most important ones are nitrogen and phosphorus fertilizers but in the long run a number of other elements such as potassium, magnesium (if the lime used does not contain magnesium) and some micronutrients are required. Some nitrogen liberation can be expected during the initial cultivation due to decomposition of organic matter. However, this effect will be of short duration. Cultivation of legumes may provide some nitrogen input but hardly sufficient to avoid application of nitrogen fertilizers. Phosphorus fertilizers will be required in rather large amounts, not only to satisfy the requirements of the crops but also because the soils are likely to fix phosphorus in forms which are unavailable to plants. The amounts of fertilizers required depend on the crops and cropping pattern, and on the number of crops to be cultivated per year. In the season with the lowest precipitation the risk of drought is rather high. A cropping pattern with two crops, each of about 4 months, seems to be suitable.
In the settlements established for transmigrants no livestock except poultry and other small animals is provided for. Hence, animal manure will not be available in significant amounts, and the plant nutrients must, therefor, be provided mainly from commercial fertilizers.
From the discussion above it may be concluded that viable settlements based on rainfed dryland agriculture may be established in those parts of Central Kalimantan, where the land is sufficiently level and the soils are deep, well drained and have a sufficiently high water holding capacity. However, due to the inherent acidity and low content of plant nutrients in all soils, large and expensive inputs of lime and fertilizers are required.
The development costs probably exceed the benefits for a rather prolonged period. However, the benefits of the land development cannot be assessed only from the amount of crops produced. Since transmigration involves establishment of service facilities, including medical facilities, a road network etc., it will have a significant impact on the entire region and its indigeneous population.
The population density of Indonesia ranges from 750 persons per km2 in Java and nearby islands to 3 persons per km2 in Irian Jaya. Some consequences of this are a serious overpopulation in the Java region and a low stage of development in the thinly populated regions. To relieve these problems the Indonesian Government supports moving of people from the Java region to the provinces having a low population density.
The province of Central Kalimantan, which at present has a population density of about 7 persons per km2, is planned to receive a substantial number of settlers from Java. These settlers will be occupied in agriculture. The climate is, in most seasons, suitable for agriculture, but the suitability of the land varies. In certain parts of the province the land suitability is limited by steep slopes, shallow soils, a sandy soil texture or poor soil drainage. In some areas, mainly in the central parts of the province, such constraints are not serious. However, the soils are acid and low in most plant nutrients. In order to utilize this land for agricultural production, and hence provide a basis for settlers, application to the soil of rather large amounts of lime and fertilizer are required.
Indonesiens befolkning er ekstremt ujævnt fordelt mellem landets forskellige regioner. På Java og nærliggende øer bor over 100 millioner mennesker, og den gennemsnitlige befolkningstæthed er 750 personer pr. km2. I Irian Jaya (den vestlige del af New Guinea) bor kun omrking 3 personer pr. km2 og i Kalimantan (Borneo) ca. 14. Den gennemsnitlige årlige befolkningstilvækst er over 2%, hvilket medfører, at befolkningen vokser med over 3 millioner om året, heraf omkring 2 millioner på Java og nærliggende øer. Nogle af følgerne af den skæve fordeling er alvorlige overbefolkningsproblemer i de tæt befolkede egne og en lav grad af udvikling i de tyndt befolkede områder.
For at reducere befolkningspresset på Java og især for at fremme udviklingen i de tyndt befolkede provinser har landets regering igennem en årrække støttet flytning af personer fra tæt befolkede til tyndt befolkede områder. I perioden 1950-1983 er der ialt flyttet ca. 2,7 millioner mennesker fra Java til andre øer. Af disse er de fleste blevet bosat på Sumatra. Flytningen forventes at fortsætte og stige i de kommende år.
De mennesker, som bosættes i de tyndt befolkede områder, beskæftiges næsten udelukkende ved landbrug. Bosættelse finder i almindelighed sted i områder, som på nuværende tidspunkt ikke benyttes til landbrug, og hvor den naturlige vegetation ofte er tropisk regnskov. Før bosættelsen udføres undersøgelser, som danner grundlag for valg af egnede områder, og der opføres boliger, skoler, sundhedscentre og andre faciliteter.
Om et område kan
anvendes til bosættelse afhænger af, om der
I artiklen er mulighederne for at etablere landbrug i provinsen Central Kalimantan behandlet. Denne provins ligger i den sydlige del af Borneo og strækker sig fra lidt nord for ækvator til omkring 3° 30' sydlig bredde. Provinsens areal er godt 150.000 km2, og dens befolkning godt l million. En stor del af befolkningen ernærer sig ved svedjebrug, hvor jorden dyrkes i 1-2 år, hvorefter den henligger 15-20 år, før den igen kan give et rimeligt udbytte. Provinsen hører til de mindst udviklede områder i Indonesien og har indtil 1983 modtaget godt 100.000 tilflyttere fra Java-regionen.
Klimaet er varmt og fugtigt med en gennemsnitlig temperatur på 25-26 °C. Temperaturforskellene mellem årets forskellige måneder er meget små. Nedbøren er 2-3 m fordelt over hele året, men der er en relativ tør periode i månederne juli-oktober.
Provinsens nordlige del er et bjergland med forskellige prætertiære bjergarter. Syd for bjergområdet findes et kuperet landskab, som overvejende er udviklet på sedimentære bjergarter, dog med intrusioner af vulkanske bjergarter fra tertiærperioden.
Provinsens sydlige del er en lavt beliggende flad slette, hvor de øverste jordlag næsten udelukkende består af tertiære og kvartære sedimenter. Langs kysten findes tørveaflejringer over store områder, og i den østlige del af provinsen, hvor der er sket en meget betydelig landsænkning, strækker tørveaflej ringerne sig flere hundrede km ind i landet. Nord og vest for de sumpede tørveområder findes flade, meget sandede terrasser, som er aflejret i kvartærperioden eller sent i tertiærperioden.
vegetation er tropisk regnskov. I de sumpede
Jordbunden varierer i relation til bl.a. geologiske og topografiske forhold. I provinsens sydlige del dominerer dårligt drænede organiske jorde samt svagt udviklede mineraljorde på unge flodsedimenter. De organiske jorde klassificeres efter Soil Taxonomy (SMSS, 1985) som Histosols, mineraljordene som Entisols. På de sandede terrasser nord for sumpområderne kan træffes kraftigt udviklede podzoljorde (Spodosols). I det kuperede terræn længere mod nord findes især stærkt forvitrede og kraftigt udvaskede jorde med et ret højt lerindhold. Disse jorde har været udsat for lernedslemning og klassificeres derfor som Ultisols. Lernedslemningen har medført, at det øverste jordlag har et lavere lerindhold end de underliggende jordlag. Lignende jorde kan findes i bjergområderne i provinsens nordligste del, men her findes jordene ofte på stejle skråninger, og i mange tilfælde findes der fast klippegrund nær jordoverfladen.
I de nordlige områder begrænses mulighederne for etablering af landbrug således af stejle skråninger og ringe jordprofildybde. Dyrkning af egentlige landbrugsafgrøder i disse områder vil bl.a. kræve dyre foranstaltninger til modvirkning af jorderosion.
I provinsens sydlige del er jordene vandlidende. De vil kunne anvendes til risdyrkning, men tørvejordene er ikke specielt egnede nedehertil, bl.a. fordi de er meget bløde i oversvømmet tilstand. En del af jordene i dette område indeholder pyrit, som ved oxidation kan gøre jorden sur. De sandede jorde på terrasserne nord for det sumpede område er heller ikke velegnene til landbrugsproduktion, hvis kunstig vanding ikke kan praktiseres. De har nemlig en lav kapacitet for plantetilgængeligt vand, og der vil derfor være stor risiko for, at afgrøder tørkeskades på disse jorde.
De bedste muligheder for udvikling af landbrugsproduktion findes i de mere eller mindre kuperede områder i provinsens centrale del. Ganske vist forekommer en del stejle skråninger, men der findes betydelige områder, hvor hældningen er lav nok til, at dyrkning ikke medfører større risiko for erosion. Jordene her er generelt dybe og har et lerindhold, som er højt nok til at give en rimelig sikkerhed mod tørkeskader.
Imidlertid er jordene meget sure og fattige på plantenæringsstoffer. Etablering af et landbrugssystem baseret på permanent dyrkning forudsætter derfor, at jordens surhed reduceres ved tilførsel afkalk, og at der tilføres de plantenæringsstoffer, som planterne behøver. Uden disse foranstaltninger kan et rimeligt udbytte ikke opretholdes.
Før dyrkningen kan påbegyndes, vil der være behov for en kalktilførsel på nogle få tons pr. ha. Senere i dyrkningsforløbet vil der også være behov for jævnlig tilførsel af jordbrugskalk. Selv om de nødvendige kalkmængder ikke er overvældende store, vil det alligevel være meget vanskeligt og kostbart at få dem transporteret til de pågældende områder. Dette skyldes, at der ikke findes kalk i nærheden, og at transportsystemet er meget svagt udviklet.
tilfredsstillende forsyning af afgrøderne med
De tilflyttere, som kommer til området, vil ikke få rådighed over større husdyr, hvorfor husdyrgødning i større mængder ikke produceres. Det vil derfor være nødvendigt at tilføre de nødvendige plantenæringsstoffer i form af handelsgødning.
Det er klart, at etablering af permanent landbrug i de nævnte områder er forbundet med store vanskeligheder og omkostninger, og der vil gå en lang periode før omkostningerne er dækket ind. Imidlertid medfører tilflytningen en udvikling, herunder etablering af servicefaciliteter og forbedring af infrastrukturen, som er til gavn for hele regionen og den lokale befolkning.
(1983): Transmigration: Achievements, Problems,
(1974): Soil Map of the World 1:5,000,000 Vol. I.
(1986): Soil Loss and Population Pressure on Java.
Keys to Soil Taxonomy. Soil Management Support
(1976). Properties and Management of Soils in the
P.A., Bandy, D.E., Villachia, J.H. & Nicholaides,
Indonesia (1984). Biro Pusat Statistik Jakarta