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SWAMP DEVELOPMENT IN INDONESIA
Reclaimed Swamp land in Indonesia is situated in the coastal areas and its environment is mainly influenced by the tidal movements of the sea, estuaries and tidal rivers. Watershed management has in practice little influence on the major tidal rivers and estuaries in Sumatra, Kalimantan and Papua (Irian Jaya).
Indonesia can fulfill their need for increased rice production for the next 20 years in the existing reclaimed swamp areas.
Water Management in the main system, focussing on leaching of the soil during the first rains after the dry season and flushing the canals by one-way flow is a key requirement for successful development, as is proven in Indonesia and Vietnam. Computer modeling (SMASS) confirms that leaching before and during land preparation is sufficient to keep the soil at the required pH for rice growth after a dry season with pyrite exposure in the acid sulphate soils.
Further On-Farm Water Management, Mechanization for soil tillage and post-harvest management are the key words for this development.
See Webpage Agriculture
The second crop for rice is in most places only possible when after harvest of the first crop within a month the second crop can be planted, including land preparation. This requires short growing HYV (80-90 days), mechanized harvesting, drying facilities of husked rice (gabah), mechanized land preparation (usually cultivator/rotator)
There is no need to reclaim new areas presently as the potential to increase rice yields in already developed areas is still very large, such that it can produce enough extra rice for self-sufficiency in Indonesia in the near future. This choice should have a priority over alternatives such as making new dams and reservoirs to increase the cropping intensity of the gravity irrigated rice fields outside Java. Still planning of reclamation of new areas might be considered in the near future. Analaysis of Environmental Impacts should be considered. Also a time planning of 10 years should be expected before these new areas are fully productive. At the moment Indonesia has still about 4 million ha not yet reclaimed suitable Tidal Lowlands available for rice crop production. (However the major part of Tidal Lowlands, about 15 million ha, are deep peat soils that are not suitable for rice production).
The main advantage of the swamp schemes is the size of the fields, which is 1 Ha and farmers own in most cases 2 Ha in the swamps. There is a tendency that they own even larger fields in the swamps up to 5 Ha. In most irrigated areas on Java the farmers own not more than 0.5 Ha and often their fields are even smaller. In many gravity irrigated rice fields outside Java the conditions are not much better.
In that case mechanization favors very much the swamps for rice cultivation with the present world-wide low farm-gate rice prices. Of course rice fields of the coastal plains of Java can well be mechanized also. The problem is only that the advantage of mechanization for the farmer is only marginally, because he owns such a small farm-holding.
It is the optimization of the income of the farmer in his environment and conditions that will determine the trends. For rice cultivation that most probably means that only the larger farm-holdings will survive in the coming 20 years. Presently the World Bank apparently ignores still the need in Indonesia to produce rice at competitive world market prices. It presents only more of the same, when promoting gravity irrigation outside Java by making dams and reservoirs for all irrigation schemes.
Local Governments at Provincial level and District level are much more aware of the higher potentials at lower costs by the development of Tidal Lowland Schemes.
A new threat to the environment is the development of pulpwood and oil palm plantations on Peat Swamp Soils in former Forestry Concession areas. Many of these plantations can not be sustained in the future by lack of drainability caused by subsidence. For oil palm cultivation the peat areas will be mostly not drainable with 15-20 years, while pulp wood plantations could be maintained for more than 40 years at least. For that reason also a new Forestry System is proposed which can maintain the peat soil for the Future. This Forestry system might be an attractive alternative for the Peat Swamp Soils with no sustainable drainability potential. See Webpages Impact, Forest Fires , Landsat and Problems. The existing already reclaimed peat lands should be mainly used for pulp wood production with high water tables (40 cm). This requires not drained central peat domes to provide sufficient water supply to the plantations on the borders of the peat domes during the dry season. In this way the CO2 emissions from the peat domes can be minimized.
Potentials. About 16 million ha of tidal swampland outside Java island are unsuitable for any sustained agricultural use.(*) It is thought that 8.8 million ha can be used for agriculture. Presently 3.6 million ha are wholly or partly used for agriculture. These already occupied areas should have the first priority for development. Concentrating development on the already occupied lands might contribute to the highly needed effort to conserve most of the swamps in Indonesia. Also environmental management for Swamps Schemes is a subject which requires more attention. It appears that fisheries and waterbird life are as important inside as outside the Swamp Schemes. Swamp Development and Conservation Planning should be an integrated effort. See WebPage Impact and Problems. (*) Some peat soils, mainly found in Riau province along the Indragiri and Guntung river are sustainable for tree crops as the bottom of the peat layers lies above mean sea level and the tidal range is more than 3-m.
Thesis. Water Management is the key to sustained development. Water quality is the most important feature in the water management of the Tidal Swamp Schemes. It refers to canal water quality and to groundwater quality in the fields. Canal water quality has mainly an influence on local fish potential and domestic water uses within the Scheme. It is groundwater quality, especially quality of the root zone of rice that determines largely the agricultural potentials. The most important agronomic problem is related to stagnant water conditions in the groundwater. Under stagnant water conditions the groundwater becomes toxic to the rice plant. This toxicity may reach levels no rice growth is possible. The toxicity of the groundwater shows mainly in some characteristic rice diseases.
The most common Physiological and Foliage diseases of the rice plant, found in the Swamp Schemes of Indonesia, are:
Fe-toxicity, Brown spot (Helminthosporium) and Blast. In some cases also zinc deficiencies are suspected in stagnant water conditions
Optimum yields of 6 ton/ha and more are found using improved rice varieties with high inputs in conditions with frequent tidal flooding. In the Telang-Saleh project (South Sumatra) these yields are also obtained in non-tidal flooded areas. In this project, water control structures are installed and existing canals are upgraded, more drains at tertiary level are constructed, farmers have been encouraged to construct and maintain an on-farm water management system . Presently two crops per season are possible.
It has been proven that repeated cycles of mechanised land preparation, including puddling combined with pump irrigation, will have the best results to control the toxicities. Puddling also will contribute to better water control in the highly permeable soils.
In previous non-producing and abandoned areas in Jambi province, Sumatra, now rice yields of up to 2.5- 3 ton/ha are obtained with local varieties receiving low inputs after implementing a new water management system based on continuous leaching of the rootzone.
Conditions for good results. Most important will be the farmer's group organization and institutional strengthening, based on the technical knowledge how to manage the system and how to introduce these technologies.
Problem Analysis for areas Suitable for Rice resulted in a formulation of the core problem:
CORE PROBLEM: Low Yields
However Farmers are presently little interested in O & M.
The reason is that farmers do not see the relation between O & M and having high yields in the field.
That has several reasons: ( this is only valid for potential suitable areas)
*) Note: toxic components include Ferrous iron; organic compounds in strongly reduced conditions, H2S at relatively high pH.
Mitigating measures: The main incentive to obtain the farmers interest in O & M is to improve the yields in the field. That requires an integrated approach with an upgraded infra-structure, combined with the on-farm improvements for water management. The proposed micro-system of ditches or the subsurface drainage system might greatly improve the on-farm conditions. Implementation needs Model Areas in farmer's fields to show farmers how to manage the improved system. Much more emphasis should be put on mechanised land preparation, combined with pump irrigation during the puddling of the rootzone. This requires the cooperation of the Ministries of Public Works and Agriculture at field level.
Swamp Scheme Environment and its Potentials:
Effective Drainage Depth and the Percolation Quantity are two key factors, related to each other, and determining the potentials in the suitable areas for agricultural development. (with little peat but mainly acid sulphate soil). For rice cultivation, the Effective Drainage Depth is important to guarantee sufficient potential to leach out the toxic elements from the subsoil and the adjoining canals; the Percolation Quantity is depending on the water supply (rainfall & irrigation) to the rice field and the lay-out and operation of the system. These two factors determine how much leaching can be applied.
Potentials for tree crops are mainly related to the Effective Drainage Depth, which depends on land levels and the tidal range in adjoining canals.
For many degraded areas the main factor determining suitability is the fertility level of the organic surface layers, or the Effective Drainage Depth of these soils, after subsidence. Degraded, abandoned areas with sufficient high fertility level of the organic surface layers and a sustainable Effective Drainage Depth could be reclaimed back into agricultural land. Degraded lands with extreme low fertility and/or a non-sustainable Effective Drainage Depth should return to forestry plantations as soon as possible.
There are recognized five major Swamp Scheme Environments:
CORE PROBLEM: Acidity can not be washed out by lack of effective drainability. Flooding hazard.
Mitigating measures: Acid sulphate soils require pumped irrigation to grow rice to have sufficient percolation and to minimize the effect of the low effective drainability. In presence of acid sulphate soils: double connected canals with overflows on the transition of supply and drainage canals. There are few other options than pump irrigated rice, except for relatively high areas where other foodcrops might be possible. Along the rivers flood protection and control structures are necessary. Most drainage and leaching will be only possible outside the flooding season. There is No tree crop potential. Melaleuca plantations might be an option.
CORE PROBLEM: Too little percolation; by absence of an on-farm water management system there is insufficient leaching and lack of water control in canal system.
Mitigating measures: Control structures in canals, improved water supply system for tidal freshwater. Improved on-farm water management system (open field ditches or an subsurface drainage). Potentials are for rice and other foodcrops. Pumped irrigation is recommended during land preparation (using two-wheel tractors) and during early growth of the planted rice.
There are two type of environments recognized with an influence on potentials. 1) Tree crops are the best option in areas with a tidal range of more than 3 m. 2) Rice crops are the best option in areas with a tidal range of less than 3 m.
CORE PROBLEM: Relative small areas have a potential for tidal irrigation. Low oxygen content in subsoil by lack of percolation. Tidal flooding hazards.
Mitigating measures: Improved water supply system to extend the area with a potential for tidal irrigation. Flood protection. Improved on-farm water management system. Potentials are for rice.
CORE PROBLEM: Low fertility in peat soils, no sustainable land use by lack of effective drainage depth, destruction of environment. When used for agriculture, a subsidence of 1.5 m in the first seventeen years after reclamation is common. For rice soils the continuation of flows from the peat domes should be maintained.
Mitigating measures: Adapted lay-out, which should protect the peat areas with a peat depth of more than > 3m.Control structures required in the Canals perpendicular to peat domes along the slope. The Potentials for peat areas with less than < 3m peat soil are mainly for Forestry plantations. Coastal regions with a tidal range of more than >3.5 m; tree crops might be an option if effective drainage depth will be sustainable after subsidence of the peat.Clay soils are very suitable for rice growth when using the flow from the peat dome for irrigation.
Degraded peat forests require special measures (see degraded and abandoned areas). Drainage will be required for sustainable forestry in these areas, but this drainage should be minimized to prevent excessive subsidence. Ramin tree plantations are recommended.
CORE PROBLEM: Hazard of saline water intrusion limits the options for development only to tree crops or brackish water fisheries.
Recommendations: Mangroves should remain protection area near the coast line. For tree crops is required Flood control along the saline water course with a collector drain inside of the floodprotection dike. Control structures should be built in the dike at regular intervals with as main objective controlled drainage for tree crops. In cases the control structures should be made high enough for the passage of boats for transport of tree crop products at high tide.
CORE PROBLEM: Acidity can not be washed out by lack of effective drainage depth. For development is required a major construction input.
Mitigating measures: Construction of major supply canal in the backswamp areas. (with control structures to promote flow in this canal). Acid sulphate soils require pumped irrigation to grow rice. Few other options, except for relatively high areas. No tree crop potential. Melaleuca plantations will be an option.
Occupied Lands and Abandoned areas:
Schemes suitable for so-called second stage development are mainly found in South Sumatra province and in the present ISDP Schemes. They belong to the Swamp Scheme Environments II and III (see above).
Local development by Buginese and Banjarese farmers occurred in Swamp Scheme Environments II and III (see above).
Remaining Government sponsored Swamp Schemes cover large areas in Swamp Scheme Environments I, IV and V (see above).
Degraded or abandoned areas with little agricultural potential mainly are found in Peat Forests . Proposals for rehabilitation of these degraded and abandoned areas are found on WebPage Environment & Problems.
For environment II significant large areas of abandoned rice fields are found by an accumulation of toxic components (mainly ferrous iron). This is caused by years of insufficient percolation, especially after a long dry season. WebPages Model Area shows how such an area can be improved and return to successful rice cultivation within one cropping season.
For design proposals and lay-outs of schemes for these various Swamp Scheme Environments, see WebPages Design Macro.
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