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Agriculture and Economic Development
Map 1. Medieval Agriculture
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Kampuchea's Ecology and Resource Base: Natural Limitations on Food Production Strategies
John V. Dennis, Jr.
Introduction
As in other countries, agricultural development in Kampuchea has always entailed a struggle by man to obtain greater control over his physical environment and resource base. The irony of this struggle is that the more successful man is in gaining control over his environment, the more rapidly the resource base tends to be depleted. This is readily apparent in Kampuchea. Within a central zone around Tonle Sap and Kampuchea's major rivers, annual flooding during the wet season months of July to October rejuvenates the soil but makes careful water control impossible. The mixed result is that this area can produce low rice yields indefinitely. By contrast, irrigation schemes on higher terrace soils outside this zone have allowed periods of superior productivity that ended with permanent deterioration of the soil. According to several contemporary development strategies, it is now time to curtail the extent of the annual flooding within Kampuchea's zone of flooding.
The annual flooding, however, is crucial to the maintenance of soil fertility and high rice and fish production. A greater awareness of the ecological relationships involved may encourage aid donors and Kampuchean planning officials to develop improved food production strategies that take advantage of the existing strengths of the natural resource base but do not destroy them at the same time. This strategy would lessen the perceived need to implement a standardized package of Green Revolution rice technology. Such a package requires costly petrochemical imports and a high level of water control that would be both very difficult to achieve and incompatible with the rejuvenating floods.
Contrasting Strategies of Water Use
The rice agriculture of the Khmer empire, which flourished from the ninth to the twelfth century, was based on Pleistocene terrace soils north of Tonle Sap in what is now Siem Reap province. This agriculture was located beyond the zone of flooding (see maps 1 and 2) and depended on gravity-flow irrigation systems to divert water from the Puok, Siem Reap, and Roluos rivers. The location of all major Kampuchean towns and cities, with the exception of Phnom Penh, just beyond the zone of flooding suggests that both agriculture and political power were based outside this zone for many centuries. However, the high agricultural productivity that supported the building of Angkor Wat was not sustainable, and today the rice soils of Siem Reap are some of the worst in Kampuchea.
The French decision m 1866 to establish the political capital at Phnom Penh in the very center of the flooded zone suggests an implicit recognition that the old terrace soils were exhausted and that consequently the focus of both agriculture and political power had shifted to the zone of flooding.1 The French evidently recognized the relationship between flooding and the maintenance of soil fertility, for they supported a practice called colmatage in which canals (prek) were dug through the natural levees of the rivers in order to allow silt-bearing flood waters to penetrate behind the levees to agricultural land or areas where farmers wished to create new arable land (See Figure 1). By the early 1940s some 370 colmatage canals existed in Kandal province.2 It is estimated that these canals deliver a layer of fresh silt about 20-25 mm thick each year to an area of about 17,600 hectares.3 Upstream from Kandal province the Mekong River tends naturally to flood its banks in the wet season, so colmatage is rarely used except where roads block the flood waters.
Although colmatage rice lands have never comprised more than 15 percent of the total rice lands in Kampuchea, the adoption of the practice in the mid-1800s was probably a response to the irrevocable ecological degradation that deforestation and farming had caused in the nonflooded zone in the preceding centuries. As deforestation proceeded, the arable land in the nonflooded zone became increasingly drought-prone as well as infertile. Just as the bamboo tree in Asian proverbs survives by bending with the wind, colmatage was a pragmatic response that derived impressive benefits from the disruptive annual flooding.
By contrast, some food production strategies of the Khmer Rouge regime were like the oak tree which stands straight in the wind but is eventually broken by it. Farmers in Kandal province were ordered to close off colmatage canals to the wet-season flood waters and in some cases to fill them in as well.4 Under the colmatage system the land grows no crops during the months of flooding and a rice crop is transplanted either as the flood waters recede or early in the year to allow the crop to be harvested before the flood waters rise.
The Khmer Rouge regime sought to grow more than one rice crop per year on the colrnatage fields, evidently determining that the only way to do this was block the flood waters from the fields altogether. The plan failed, not because of an immediate loss of soil fertility, but because flood water no longer reached the inland lakes (beng) where it was needed for dry season irrigation. Whether or not this particular project succeeded in the short run, it suggests that Khmer Rouge leaders either were not aware of the critical role flooding plays in maintaining soil
Map 2 Major Rice-Growing Areas in Kampuchea
fertility or were confident that they could replace the silt deposits with Chinesestyle fertilization practices.
The present Heng Samrin regime's policy on the management of the annual flood water is ambiguous. On the one hand, it has sought to reestablish practices and structures in place prior to the Khmer Rouge regime. Farmers have been allowed to reopen colmatage canals, in some cases assisted by the government and Western aid. A long dike that broke during the Khmer Rouge regime has been repaired, allowing a large area in Kompong Cham and Prey Veng provinces to be returned to wet-season rice cultivation. On the other hand, three years after aid agencies began sending in Green Revolution-type rice seed and chemicals, the regime continues to emphasize these types of materials in its requests to foreign donors. Heng Samrin officials admit that most of the Green Revolution-type rice inputs are used for the much smaller dry-season rice crop when water control is more often sufficient to use these inputs successfully.
These officials are confronted with a policy choice that has profound implications for the future of Kampuchean agriculture. Food and Agricultural Organization (FAO) and some other agricultural aid donors have argued that the best way for Kampuchea to achieve food self-sufficiency is to replace local rice varieties and low-cost cropping practices with input-intensive cropping using the short-stemmed Philippine rice variety, IR36.5 In my opinion, it is misleading simply to point to the fact that IR36 and similar varieties have enabled the Philippines, Indonesia, and Malaysia to achieve rice self-sufficiency. All three of these countries have export-oriented capitalist economies that either can afford to import the energy-intensive inputs essential to Green Revolution technology or have the resources to produce these inputs themselves. And unlike Kampuchea, none of these countries is dominated by a central floodplain that is annually refertilized by flood waters. At present, less than 10 percent of Kampuchea's agricultural production teams have access to land with sufficient water control to implement the Green Revolution technology. A food production strategy that focuses on such a small area will result in either increased social inequality or, if the surplus is rigorously redistributed, political discontent within the more productive areas. To date the Heng Samrin regime has shown no signs of embarking on any massive campaign to greatly increase the amount of rice land with good water control.
The other, and in my opinion, more appropriate strategy open to Kampuchean agricultural planners is not to tight the annual hydrological cycle, but rather to launch an intensive program to improve the yield potential of the numerous local rice varieties which over the past few thousand years have been adapted to the diversity of soil, water, and disease conditions existing in Kampuchea. Such a program could still incorporate various desirable genetic traits already identified in rice germplasm in neighboring countries or at the International Rice Research Institute (IRRI) in the Philippines, but in ways compatible with the existing hydrological cycle in Kampuchea.
Figure 1. Silt Deposition Along Typical Colmatage Canal
The Mekong Secretariat based in Bangkok has planned a more radical strategy for water control in Kampuchea. This plan, whose principal objective is the production of hydroelectricity, calls for a massive dam across the Mekong River between Thailand and Laos at Pa Mong. This dam would reduce both the extent and the duration of the annual flooding in Kampuchea by at least 15 percent.6 According to one study sponsored by the Mekong Secretariat, Kampuchean agriculture is "at the mercy of natural hydrologic conditions" and the reduction of "this violent water regime" would allow more intensive cropping within the zone of flooding, though at the same time it would increase the extent of drought-prone areas.7 Fish production and soil fertility would also be adversely affected.8
Careful analyses sensitive to long-term effects (100-500 years) on Kampuchea's soils and fish-producing capacity need to be carried out before such a plan is acted upon. The reduction of silt deposition would probably help prolong the existence of Tonle Sap, which is already very shallow, but otherwise the Pa Mong scenario suggests that it would achieve short-term gains (50-100 years) at the cost of permanently degrading crucial portions of the natu...
