Grupos Cíclicos

Paddy cultivation

The ideal climatic conditions make paddy cultivation possible throughout the year and double- cropping in areas with adequate water supply. The total paddy area in Malaysia is estimated to be 598 480 hectares of which 379 470 hectares are located in Peninsula Malaysia and the balance in the states of Sabah and Sarawak in East Malaysia. In Peninsula Malaysia, 76% of the paddy area are provided with irrigation facilities while only 15% of the paddy area in East Malaysia are irrigated. The irrigated areas have been classified into major granary areas consisting of 8 schemes with a combined area of 212 500 hectares, 74 secondary granary areas with a total area of 28 440 hectares and 172 minor granaries which are scattered throughout the countries.

Before the introduction of double-cropping, organic fertilizers such as bat guano were widely used by the farmers. As the adoption of modern high yielding rice varieties requires increased fertilizer usage, the farmers were encouraged to apply inorganic fertilizers. Very often some progressive farmers apply more fertilizers in order to increase yield. Most farmers use nitrogenous fertilizers, namely urea as well as urea–based mixtures. As a direct seeding method is widely practiced among the farmers, the plant density is much higher than when the traditional replanting method is used and this results in higher application of fertilizers. When the direct seeding method is used weed control is more difficult. Also a dry direct seeding method results in noxious weed infestation. Herbicides are widely used to control weed infestation so that yield loss is minimized.

The change of cropping intensity from single to double cropping could result in an increased availability of hosts for pest insects and diseases for the rice plants. The change in the cultivation method from transplanting to direct seeding could have led to a modification of field habitats and changes in microclimate which in turn would affect the occurrence of rice pests. For instance the increase in the proportion of direct-seeded fields results in an increase in the proportion of fields infested by weeds, a situation favoring the outbreak of the ear-attacking bug. Various types of insecticides and other agro-chemicals are used to control this problem.

As the water from the paddy fields gets discharged into the drainage system without any treatment, residues of the agro-chemicals applied will definitely pollute the drains as well as the receiving waters. This problem will become more acute if the application of these agro- chemicals is not controlled. However, samples of water taken from strategic locations have been tested and the quality of the water has been found to be consistently good except for some isolated cases with pollution of little impact. But the long term impact on water quality due to the widespread application of these chemicals should not be underestimated. In order to ensure that water quality remains consistently good, Integrated Weed Management (IWM) and

Integrated Pest Management (IPM) are being developed by the department of Agriculture as approaches to minimize the application of agro-chemicals. These programs involve a biological control using selective biological agents that control weeds, insects and pests without affecting the growth of paddy plants. As well they promote an effective application of pesticides, insecticides and herbicides as a mitigating measure to reduce possible adverse effects of using these agro-chemical in rice production. The features of some of these programs are enumerated below.

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The release of barn owls (Tyto alba), which are the natural enemy of rats, by establishing

nests around the paddy field as a step to control the rat population and reduce the destruction of paddy crops. Results obtained in IADP Trans-Perak show that the area destroyed by rats had been reduced from 8% in 1988, prior to the release of barn owls, to less than 1% in 1998.

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The rearing of catfish and Muskovi ducks is a measure to control a number of pests and

weeds. This program is still at the pilot stage and more data are being collected to assess its effectiveness before management action is taken.

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The installation of ultra-violet lamps to trap black bugs during moonlit nights has significantly

reduced the application of chemicals to control this pest as the chemical approach is only used when the out-break is beyond control by this means alone.

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Proper water level management to ensure adequate depth of flooding in the fields at the

right time will control the growth of weeds and enhance the effectiveness of any herbicide applications.

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An adequate surveillance and forecasting of pests and diseases is an effective means to

counter these problems as control measures can be taken before any out-break occurs. Even though the quality of drainage water from the paddy fields is generally good, it is inevitable that agro-chemicals will continue to be used especially if there is an outbreak of pest and diseases. Therefore, a comprehensive monitoring system is necessary to check the quality of drainage water and to assess the effectiveness of management actions put in place, such as controlling the use of agro-chemicals by farmers. As part of a project entitled “Study On Modernization Of irrigation Water Management in Granary Areas Of Peninsula Malaysia” and carried out in 1997-98 by the Japan International Cooperation Agency (JICA), it was recommended that permanent monitoring stations be established at major drains and rivers and at pumping stations for the recycling of irrigation water. It was also recommended that water sampling be carried out at least twice a month at each sampling station to obtain representative data for each month. The frequency of the sampling could be adjusted subsequently according to the adequacy of the results and the timing of sampling would be during the agro-chemical application period.

Upland crops cultivation

The conversion of forests for cultivation of upland crops such as vegetables and flowers leads to an increased rate of soil erosion in the watershed area due to the land clearing process involved. For instance, in Cameron Highlands, a region which is in the watershed of some of main rivers in Peninsula Malaysia, the clearing of forests on steep slopes for cultivation of vegetables and flowers has led to widespread soil erosion on the unprotected land surface and resulted in the sedimentation of rivers and a reservoir used for hydroelectric power generation. The sediments were carried further downstream of the river and silted up at a diversion headwork

set up for irrigation purposes. As the sediments are also transported into the canal systems, they have to be removed from these canals regularly.

Various types of agro-chemicals are also widely used in the cultivation of upland crops. Monitoring data have shown that some stretches of rivers flowing from the Cameron Highlands are contaminated, with levels of some chemical residues exceeding the acceptable limits set by the European Union. However, as the water reaches further downstream the water quality remains reasonably good after proper treatment for irrigation purposes as well as for domestic and industrial consumption.

Even though the water quality remains reasonably good in spite of sedimentation and excessive application of agro-chemicals in the upstream portion of the rivers, this situation is not expected to continue in the future and mitigation measures must be taken to not only prevent further deterioration of the water quality but also to improve it. To achieve this goal, the clearing of forests for agriculture must be strictly regulated and prohibited on steep slopes. Anti-erosion measures such as the cultivation of cover crops on the cleared surface and the provision of proper drainage systems with silt retention ponds must be taken. With regards to agro-chemicals, only those characterized by low toxicity, low dosage and pest-specificity are to be allowed and the use of those with high potential for leaching through the soil must be restricted or prohibited. The amount of chemical residues allowed to enter any water body has to be controlled by law as such control does not exist at the moment. The Department of Environment is currently reviewing its approach to water quality monitoring of rivers and considering additions to the list of pollutants to be monitored. However, the most effective way to prevent water from being polluted by chemicals is to overcome chemical dependency and promote organic farming. It is a sad fact that this approach is only practiced by a small number of farmers who are environmentally conscious. Therefore various steps have to be taken to reduce the dependency on agro-chemicals and to promote more sustainable and safer methods of food production. In this context, consideration should be given to the following recommendations:

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the government should set up an effective mechanism to control the sale of pesticides, with

the long-term view of phasing them out;

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the government should strictly enforce the law that regulates the highly toxic pesticides;

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the Pesticides Board should ban all highly toxic pesticides and control the use of the other

pesticides;

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those pesticides banned or severely restricted overseas should be banned or severely restricted

as well in Malaysia;

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farmers should be encouraged and guided (and even given incentives) to turn to pesticide-

free farming in order to phase out the usage of pesticides;

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subsidies and loans to organic farmers would encourage crop growers to adopt organic

farming practices.

Tree crop cultivation

There are more than 5 million hectares of tree crop plantations in Malaysia, mainly comprising rubber and palm oil trees. With the revised National Agricultural Policy’s emphasis on increasing food production, more land will be opened up for palm oil cultivation. Any clearing and opening up of new land for agriculture will definitely cause erosion on the land surface and results in sedimentation of the waterways and deterioration of water quality. Soil erosion will also occur

when replanting of the tree crops takes place as the land surface will be left barren for a long time after the existing old trees have been cleared. The problem will become more acute on hilly terrain and. To overcome this situation, the barren soil surface must be planted with cover crops. Proper terracing on hilly areas and the construction of proper catch drains leading to silt retention ponds need to be carried out. Water discharging from these retention ponds will carry minimum amounts of silt and thus minimizing the sedimentation and pollution of the receiving waters.

As is the case with the upland crop cultivation, agro-chemicals are widely used in tree crop cultivation. While multinationals in the plantation sector who are conscious about their public image and are carrying out audits to comply with the Pesticide Act, other smaller plantations and small holders may practice widespread misuse of pesticides. Pesticides residues may be flushed away and become diluted during the wet season, a situation that does not happen when there is a low flow during the dry season. Even though most of the pollution in rivers is due mainly to industrial effluents, sewerage and household wastes, agro-chemicals do also contribute even though their residues escape detection under the existing monitoring systems. In order to safeguard the water quality, as the water supply becomes more and more scarce due to an increasing demand, mitigation measures must be applied through both enforcement and education so that the agriculture sector will be reformed and the dependency on agro-chemicals minimized.

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