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by Dr. Sumith Abeysiriwardena

Rice is one of the oldest crops cultivated on earth and it is the staple food of about half of the world's population, so that many people are engaged in rice cultivation around the world. Many scientists from different countries continue to work on rice to increase its productivity and quality and to reduce cost of cultivation.

Since rice is grown over a wide range of diverse ecological conditions, many different methods of crop establishment and associated cultural practices in rice have been adopted in different countries depending on their traditions and availability of resources. Such broadly classified crop establishment methods are transplanting, broadcasting and row seeding.

Crop establishment

System of Rice Intensification (SRI) is one of the variants of transplanting, which is said to be adopted in Madagascar so that SRI is also called 'Madagascar method' by the people in other countries. Since recent past, some individuals in Sri Lanka with an incomplete knowledge about SRI are over emphasizing this method through media and other means of publicity as a miracle technology for rice cultivation by which a grain yield as high as 400 bushels per acre (bu/ac) could be obtained.

This is totally a misconception. The concept of SRI may be novel to those individuals who promote it but not to rice scientists in Sri Lanka where introduction of such a concept in rice cultivation dates back to as early as 1906. This is the reason behind writing this article to make the interested public aware of the basic principles and the reality of SRI in rice cultivation.

Rice is a semi aquatic cereal that can produce many tillers in addition to the mother culm whereas other popularly grown highland cereals such as corn, sorghum, wheat and barley are uni culm cereals. This unique feature of tillering ability in rice has led to a range of crop establishment methods of rice between two extreme conditions. In one extreme condition, rice crop is allowed to have only the main culm (uni culm approach).

This is practically achieved by high density sowing (5-7 bu/ac) where no adequate space among plants is allowed for tillering. Under this situation, competition among plants is maximised so that plant growth is retarded resulting small but comparatively more number of panicles per unit land area preventing any yield reduction. Microclimate within the crop canopy under this situation is, however, very conducive to occurrence of pest and disease epidemics.

Tilling capacity To our knowledge, the only farmers in the world, who are cultivating rice at this extreme, are from Ampara district in Sri Lanka. The practical implication of this extreme method of crop establishment is that it saves cost on labour at the expense of seed paddy.

In the other extreme condition, rice plants are allowed to have as many tillers as possible with a minimum number of mother plants or culms per unit land area. The SRI falls into this extreme. Under this method of crop establishment, competition among plants is minimized by maintaining an ample and uniform space between plants so that plant and root growth is facilitated with profuse tillering.

In this method the panicles are relatively bigger but the number of panicles per unit land area is relatively less. Microclimate of the crop under this situation is not conducive to some of the rice pests and diseases such as brown plant hopper, leaf roller and sheath blight due to light penetrating loose canopy of the crop. However, this is not a great advantage of SRI since most of the present day varieties are tolerant to major pests and diseases of rice.

On the other hand, under SRI, there is a tendency to occur high incidence of stem borer, a major pest of rice, due to comparatively thick stems and less absorption of silica by the plant. The success of SRI is totally dependent upon the tillering capacity of the crop.

The unique feature of SRI is that it saves seed paddy at the expense of labour needed for careful manual transplanting weed control and water management. The crop establishment methods that fall mid way between these two extremes are seedling broadcasting, standard transplanting, broadcasting and row seeding which have been recommended by the Department of Agriculture for rice cultivation except seedling broadcasting. In these methods, both the mother culms and tillers are considered equal. That saving labour is more important than saving the seed paddy.

Difficult drainage system

In addition complete drainage which is a requirement for profuse tillering is practically difficult during peak rains in majority of rice lands in Sri Lanka. Furthermore, SRI is the practically least feasible and least adaptable one under Sri Lanka condition due to its high labour requirement and high sensitivity to changing environment out of all the crop establishment methods in rice cultivation. This is the reality and under these circumstances could the promotion of SRI in Sri Lanka be justified?

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