Dr. D.V. Tran pointed out that rice is the staple food for more than half of the world’s population. The Green Revolution has enabled rice production to meet the demand of the growing population. However, since 1990 rice production has grown at a lower rate than the population. This deceleration in the growth of rice production is a cause for concern in terms of world food security. It has been the topic of numerous reviews and several rice scientists have alerted of the risk of a pending food crisis. Based upon the 1997 estimated production of 524 million tonnes, an additional 180 million tonnes of paddy rice will be required in the year 2025. Most of the increased demand will be required by developing countries.
Yield gaps are still observed in many countries, while evidence of productivity decline in intensive rice production has been increasingly noticed both at research stations and farmers’ fields. Due to its complexity, there are different points of view regarding the possibility of narrowing yield gaps as a tool for increasing rice production. A number of experts are of the opinion that yield gaps in favorable rice ecologies are not significant for exploitation for increasing rice yield and production. Others believe that large rice yield gaps still exist. In 1995, the average rice yields in 78 countries were less than the world average yield of 3.77 t/ha, indicating the existence of yield gaps. Also, progressive farmers usually obtain higher yields and more profits than the ordinary farmers.
There is little doubt that intensified rice cropping has significant effects on soil chemical and biological processes. The chemistry of submerged soils is complex and the addition of organic matter from crop residues and continuous soil reduction from puddling further complicates the soil chemical and biological processes. Moreover, the socio-economic factors and the degradation of irrigation infrastructures may contribute to yield gaps, thereby bringing about productivity decline under farmers’ field conditions.
Narrowing the yield gaps aims not only to increase rice yield and production but also to improve the efficiency of land and labour use; also, to reduce the cost of production and increase sustainability. Exploitable yield gaps of rice are often caused by various factors which may be classified into physical, biological, agronomic, socio-economic and institutional constraints; these can be effectively improved through participatory approach in action. The narrowing of the yield gap is not static but dynamic with the technological developments in rice production, as the gaps tend to enlarge with increase in yield potential due to the use of improved varieties.
The narrowing of the yield gap of rice requires integrated and holistic approaches, including appropriate concept, policy intervention, understanding of farmers’ actual constraints in achieving high yield, deployment of new technologies and promotion of integrated crop management, adequate supplies of inputs and farm credit, and strengthening of research and extension and the linkages between them. If one of these components is missing or weak, the narrowing of the yield gap in a particular rice production area cannot reach its full potential.
The causes of yield gaps of rice differ widely from season to season, country to country and/or even from location to location within a country or region. It is essential, therefore, to promote close collaboration between research, extension, local authorities, non-governmental organisations (NGOs) and the private sector in order to identify specific constraints to high yield and appropriate technologies and solutions, and take concerted action to bridge yield gaps of rice, through participatory approaches. This will depend mainly on the will of the Governments to support, co-ordinate and monitor such integrated and holistic programmes. International support to Governments’ initiatives in this direction could speed up sustainable increased rice production and the conservation of natural resources and the environment for the benefit of future generations.
