Dr.Anuradha Saha and Dr.Vijay Bharti
Water scarcity is already an intractable problem in many parts of the world. The United Nations estimates that about one third of the world’s population live in regions that experience water scarcity and the situation continues to deteriorate. Scarcity of water is acute in the world’s rice bowls particularly China and India, with competing demands on fresh water sources triggering conflicts. About 70-80% of global fresh water withdrawals are for the agricultural sector, particularly irrigation and rice accounts for about 85 % of this, mainly due to inundated production. If we compare the relative water requirements of the world’s three main cereal staples viz. maize, rice and wheat, global paddy crop needs approximately five times the irrigation withdrawals needed by the two other major cereals combined. In the most intensively cropped areas under rice, where ground water is often used for irrigation, water tables have been falling at the alarming rate of one meter per year or more.Rice is the only crop that can survive but does not thrive in submerged conditions, which is the cause of limiting the plant’s ability to absorb nutrients. Standing water, in fact suppresses yield by limiting the ability of the roots to respire. This slows down the plants metabolism, ion transport and growth. Moreover, almost all time flooding of rice field is the cause of emission of methane gas. The main benefit of flooding the rice plants is that it checks the proliferation of weeds, thereby saving labour.Rice production in India increased 4.5 times during the last 60 years. The enhanced rice production is deemed to be largely productivity-led, though rice productivity is now improving at a much slower rate.
Low productivity is attributed to many factors, including high dependence on rains, delayed sowing / transplanting, inadequate plant population, low seed replacement rate, frequent floods and droughts, deficiency of micro nutrients and impaired soil health. This signifies reduced rate of response in terms of unit gain in productivity with application of similar inputs over time. Rice crop is mainly transplanted upon 25-35 days old seedling in puddle field and continuous submergence is maintained throughout crop growing season. Thus anaerobic soil conditions are created throughout crop growth. These soils are put to intensive cultivation, raising 2-3 crops in a year continuously. Farmers have relied on chemical fertilizers, pesticides to ensure higher productivity since the Green Revolution. However, of late overall productivity of such lands has been observed to decrease due to several constraints. Demand for rice is expected to increase by about 38% by 2040. India needs to increase rice production almost double on its current production. India cannot expand its irrigated area to a level that can match production goals in any land extension strategy, as there is paucity of additional land and water.
Therefore, field enhancing measures, including introduction of improved rice varieties and production technologies are expected to help meet the projected increase. If we have to meet food needs without compromising on environmental integrity, it is essential to identify and adopt solutions that are environmentally more sustainable. That is, the methods adopted should reduce water consumption and increase productivity. Currently, several emerging technologies intended to boost paddy yield per hectare require less water. The System of Rice Intensification (SRI) is a well documented methodology belonging to this ilk. SRI emerged in this context as a potential alternative promising yield enhancement with over 30% saving in water, more than 75% saving in seed and improvement in soil quality and soil biota. Transition to SRI helps in addressing the issues of resource degradation in rice production systems, saves precious surface and ground water and at the same time, helps in enhancing households and national level food production. SRI is not a standardised technological method. It is a methodology for comprehensively managing resources-changing the way land, seeds, water, nutrients and human labour are used. SRI is an amalgamation of multiple beneficial practices which improves the production of land, labour, water and capital used in rice cultivation. It improves yields with less water, less seed and less chemical inputs than most conventional methods of rice cultivation.
The returns on inputs are higher, making the method potentially more profitable than most of the traditional methods. However, the actual yield increases depend on how well farmers practice SRI.SRI involves changes in the management system in transplanting early i.e. two leaves stages, single seedlings in a square method followed by practising alternate wetting and drying irrigation and mechanical weeding. This involves new skills both for farmers and labour, whereby timeliness of the operations is extremely crucial. Since SRI does not involve seed based technology, farmers can easily adopt the method. SRI offers unlimited opportunities for exploration and innovation for local adoption in most of the ecosystems. This method improves soil structure and boost productivity through addition of compost and other organic matter. It is a water saving production system through enabling the transition to better management and skills. In case of groundwater scarce area, this also results in saving ground water by about 30% and saves electricity consumed per acre of rice.
If surface irrigation system is followed, savings in irrigation water leads to possibilities of expansion of irrigated area. So, Irrigation Systems renovation needs to provide small quantities of water with precision and reliability than with continuous flooding. SRI can also improve soil carbon sequestration and other climate change mitigation benefits such as reduction in methane and other GHGs. The challenge now is to scale up the SRI kind of farm based methods to reduce the water input for rice cultivation, while increasing production and reducing the need for use of agrochemicals, which could negatively impact soil and water quality. The larger objective is to scale up SRI as a method that can effectively address global water crisis. As a way to increase rice productivity, the Government of India has launched several programmes that encourage the use of high yielding varieties, improved nutrient inputs and modern technological methods. These include the Special Rice Production Programme (SRPP) and the Integrated Programme for Rice Development (IPRD). Similarly, SRI needs support from Governments, aid agencies and research organisations. As part of programmes designed to address global water crisis, SRI and similar methods need greater attention. The need of the hour is a shift in policies so that authorities at the local, state and national levels can actively promote the SRI method.
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