Rice is an important food and cash crop across the globe. The term ‘rice is life’ is most appropriate for India as this crop plays vital role in country’s food security and is the backbone of livelihood for millions of rural households. India is the second largest producer of rice preceded by China. Rice (Oryza sativa L) being the major source of food after wheat, it meets 43 % of calorie requirement of more than two third of the Indian population. Traditionally, rice is grown by transplanting one month-old seedlings into puddled and continuously flooded soil. Direct seeding of rice refers to the process of establishing a rice crop from seeds sown in the field rather than by transplanting seedlings from the nursery. There are three principal methods of direct seeding of rice, first is dry seeding in which there is sowing dry seeds into dry soil, second is wet seeding in which sowing pre-germinated seeds on wet puddle soils and third is water seeding in which seeds sown into standing water. Increasing water scarcity and labour wages triggers the search for such alternative crop establishment methods which can increase water productivity. During Covid-19 pandemic, labour shortage would be an issue during rice transplanting season. So in this context, DSR with machine seems to be one of the possible solutions. Direct seeded rice is the only viable option to reduce the unproductive water flows. Improved short duration and high yielding varieties, nutrient and weed management techniques encouraged the farmers to shift from traditional system of transplanting to DSR culture. A new DSR technique called ‘tar-wattar DSR’ has been developed and successfully tested on good scale at farmers’ field. In this new technique, rice is sown in water fields and the first irrigation is applied 21 days after sowing.
Merits of Direct Seeded Rice
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Saving of water as nursery raising, puddling, seepage and percolation are eliminated.
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Early maturity (7-10 days) helps in timely management of paddy straw, hence timely sowing of succeeding crops.
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Soil structure is not disturbed as it prevent formation of hard pan just beneath the plough layer in direct seeded rice as occurs in puddled transplanted system.
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Labourrequired for nursery raising, uprooting and transplanting of seedlings are saved.
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Cost of cultivation is reduced.
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Reduction in methane emission and global warming potential.
Management of stubble burning
The urgency to remove stubble arises from the necessity to sow wheat seeds by early November. After harvesting of transplanting rice, very little time for farmers left to prepare the field for wheat sowing. Burning left-over stubble becomes an easy rescue option. The burning of rice straw is environmentally unacceptable as it leads to the release of soot particles and smoke, causing human health problems such as asthma or other respiratory problems. The higher moisture content in the winter air accentuates the problem as it traps the pollutants and prevents their dispersal. Emission of green house gases like carbon dioxide, methane and nitrous oxide cause global warming. DSR paddy takes less time for establishment and there is no transplanting shock. This method enhances the window between paddy harvest and wheat sowing, potentially reducing the stubble burning problem.
Management of water
Conventional rice cultivation needs 3000 to 5000 L of water to produce 1 kg rice. At global level 70-80% of fresh water is used in agriculture and rice accounts for 85% of this water. The declining availability and quality of water, increased competition from domestic and industrial sectors are already affecting the sustainability of irrigated rice production systems. The establishment technologies, which inherently require less water, and are more efficient in water use are demanded. Water application in rice production, therefore, needs to be decreased by increased water-use efficiency and the direct seeded rice has the potential to improve the efficiency of water use. DSR being a water wise technology provides the solution.
Soil Health
Intensive use of irrigation water in rice led to a salinity buildup. In the short term, salinity buildup leads to reduced yields, whereas, in the long term, it can lead to abandoning of crop lands. Also the heat from burning paddy straw penetrates 1 cm into the soil, elevating the temperature to 33.8 to 42.2 degree Celsius. This kills the bacterial and fungal populations critical for a fertile soil. Burning also causes damage to other micro-organisms as well as its organic quality. One tonne of stubble burning leads to a loss of 5.5 kg N, 2.3 kg P, 25 kg K and more than 1kg of sulphur. So these all things can be eliminated with DSR technique and can improve soil health.
Economics
DSR saves labour as it avoids nursey raising, uprooting seedlings, transplanting as well as puddling. Further the demand for labour is spread out over a longer period in DSR as compared to PTR, where more labour is required at the time of transplanting thus resulting in its shortage. Covid-19 pandemic has led the labourers to reverse migrate to their villages, which has created a shortage of labourers. Due to labour shortage, farmers are now being encouraged to adopt ‘direct seeded Rice in place of conventional transplanting.
Normal Transplanting of Paddy versus Direct Seeding of Rice
In transplanting paddy, farmers prepare nurseries where the paddy seeds are first sown and raised into young plants. The nursery seed bed is 5-10% of the area to be transplanted. These seedlings are then uprooted and replanted 25-35 days later in the puddled field. In DSR, the pre-germinated seeds are directly drilled into the field by a tractor-powered machine. There is no nursery preparation or transplantation involved in this method. Farmers have to only level their land and give one pre sowing irrigation. In transplanting for the first three weeks or so, the plants have to be irrigated almost daily to maintain a water depth of 4-5 cm. Water prevents growth of weeds by denying them oxygen in the submerged stage, whereas the soft aerenchyma tissues in paddy plants allow air to penetrate through their roots. Water, thus, acts as a herbicide for paddy. In DSR as flooding of fields is not done during sowing, chemical herbicides are used to kill weeds. So, transplanting of rice is more water demanding, laborious, cumbersome, time consuming and entails a lot of expenditure on raising nursery, uprooting, and transplanting. Scarcity of labour during peak period of transplanting, uncertain supply of irrigation water, depletion of groundwater and increasing production cost necessitate the search for an alternative to the conventional puddled transplanting of rice. The advantages of the traditional system include increased nutrient availability (e.g. iron, zinc, phosphorus) and weed suppression. On the other hand direct seeding offers certain advantages like saving irrigation water, labour, energy, time, reduces emission of greenhouse-gases, better growth of succeeding crops, etc.
Challenges
Several challenges confront the wide scale adoption of DSR by farmers, such as weed infestation, stagnant yield, availability of purposely developed varieties, pests and diseases management. Despite of the numerous controversies, comparable grain yields may be obtained from DSR. In the present time, DSR is the most viable option for getting sustainable yields without any over exploitation of the available natural resources.
With increasing water scarcity, global warming and labour rates, the future of rice production is under threat and the only alternative is direct seeded rice. DSR technology is better than transplanted method of rice cultivation keeping in view the present scenario. However, better weed management practices and continuous awareness programmes among the farmers can lead to more adoption of DSR.
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