Direct seeding of rice needs a fillip to improve yield

MS Bajwa

THE prevailing water crisis is posing the biggest threat to agro-economic sustainability and socio-economic stability in India. This problem is being aggravated by global warming and climate change. Saving water and using it judiciously are now recognised as one of the top priorities in the country.

The governments and extension agencies in Punjab, Haryana and other states are motivating farmers to adopt water-efficient crop production approaches, particularly for the cultivation of rice, which is a high-irrigation crop (requiring 3,000-5,000 cubic metres of water per tonne of grain produced). One recommendation is to shift from conventional water-intensive transplanted rice (TPR) cultivation in flooded/saturated soil towards direct seeding of rice (DSR) — sowing/drilling seed in the soil at a workable moisture content, pre-emergence spraying of herbicide, first irrigation 21 days after sowing and thereafter at 5-7 days’ interval. The DSR system can save water, eliminate the labour-intensive step of transplanting, reduce costs, increase income and ensure better soil conditions for the following crops. The DSR is eco-friendly as it reduces methane (a potent greenhouse gas) emissions associated with anaerobic conditions in submerged soils (as in the TPR system), and hence can play a pivotal role in mitigating climate change.

All-out efforts are being made by the governments to increase area under the DSR in Punjab and Haryana, with proposed targets to bring 7 and 2-2.5 lakh acres, respectively, under it during 2024. Experiences of farmers in recent years and research reports of PAU, the International Rice Research Institute and others show that compared to the TPR, the DSR approach can reduce water usage by over 70 per cent for land preparation and over 20 per cent during the growth of the rice crop. However, water-saving under the DSR system comes at the cost of up to 30 per cent lower yield than the TPR system. The extent of yield loss varies with soil properties, seeding practices, water management, weed infestation, efficiency in adoption of recommended crop production management practices and agro-ecological conditions. The adoption of the DSR system by the farmers is, therefore, not growing as desired despite incentives of Rs 1,500 per acre in Punjab and Rs 4,000/acre in Haryana, being offered to them by the governments. During 2023, against the targets of bringing under the DSR about 5 lakh acres in Punjab and 2 lakh acres in Haryana, these states could manage to achieve only about 1.7 (even less than about 2.12 lakh acres achieved during 2022) and 1.78 lakh acres, respectively.

While shifting to the DSR system, the most crucial issue is that the currently cultivated high-yielding rice varieties/hybrids characteristically produce potential (maximum achievable) yields when grown under reduced (i.e. low oxidation reduction potential) anaerobic soil conditions created by keeping the rice root zone soil system submerged or saturated with water. It is well established that electrochemical and chemical properties of the soil under flooded and saturated conditions remain similar. The DSR yields remain significantly lower than the obtainable potential yield when root zone soil is below the saturation level i.e. under aerobic conditions. Plant breeders must respond to the challenge of developing aerobic-resilient rice varieties specifically suitable for the aerobic DSR system. These varieties should have high-yield potential, drought tolerance, early seedling vigour, resistance to biotic and abiotic stresses, weed competitiveness, deeper rooting and strong stems to resist lodging at maturity.

In addition to the availability of DSR-specific suitable variety, the key rice-yield reducing factors under the DSR system include: (i) poor seed germination and crop establishment due to inefficient management of soil moisture at sowing, and damage by birds, rats, snails, desiccation of surface sown seeds; (ii) failure to control weeds and insect pests because of inefficient use of herbicides and pesticides; (iii) iron deficiency at early seedling and later stages of plant growth, particularly in plants grown on light-textured soil; (iv) lodging at maturity due to poor root anchorage; (v) unsuitable soil properties; (vi) inappropriate crop and input management practices. All these issues have to be addressed to enable farmers to enhance crop production efficiency of the DSR system and achieve assured high productivity, profitability and net income comparable to the TPR system.

Soils in large tracts of land in Punjab (about 0.7 million hectares), Haryana and across the country (about 7 million hectares) are salt-affected kallar/usar. These soils are not suitable for the DSR system until they are adequately reclaimed. Rice plants are known to be highly sensitive to salinity/alkalinity in the soil during seed germination and early seedling development stage, because of which the yield of the crop grown in salt-affected kallar/usar soils gets significantly reduced. The yield losses under the DSR system would be significantly greater (can be even total crop failure) than under the TPR system because of much higher concentration of salts in the surface soil where the seed is directly sown. The TPR system is recommended in these soils because well-grown healthy seedlings get established in a much better way. Moreover, salinity/alkalinity in the root zone soil appreciably decreases (effect of dilution) due to flooding/saturation.

An integrated package of management technologies must be developed and applied to deal with the challenges of the DSR system and enable farmers to obtain yield levels comparable with the TPR system. This requires strengthening of the multidisciplinary research system to provide technological solutions for the DSR rice yield-reducing factors.

Direct seeding of rice is a promising alternative planting system amid water shortage. But participatory linkages need to be developed between farmers, technology generators and disseminators for generating and disseminating synergistic combinations of technologies to achieve assured maximisation of productivity of DSR rice and narrow the gap between the DSR and TPR systems in terms of economic returns to the farmers.

Less labour-intensive, tends to mature faster than transplanted crop

• Direct-seeded crops require less labour and tend to mature faster than transplanted crops.
• In this method, plants are not subjected to stresses such as being pulled from the soil and re-establishing fine rootlets. However, they have more competition from weeds.
• Depending on the land preparation method used, direct seeding can be done in two ways: dry or wet.

Dry direct seeding

• This method is usually practised for rainfed and deepwater ecosystems. Farmers sow onto dry soil surface, then incorporate the seed either by plowing or harrowing.

Broadcasting

• Broadcast 60-80 kg of seeds uniformly by hand or in furrows in one hectare.
• Make shallow furrows by passing a furrower along the prepared field.
• After broadcasting, cover the seeds using a spike-tooth harrow.

Drilling

• Precision equipment, such as the Turbo Happy Seeder, can be used to drill seeds.
• Drill 80-100 kg of seeds per hectare.
• Seeds are placed by the machine into both dry and moist soil, and then irrigated. A smooth, level seedbed is necessary to ensure that seeds are not planted at depths greater than 10-15 mm.
• Fertilisers can be applied at the same time as the seed. Manual weeding is easier in machine-drilled crops than in broadcast crops.

Dibbling

• It is usually practised along mountain slopes or where plowing and harrowing are difficult.
• Use a long wood or bamboo pole with a metal scoop attached for digging holes.

Source: International Rice Research Institute’s Rice knowledge Bank

This article has been republished from The Tribune.