Direct-Seeded Rice Method

In News

• Direct-seeded rice method failed in Punjab as only 77,000 hectares (ha) was brought under direct-seeded rice (DSR), way below the 1.2 million ha (mha) target.

What do you mean by Direct seeded rice?

• DSR refers to the process of establishing a rice crop from seeds sown in the field rather than by transplanting seedlings from the nursery. 
• It has been recognized as the principal method of rice establishment since the 1950’s in developing countries.
• Direct seeding can be done by sowing pre-germinated seed into a puddled soil (wet seeding) or standing water (water seeding) or prepared seedbed (dry seeding). 
• Improved short duration and high yielding varieties, nutrient and weed management techniques encouraged the farmers to shift from the traditional system of transplanting to DSR culture. 

Different methods of direct seeding

Rice can be established by three principal methods: transplanting, dry-DSR and wet- DSR.

Dry DSR:

• In Dry-DSR, rice is established using several different methods, including :
  • broadcasting of dry seeds on unpuddled soil after either ZT(zero tillage) or CT(conventional) 
  • dibbled method in a well-prepared field and 
  • drilling of seeds in rows after CT, minimum tillage (MT) using a power tiller-operated seeder, ZT or raised beds. 

• In case of both CT or ZT, a seed-cum-fertilizer drill is used, which, after  land preparation or in ZT conditions, places the fertilizer and drills the seeds

Wet DSR:

• Wet-DSR involves sowing of pregerminated seeds (radicle 1- 3 mm) on or into puddled soil. 
• When pregerminated seeds are sown on the surface of puddled soil, the seed environment is mostly aerobic and this is known as aerobic Wet-DSR. 
• When pregerminated seeds are sown/drilled into puddled soil, the seed environment is mostly anaerobic and this is called as anaerobic Wet-DSR.  
• Wet-DSR under aerobic and anaerobic, seeds can either be broadcasted or sown in-line using a drum seeder81 or an anaerobic seeder with a furrow opener and closer.

Transplanting:

• The other way of establishment is not by sowing seeds but by transplanting seedlings that are grown in nurseries first.
• Transplanting of rice seedlings into puddled fields is widely practiced in Asia, primarily to better control weeds.
• Transplanting requires less seed but much more labor, and the crop takes longer to mature because of the transplanting shock.

Advantages of DSR 

1. Saving in water up to 25% in DSR
2. Saving in energy up to 27% of diesel as pumping energy is saved for field preparation, nursery raising, puddling and reduced frequency of applying irrigation water
3. Saving of labour -35 to 40 man days / ha
4. Enhanced fertilizer use efficiency due to placement of fertilizer in the root zone
5. Early maturity of crops by 7-10 days helps in timely sowing of succeeding crops
6. Reduction in methane emissions and global warming potential
7. Little disturbance to soil structure
8. Enhanced system productivity

Constraints Associated with DSR

Weeds 

• Weeds are the most important constraint to the succeess of  DSR in general and to Dry-DSR in particular.
• The  weeds pose to be more problematic in DSR than in puddled transplanting because :
  • The emerging weeds are more competitive as compared to the simultaneously emerging DSR seedlings and  
  • lack of water layer in Wet- and Dry-DSR make these crops more prone to initial weed infestation which lacks otherwise in case of transplanting

Development of Herbicide Resistance

• The practice of direct seeding on large scale increased herbicide use for weed control in rice, which slowly resulted in the appearance of resistance in weeds against certain herbicides.

Emergence of Weedy Rice

• Weedy rice/red rice has emerged as a serious concern to rice production in areas where direct seeding especially Dry-DSR widely replaces CT-PTR. 
• Weeds in rice are highly efficient and causes severe rice yield losses ranging from 15 to 100 %

Increase in soil-borne pathogens such as nematodes

• Root-knot nematodes pose a severe constraint when shift from PTR to DSR takes place.

Higher emissions of nitrous oxide 

• Although direct seeding can help in reducing CH4 emissions, but aerobic soil conditions can also increase N2O emissions.

Source: BS