Introduction
Paddy (Oryza Sativa) is associated with wet, humid climate. It is best suited to regions which have high humidity, prolonged sunshine and an assured supply of water. Perennial wild rice still grows in Assam and Nepal. In India, paddy cultivation extends from 8 to35ºN latitude and the average temperature required throughout the life period of the crop ranges from 21 to 37ºC.
To enhance resource use efficiency and improve yields, two new technologies for paddy cultivation are designed: System of Rice Intensification (SRI) and Direct Seeded Rice (DSR).
Monsoons 2021
As monsoon rains are approaching in India, and majority of farmers are busy in preparing their fields for Kharif plantation. Thus, it becomes very essential to introduce more profitable and resource-efficient technologies like Direct Seeded Rice (DSR) and System of Rice Intensification (SRI) to farmers, so that they can improve their livelihood conditions.
Direct Seeded Rice (DSR) Technology
(Source: Bista B, 2018)
In recent years, there is a shift to DSR technology mainly due to labour problems, high input costs and water scarcity issues associated with transplanted rice. But, still only 23% of rice is under DSR, globally.
Direct seeding of rice is the process of growing rice crop by sowing of seeds in the field rather than by transplanting seedlings from the nursery. Once germination and seedling establishment are complete, the crop can then be sequentially flooded and water regimes maintained as for transplanted rice.
Alternatively, the crop can remain rainfed, the upper surface soil layers fluctuating from aerobic to non-aerobic conditions.
Unlike conventionally tilled transplanted rice; puddling, transplanting and standing water are outside the realm of direct seeded rice.
Environmental benefits
Flooded rice culture with puddling and transplanting are the major sources of methane emissions in the rice fields attributed to anaerobic soil condition due to prolonged flooding. This accounts 10-20% of the total annual methane emissions globally.
Prolonged flooding leads to anaerobic conditions in soil and creating a favourable environment for methanogenic bacteria.
DSR has an immense potential to reduce methane emission through various management practices such as reducing the number of irrigations, multiple drainage system during the crop cycle, alternate wetting and drying, Azolla application, semi-dry cultivation, arbuscular mycorrhiza and methanotrophs application.
Methods of DSR
Basically, there are three principal methods of establishing direct seeded rice (DSR):
1. Dry-seeding - sowing dry seeds in dry soil,
2. Wet-seeding - sowing pre-germinated seeds on wet soils
3. Water seeding - seeds sown in standing water
|
Direct-Seeding method |
Depth of Seeding |
Seeding method/ pattern |
Rice ecology |
|
A. Dry Seeding |
|||
|
Conventionally tilled, broadcast rice |
Surface or 0-3 cm |
Broadcasting/ random |
Mostly rainfed upland and flood-prone, some rainfed lowland |
|
Conventionally tilled (dry), dibbled rice |
1-3 cm |
Dibbling/ rows |
Mostly rainfed upland and flood-prone, some rainfed lowland |
|
Conventionally tilled (dry), drill-seeded rice |
2-3 cm |
Drilling/ rows |
Irrigated and favourable rainfed lowland |
|
Reduced tillage (dry), drill seeded with a power-tiller operated seeder |
2-3 cm |
Drilling/ rows |
Irrigated and favourable rainfed lowland |
|
B. Wet-seeding |
|||
|
Conventionally tilled (wet) broadcast rice on surface of puddle soil |
Surface |
Broadcasting |
Irrigated and favourable rainfed lowland |
|
Conventionally tilled (wet) drum-sown rice on surface of puddle rice |
surface |
Line sowing |
Irrigated and favourable rainfed lowland |
|
Conventionally tilled (Wet) drill seeded rice using anaerobic seeder |
0.5-1 cm |
Drilling/ rows |
Irrigated and favourable rainfed lowland |
|
C. Water Seeding |
|||
|
Water seeding after dry tillage |
Standing water of 15 cm |
Broadcasting |
Irrigated lowland |
|
Water seeding after wet tillage |
Standing water of 5-10 cm |
Broadcasting |
Irrigated lowland |
Major constraint in DSR
Direct-seeded rice (DSR) with appropriate conservation measures and variety has proved to offer similar and comparable yields as that of Transplanted rice.
Weeds are the major constraint in DSR fields contributing to higher yield losses and sometimes complete crop failure. So integrated weed management options are to be discussed and conclusions should be drawn for successful DSR cultivation.
System of Rice Intensification (SRI)
(Source: FAO)
SRI is an agro-ecological methodology for increasing the productivity of irrigated rice by changing the management of plants, soil, water and nutrients, with an aim to promote the growth of root system, abundance and diversity of soil organisms and more outputs from less inputs.
SRI management –
1. Transplant young seedlings, certainly less than 15 days old to preserve subsequent growth potential
2. Transplant seedlings singly, one per hill, and in a square pattern 25x25 cm, or wider. Transplant quickly (15 – 30 minutes after removal from nursery), shallow (1-2 cm deep)
3. Keep paddy soil moist, but not continuously saturated, so that mostly aerobic soil conditions prevail
4. Control weeds with frequent weeding by a mechanical hand weeder (rotating hoe or cono weeder) that also aerates the soil
5. Apply as much organic matter to the soil as possible
Conclusion
System of Rice Intensification aims at providing paddy plants such conditions so that they can grow to their full potential. The increase in yield and profits is mainly due to improved soil biota, reduced competition among plants and efficient use of resources.
Reference
Bista B. 2018. Direct Seeded Rice: A New Technology for Enhanced Resource Use Efficiency. International Journal of Applied Sciences and Biotechnology6(3):181-198.
Image source: Google
