In this article we will discuss about:- 1. Introduction to System of Rice Intensification 2. Raising Nursery of System of Rice Intensification 3. Important Steps 4. Benefits.
Introduction to System of Rice Intensification (SRI):
The resource conservation technology for rice cultivation was evolved by Fr. Henrie Laulanie at Madagascar during 1983. He migrated from France in 1961 and settled at Madagascar to practice and profess agriculture. In this system, young seedlings (8-10 days old) are transplanted at optimal spacing and the crop is aerobically grown during vegetative phase.
The economy in water has led to its wider adaptation by farmers. Research experiments have shown that SRI gave higher yields than transplant crop in many parts of India. The SRI also proved better in clay loams than sandy loam, clay or silty loam soils.
The increase in yield with SRI has been attributed to more panicles/m2 and greater panicle weight. It also economizes up to 50% of water for rice cultivation. In fact rice is not an aquatic plant. It can only survive in water but does not thrive well under hypoxic conditions. Under continuous inundation, rice plant spends lot of energy to develop air pockets (aerenchyma tissue) as survival mechanism. Under SRI, paddy fields are not flooded but only kept moist by alternate wetting and drying.
Raising Nursery of System of Rice Intensification (SRI):
i. Preparation of Nursery Area:
Prepare 100 m2 nurseries to plant 1 ha. Select a level field near the water source. Spread a plastic sheet or used polythene gunny bags on the shallow raised bed to prevent roots growing deep into soil.
ii. Preparation of Soil Mixture:
Four (4.0) m3 of soil mix is needed for each 100 m2 of nursery. Mix 70% soil + 20% well-decomposed press mud/bio-gas slurry/FYM + 10% rice hull. Incorporate in the soil mixture 1.5 kg of powdered di -ammonium phosphate (DAP) or 2 kg 17-17-17 NPK fertilizer.
iii. Filling in Soil Mixture:
Place a wooden frame of 0.5 m long, 1 m wide and 4 cm deep divided into 4 equal segments on the plastic sheet or banana leaves. Fill the frame almost to the top with the soil mixture.
iv. About 9-10 kg seed/ha is sufficient. Pre-germinating the seeds 2 days before sowing: Soak the seeds for 24 h, drain and incubate the soaked seeds for 24 h, sow when the seeds sprout and radical (seed root) grows to 2-3 mm long.
v. Sowing:
Sow the pre-germinated seeds weighing 90 -100 g/m-2 (100g dry seed may weigh 130g after sprouting) uniformly and cover them with dry soil to a thickness of 5mm. Sprinkle water immediately using rose can to soak the bed and remove the wooden frame and continue the process until the required area is completed.
vi. Watering:
Water the nursery with rose can as and when needed (twice or thrice a day) to keep the soil moist. Protect the nursery from heavy rains for the first 5 DAS. At 6 DAS, maintain thin film of water all around the seedling mats. Drain the water 2 days before removing the seedling mats for transplanting.
vii. Spraying Fertilizer Solution (Optional):
If seedling growth is slow, sprinkle 0.5% urea + 0.5% zinc sulfate solution at 8-10 DAS.
Important Steps of System of Rice Intensification (SRI):
1. Early Transplanting:
About 10 to 12 days an old seedling with just two leaves needs to be transplanted. This ensures more tillers and more root growth. While 30 tillers per plant are fairly easy to achieve, 50 tillers per plant are quite attainable.
2. Pulling Out Seedlings from the Nursery:
Take an Iron sheet of sufficient thickness. Push through this sheet into the nursery bed beneath the plants about 3 inches down from the surface. Then lift the sheet gently with some of the mud. Carry seedlings with the soil to the main field. With your right thumb and forefinger, take plant by plant along with soil and place the plant along with mud and roots gently at the intersection of grid lines made for the purpose to plant at wider spacing in a square pattern.
3. Main Field Preparation for Transplanting:
Plough and puddle the field in a similar way as is done for conventional method of transplanting. At every two-meter interval make 30 cm wide channels. To make channels, place sticks at appropriate intervals (i.e. 2 m, 30 cm) along the edge of the field and stretch tine rope between them. Hold two ropes, at 30 cm apart. Remove the soil within the two ropes and spread it on the adjacent beds thereby a channel is made.
Level the field thoroughly. Then take a “rake” that has teeth at 25cm apart which can be constructed simply from wood. It is pulled across the surface of the prepared muddy field, marking lines on the surface at 25 cm intervals.
Drawing the rake across the first set of lines perpendicularly (at a right angle) to them creates the desired square pattern on which seedlings are planted at the intersections of lines. In traditional method, a thin film of water is maintained at transplanting. But in SRI, there should not be standing water at the time of transplanting. Sixteen plants are transplanted per Sq.m in this method as against 33 hills per sq. m conventional method.
4. Careful Transplanting:
It is important to avoid ‘shock’ or ‘trauma’ while transplanting the seedlings. Remove seedlings from nursery with seed, soil and roots intact carefully and plant it in the field without plunging too deep into the soil. The seed should be attached to the seedlings and transplanted as soon as possible after being removed from the nursery – within half an hour and preferably within 15 minutes to avoid desiccation and traumatization of the plant.
Care is to be taken to ensure that when the seedlings are transplanted that their root tips are not inverted as usually happened during the hurried, rough transplanting done in the conventional method. If the root tip was turned upward – shaped like a J, rather than an L it could take a week or more for the tip to reorient itself downward and resume growth. Hence, do not thrust seedlings downward into the soil.
Rather, each seedling is slipped into the soil very ‘gently’ and close to the surface, so that its root lies horizontally in the moist soil. This makes the shape of the transplanted seedling more like ‘L’ than like ‘J’ and facilitates root growing quickly downward. Only single seedling is to be planted at the intersection rather than in clumps of 2 or 3 or more.
5. Wider Spacing:
Rice plants can better realize their potential for tiller and root growth and for subsequent grain filling, if spaced widely rather than densely. Seedlings are to be planted in a square method at 25 x 25 cm spacing. Leaving wide space between each plant ensures that roots have adequate room to grow and the plants will be exposed to more sunlight, air and nutrients. This result in more root growth and profuse tillering. The square pattern also facilitates weeding in both directions. This means that individual plants got more room to spread.
6. Weeding and Aeration:
As there is no standing water in rice fields under SRI method, weed growth is very high. Use simple mechanical rotary weeder (Cono weeder) to churn the soil for weed control. Rotate the weeder at least 2 to 4 times in order to incorporate the weeds into the soil. The first weeding should be done at 10-12 days after transplanting to eliminate the newly germinated weeds.
Subsequent weeding is done at 10 days interval. Rotary weeding helps in greater aeration which results in more root growth, reduced weed competition. Weeds incorporated into the soil may add about 1 ton green manure per hectare per weeding and encourage the diverse microbial population in the soil. Herbicides are not recommended under SRI method.
7. Water Management:
Rice has traditionally been grown under standing water continuously. However, standing water creates hypoxic soil conditions. Under such conditions three-fourths of rice root system gets degenerated by the time of flowering. Water is not allowed to stagnate under SRI method which sustains large and intact root system throughout the growth and reproductive stages of rice plant.
Regular irrigation is provided, just to keep the soil moist. Alternate ‘wetting and drying’ is allowed, which give aerobic and anaerobic soil conditions for better nutrient mobilization by soil biota. This avoids root degeneration, which usually happens under continuous flooding.
Un-flooded conditions, combined with mechanical weeding, result in more air in the soil and greater root growth. Higher root growth provides access to more nutrients. Irrigate the field on the previous evening before the periodic wetting. Drain out water in the morning to facilitate rotary weeder operation. To produce 1 kg grain 2,710 liters of water was needed through this novel approach (SRI) in contrast to the 3,720 liters through the conventional method.
8. Manuring:
Instead of chemical fertilizers, FYM or compost is applied @ 10t/ha which is quite sufficient as a source of nutrients. As a result, more plant growth is achieved because of better soil health and more balanced nutrient supply. Apply diverse organic manures. Organic manures act as food for microorganisms.
9. Pest and Disease Control:
Pest and disease problems appear to be less with SRI method, perhaps healthier and vigorous plants have more capacity to resist pest and disease attacks. It was observed that, sheath blight and BPH incidence is low under SRI method.
Benefits of System of Rice Intensification (SRI):
i. Higher grain and straw yields and reduction in duration by about 10-15 days.
ii. Lesser use of chemicals and low water requirement (about ½ of conventional method)
iii. Higher head rice recovery, more seed weight and less chaffy grain.
iv. Soil health improves through biological activity.
v. The SRI technique is also eco-friendly as the fields are not flooded but kept moist ‘methane’ the major green-house gas is not produced.