Dr N Khumdemo Ezung
Senior Scientist & Head (i/c) KVK (ICAR), Kiphire
SRI was developed in Madagascar by Fr. Henri de Laulanié, S.J., who between 1961 and 1995 worked with Malagasy farmers and colleagues to improve the possibilities of rice production in this country. It is now being studied and evaluated by scientists and rice growers in other countries. SRI begins with a philosophy that rice plants are to be respected and supported as living creatures that have great potential. This potential will only be realized if we provide plants with the best conditions for their growth. This new system of rice intensification changes these traditional practices to bring out of the rice plant significant possibilities for increasing production. Neither new seeds nor chemical fertilizer is necessary for farmers to get much increased yields. The increases can be very great as rice plants grown with SRI methods have a very different structure than usual, with several times more tillers and much larger root systems that can absorb more nutrients from the soil.
THE BASIC IDEAS
The system of rice intensification has discovered and demonstrated some important methods for helping rice plants to achieve their real potential. This potential has been obscured by previous practices. We begin by presenting the ideas on which SRI is based.
For rice plants to be more productive, they need to have:
• More tillers per plant,
• More fertile tillers (panicles) which form from the tillers that a plant puts out,
• More grains per fertile tiller, and
• Larger grains.
If rice plants are spread out and not planted very close together, they have more room to grow. They will get more sunshine and air and can produce more tillers. More of these tillers will become fertile and produce grains of rice. With more space in which to grow, rice plants’ roots become larger and are better able to draw nutrients from the soil. This enables rice plants to produce more grains, which is the reason for growing rice.
Although it may be surprising, it is possible to get many more grains of rice from a field by planting fewer plants and by putting them farther apart, so that each plant is healthier and more vigorous in its growth. That “less” can be “more” seems strange, but it is true. For the plant to grow successfully above ground, it needs a healthy and vigorous root system below ground. The “trick” of SRI is to have both a larger root system for each plant below ground and more growth of tillers, leaves and grains above ground. Planting rice plants densely and close together wastes seeds. The individual plants will be smaller and less productive. Having more rice plants is not as beneficial as having fewer plants that are very productive. Transplanting older seedlings also wastes potential.
Preparing the Nursery and Starting Seedlings
The nursery for growing seedlings not be regarded as a miniature field — to be kept flooded — but rather it should be treated like a garden, where the soil is kept moist but not saturated. Watering by hand is sufficient if there is not enough rainfall to maintain moisture in the soil and for the seedlings. With SRI, the nursery is quite small. It can be only a small fraction of the size of the field to be planted. The following steps are recommended for a modified “dry bed” method of nursery development for SRI seedlings.
• Rice seeds should first be soaked in warm water for 24 hours. Any that are irregular or float should be discarded.
• Next, put the seeds in a sack/polythene for another 24 hours for slow warming of the seeds.
• The seedbed should be prepared as closely as possible to the field that will be planted, so as to minimize transport time between seedlings’ removal from the seedbed and their transplanting in the field.
• Compost should be mixed into the soil of the seedbed at a rate of 100 kg per acre (10 m x 10 m).
• Broadcast the pre-germinated seeds onto the bed at a rate of about 200 grams for every 3 square meters, and then cover the seeds with a fine layer of soil.
• Water the seedbed every day in the late afternoon, or as often as needed to maintain a moderate level of soil moisture. The soil should not be saturated or kept continuously wet. If there has been rain during the day, no watering may be needed.
• Transplanting should be done when the seedlings have just two leaves and before they have more. This usually occurs between 8 and 15 days.
The land preparation does not require special steps, though the soil should be well worked as it would be to get the best results from any method for growing rice.
Make sure that there are adequate drainage canals either through the center of the field or along the edges of the field to ensure proper water control. With SRI, one does not want to have standing water in the field or saturated soil. In general, we have found that compost is quite sufficient as a source of nutrients. SRI does not require any special preparation, only good normal preparation for having best results. Having cattle trample the soil when it has been puddled both breaks up clods and forces air into the soil for later plant use. Leveling the field is important but need not be as precise as when one is trying to maintain a uniform layer of water on the field. It is more important to ensure that the soil can be well drained, by constructing channels or furrows around sections within the field and around the whole field.
Taking Seedlings from the Nursery
Seedlings should be lifted out of the seedbed gently and WITH A TROWEL, rather than being pulled up. It is important that the seed sac remain attached to the infant root. Seedlings should be removed from the seedbed as one would cut sod for landscaping purposes.
The sod cutting should then be moistened, and a single seedling (with two leaves) should be gently removed from the cutting with the thumb and forefinger. When transplanting the seedling, the root should LIE HORIZONTALLY, so that the plant’s shape (including the root) is like the letter L, with the root tip able to grow downward easily and quickly. Planting the seedling with a vertical motion, plunging it into the soil in a downward movement, is liable to leave the root tip inverted upwards. This will delay the root’s resumption of downward growth, a delay that must be avoided if the plant is to reach its full tillering potential. Seedlings should always be transplanted from the nursery into the field within half an hour, and preferably within 15 minutes. The roots should never be allowed to dry out. They should also not be handled roughly or slammed or hit with the palm of the hand. Bamboo splits or banana sheaths can also be used for growing the nursery which enables in carrying the nursery to the main field.
To plant in a uniform square pattern, with regular spacing, one method is to use lines (strings or ropes) tied between sticks on the edge of the field, spaced 25 cm apart. The lines should be marked (or knotted) at similar intervals to match the width of the rows so that there will be uniform spacing that facilitates weeding or one can use a specially constructed simple “rake” that has teeth spaced the desired distance apart.
Spacing is a variable to be tested and evaluated. It is usually best to start with 25 x 25 cm spacing, possibly increasing the distance between plants as farmers’ gain skill and confidence, and as soil fertility is enhanced by compost. An alternative is to use a special rake to score the surface of the field in a “grid” with a square pattern for planting seedlings at the intersections of the lines. Farmers find that this can be a faster method than using strings or ropes. Plants should not be washed, or wrapped, or shaken. They should be handled carefully and gently. There are two important points: first, reduce as much as possible the period of time between removal of the seedlings from the nursery and their planting in the rice paddy, and second, place the plant correctly so that it can grow in the most natural position.
The importance of keeping the soil unsaturated to get more air to plant roots is evident. But how long can a field be left without water? How dry can they become? What is the role of rainfall in providing water for field? What differences in practice will be necessary with different kinds of soil? The addition of water should occur on or about a week after transplanting, and then the first weeding (using the rotary hoe) should be done after soil is sufficiently moist, within the first 10 days. If there is intermittent rain, sufficient to keep the soil moist, no water additions are needed. The best time to add water is before the periodic weeding. During the growth phase, roughly the first three months, water should be applied only to the fields for weeding purposes, being left to dry out even to the point of surface cracking. This drying should be done at least 3 or 4 times before the phase of flowering and panicle initiation.
Weeding is done by using rotary weeder. This results in getting best effect for both weed removal and for soil aeration. The practice of planting seedlings in a square pattern (25 by 25 cm or wider) permits weeding in both directions, up and down rows and across them. This should be done until the growth of plants’ canopy makes it difficult to pass the weeder between them.
Pest and Disease Control
Pest and disease problems appear to be less with SRI methods, perhaps because the fields are kept less humid. It is known that healthier, more vigorous plants have more capacity to resist pest and disease attacks. However, pest monitoring activities should be undertaken regularly and preventive and curative measures be adopted for the same.
Management after Flowering
SRI focuses most of its efforts on getting the rice plants well established in the soil and on encouraging their active increase of roots and tillers during the vegetative growth stage. The water management strategy changes once flowering begins, with a thin layer of water (1-2 cm) being maintained continuously on the field, though there can be some interruptions in this. It is recommended that farmers drain their fields about 25 days before harvesting, to let the soil dry out and encouraging the plant to transfer as much of its nutrient supply to the grains as possible.
SRI rice is harvested just like any other rice, except there should be much more rice to harvest. This makes the farmer’s task more difficult, but this is the kind of difficulty everyone should wish for: a bountiful harvest. Some farmers find that the way rice grows with SRI management makes harvesting easier. For one thing, there is almost never any lodging, even with larger panicles. Also, the panicles are easier to collect off the plants.
On Farm Trial on SRI with variety RCM-5 was conducted at Longsachung village during moisture deficit kharif season of 2009 under Wokha District to assess the potential of the technology in the district, the result of which is depicted in Table-1. As such, observation was recorded between SRI (RCM-5) and Existing Farmers practice with local variety. It was observed that the average number of fertile grains per panicle with SRI was 225 as compared with farmers practice which was 138 nos. The number of effective tillers per hill under SRI was 26 nos. as compared with farmers practice which was observed to be 6 nos. It was observed that the average yield under SRI method was 46.42 q/ha as compared with farmers practice which was 21.42 q/ha. This result indicates the potentiality/suitability of the technology in the district giving higher yield (46.42 q/ha) compared with the existing farmers practice (21.42 q/ha) and hence it is recommended to conduct extensive training and demonstration programmes before taking up on a large scale.
Table-1 : Average observation from SRI and Farmers practice under farmers field trial conducted at Longsachung Village, Wokha District