Water-saving irrigation techniques for rice

(Baonghean) - In our country, the traditional irrigation practices (flooding, watering many times/crop) of farmers have been maintained for generations but have not been very effective, and water has been wasted at some stages. To overcome this waste, based on the physiological characteristics and water needs of rice plants at each growth stage, water-saving irrigation solutions for rice are being gradually applied to production.

In zone 4, due to harsh weather, prolonged heat and drought, the scarcity of fresh water, especially water for rice irrigation, has occurred frequently. Therefore, scientific and economical water irrigation for rice is more urgent. Here is an introduction to the water-saving irrigation technique for rice "Alternating wet and dry - shallow drying" of the International Rice Research Institute (IRRI) as follows:

During the first week after sowing, keep the water level in the field from saturation to about 1cm high. The water level in the field will be kept about 1-3cm high according to the growth stage of the rice plant and maintained continuously until fertilizing to promote tillering (about 20-25 days after sowing), at this stage water is an essential need for rice to grow. Keeping water in the field at this stage limits the germination of weeds (water makes the environment anaerobic, weed seeds will not be able to grow). It is necessary to use appropriate post-emergence herbicides to spray to control weeds during this stage.

Rice with brown planthopper burn in the control field (watered according to farmers' tradition).

The period from 25-40 days after sowing (maybe 35-45 days depending on the season and the growth period of the rice) is the period when the rice tillers are most active and maximum, most of the ineffective shoots (branches) usually develop during this period so only enough water is needed. Keep the water level in the field from ground level to 15cm below ground level (place a plastic pipe with holes on the side, with 5cm markings inside for monitoring). When the water level drops below the 15cm mark, pump water in to cover a maximum of 5cm above the ground level of the field. When the water level slowly drops below the 15cm mark, pump more water in. This method of water regulation will expose the field surface, so it is called "alternating wet and dry" irrigation, in many places it is called "nong lo sua".

Place a perforated plastic tube on the side with 5cm markings inside for monitoring.

At the stage of rice growing 25-40 days (maybe 45-55 days depending on the season and growth period of rice), the rice leaves develop close to the canopy, and germinating grass seeds do not develop and compete with the rice plants. This is also the stage when rice plants are very susceptible to sheath blight disease. The low water level prevents the sheath blight fungus from spreading in the field, and the disease is less likely to spread.

Rice stage 40-45 days after sowing (can be 55-65 days depending on the season and growth period of rice), this is the stage of fertilizing to promote panicle formation or initial mass fertilization). At this time, it is necessary to pump water about 1-3cm before fertilizing to avoid light decomposition and fertilizer evaporation, especially nitrogen fertilizer.

The rice stage is from 70-80 days after sowing (can be 80-95 days depending on the season and growth period of the rice), this is the stage when the rice blooms, so it is necessary to keep the water level in the field 3-5cm high continuously for about 10 days to have enough water for the rice to bloom and pollinate easily, the rice grains are not empty or half-filled.

From the milk stage, the rice grains are firm and gradually ripe, so it is only necessary to keep the water level from ground level to 15cm below ground level (when necessary, pump in more water). Note that the water must be "tightened" 10 days before harvesting so that the field surface is dry, making it easy to apply with a harvester.

Nguyen Tuan Loc

(Plant Protection Center Region 4)