When is the rice tillering stage? Detailed explanation of duration, fertilization and management measures
Tillering is an inherent physiological characteristic of rice. Rice tillering is essentially the branching of the rice stem. The timing of tillering and the height of the node position both have a significant effect on the growth and development of tillers and whether they produce panicles. So when is the rice tillering stage? How long does it last? How should it be managed?
Timing of rice tillering
From transplanting to young panicle differentiation, rice goes through the tillering stage. This process takes about 30 days (it varies depending on variety, planting period and seedling-raising method), and most fields begin to enter the tillering stage in June. The tillering stage can be further divided into the reviving stage (for transplanted rice), the effective tillering stage and the ineffective tillering stage.
Reviving stage: transplanted seedlings suffer damage during seedling pulling, transport and transplanting, which is called transplanting injury. Therefore, after transplanting, the seedlings need a period of time to recover, turn green again and grow new roots; this period is called the reviving stage. The length of the reviving stage is related to the extent of transplanting injury: when the injury is small the reviving stage is short, and when the injury is large the reviving stage is long. Generally, seedlings can revive 5-7 days after transplanting. Early rice transplanted on clear, warm days and late rice transplanted on cool, shady days revive easily; seedlings transplanted with soil attached revive earlier than those pulled bare-root, and some soil-attached seedlings have no reviving stage at all (that is, they do not turn yellow after transplanting).
Effective tillering stage: after reviving, if conditions are suitable, new shoots emerge from the axillary buds in the leaf axils at the base of the false stem; this is called tillering. When 10% of the plants in the whole field have produced tillers, it is the beginning of tillering; when 50% of the plants have produced tillers, it is the peak tillering stage; when 80% of the plants have stopped tillering, it is the end of tillering. When the number of tiller stems equals the number of panicles produced by tillers, it is called the effective tillering stage. Under normal conditions, tillers produced within about 10 days after tillering begins mostly produce panicles.
Ineffective tillering stage: generally, tillers that appear more than 20-25 days after transplanting mostly stop growing midway and cannot produce panicles; they effectively waste nutrients, so they are called ineffective tillers. This period is called the ineffective tillering stage. Therefore, in cultivation, effective measures should be taken before the end of the effective tillering stage, that is, within 20 days after transplanting, to promote early and abundant tillering; after the end of effective tillering, ineffective tillering should be controlled. Only in this way can rice have more and larger panicles, reduce shading in the field, and achieve stable and high yields.
Management measures for the rice tillering stage
1. Apply tillering fertilizer early
Apply 30% of the total nitrogen fertilizer immediately after rice revives or promptly 3-4 days after transplanting. The tillering fertilizer is applied in two rounds: the first round applies 80% of the total tillering fertilizer over the whole field, and the remaining 20% is applied at the 6-leaf stage of 11-leaf varieties by inspecting the field and applying it wherever plants are yellow or weak. While keeping the total fertilizer amount unchanged, 3-4 kg of ammonium sulfate may be applied as tillering fertilizer. If tillering fertilizer is applied too late, a large number of ineffective tillers will increase and the field will close in too early. Excessive nitrogen fertilizer at the peak tillering stage causes the basal internodes of rice to become too long, reducing lodging resistance.
2. Shallow-water irrigation
After rice revives and establishes, irrigate with shallow water to a depth of 3-5 cm. At the beginning and peak of tillering, high-fertility fields should use intensive intermittent irrigation, and medium-fertility fields should use light intermittent irrigation; alternatively, depending on seedling conditions, shallow irrigation can be used at the beginning of tillering and intermittent irrigation at the peak of tillering. Shallow-moist irrigation during the tillering stage can enlarge the oxidized layer, increase nitrogen-fixing bacteria, organic phosphorus bacteria and cellulose-decomposing bacteria, promote the decomposition of organic fertilizer and the release of nutrients, and improve the nutritional conditions of rice. The combined effect is to promote early and abundant tillering and increase the effective tillering rate.
3. Pest and disease prevention
Follow the principles of prevention first and integrated control, with emphasis on “early” action; in particular, control rice blast in a timely manner according to the leaf-age progress of the rice field.
1. Rice leaf miner: at the early larval stage, use 70% (imidacloprid) water-dispersible granules at 4-6 g/mu; or 25% (thiamethoxam) water-dispersible granules at 6-8 g/mu; or 40% dimethoate at 100 mL/mu, mixed with 5 L of water and sprayed on stems and leaves with a mist sprayer.
2. Rice leaf beetle: when larval damage shows a worsening trend, use 2.5% deltamethrin emulsifiable concentrate at 15-30 mL/mu, or 2.5% cyhalothrin (Kung Fu) emulsifiable concentrate at 30 mL/mu, mixed with 5 L of water and sprayed with a mist sprayer for control.
3. Leaf blast: when fungal spores are found in the field and leaf blast lesions appear on leaves, use 40% tricyclazole at 40-50 mL/mu, or 20% tricyclazole at 100 mL/mu, or 75% tricyclazole at 20-30 mL/mu, mixed with 5 L of water and sprayed on stems and leaves with a mist sprayer, or controlled by aerial spraying.
How to manage rice in the late tillering stage
The low temperatures in 2018 caused a general shortage of rice tillering, with 1 fewer tiller than in normal years. Now, at the end of June, rice has successively entered the late tillering stage and is at the 7.1-7.5 leaf stage. There is still 1-2 tillers that can be gained, namely the tiller emerging at the same time as the 8th leaf and the secondary tiller from the 2nd leaf. Around July 10, rice enters the beginning of jointing and booting. This platform reminds farmers that the following points must be grasped in rice management:
1. Promote tillering: adopt the method of shallow water to promote tillering, maintaining a water layer of 2-3 cm; do not use deep water and do not dry the field heavily. If there are bubbles, off-odors, black roots, gray roots in the field, or roots extending upward, indicating oxygen deficiency or excessively high concentrations of toxic gases, drain the water and air the field, that is, leave no water on the mud surface while there is water in the foot holes; after oxygenating and strengthening the roots, promptly add fresh water. Shallow water can balance the day-night temperature difference, raise mud temperature, and promote the growth of tiller buds.
2. Fertilization: when rice enters the 8-leaf stage, it is time to apply regulating fertilizer, but note that the amount applied at the 8-leaf stage should account for only about 10% of the total nitrogen fertilizer applied during the whole growth period, and should not be too much; otherwise the fertilizer effect will be expressed at the 10-leaf stage, which is the stage of rice spikelet differentiation and jointing, and will cause elongation of the first basal internode and easy lodging. If the field is uneven, with uneven green and yellow areas, or if there is nutrient deficiency, supplement nitrogen fertilizer promptly to prevent nutrient deficiency from affecting tillering or causing uneven field growth. Ammonium sulfate is recommended, at 50-60 kg per hectare. When fertilizing, observe the field growth: do not topdress where the color is deep and dark, and appropriately regulate yellow, sparse, thin and short areas.
If the seedlings are weak, at the late tillering stage a foliar fertilizer specifically for rice from Israel, Nuopufeng, can be sprayed once, which has a relatively good effect on improving seedling quality, strengthening seedlings and capturing accumulated temperature in rice.
3. Water layer: at the 8-leaf stage, the field should be sun-dried to control tillering. For plots with insufficient tillering, it is recommended to delay sun-drying the field and use shallow water to promote tillering; wait until after June 25, when the field reaches 600 plants per square meter, before sun-drying. If there is an off-odor or bubbling or other oxygen-deficient conditions, the field can be aired to oxygenate and strengthen the roots and restore root vitality. If there are enough tillers, sun-dry the field in a timely manner, and do so before jointing; the standard for sun-drying is to add fresh water only when the surface has slight cracks. After jointing, use the “shallow-moist-dry” irrigation method to ensure the roots do not lack oxygen. July 10-20 is the rice meiosis stage; when low temperatures below 17 degrees occur, deep water should be added to protect the seedlings. It is recommended to add water when nighttime temperatures are low, or to let water stand in a sunning pond and warm up before entering the field.
4. Weed control: for plots with many weeds in the field, it is recommended to use stem and leaf treatment, mainly with bentazone; during the tillering stage, try not to use MCPA to prevent phytotoxicity. For barnyardgrass, cyhalofop-butyl can be used for control. Rice is sensitive to chemicals during the tillering stage, so herbicides with high safety should be selected for weed control.
5. Disease prevention: in plots with large fertilizer amounts and high density, long-term flooding can cause oxygen deficiency in the rice root system, resulting in few roots, weak growth, and low resistance to disease and lodging, making plants prone to sheath blight, rice blast and other diseases. Sheath blight is an important factor causing lodging and yield reduction.
Control method: the “shallow-moist-dry” irrigation method must be adhered to, that is, the previous water is not seen when the next water is added. Each time, add fresh water only after the field surface has drained dry to the point of slight cracking. Only in this way can toxic gases be discharged, root vitality be restored, and resistance to disease and lodging be improved.
The next step is the rational use of chemicals; under the shallow-moist-dry condition, the root system must be restored before applying chemicals, otherwise the efficacy will not be high. It is recommended to use chemicals with a good reputation on the market, strictly follow the instructions, and when applying, first prepare a mother solution and then dilute it with water for spraying.