Key Technical Points for No-Till Rice Seedling Broadcasting Cultivation

(1) Requirements for Selecting Demonstration Paddy Fields and Rice Varieties
1. Selection of No-Till Paddy Fields
For no-till seedling broadcasting, paddy fields with abundant water sources, convenient irrigation and drainage, level plots, deep topsoil, and good water and fertilizer retention capacity should be selected. Drought-prone fields, shallow poor fields, leaky fields, and sandy fields are not suitable for no-till seedling broadcasting. If the previous crop is rice, the stubble height should be kept as low as possible, generally not exceeding 10 cm, to prevent seedlings from landing on rice stubble and affecting survival. For low-lying fields, mountain valley fields, and cold-waterlogged fields, before chemical weed control, ring ditches and cross ditches should be opened and water drained.
2. Variety (Combination) Selection
No-till seedling broadcasting cultivation generally has no special requirements for varieties (combinations). Based on the characteristics of no-till seedling broadcasting, rice varieties (combinations) with strong tillering ability, well-developed root systems, thick sturdy stems, lodging resistance, and strong stress resistance should be selected. As with conventional tillage seedling broadcasting, attention should be paid to selecting varieties (combinations) with moderate or moderately early growth periods, coordinating maturity schedules, and ensuring safe full heading for the second late rice crop.
(2) Weed Control and Field Management Before Seedling Broadcasting
1. Selection of Chemical Herbicides
For chemical weed control before no-till seedling broadcasting, non-selective herbicides should be chosen. The selected herbicides should preferably have advantages such as being safe, fast-acting, highly effective, low in toxicity, short in residual period, and relatively rain-tolerant. Currently, there are two types of no-till herbicides used in paddy fields: one is systemic herbicides, such as domestic glyphosate, Nongda, Nongminle 747, etc.; the other is contact herbicides, such as paraquat, Gramoxone, etc. Systemic non-selective herbicides have good weed control effects but act slowly; after spraying, the root system is poisoned and dies first, leaves begin to yellow after 3-7 days, and roots, stems, and leaves all die after about 15 days. Contact non-selective herbicides act quickly; on sunny days after spraying, weed stems and leaves begin to wilt within 2 hours, and most above-ground parts of weeds and rice stubble die within 2-3 days, but underground rhizomes, stolons, and some dicotyledonous aquatic weeds cannot be eliminated. Both types of herbicides are safe and highly effective and can be used alone or in combination.
2. Weed Control, Field Management, and Fertilization Before Seedling Broadcasting
(1) Management Before Herbicide Application
Maintain a thin water layer or moist condition one week before spraying to promote weed germination and soil softening; drain water 1-2 days before application.
(2) Herbicide Spraying
Choose sunny days for herbicide spraying when possible. Generally, early rice should be sprayed 9-15 days before seedling broadcasting; late rice should be sprayed on the evening of the day of early rice harvest or the following morning. For green manure fields and fields using glyphosate for chemical weed control, the waiting period should be longer; for ordinary fields using Gramoxone for chemical weed control, the waiting period can be shorter.
For paddy fields with malignant weeds such as cogongrass, cyperus, and alligator weed, Gramoxone can be used for weed control. Method: mix 200-250 mL of 20% Gramoxone per mu with 2-2.5 kg of ammonium bicarbonate or potassium chloride, dilute with 50-60 kg of water, and spray evenly on weed stems and leaves, rice stubble, straw, and green manure. For paddy fields where the previous crop was a winter fallow field with many malignant weeds, glyphosate must be used for weed control. Method: dilute about 1000 mL of 10% glyphosate aqueous solution per mu with 30-50 kg of water and spray; 7 days after application, flood and soak for 2-5 days.
When applying herbicides, note the following: ① The sprayer should have good atomization; the higher the atomization degree, the better the effect. It is strictly prohibited to use a watering can for spraying. ② For early rice no-till fields, Gramoxone or glyphosate herbicides can be used; for late rice no-till fields, Gramoxone is best. ③ Regardless of which herbicide is used, field water must be drained before application to ensure the field surface is dry; otherwise, the non-selective effect cannot be achieved. ④ Herbicides must be mixed with clean water; do not use sewage or muddy water, otherwise the efficacy will be reduced. ⑤ For glyphosate herbicides, if it rains within 4 hours after spraying, the effect will be affected and re-spraying is needed. ⑤ Spraying should be uniform and thorough, with no missed spots.
3. Management and Fertilization After Herbicide Application
(1) Promptly re-flood and soak the paddy field. For no-till early rice fields, re-flood and soak the field for 7-10 days after spraying, 5-7 days after application. For no-till late rice fields, re-flood and soak the field for 2-4 days after spraying, 2-5 days after application. The water depth should be sufficient to submerge crop residues, after which the water layer is allowed to drain naturally (shallow).
(2) Fertilization. For no-till early rice fields where the previous crop is green manure, an appropriate amount of lime can be applied several days after herbicide spraying (30-60 kg of lime per 1000 kg of green manure) to accelerate decomposition. Before re-flooding no-till fields, straw can be returned to the field. The amount of returned straw can reach half of the previous crop's straw. The straw should have essentially no mature rice grains remaining. Returned straw should be evenly placed between rice stubble rows and pressed against the soil; it should not be casually scattered and left suspended on top of rice stubble, otherwise remedial measures should be taken to push and step the straw down to the ground. To accelerate the decomposition of returned straw, 1-2 kg of "Fuganling" (straw decomposer) can be applied per mu.
Base fertilizer should be applied 2-4 days before seedling broadcasting, combined with field soaking. Based on the growth characteristics of no-till paddy fields - nutrient enrichment in the surface soil layer, fewer nutrients in lower layers, slightly slower seedling establishment, shallow root distribution, slightly delayed tillering, slower tillering speed, delayed time to sufficient seedlings, and lower seedling peak - the principle of light base fertilizer application and heavy application of green-restoring fertilizer and tillering fertilizer should be adopted. Base fertilizer should mainly consist of compound fertilizer and phosphate fertilizer, with less ammonium bicarbonate, and no application of undecomposed manure. The nitrogen applied as base fertilizer should account for 25-35% of the total nitrogen applied throughout the growth period. Generally, for fields where Gramoxone was used for weed control, when soaking the field, 25 kg of decomposed organic fertilizer and superphosphate per mu, 20-25 kg of ammonium bicarbonate, or about 25-30 kg of compound fertilizer can be applied as base fertilizer to accelerate the decomposition of rice stubble, straw, and weeds. For fields where glyphosate was used for weed control, the water containing herbicide from soaking should be drained, and fresh shallow water should be added before seedling broadcasting and base fertilizer application.
(3) Minimum Tillage and Supplementary Elimination of Malignant Weeds. Contact non-selective herbicides such as Gramoxone have poor control effects on some weeds. If a small number of malignant weeds are found remaining before seedling broadcasting, manual pulling can be done. For paddy fields where the soil surface is not sufficiently softened and there are a certain number of malignant weeds such as cogongrass, cyperus, and alligator weed, as well as fields where fallen grains have germinated and grown into seedlings, use an iron-toothed harrow to roll and press 1-2 times.
(3) Sowing and Seedling Raising
No-till seedling broadcasting sowing and seedling raising methods are basically the same as those for tillage seedling broadcasting, but the requirements for seedling quality are higher. Use seedling trays with larger apertures of 353 holes or 434 holes, use strong seedling agent for seedling raising, or use special seedling fertilizer for seedling raising, and treat seedlings with paclobutrazol to improve seedling quality, so that after broadcasting, seedlings root early, establish early, and turn green early.
(4) Seedling Broadcasting
1. Seedling Age and Broadcasting Time. Determined based on temperature and seedling age. Within the suitable temperature range, the principle of "late sowing, early broadcasting" is advocated. Appropriate young seedling broadcasting is beneficial for early rooting, fast establishment, early tillering, extending the effective tillering period, and increasing the number of effective panicles. The suitable leaf age for broadcasting is 2.5-3.5 leaves; early rice and second late rice generally should not exceed 4.0 leaves and 4.5 leaves respectively.
Early rice broadcasting should be done on sunny days, avoiding broadcasting on windy and rainy days. Second late rice should be broadcast on cloudy days or after 4 PM on sunny days to facilitate seedling survival.
2. Broadcasting Density. No-till broadcasting density should be determined based on factors such as variety characteristics, seedling quality, soil fertility, fertilization level, broadcasting time, and yield level. Compared with tillage seedling broadcasting, it should generally be increased by about 10%. Early rice should be broadcast at 2.2-2.4 million hills per mu; second late rice at about 2.2 million hills per mu.
3. Water Requirements. For no-till paddy fields where straw is returned, during broadcasting, maintain a water layer that submerges the straw without causing it to float, keeping the straw in a moist state. This ensures water supply for seedling rooting and establishment while promoting straw decomposition. For ordinary no-till paddy fields, during broadcasting, the soil should be in a moist state or only a thin shallow water layer should be maintained.
(5) Field Management
1. Weed Control After Seedling Broadcasting
After seedling broadcasting, manual weeding is not possible, so herbicides that can control all weeds in the paddy field at once and are safe for rice seedlings must be selected, such as Dingbian, Nongdeshi, etc. Try not to use one chemical for a long time, and do not arbitrarily increase the dosage. Herbicides containing acetochlor or metsulfuron-methyl, such as Lecalong, Daocaolong, Daocaowei, etc., are prohibited. For new herbicides, test first before demonstration and application.
For chemical weed control, early rice should be treated 5-7 days after broadcasting, and late rice 4-5 days after broadcasting, combined with the application of green-restoring and tillering fertilizer. Herbicides should not be used before seedling establishment, and should not be applied too late after establishment. Herbicides suitable for seedling broadcasting paddy fields and application methods: per mu, choose 30% Dingbian 100-120 g, or 35% Bencao (also known as Tianqing, Paoyangjing) 20-30 g, or 53% Benxai·Bian 35-40 g, or 50% Kuishabai wettable powder 20-25 g plus 10% Nongdeshi wettable powder 15 g, mix with fine soil or urea and broadcast to control weeds, or spray with water. During application, the paddy field should have a 3-5 cm water layer, and water should be maintained for 5-7 days after application.
2. Scientific Water Management
No-till seedling broadcasting is relatively sensitive to water requirements. In water management, the principles of frequent shallow irrigation, more exposure, and light drying should be mastered. After broadcasting, use shallow water for seedling establishment and tillering (absolutely avoid deep water during early tillering). After applying (pre-emergence) herbicides, maintain a water layer for several days, replenishing when water is lacking. When 75% of sufficient seedlings are reached, implement field exposure and drying. After the young panicle differentiation stage, maintain moisture; during heading and flowering, maintain a shallow water layer. During grain filling and maturation, maintain moist soil conditions, preventing premature water cutoff to improve seed-setting rate and 1000-grain weight.
3. Scientific Topdressing: Nitrogen applied during the green-restoring stage accounts for 20% of total nitrogen applied throughout the growth period; apply 4-5 days after early rice broadcasting and 3-4 days after late rice broadcasting. Nitrogen applied during the tillering stage accounts for 25% of total nitrogen; apply 10-12 days after early rice broadcasting and 7-8 days after late rice broadcasting. At the sufficient seedling stage, 20-23 days after early rice broadcasting and 15-18 days after late rice broadcasting, or when the number of hybrid rice seedlings per mu reaches 130,000 or conventional rice reaches 220,000, if rice seedlings are yellow and weak, a small amount of supplementary fertilizer can be applied. At the early stage of young panicle differentiation, carry out field exposure and drying to fade leaf color; before irrigating when the second-to-last leaf emerges, promptly apply panicle fertilizer at 15-20% of total nitrogen. If leaf color fading is not obvious or light conditions are poor, delay or apply in reduced split doses. In the later stage, appropriately apply grain-filling fertilizer at the full heading stage at 5-10% of total nitrogen to prevent premature aging. After the full heading stage, carry out one foliar topdressing.
4. Pest and Disease Control: To reduce insect sources in no-till paddy fields with straw return, timely apply non-selective herbicides to kill weeds and stubble, and promptly re-flood and soak the field to kill borer pupae and reduce insect sources. The control of other major pests and diseases such as rice planthopper, rice leaf roller, sheath blight, rice blast, bacterial leaf blight, and bacterial leaf streak is largely similar to that for tillage seedling broadcasting, but field observation and forecasting should be done well, and timely pest and disease control should be carried out.