Tutorial and Requirements for the Latest Rice Transplanting Techniques

The key points of rice transplanting techniques can be summarized as: suitable water depth, field surface hardness, three treatments before transplanting, optimal transplanting depth, age-appropriate strong seedlings, rational close planting, scientific irrigation, early application of tillering fertilizer, timely pest control, timely early transplanting, full and tight transplanting, and transplanting in sequence.

1. Suitable water depth

The day before transplanting, the water layer in the paddy field should be adjusted to about 1 cm (in a partially exposed water state) to facilitate the operation of the transplanting machine. If the field surface water is too little, the transplanting machine has difficulty moving, mud easily sticks inside the seedling claws and grips the seedlings, the seedling grooves easily become clogged with debris, seedling supply is uneven and irregular, and seedlings may even be broken, causing serious gaps in the field. If the field surface water is too deep, the seedlings stand crookedly, transplanting depth is uneven, floating seedlings and gaps are numerous, and the transplanting machine easily pushes over and presses down seedlings during operation, making it impossible to guarantee transplanting quality.

2. Field surface hardness

When transplanting, the method for checking field surface hardness is to insert the index finger one joint deep (about 2 cm) into the field surface and draw a furrow. If the surrounding soft mud slowly closes back together, this is the optimal transplanting state. If settling is poor and the field surface is too soft and thin, the seedlings cannot be planted firmly, the standing posture of the seedlings is disorderly, the transplanting machine pushes and presses the edge-row seedlings, and after transplanting the seedlings easily sink, affecting recovery and tillering growth. If the field surface is too hard, transplanting resistance is great, seedlings are easily damaged, transplanting depth becomes shallower, and the marks after transplanting cannot close in time, causing floating seedlings and gaps.

3. Optimal transplanting depth

Whether the depth of mechanical transplanting is appropriate has an enormous effect on the greening-up, tillering, and full stand of the seedlings. Generally, when transplanting depth is 0.5 cm, seedlings easily scatter, fall over, and float in relatively large numbers. When transplanting depth is more than 3 cm, it inhibits seedling greening-up and tillering, especially noticeably inhibiting tillering at lower nodes, increasing late tillering at higher nodes, delaying tillering, and reducing tillering quality; deep transplanting of weak seedlings can also turn them into stiff seedlings. When transplanting depth is about 2 cm, however, falling and floating seedlings do not occur, plants develop more roots, grow robustly, and have strong tillering ability. Therefore, the depth of mechanical rice transplanting should be controlled at about 2 cm; manual transplanting depth should be 1-1.5 cm; for pot-raised carpet transplanting, the pot surface should be level with the mud surface; for seedling-throwing cultivation, it is appropriate for 2/3 of the pot surface to enter the soil (seedling throwing in muddy condition).

4. Three treatments before transplanting

According to the agricultural timing of transplanting, the three treatments should be carried out in a planned way one day before transplanting, with transplanting done as the three treatments proceed. The three treatments before transplanting must not all be completed at once, in order to avoid excessive fertilizer concentration causing seedling burn. At the same time, this can also extend the period for controlling leaf miners and improve the preventive effect against leaf miners. The three treatments before transplanting are: first, phosphorus: diammonium phosphate 125-150 g/sq m; second, pesticide: 70% Admire 6-8 g or 25% Actara 6-8 g per 100 sq m; third, biological fertilizer, such as Yiwang yield-increasing bacteria, Shilv biological fertilizer, etc., used according to the instructions.

5. Age-appropriate strong seedlings

The quality of seedlings at the transplanting stage has an enormous effect on seedling greening-up and tillering. Generally, dry-raised medium seedlings (3.1-3.5 leaves) and dry-raised large seedlings (4.1-4.5 leaves) are required to be strong seedlings with white and vigorous roots, thick and sturdy stems, upright green leaves, appropriate seedling age, uniformity and evenness, high dry matter weight, and strong stress resistance. Such seedlings green up quickly after transplanting, tiller early, and grow vigorously. In contrast, overgrown seedlings with poor seedling quality have leaves that droop on the water surface after transplanting, are highly susceptible to leaf miner damage, and their leaves rot quickly. Even if the leaves remain intact, after water is drained the leaves stand upright very slowly, recovery is slow, greening-up is delayed, and under adverse environmental conditions the rates of dead leaves and dead seedlings are high.

6. Rational close planting

Transplanting density (basic number of seedlings per square meter) should be determined according to comprehensive factors such as soil fertility, seedling quality, climatic conditions, and cultivation level. The basic number of seedlings per unit area is best set at 1/4-1/5 of the planned number of panicles (more than 600 harvest panicles per square meter). Generally, for fields with fertile soil, high fertilization level, strong fertilizer supply capacity, good seedling quality, and good climatic conditions, sparse transplanting may be appropriate, and the basic number of seedlings per square meter should not be too high, generally about 125 plants/sq m is relatively suitable; for fields with relatively barren soil, poor fertilizer supply capacity, and poor climatic conditions, density may be appropriately increased, and the basic number of seedlings per square meter controlled at 140 plants/sq m is relatively suitable.   

7. Scientific irrigation

Immediately after transplanting, add seedling-protection water to preserve greening-up, with a water depth of about 4-6 cm, reaching 2/3 of seedling height, with the criterion that the heart leaves of the seedlings are not submerged, to promote early greening-up, early tillering, and early rapid growth of the seedlings. At normal temperature, when the surface water is in a partially exposed water state, the number of days required for seedling greening-up is 9-10 days; when seedling-protection water depth is 2 cm, the number of days required for seedling greening-up is 6-7 days; when seedling-protection water depth is 4 cm, the number of days required for seedling greening-up is 4-5 days. Under certain conditions, for every 2 cm increase in seedling-protection water depth, plant height increases by 1 cm and the number of roots increases by about 2. After rice greens up, immediately drain to a shallow water layer and maintain a shallow water layer of about 3 cm to help increase water temperature and mud temperature and accelerate rice tillering. The optimal air temperature for rice tillering is 30-32°C, and the optimal water temperature is 32-34°C. When air temperature is below 20°C and water temperature is below 22°C, tillering is slow; when air temperature is below 15°C and water temperature is below 16°C, or when air temperature exceeds 40°C and water temperature exceeds 42°C, tillering stops. Maintaining a shallow water layer can increase mud temperature, reduce the diurnal temperature difference, improve the availability of soil nutrients, and help promote tillering. No water or deep water easily lowers mud temperature and inhibits tillering. An outlet should be prepared in advance, with an outlet height of 5 cm, to prevent water depth from submerging seedlings when rainfall is excessive or from long-term deep-water flooding, which reduces root vigor.

8. Early application of tillering fertilizer

3-5 days after transplanting, immediately after the seedlings green up, apply tillering fertilizer. The application amount is 30% of the total nitrogen fertilizer. Of this, 80% of the total tillering fertilizer should be applied to the whole field 4-5 days after transplanting, and the other 20% (about 1 kg urea/mu) should be applied 7-9 days later by inspecting the field and applying where yellow and weak, so as to make the fertilizer effect occur at the 6-7 leaf stage (the leaf position of vigorous effective tillering), promote early tillering, fast tillering, and more tillering of seedlings, and reduce ineffective tillering. To extend the fertilizer effect period, sulfuric acid and urea can be mixed for use, with 3 kg ammonium sulfate replacing 1 kg urea. During the tillering stage, the critical amounts of the three major elements in rice plants are nitrogen 2.5%, phosphorus pentoxide 0.25%, and potassium oxide 0.5%. When leaf nitrogen content is 3.5%, tillering is vigorous, and when potassium content is 1.5%, tillering proceeds smoothly. Biological silicon fertilizer should all be used on tillering fertilizer, 5 kg/mu applied together with the first tillering fertilizer.

9. Timely pest control

Before the occurrence of rice leaf miners, from late May to early June, conduct timely pest surveys after transplanting, and spray pesticide promptly for control when leaf miner damage is found. The survey method is to select seedlings 8-10 days after transplanting and examine the leaves near the water surface and lying flat (drooping) on the water surface. Gently stroke the leaves by hand; if small granules are found in the middle of the leaves, these are leaf miner larvae, and pesticide should be sprayed immediately for control.

10. Timely early transplanting

The starting temperature for rice transplanting is when air temperature stably passes 13°C and mud temperature reaches 15°C. The high-yield transplanting period is May 15-25, and for pot-raised carpet transplanting it is the 18th-23rd; May 10-15 and May 26-30 are average-yield periods; before May 10 and after June 1 are yield-reduction periods. As time is delayed, yield decreases markedly. Taking the yield of transplanting on May 15 as 100, the yield of transplanting on May 20 is 94, the yield of transplanting on May 25 is 90, and the yield of transplanting on May 30 is 79.9.

11. Full and tight transplanting

Replant gaps synchronously after transplanting, transplant to the end and to the edges, and fill the four corners of the paddy field fully and tightly, to ensure that the basic number of seedlings in the field is reasonable and the cultivated land utilization rate is 100%. Seedlings should be planted upright, not leaning in all directions. Transplanting rows should be straight, row and hill spacing regular, the number of seedlings per hill uniform, and planting depth neat and consistent. Do not plant high and low seedlings or broken-head seedlings.

12. Transplanting in sequence

When transplanting, start from the lower end of the paddy field and gradually advance toward the upper end. After the next paddy field is fully transplanted, release the water from the previous paddy field into the next paddy field as seedling-protection water. In this way, water is saved, water temperature is increased, and fertilizer loss and waste are reduced. At the same time, the first two rows of paddy fields on both sides of the main highway should be transplanted after May 15.