What are the key technical points for field tillage and preparation for machine-transplanted rice?

For machine-transplanted rice fields, different tillage and preparation methods should be adopted according to the cropping sequence, soil characteristics and other conditions, and base fertilizer should be applied according to local conditions based on soil fertility.

Tillage and preparation of fields following a previous crop

1. Crushing the straw of the previous crop. When the previous crop is harvested, the straw must be crushed and evenly spread. If crushing was not carried out during mechanical harvesting, an additional straw-crushing operation should be added or the straw should be removed from the field.

2. Dry tillage. Under suitable soil moisture and water content conditions, three methods can be used to kill stubble: forward (reverse) rotary tillage, shallow plowing and harrowing of stubble, among which the reverse rotary stubble-killing method is better. Deep plowing and turning should be avoided as much as possible. During operation, the depth should be controlled within 15 cm, with stable tillage depth, a high stubble coverage rate, and no missed tillage. For uneven plots, one additional crosswise dry leveling should be carried out, so that there are no hidden ditches or hollows in the field, and the height difference and flatness of the field meet the standards. For leveling large-area fields, laser leveling technology may be considered for dry tillage. If conditions for using laser land-leveling technology are not yet available, fields with large height differences should be divided into grids for operation, turning large fields into smaller ones, so as to achieve dry tillage quality within a relatively limited area.

3. Wet tillage. Irrigate with shallow water and soak for 24 hours, then carry out wet tillage and leveling. When conditions are suitable, the soil can be dried to an appropriate degree after dry tillage, then irrigated and soaked, which makes it less likely to form hardened clods. For wet tillage, equipment such as paddy field stubble-burying and puddling machines and paddy field drive harrows can be used. During wet tillage, attention should be paid to controlling the appropriate irrigation amount, preventing both muddy operations and water-deficient, hardened, and compacted operations.

Because the depth of rotary tillage and stubble killing before wet tillage is shallower than the original plow layer, and combined with puddling and leveling, the operating conditions are complex, so it is necessary to prevent uneven mud depth and the buried stubble being brought back to the surface.

After wet tillage, the surface of the field should be level, with no residual stubble, straw or weeds, the stubble-burying depth should be more than 4 cm, the mud depth should reach 5-8 cm, and the height difference of the field should not exceed 3 cm.

4. Settling. After wet tillage, the machine-transplanted field must be settled to an appropriate degree. Sandy soil should be settled for 1 day, sandy loam for 2-3 days, and clayey soil for about 4 days before machine transplanting, and it is best when the water layer on the field surface shows so-called "patchy water." It is necessary to strictly prevent deep water and muddy fields, which can cause water and mud mounding during machine transplanting. For fields with a relatively high density of weeds, in combination with mud settling, after harrowing an appropriate herbicide may be mixed with moist fine soil and evenly broadcast, and a 6-10 cm water layer should be maintained for 3-4 days for sealed killing and weed control.

Tillage and preparation of winter-plowed or winter-fallowed stubble fields

For fields that have undergone winter plowing and rotation, cross-cutting harrowing for dry tillage and leveling can be adopted, followed by wet tillage. For uncultivated winter-fallow fields with relatively little residual stubble on the surface, shallow plowing or rotary tillage for dry tillage can be adopted, followed by wet tillage. For fields with no residual stubble on the surface, good winter plowing quality and a level surface, wet tillage can also be carried out directly.

Tillage and preparation of winter waterlogged fields

In some areas, because farmers are reluctant to part with water, the field keeps water from the harvest of the previous late rice until the transplanting of early rice. Such winter waterlogged fields, after long-term soaking in cold water, have poor soil aeration, deep mud, poor reducibility and relatively low soil temperature. For such fields, ditches should be opened in the field in advance on sunny days to raise the field, and after fertilizing, shallow rotary tillage should be carried out, taking advantage of fine sunny weather for sun exposure to increase temperature, and about 3 days before transplanting, the field should be flooded level and settled.