Technical instructions for preparing land for rice cultivation

Land preparation is the foundation for the entire rice crop. Wrongly made soil reduces productivity by 15-30% despite good care afterwards. Instructions on the three steps of plowing, drying, leveling and how to adjust for each region of the Mekong Delta.

Summary: Well-made rice land will reduce pests and diseases, reduce weeds, and rice will produce even branches. Hastily prepared land reduces productivity and requires a lot of crop-protection products during the crop. This article is not a general guide to "what is soil preparation" but focuses on the three most important steps — plowing, drying, leveling — and how to adjust to each common soil type in the Mekong Delta.

Applies to: Winter-Spring, Summer-Autumn and Seasonal crops in the Mekong Delta. The Red River Delta region is different — this article does not cover it.
Duration: 15-30 days before sowing.
Difficulty level: Basic but many people do it in a hurry.
Estimated additional costs: 2-4 million VND per hectare for plow rental + land preparation.

Why is soil preparation important

Good soil preparation brings 5 benefits:

Kills pests and diseases in the soil — especially golden apple snails, weeds, and zebra sclerotia.
Improves soil structure — loose soil, deep rice roots develop.
Evenly distributed nutrients — straw, organic fertilizer mixed evenly with soil.
Increases water holding capacity + drainage — disturbed soil is better than hard mud soil.
Flat field surface — most important, affecting water management for the whole crop.

Rush-made land often has 2-3 combined problems — low-lying areas with stagnant water, high areas lacking water, weeds growing back quickly from unkilled roots.

Three main types of soil in the Mekong Delta

Soil preparation methods vary according to soil type. Before starting, determine the type of field:

Ancient alluvial soil

Distribution: An Giang, Dong Thap, part of Long An.
Characteristics: spongy, easy to make. pH 5.5-6.5.
Need: light plowing and smoothing. The land is naturally good.

New alluvial soil (plain)

Distribution: Tien Giang, Vinh Long, Can Tho, Hau Giang, Soc Trang.
Characteristics: rich in nutrients but heavy clay. pH 5.5-6.5.
Need: plow deeper, flatten thoroughly. Dry the soil if you have time.

Aluminum soil

Distribution: Dong Thap Muoi area, Long My area, some An Giang areas.
Characteristics: pH below 5, possibly below 4 in heavy alum areas. Iron and aluminum are toxic.
Need: wash alum with water before tilling. Apply high doses of lime. Need to renovate before planting.

Three-step process

Step 1 — Plow the land

Time: 20-30 days before sowing. The soil is moderately dry, not too wet nor too dry.

How to plow:

First plowing 18-22 centimeters deep. Turn over the soil from the bottom layer up, expose it to the sun to kill pests.
Plow directly when the soil is slightly damp — do not plow when the soil is mushy (soil sticks to the plow shaft) or the soil is too dry (too hard).
Plowing deeper than 25 centimeters is only necessary for fields with heavy clay soil or fields with perennial rice with hard mud bottoms.
Plowing 15-18 centimeters deep on ancient alluvial land is enough — the soil is loose.

Note:

Plow in the same direction throughout the field — easy to harrow later.
Place furrows deeper at the edge of the field — to drain water.

Step 2 — Dry the soil

Time: 7-15 days after plowing, before harrowing.

How to dry:

Let the field dry naturally in the sun. The target's ground is slightly cracked, the soil loosens when hit.
Winter-Spring crop (soil is usually dry after the Summer crop): 7-10 days of drying is enough.
Summer-Autumn crop (wet soil after Winter-Spring): needs drying for 10-15 days, maybe longer.

Benefits of drying soil:

Kills 60-80 percent of golden apple snails in mud.
**Kills 40-50 percent of soil nematodes.
Decomposes old straw — reduces sheath spot disease in the next crop.
Improves soil structure — clay cracks into small lumps, easy to harrow.

Many growers leave the soil exposed to sow early — a costly mistake. Drying the soil is the cheapest + most effective step to kill pathogens.

Step 3 — Harrowing and smoothing

Time: 5-7 days before sowing.

How to do:

Coarse harrow (1st time):

Pour water into the field at a level of 3-5 centimeters before harrowing.
Use disc harrow or tooth harrow. Crush a large lump of soil into small lumps.
Harrow the whole field 1-2 times.

Fine harrowing (second time, after 2-3 days of coarse harrowing):

Increase the water level by 5-10 centimeters.
Harrow more carefully, creating a thin layer of mud on the surface.
Elevated areas excavate soil and move it to low areas.

Flatten:

This is the most important step. The flat field surface determines water management for the whole season.
Use a "drag plane" or rake your hand with the board.
Standard: the difference between highest and lowest is no more than 5 centimeters in a field.

Flat field surface helps:

Distribute water evenly.
The rice germinates evenly — no area is waterlogged, no area is dry.
Fertilize evenly.
Effective spraying.

Additional land reclamation stage

Apply lime (for acidic soil)

Soil pH below 5.5 needs lime:

pH 5.0-5.5: apply 300-500 kilograms of lime per hectare.
pH 4.5-5.0: apply 800-1,200 kilograms.
pH below 4.5 (alum soil): apply 1,500-2,000 kilograms.

Apply lime after the first plowing, spread evenly on the surface, then plow and mix the second time or harrow and mix.

Organic fertilizer

Long-term cultivated land gradually runs out of organic matter. Additional:

2-5 tons of manure per hectare.
Or 5-10 tons of composted straw.
Fertilize after the first plowing, mix well when harrowing.

Regularly fertilized soil has:

Better structure — easier to prepare soil for future crops.
Rich soil microorganisms — naturally reduces pests and diseases.
Better hydration + nutrition.

Fertilize with fused phosphate

Phosphorus lasts a long time in the soil, apply as fertilizer when preparing the soil properly:

Apply 250-400 kilograms of fused phosphate per hectare.
Mix when harrowing for the first time.
Good for acidic soil because fused phosphate has calcium.

Monitor and evaluate land after construction

[ ] Is the field surface evenly flat — measure with a 3-5 meter long board, check 3-5 points.
[ ] How loose the soil is — dig lightly to check.
[ ] Are there any remaining golden apple snails and eggs?
[ ] Are the weeds completely dead?

Common mistakes

Leaving the soil to dry for early sowing: there are many yellow snails, weeds, and nematodes. Drug waste case.

Plow when the soil is too wet: the soil sticks to the shaft and does not loosen. Must wait until the soil is dry.

Improper harrowing: large lumps of soil remain, rice germinates unevenly.

Abolished flattening because it was "wasting effort": high areas lacked water, low areas were waterlogged. Managing water throughout the season is difficult.

Overdosing on lime once: soil shock, microorganisms die. Divide into 2 crops if the dose is high.

Example calendar for Winter-Spring crop

November-December sowing:

Day -30: 1st plowing, 20 centimeters deep.
Day -20: soil drying begins.
Day -10: apply lime and phosphorus if necessary. First harrowing (coarse harrowing).
Day -7: Second harrowing (seed harrowing). Organic fertilizer.
Day -5: flatten thoroughly.
Day -3: soak in water, prepare to sow.
Day 0: sowing seeds.

Take notes

Plowing date, depth, soil quality.
Renovation materials — lime, organic, phosphate — volume.
Number of days to dry the soil.
Quality of field surface after work.

References

*Land preparation techniques for rice cultivation* — Mekong Delta Rice Institute, 2022.
*Handbook for preparing land for the Winter-Spring crop* — Department of Crop Production, 2023.