In plant protection operations, the efficacy of herbicides depends not only on product quality but, more importantly, on "precision application." The following summarizes the standardized operating procedures, ranging from land preparation to application and equipment maintenance:

1. Land Preparation: Level and Fine

The plots designated for herbicide application must meet the standards of being "level, fine, and uniform."

Levelness: If the ground contains potholes or large soil clods, it will lead to uneven distribution of the liquid herbicide, creating "dead zones" (areas missed by the chemical) or causing localized phytotoxicity.

Preparation Requirements: Practice intensive and meticulous tillage to ensure the soil layer is loose and free of large clods, thereby creating a uniform contact surface for either pre-mixing or spraying applications.

2. Mixing and Application: Dual Uniformity

Whether applying liquid sprays or broadcasting herbicide-treated soil, **"uniformity"** is the critical factor determining the success or failure of weed control:

Uniform Mixing: Employ the "secondary dilution method" to ensure the herbicide is fully dissolved or thoroughly mixed within its carrier medium.

Uniform Spraying: Strictly prohibit overlapping sprays or missed spots to ensure a consistent application rate per unit area.

3. Data Precision: Three Quantifiable Metrics

Strictly adhere to the requirements of "Precision Agriculture":

Precise Timing: Strictly follow the application window specified in the product instructions (e.g., post-sowing but pre-emergence, or during a specific leaf stage of the weeds).

Precise Dosage: Strictly prohibit arbitrarily increasing the concentration. For example, when using 40% Difenzoquat to control wild oats, the dosage must strictly adhere to the prescribed rate of 3 kilograms per hectare.

Precise Area: Accurately verify the actual area of ​​operation to calculate the exact quantity of herbicide required.

4. Flexible Response: The "Four Observations" Principle

Adjust the herbicide application strategy based on dynamic field conditions:

Observe Crop Status: Weak seedlings or seedlings that have not yet established roots have poor chemical tolerance; therefore, herbicides should be applied with caution or avoided in such areas.

Observe Weed Status: Select herbicides specifically tailored to the weed species, leaf stage, and growth vigor present in the field.

Observe Weather Conditions: Herbicide activity decreases in low temperatures, so the dosage should typically be set at the upper limit of the recommended range; conversely, do not apply herbicides during strong winds or when rain is imminent.

Observe Soil Texture: Clay soils possess strong adsorption capabilities, so a slightly higher dosage may be required; sandy soils are prone to leaching, so the dosage should be appropriately reduced; herbicide application is generally not advisable in dry soil conditions.

5. Safety Bottom Line: Five Situations Where Application is Prohibited

Operations are strictly forbidden under the following conditions to prevent herbicide injury:

Weak Crop Growth: Do not apply to weak seedlings or those exhibiting signs of disease.

Improper Water Levels: In paddy fields, do not apply if the water level is below 3 cm or if the water submerges the heart leaves (central growing points) of the rice seedlings.

Extreme Drought: Do not apply if the soil is excessively dry; under such conditions, weed metabolism slows down, reducing herbicide efficacy and increasing the risk of injury to the crop seedlings.

Adverse Weather Conditions: Do not apply if dew is present on the leaves, or immediately before or after heavy rainfall.

Soil Defects: The use of soil-applied herbicides is strictly prohibited in "leaky fields"—paddy fields with severe water seepage issues.

6. In-Depth Understanding of Herbicide Physicochemical Properties

Agricultural technicians must fully grasp the volatility, photolytic stability, and soil persistence (residual period) of the herbicides they employ. Understanding whether a specific herbicide is susceptible to physicochemical reactions is a prerequisite for determining the appropriate application depth and soil coverage method.

7. Targeting the "Core Zone"

Clearly define the primary targets of the herbicide application:

Soil-Applied Herbicides: These target weed seeds and young shoots that are on the verge of germination (typically before the 3-leaf stage).

Foliar-Applied Herbicides: Herbicides such as fomesafen should be applied during the weed's vigorous growth phase, allowing for absorption through the leaves and subsequent translocation throughout the entire plant.

8. Strategic Management of Water and Timing

Leaf-Stage Matching: For instance, propanil should be applied when weeds are at the 2-leaf stage; conversely, herbicides such as paraquat and glyphosate are most effective when applied after the weed foliage has expanded sufficiently.

Water Level Management: Herbicides such as simetryn and oxyfluorfen require a sustained water layer of 4–6 cm after application to ensure efficacy; conversely, herbicides such as thiobencarb can easily cause crop injury if applied in fields with standing water.

9. Strict Prohibition of Unauthorized Tank Mixing

Indiscriminate mixing of herbicides can lead to crop injury or a complete loss of efficacy:

Propanil must never be tank-mixed with organophosphate or carbamate pesticides.

Acidic herbicides (e.g., MCPA) must not be allowed to come into contact with alkaline pesticides.

10. Proper Cleaning of Application Equipment

Herbicide sprayers should ideally be dedicated solely to herbicide application. If a sprayer must be switched to apply a different product:

Begin by performing an initial rinse with clean water. Next, repeatedly flush the area using a circulating solution of soapy water or a 2–3% alkaline solution.

Finally, thoroughly rinse with clean water to prevent residual chemicals from causing fatal damage to subsequent crops.