Recommended Plant Growth Regulators for Rapeseed Cultivation
The plant growth regulators recommended for use during the growth cycle of rapeseed (canola) primarily include Paclobutrazol (Paclo), Uniconazole, Brassinolide, and DCPTA. Their core functions are to control excessive vegetative growth, prevent lodging, promote branching, enhance stress resistance, and significantly boost yield.
By scientifically selecting regulators based on the physiological requirements of rapeseed at different growth stages, growers can achieve the high-yield objectives of producing "robust seedlings, strong stems, abundant flowers, and full pods." The following outlines a stage-specific recommendation plan:
I. Seedling Stage (3–6 Leaf Stage): Cultivating Robust Seedlings; Controlling Excessive Growth and Promoting Root Development
The primary focus during this stage is to prevent "leggy" seedlings (excessive stem elongation) and to enhance cold and drought resistance, thereby laying a solid foundation for safe overwintering.
Paclobutrazol (Paclo)
Inhibits excessive elongation of stems and leaves, while promoting thickening of the stem base and robust root system development.
**Application Timing:** During the 3–5 leaf stage, or 7 days prior to transplanting.
**Recommended Dosage:** 40–60 grams per *mu* of 15% Paclobutrazol Wettable Powder, diluted in 30–40 kilograms of water for foliar spraying.
**Yield Enhancement:** Can increase yield by 8%–12%, while significantly enhancing lodging resistance.
Uniconazole
Possesses higher biological activity and requires lower application rates; suitable for dryland rapeseed cultivation or fields where minimizing chemical residues is a priority.
**Recommended Dosage:** 30–45 grams per *mu* of 5% Uniconazole formulation, diluted in water for uniform foliar spraying.
Brassinolide / Diethyl aminoethyl Hexanoate (DA-6)
Suitable for fields with weak seedlings; promotes growth and accelerates the transition to a robust seedling stage.
**Combination Suggestion:** Mix-spray with Monopotassium Phosphate to enhance stress resistance.
II. Budding and Bolting Stage (Stem height: 5–15 cm): Control Vigorous Growth and Prevent Lodging; Promote Branching
This stage marks the critical transition from vegetative growth to reproductive growth. Controlling excessive vegetative growth prevents premature bolting and flowering, while promoting branch differentiation.
Paclobutrazol (Paclo)
**Optimal Timing:** Early bolting stage (stem height: 5–10 cm).
**Function:** Inhibits the etiolation (leggy growth) of the main stem, increases the number of effective branches by 2–3, and boosts pod density by 20%.
**Recommended Formula:** 50–60 g of 15% Paclobutrazol + 100 g of 99% Monopotassium Phosphate per 15–20 catties (30–40 *jin*) of water. Apply via foliar spray 2–3 times, with an interval of 10–15 days between applications.
Brassinolide
Can be used synergistically with Paclobutrazol to alleviate the growth inhibition caused by growth-control treatments and to enhance photosynthetic efficiency.
III. Flowering to Pod-Setting Stage (Early Flowering – Peak Flowering): Preserve Flowers and Pods; Prevent Premature Senescence
The objective during this stage is to improve pollination quality, prevent "blind flowers" (flowers that fail to set pods), and prevent premature ripening induced by high temperatures.
Brassinolide + Monopotassium Phosphate + Boron Fertilizer
Implement the "One Promotion, Four Preventions" strategy: Promote growth; prevent pests and diseases; prevent premature senescence; prevent blind flowers; and prevent premature ripening caused by high temperatures.
**Recommended Timing:** Apply once during the early flowering stage (when 20% of flowers have opened) and once during the peak flowering stage (when 50% of flowers have opened).
**Fungicide Combination:** Can be mixed with fungicides such as Prochloraz or Procymidone to prevent Sclerotinia stem rot.
DCPTA
Applicable from the bud-stalk stage through the early flowering stage, it acts directly upon the cell nucleus to enhance photosynthetic efficiency, yielding a measured increase in crop production of 15%–25%.
IV. Prior to the Onset of Frost Damage or Environmental Stress: Enhancing Stress Resistance
10–15 days before the arrival of low temperatures, apply a foliar spray of Brassinolide, water-soluble amino acid fertilizer to bolster frost resistance.
In the Event of Frost Damage: Promptly apply a fungicide spray to seal the wounds, and use in conjunction with a plant growth regulator to facilitate recovery.
By scientifically selecting regulators based on the physiological requirements of rapeseed at different growth stages, growers can achieve the high-yield objectives of producing "robust seedlings, strong stems, abundant flowers, and full pods." The following outlines a stage-specific recommendation plan:
I. Seedling Stage (3–6 Leaf Stage): Cultivating Robust Seedlings; Controlling Excessive Growth and Promoting Root Development
The primary focus during this stage is to prevent "leggy" seedlings (excessive stem elongation) and to enhance cold and drought resistance, thereby laying a solid foundation for safe overwintering.
Paclobutrazol (Paclo)
Inhibits excessive elongation of stems and leaves, while promoting thickening of the stem base and robust root system development.
**Application Timing:** During the 3–5 leaf stage, or 7 days prior to transplanting.
**Recommended Dosage:** 40–60 grams per *mu* of 15% Paclobutrazol Wettable Powder, diluted in 30–40 kilograms of water for foliar spraying.
**Yield Enhancement:** Can increase yield by 8%–12%, while significantly enhancing lodging resistance.
Uniconazole
Possesses higher biological activity and requires lower application rates; suitable for dryland rapeseed cultivation or fields where minimizing chemical residues is a priority.
**Recommended Dosage:** 30–45 grams per *mu* of 5% Uniconazole formulation, diluted in water for uniform foliar spraying.
Brassinolide / Diethyl aminoethyl Hexanoate (DA-6)
Suitable for fields with weak seedlings; promotes growth and accelerates the transition to a robust seedling stage.
**Combination Suggestion:** Mix-spray with Monopotassium Phosphate to enhance stress resistance.
II. Budding and Bolting Stage (Stem height: 5–15 cm): Control Vigorous Growth and Prevent Lodging; Promote Branching
This stage marks the critical transition from vegetative growth to reproductive growth. Controlling excessive vegetative growth prevents premature bolting and flowering, while promoting branch differentiation.
Paclobutrazol (Paclo)
**Optimal Timing:** Early bolting stage (stem height: 5–10 cm).
**Function:** Inhibits the etiolation (leggy growth) of the main stem, increases the number of effective branches by 2–3, and boosts pod density by 20%.
**Recommended Formula:** 50–60 g of 15% Paclobutrazol + 100 g of 99% Monopotassium Phosphate per 15–20 catties (30–40 *jin*) of water. Apply via foliar spray 2–3 times, with an interval of 10–15 days between applications.
Brassinolide
Can be used synergistically with Paclobutrazol to alleviate the growth inhibition caused by growth-control treatments and to enhance photosynthetic efficiency.
III. Flowering to Pod-Setting Stage (Early Flowering – Peak Flowering): Preserve Flowers and Pods; Prevent Premature Senescence
The objective during this stage is to improve pollination quality, prevent "blind flowers" (flowers that fail to set pods), and prevent premature ripening induced by high temperatures.
Brassinolide + Monopotassium Phosphate + Boron Fertilizer
Implement the "One Promotion, Four Preventions" strategy: Promote growth; prevent pests and diseases; prevent premature senescence; prevent blind flowers; and prevent premature ripening caused by high temperatures.
**Recommended Timing:** Apply once during the early flowering stage (when 20% of flowers have opened) and once during the peak flowering stage (when 50% of flowers have opened).
**Fungicide Combination:** Can be mixed with fungicides such as Prochloraz or Procymidone to prevent Sclerotinia stem rot.
DCPTA
Applicable from the bud-stalk stage through the early flowering stage, it acts directly upon the cell nucleus to enhance photosynthetic efficiency, yielding a measured increase in crop production of 15%–25%.
IV. Prior to the Onset of Frost Damage or Environmental Stress: Enhancing Stress Resistance
10–15 days before the arrival of low temperatures, apply a foliar spray of Brassinolide, water-soluble amino acid fertilizer to bolster frost resistance.
In the Event of Frost Damage: Promptly apply a fungicide spray to seal the wounds, and use in conjunction with a plant growth regulator to facilitate recovery.
