Base Fertilizer, Seed Fertilizer, Seedling Fertilizer, and Topdressing — Do You Know the Differences?

Every spring-sowing season, many farmers ask our agronomy team:“We already applied autumn fertilizer. Now that we’re sowing in spring, should the first irrigation also include fertilizer?”Once you clearly understand the timing and purpose of base fertilizer, seed fertilizer, seedling fertilizer, and topdressing, the answer becomes obvious.

I. Base Fertilizer: The “Nutrient Foundation” for the Entire Growth Cycle

1. Definition

Base fertilizer — also called pre-plant fertilizer — refers to fertilizer applied before sowing or transplanting, or at the end/beginning of the growing season for perennial crops. It serves as the fundamental nutrient guarantee throughout the entire growth period.Its key features: early application, long-lasting effect, and soil-improving capability, distinguishing it from in-season supplemental fertilizers.

2. Functions

1. Provides long-term nutrients:

   Supplies N, P, K and secondary/micronutrients throughout the season, especially when root absorption weakens later, preventing nutrient depletion.

2. Improves soil properties:

   Organic base fertilizers increase organic matter, improve soil aggregation, enhance water and nutrient retention, and create a better environment for germination and root growth.

3. Enhances nutrient use efficiency:

   Placing low-mobility nutrients (e.g., P, K) deeper (15–30 cm) reduces losses and increases uptake efficiency.

3. Application

1. Timing:

   7–15 days before sowing/transplanting.

   For perennial crops: applied in late season (e.g., autumn) to allow full soil incorporation.

   
   

2. Fertilizer selection:

   • Mainly slow-release organic fertilizers (compost, manure).

   • Combined with slow-release mineral fertilizers (P, K).

   • Poor soils may require some nitrogen fertilizer.

     
     

3. Application methods:

   • Broadcast + incorporation: Even distribution before plowing (15–30 cm).

   • Band / pit application: Concentrated placement near seed rows (20–25 cm deep).

   • Layered application: Organic fertilizers deep, quick-acting fertilizers shallow.

4. Suitable Fertilizer Types

Category	Products	Rationale
Organic / Soil amendments	Potassium humate, potassium fulvate	Improve soil structure and enhance long-term nutrient retention
Phosphorus–potassium base fertilizers	DAP (21-53-0), MAP (12-61-0)	High-P products ideal for deep application
Secondary & micronutrients	SOP (50/52% K₂O), magnesium sulfate	Replenish long-term K and Mg; reduce nutrient loss when mixed with organics

II. Seed Fertilizer: The “Emergency Nutrition” for Early Seedlings

1. Definition

Seed fertilizer is applied at sowing or transplanting, placed near the seed or applied simultaneously.Its purpose: supply fast-acting nutrients during the seedling’s critical nutrition phase, compensating for limited seed endosperm nutrition.Characteristics: small amount, concentrated nutrients, fast action, and strict distance control to prevent seed burn.

2. Functions

1. Promotes uniform and strong seedlings.

2. Shortens the recovery period after transplanting.

3. Enhances stress resistance (cold, drought) when micronutrients like Zn and B are included.

3. Application

• Timing: At sowing or during transplanting.

• Selection: Use low-salt, fast-acting, non-volatile fertilizers.

  Avoid ammonium bicarbonate, ammonium chloride, ammonia water, etc.

• Methods:

  • Placement 5–8 cm away from seeds.

  • Seed coating or soaking with micronutrient solutions.

  • Root dipping during transplanting.

4. Suitable Fertilizer Types

Category	Products	Rationale
High-phosphorus soluble fertilizers	MKP (0-52-34)	Low salt, promotes rooting
Low-N high-P fertilizer	MAP (12-61-0)	Strongly promotes early rooting
Micronutrients	Boric acid, zinc sulfate	Prevents early-stage micronutrient deficiency

III. Seedling Fertilizer: The “Rapid Boost” for Weak Seedlings

1. Definition

Applied after emergence (1–4 leaf stage) to quickly solve nutrient gaps before roots fully develop.Characteristics: very fast-acting, small amounts, highly flexible.

2. Functions

1. Quickly fills nutrient gaps (N and P).

2. Stimulates lateral root growth.

3. Prevents early micronutrient deficiency (iron chlorosis, zinc deficiency).

3. Application

• Timing: 3–7 days after emergence, or when mild chlorosis appears.

• Selection: Highly soluble, suitable for foliar spraying or fertigation.

• Methods:

  • Fertigation with soluble N or P–K fertilizers.

  • Foliar spraying with 0.2%–0.5% solutions.

  • Small shallow-hole application if no irrigation is available.

4. Suitable Fertilizers

Category	Products	Rationale
Fast-acting N	CAN (15.5% N, 19% Ca)	Relieves nitrogen deficiency
Fast-acting P–K	MKP, UP (17-44-0)	Promotes rooting; UP works well in alkaline soils
Micronutrients	EDTA-Fe, ferrous sulfate	Corrects iron chlorosis

IV. Topdressing: The “On-Demand Supply Station” During Critical Growth Stages

1. Definition

Topdressing refers to in-season fertilization based on crop growth stages (e.g., tillering, flowering, fruit enlargement) to meet short-term nutrient peaks.

2. Functions

1. Meets stage-specific high nutrient demand.

2. Improves stress resistance (especially with K fertilizers).

3. Optimizes yield and quality.

3. Application

• Timing:

  • Wheat: jointing stage

  • Corn: V-tassel stage

  • Rice: booting stage

  • Fruits & vegetables: flowering + fruit enlargement

• Selection:

  • Growth stage = nitrogen

  • Flowering/fruiting = phosphorus + potassium

  • Deficiency = Ca/Mg/micronutrients

• Methods:

  • Soil application (banding, fertigation).

  • Foliar spray (P–K, Ca, B).

  • Fertigation for greenhouses.

4. Suitable Fertilizers

Category	Products	Rationale
Nitrogen topdressing	KNO₃, CAN	N + K boost; prevents fruit cracking
P–K fruit swelling fertilizers	MKP, SOP	Improves flowering, fruit set, sweetness
Secondary/micronutrients	Cal-Mag, EDDHA-Fe	Prevents Ca/Mg deficiencies; corrects iron chlorosis

V. Summary: Key Differences and Selection Principles

1. Comparison Table

Dimension	Base Fertilizer	Seed Fertilizer	Seedling Fertilizer	Topdressing
Timing	7–15 days before sowing	At sowing	3–7 days after emergence	Key growth stages
Purpose	Long-term supply + soil improvement	Early emergency nutrition	Rapid correction for weak seedlings	Meet peak nutrient demand
Features	Slow-release, long-lasting	Fast-acting, low salt	Fast-acting, highly soluble	Fast-acting, targeted
Method	Deep incorporation	Layered placement	Fertigation / foliar spray	Soil/foliar/fertigation

2. Fertilizer Selection Principles

1. Base fertilizer: long-acting + soil improvement.

2. Seed fertilizer: safe + fast-acting (low salt).

3. Seedling fertilizer: fast rescue + flexible.

4. Topdressing: targeted + efficient, matched to growth stage.