Chapter 7 (Part 2): Artificial Regeneration
Chapter 7 (Part 2): Nursery Management & Seedling Production
Forest Nursery • Nursery Beds • Containers • Root Trainers • Seedling Care
1. Key Concepts
Forest Nursery: A defined area set aside for raising young plants (seedlings, transplants, or vegetatively propagated cuttings) under intensive management until they attain suitable size and vigor for field planting.
Temporary Nursery: A nursery established for a short duration (1–3 years) in or adjacent to a specific plantation site to meet immediate planting material demands.
Permanent Nursery: A central, long-term, well-equipped nursery designed to supply high-quality planting stock to multiple plantation areas over many years.
Nursery Bed: A prepared narrow strip of land in a nursery used for sowing seeds (seedbed) or transplanting young seedlings (transplant bed).
Pricking Out (Transplanting): The delicate transfer of tiny young seedlings from dense seedbeds into transplant beds, polybags, or root trainers to encourage lateral root development.
Root Trainer: A rigid plastic container possessing internal vertical ridges and an open bottom, engineered to prevent root coiling and induce natural air-pruning of root tips.
Hardening Off: The gradual reduction of watering, shading, and shelter given to nursery plants prior to field planting, adapting them to withstand harsh outdoor conditions.
Damping-Off: A destructive fungal disease in nursery seedbeds caused by Pythium, Rhizoctonia, and Fusarium, affecting young seedlings at the ground line under high soil moisture and poor drainage.
2. Important Points
A. Nursery Site Selection Criteria
- Location: Centralized with respect to plantation areas and easily accessible by road for planting stock transport.
- Topography and Slope: Gentle slope of 1% to 3% ensures natural water drainage without soil erosion. Flat sites may cause waterlogging.
- Soil Quality: Deep, well-drained sandy loam to loamy soil rich in organic matter. Clayey soils may cause waterlogging and root breakage during lifting.
- Water Supply: Reliable, permanent year-round source of clean, non-saline water.
- Protection: Sheltered from strong desiccating winds, frost hollows, and heavy livestock interference.
Important numerical point: The preferred nursery-site slope is 1–3%. A deep, well-drained sandy loam soil and a reliable water source are also essential.
B. Layout and Bed Construction
- Width: 1.0 m to 1.2 m, allowing weeding and handling from both sides without stepping on the bed.
- Length: Usually 10 m to 12 m, adapted to ground contour and irrigation channels.
- Orientation: East-West orientation in tropical/subtropical regions to provide uniform shade coverage.
- Potting Mixture: 2 : 1 : 1 ratio (Soil : Sand : Well-rotted FYM/Compost).
C. Types of Nursery Beds
- Raised Beds: Elevated 10–15 cm above ground level with bamboo/wooden side supports; essential in heavy rainfall regions to prevent root rot.
- Sunken Beds: Excavated 10–15 cm below ground level; used in arid and dry zones to conserve soil moisture and protect from wind.
- Level Beds: Prepared at natural ground level; used in moderate rainfall regions on well-drained loamy soils.
3. Nursery Bed Types and Their Applications
| Bed Type | Position | Main Advantage | Suitable Conditions |
|---|---|---|---|
| Raised Bed | 10–15 cm above ground | Improves drainage and aeration; reduces waterlogging. | Heavy rainfall regions. |
| Sunken Bed | 10–15 cm below ground | Conserves soil moisture and protects against wind. | Arid and dry zones. |
| Level Bed | At natural ground level | Simple preparation under suitable drainage conditions. | Moderate rainfall regions with well-drained loamy soil. |
Memory trick — Bed selection:
R-Rain, S-Sand/Dry, L-Level:
R-Rain, S-Sand/Dry, L-Level:
- Raised beds → Heavy rainfall and drainage.
- Sunken beds → Dry conditions and moisture conservation.
- Level beds → Moderate rainfall and well-drained soil.
4. Modern Container Technology and Root Trainers
A. Polythene Bags (Polybags)
- Traditional flexible containers.
- Relatively cheap and widely used.
- Carry a high risk of root coiling or spiraling if seedlings are retained too long.
B. Root Trainers
- Modern rigid containers with internal vertical ribs.
- Ribs direct root growth downwards and prevent horizontal coiling.
- An open bottom allows root tips to come into contact with air.
- Exposure to air stops the growth of the root tip through air-pruning.
- This stimulates a dense, fibrous root system with lateral branching.
Core concept: Root trainers are designed to prevent root coiling and promote a well-branched root system through internal ribs and air-pruning.
C. Planting Bricks
Planting bricks are soil-manure-clay compressed blocks containing a central seedling hole.
5. Mycorrhizal Inoculation in Nursery
Role of Mycorrhiza
- Mycorrhizal association is important for exotic species such as Pinus and Eucalyptus.
- It helps plants absorb insoluble phosphorus and water.
Inoculation Methods
- Incorporating topsoil collected from healthy mature pine/eucalypt stands into nursery potting soil at a 1:10 ratio.
- Interplanting infected nurse seedlings into nursery beds.
Important fungal associations: Pisolithus tinctorius and Suillus spp. are ectotrophic basidiomycete fungi associated with pine nursery establishment.
6. Important Comparison Tables
A. Temporary Nursery vs. Permanent Nursery
| Feature | Temporary Nursery | Permanent Nursery |
|---|---|---|
| Location | Inside or immediately adjacent to plantation site. | Centrally located with good road connectivity. |
| Lifespan | 1 to 3 years. | Long-term (10 to 30+ years). |
| Cost and Infrastructure | Low initial cost; temporary fencing and huts. | High investment; permanent piping, greenhouses and storehouses. |
| Transport Damage | Minimal seedling transit shock and low transport costs. | Higher transit shock and transport costs to distant sites. |
| Seedling Vigor | Soil fertility may drop after two seasons without inputs. | Sustained soil fertility through compost and mycorrhizal management. |
B. Polybags vs. Root Trainers
| Parameter | Traditional Polybags | Modern Root Trainers |
|---|---|---|
| Root System Form | Coiled taproot and long, sparse lateral roots. | Dense, fibrous, air-pruned root system without coiling. |
| Soil Medium Volume | Requires a large volume of heavy soil. | Uses a smaller volume of lightweight potting media such as vermiculite/coco-peat. |
| Field Survival Rate | Moderate; sensitive to transplanting shock. | High; rapid field root establishment. |
| Space and Handling | High space requirement and heavy manual handling. | Compact; raised on metal stands; easier handling and automation. |
C. Types of Forest Nurseries and Containers
| Category | Classification | Primary Characteristics |
|---|---|---|
| Duration | Temporary Nursery | Near plantation; low capital cost; soil fertility may deplete rapidly; no permanent buildings. |
| Duration | Permanent Nursery | Central location; irrigation, shade nets, root trainers and permanent infrastructure. |
| Bed Construction | Raised Bed | 10–15 cm high; better aeration and drainage. |
| Bed Construction | Sunken Bed | 10–15 cm below ground; conserves moisture. |
| Bed Construction | Level Bed | Ground level; suited to well-drained soil. |
| Container | Polyethylene Bag | Flexible, cheap; risk of root coiling. |
| Container | Root Trainer | Rigid HDPE; vertical ribs; open bottom for air-pruning. |
| Container | Planting Brick | Soil-manure-clay compressed block with central seedling hole. |
7. Flowcharts and Diagrams
A. Standard Nursery Production Process
Site Selection and Layout Planning
1–3% slope and reliable water source
1–3% slope and reliable water source
↓
Bed Preparation and Soil Sterilization / Solarization
↓
Sowing Seeds in Primary Seedbeds
↓
Pricking Out
Transfer to polybags or root trainers
Transfer to polybags or root trainers
↓
Cultural Maintenance
Shading, weeding, irrigation and fertilization
Shading, weeding, irrigation and fertilization
↓
Mycorrhizal / Bio-fertilizer Inoculation
↓
Root Pruning and Grading of Seedlings
↓
Hardening Off
Gradual reduction of shade and water 2–4 weeks before planting
Gradual reduction of shade and water 2–4 weeks before planting
↓
Transportation to Field Plantation Site
B. Mechanism of Air-Pruning in Root Trainers
Seedling Root Grows Downwards
↓
Internal Vertical Ribs Prevent Horizontal Coiling
↓
Taproot Reaches Open Bottom Drain Hole
↓
Exposure to Air Causes Root Tip Desiccation (Air-Pruning)
↓
Loss of Apical Dominance in Root Tip
↓
Profuse Lateral Secondary and Tertiary Root Branching
8. Important Scientific Names and Nursery Associations
| Tree / Organism | Scientific Name | Nursery Management Relevance |
|---|---|---|
| Damping-off fungi | Pythium spp., Rhizoctonia solani, Fusarium spp. | Destructive seedbed fungal pathogens; control includes maintaining soil pH at or below 5.5 and avoiding excess watering. |
| Teak | Tectona grandis | Raised in beds for one year to prepare 1–2 cm diameter stumps; 22 cm root and 2.5 cm shoot are recommended. |
| Shisham | Dalbergia sissoo | Raised in beds for root-collar stumps or polybag seedlings. |
| Eucalyptus | Eucalyptus hybrid | Very small seeds sown in fine sand beds; sensitive to root coiling. |
| Pine mycorrhiza | Pisolithus tinctorius, Suillus spp. | Ectotrophic basidiomycete fungi required for nursery pine establishment. |
Important One-Liner Facts
- Standard Nursery Bed Width: 1.2 metres.
- Standard Potting Mixture: 2 : 1 : 1 (Soil : Sand : FYM).
- Damping-Off Control: Soil pH at 5.5 or lower and avoidance of excess watering.
- Hardening Off: Gradual reduction of irrigation and shade 2–4 weeks before field planting.
- Teak Stump Dimensions: One-year-old seedlings; 2.5 cm shoot length and 15–22 cm taproot length; collar thickness 1–2 cm.
- Air-Pruning: Root tip stops growing after exposure to air at the open base of root trainers, encouraging lateral root branching.
- Nursery Area Index: Generally 1% to 5% of the target annual plantation area.
9. Formulae and Quantitative Metrics
A. Nursery Bed Requirement Formula
Nbeds = [Ptarget × (1 + Mcull)] / [Sbed × Gcapacity]
Where:
- Ptarget: Target number of field plants.
- Mcull: Expected culling fraction (0.10–0.20).
- Sbed: Number of seeds sown per bed.
- Gcapacity: Germinative capacity fraction.
B. Teak Stump Preparation Standard
Total Stump Length = 2.5 cm (Shoot) + 18.0 cm (Root) = 20.5 cm
A taproot range of 15–22 cm is also used for teak stump preparation.
10. Mnemonics and Memory Tricks
1. Nursery Site Selection — "S-W-A-P"
- S – Slope (1–3% gentle gradient)
- W – Water (permanent clean supply)
- A – Accessibility (road connection)
- P – Propagules / Soil (deep sandy loam)
Memory line: A good nursery needs a gentle slope, water, access and suitable soil.
2. Potting Mixture — "2 : 1 : 1"
- 2 parts Soil
- 1 part Sand
- 1 part FYM / Organic Manure
Memory line: Soil is double; sand and manure are single.
3. Nursery Bed Selection — "Wet Up, Dry Down"
- Wet / high rainfall → Raised bed.
- Dry / arid → Sunken bed.
- Moderate rainfall → Level bed.
4. Root Trainer — "Rib, Reach, Air, Branch"
- Rib: Internal ribs guide roots downward.
- Reach: Root reaches the open bottom.
- Air: Root tip is air-pruned.
- Branch: Lateral roots develop profusely.
5. Nursery Production Sequence
"Select → Prepare → Sow → Prick → Maintain → Inoculate → Grade → Harden → Transport"
Remember the sequence from nursery establishment to field planting.
11. Quick Revision Box
- Temporary Nursery: Short-term, near plantation site, low transport shock.
- Permanent Nursery: Long-term, central location, high infrastructure.
- Bed Width: 1.2 m; Bed Length: 10–12 m.
- Raised Beds: High rainfall areas.
- Sunken Beds: Dry and arid zones.
- Level Beds: Moderate rainfall and well-drained soils.
- Root Trainers: Internal ribs and air-pruning prevent root coiling.
- Potting Mixture: 2 : 1 : 1 (Soil : Sand : FYM).
- Damping-Off: Maintain soil pH at or below 5.5 and avoid excess watering.
- Teak Stump: 2.5 cm shoot and 15–22 cm taproot.
- Hardening Off: 2–4 weeks before field planting.
- Mycorrhiza: Helps pine and eucalyptus absorb phosphorus and water.
- Nursery Area: Generally 1–5% of annual plantation area.
12. Interactive MCQ Quiz
15 questions. Tap an option to see the correct answer and explanation straight away, then go to the next question.
Your score
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