Hydroponics & Vegetable Production: Quick Reference Notes (Capsicum, Lettuce, Tomato, Turnip, Carrot, Radish)

Hydroponics: Key Concepts

Hydroponics is the practice of growing plants without soil, using a mineral nutrient solution or soilless media to supply all nutrients directly to the plant roots. The term was popularized by Dr. William F. Gericke, who is considered the father of modern hydroponics. Historically, cultures used soil-less systems (e.g., ancient Hanging Gardens, Aztec chinampas) and modern systems were developed in the 20th century, with Hoagland’s nutrient solution paving the way for many current formulations. The core idea is to deliver nutrients directly to roots, enabling controlled, efficient growth and often higher yields with reduced water usage and minimal weeds.

Advantages: simple-to-control process, steady and reliable production, faster harvests (often within ~ $3$ months), potential for multiple crops per year, reduced weeds and soil-borne diseases, water conservation and nutrient recycling, ability to set up in non-soil spaces.
Disadvantages: high initial setup costs, requires significant skill and management, disease and pest spread can be rapid since all plants share the same nutrient solution, environmental stress can be amplified, and protection from elements is needed to prevent losses.
Growth context: hydroponics is widely used for year-round production, including in greenhouses and controlled environments; global and urban farming implications include vertical gardens, roof gardens, and space-lparing farming.

Hydroponic Systems: Classification and Major Techniques

Hydroponics can be classified by how the plant roots receive the nutrient solution and what medium supports the roots. Main categories are:

Solution culture (liquid hydroponics): roots are exposed directly to the nutrient solution. Typical sub-methods include NFT (Nutrient Film Technique) and root dipping/floating styles.
Solid media culture (aggregate systems): roots grow in inert media (gravel, sand, rockwool, coco peat) and the nutrient solution is delivered to the roots via a supporting medium.
Aeroponics: roots are suspended in air and misted with a nutrient solution.

Open vs closed systems: closed (circulating) systems continually recycle nutrient solution; open (non-circulating) systems use a one-way flow or static setup.

Nutrient Film Technique (NFT): true hydroponics system where a very thin film (~ $0.5 ext{ mm}$ ) of nutrient solution flows through channels; seedlings with minimal growing medium are placed in the channels; flow is typically maintained at $2-3 ext{ L/min}$ and the solution is circulated back to a reservoir.
Deep Flow Technique (DFT): nutrient solution flows through large-diameter pipes (e.g., $10 ext{ cm}$ ) with plastic net pots, allowing roots to contact the flowing nutrient; pipes can be arranged in a plane or zig-zag.
Non-circulating solution culture: relies on static or semi-static submersion; root dipping and floating techniques are common variants for tuber and non-tuber crops.
Solid media/aggregate: techniques include Hanging Bag, Grow Bag, Trench/Trough, and Pot techniques, each with different media (gravel, sand, rockwool, sawdust, cocopeat, etc.).
Aeroponics: root mist or fog feed, roots in a sealed light-excluded chamber; nutrient mist is delivered briefly at intervals (e.g., every ~ $2-3 ext{ minutes}$ ); ideal for high space efficiency and leafy crops in protected structures.

NFT (Nutrient Film Technique) and DFT: Quick Reference

NFT: true hydroponic exposure of roots to a thin nutrient film; channels are often made from flexible sheets; seedling plugs placed with minimal growth medium; flow rate typically adjusted to meet plant needs; channel length determines flow settings.
DFT: nutrient solution flows through PVC pipes; planting pots touch the flowing solution; pipes can be white to reduce heating; suitable for open spaces or protected structures as part of controlled environment agriculture (CEA).

Other Hydroponic Techniques (Open vs Closed, and Attachments)

Solution culture variations: Root dipping (tubers and non-tubers), Floating, and Capillary action (root dipping visuals).
Solid media variations: Hanging Bag, Grow Bag, Trench/Trough, and Pot techniques; media types include Gravel, Sand, Rockwool, Sawdust, cocopeat.
Aeroponics variants: Root mist and Fog feed; typically used in protected environments for high-density leafy crops.

Capsicum (Capsicum annuum) Production Technology (Sweet Pepper)

Introduction: Capsicum (bell/sweet pepper) is a major greenhouse crop, rich in vitamins and minerals; >400 varieties exist. Capsicum and chilli share the Capsicum genus; pungency is due to capsaicin; red color derives from capsanthin. In many regions, capsicum is grown in protected systems for year-round production.
Climate and soil: Cool-season crop; optimal flowering temperature $26-28^{\circ}C$ day / $16-18^{ ing ext{C}}$ night; sandy loam soil with pH $5.5-6.8$ ; loose soil with bidirectional root systems.
Hybrids and varieties: Commercial hybrids with high yields (up to $100 ext{ t/ha}$ +) are common for greenhouse production; color variants include green, yellow, red, orange, and newer hues. Examples of cultivars used in teaching materials include BARI Mistimorich 1, California Wonder, Wonder Bell, Shishito, Takii’s Ace, Yolo Wonder, among others.
Nursery and growing beds: Seedlings raised in cocopeat-filled cell trays; humidity and warmth are important for germination; transplanting is typically at 35–42 days after sowing. Beds require proper drainage and fertilization; spacing often around $45 imes 30 ext{ cm}$ .
Fertigation and irrigation: Drip irrigation with inline driplines at bed centers; emitters every ~ $30 ext{ cm}$ with about $2 ext{ L/hr}$ per emitter; fertigation rates commonly include balanced NPK with micronutrients; initial fertilization involves basal and pit applications, with later post-transplant fertigation as needed (e.g., CaNO3 for calcium deficiency).
Mulching, drainage, and water management: 100 μm black polyethylene mulch, 1.0 m bed width, mulch holes spaced per crop requirements; drip lines and proper drainage rings used to prevent waterlogging; irrigation frequency often daily during peak growth.
Pruning and training: Capsicum is pruned to four main stems (four-leaf branching) and trained along plastic twine, using a two-leader or four-leader system; desuckering removes non-productive shoots; staking improves airflow and fruit quality; training starts around the 6th week after planting.
Harvesting and yield: Typical greenhouse yields range from $100-120 ext{ t/ha}$ ; field yields vary; fruit weight often ~ $180 ext{ g}$ early and reduces in later harvests. Packing uses cartons with padding; storage in cold conditions (
$7-8^{\u00b0}C$ ) with high humidity extends shelf life to about $45-60 ext{ days}$ depending on storage conditions.

Lettuce Production Technology

Overview: Lettuce is a fast-growing, cool-season leafy crop with high water content (~95 ext{%}). World production (varies by country) emphasizes high water content and low caloric density.
Growing conditions: Seed germination is light-dependent; ideal germination temperature $20-27^{ ing ext{C}}$ ; germination times vary with temperature. Optimal overall growing temperatures for leaf heads are $15-18^{ ing ext{C}}$ ; bolting and bitterness increase with higher temperatures or long days.
Types and varieties: Head types (Crisp Head, Butter Head) and Non-Head types (Cos/Romaine, Leaf, Asparagus/Celery-lettuce). Examples include BARI Lettuce-1, Great Lakes, Paris Island, Paris White, etc.
Nursery and sowing: Direct sowing in some cases; transplanting after 3–4 weeks; spacing around $45 ext{ cm} imes 20 ext{–}30 ext{ cm}$ ; nursery beds or cell-packs for seedling production; shading and humidity control in protected nurseries.
Growth and management: Fertigation and soil moisture management are key; transplanting advantages include earlier harvests and weed control; higher-density planting improves canopy cover and cooling.
Harvest and storage: Harvest 40–70 days after sowing depending on type; fresh lettuce storage around 0°C with 90–95% RH for several weeks; pre-harvest spray with a plant growth regulator or growth-enhancing agent may be used (e.g., butyric acid 5–10 ppm) to extend shelf life.
Postharvest considerations: Grading by color, size, shape, and disease/injury; packing in suitable containers; careful handling to prevent bruising; disease control and sanitation are important in protected cultures.

Tomato Production Technology

Botanical background: Solanum lycopersicum; widely grown globally with diverse uses (processing, fresh market). Varieties are grouped as determinate (bushy, early maturity, no staking required) and indeterminate (erect, protracted fruiting, requires staking).
Climate and soil: Tomato is day-neutral but has optimum fruit set around $20-24^{ ing ext{C}}$ ; red color development (lycopene) is optimal around $21^{ ing ext{C}}-24^{ ing ext{C}}$ and declines above $27^{ ing ext{C}}$ . Grows in many soils with pH around $6.0-7.0$ ; disinfection and soil solarization may be used to control pathogens.
Planting and nursery: Protected nurseries and seedling trays with sterile media for 25–30 days prior to transplant; spacing commonly around $60 imes 45 ext{ cm}$ under drip systems; mulching improves moisture retention and reduces weeds.
Irrigation and fertigation: Drip irrigation is the main method; water requirement approx. $600-700 ext{ mm/year (overall)}$ or per crop; early growth season drip rates around $8 ext{ L/m}^2$ , later around $12 ext{ L/m}^2$ ; fertigation with balanced NPK and micronutrients; growth regulators/ethylene inhibitors may be used to manage flowering and set.
Weed control: Hand hoeing early, with pre-emergent herbicides (e.g., metribuzin, fluchloralin) and, more recently, pendimethalin as pre-emergence help manage weeds.
Pruning and training: Desuckering and single/double/triple-stem systems; staking with supports; training starts around the 6th week after transplanting.
Harvesting and maturity indices: Harvest at breaker, pink, or red depending on market; maturity indices include breaker (pink at blossom end), solid red, and full red for processing; typical yield in Bangladesh: $50-70 ext{ t/ha}$ ; average world yield varies by region.
Postharvest: Grading by color, size, form, and absence of defects; packing in baskets/boxes; storage at $7-15^{ ing ext{C}}$ with high RH 90-95 ext{%}; appropriate transport handling to minimize ethylene exposure and mechanical damage.

Turnip: Production Technology

Botany and types: Turnip (Brassica rapa L.) is a biennial; two major groups: European/temperate types (Purple Top White Globe, Golden Ball) and Asiatic/Tropical types (Pusa Kanchan, Pusa Sweti, Punjab Safed).
Climate and soil: Prefers deep, well-drained loams; optimum root development at around $10-13^{ ing ext{C}}$ air temperature and $18-23^{ ing ext{C}}$ soil temperature; tolerant to cool and moderate climates; high temperatures reduce root quality.
Field preparation and sowing: Deep ploughing and fine tilth; ridges and furrows; sowing on ridges with spacing ~ $30-45 ext{ cm} imes 10-15 ext{ cm}$ ; seed rate about $3-4 ext{ kg/ha}$ ; basal FYM 20 t/ha recommended.
Manure, irrigation, and intercultural: N and P, K requirements similar to other root crops; split N applications (half at field prep, half at knob formation); irrigation every 7 days or as needed; earthing up to protect roots; weeding and thinning for stand establishment.
Harvesting and yield: Turnip roots harvested when tender; typical diameter $5.0-7.5 ext{ cm}$ ; yield $200-300 ext{ q/ha}$ with variation by cultivar and management; leaves used as fodder.
Pests and diseases: Aphids, mustard saw fly, flea beetles; common diseases include downey/mildew and brown heart; management includes chemical and cultural control strategies.

Carrot: Production Technology

Botany and soil preferences: Daucus carota; deep, well-drained loose sandy loam with high humus; pH $5.5-7.0$ ; very loose soils required for straight roots; heavy or compact soils reduce root quality.
Climate and seed germination: Cool season crop; optimum germination temp $7-23^{ ing ext{C}}$ , better root growth around $18-23^{ ing ext{C}}$ ; high heat causes short, thick roots; bolting risk in cold spells.
Land preparation and manures: Deep ploughing with final fine tilth; incorporate well-decomposed FYM at $25 ext{ t/ha}$ ; avoid fresh FYM to prevent forking; seedbed ridges aid root development.
Seed rate and planting: Seed rate ~ $5-6 ext{ kg/ha}$ ; sow on ridges with spacing ~ $30 imes 8 ext{ cm}$ ; seeds may be soaked 12–24 hours to improve germination.
Fertilization and irrigation: Base dose of FYM; N, P, K requirements depend on soil; typical base N around $100 ext{ kg/ha}$ , P around $60 ext{ kg/ha}$ , K around $60 ext{ kg/ha}$ ; irrigation after sowing, then at intervals of 5–12 days depending on season; stop irrigation 2–3 weeks before harvest to enhance sweetness.
Harvest and yield: Ready in $100-120 ext{ days}$ (variety dependent); Asiatic types often yield $25-30 ext{ t/ha}$ , European types around $10-15 ext{ t/ha}$ ; grading by size/length; postharvest handling includes washing and curing; storage in cold conditions improves shelf life (0–4.4°C with high RH for extended storage).

Radish: Production Technology

Botany and nutrition: Radish (Raphanus sativus) has a swollen root as the economic part; cool-season crop with preferred soils of light, friable sandy-loam; optimum soil pH ~ $6.0-7.0$ .
Sowing and spacing: Root crops raised on ridges for root development; seed rate around $10-12 ext{ kg/ha}$ ; tropical varieties sown at $45 imes 8 ext{ cm}$ spacing; temperate varieties at $20-30 imes 8 ext{ cm}$ .
Fertilization and irrigation: High N and P; FYM at $15-20 ext{ t/ha}$ ; irrigation frequently (10–12 days in winter, 5–6 days in summer); half N at planting then 30 days after.
Interculture and harvest: Weeding, thinning, earthing up; harvest in $25-60 ext{ days}$ depending on cultivar; yield $25-30 ext{ t/ha}$ in short cycles; postharvest: washing, grading, and bunching with tops; storage up to $2 ext{ months}$ in cold storage with high RH.

Postharvest Technology (Overview and Key Practices)

Definition: Postharvest technology covers treatments from harvest to consumer, including harvesting, handling, storage, processing, packaging, and transport to minimize losses and preserve quality.
Loss factors: Heat, drought, mechanical damage, sanitation issues, inadequate cooling, and poor environmental control.
Loss mitigation steps: Use proper maturity indices, careful harvesting practices, sanitation, quick cooling, precise grading, appropriate packaging, careful transport, and proper storage.
Maturity, grading, and packing: Maturity indices vary by crop (e.g., tomato maturity stages; cauliflower curd white; pepper maturity from green to red). Grading typically considers color, size, shape, and absence of defects; packing uses baskets, boxes, or cartons with padding; storage temperatures and humidity vary by crop (e.g., tomato: mature green to red, 12.5–15°C, RH 90–95%; cauliflower: 0–5°C, RH 90–95%).

Quick Reference: Key Numerical Anchors (for last-minute recall)

Capsicum yield (greenhouse): $100-120 ext{ t/ha}$ ; bed spacing $45 imes 30 ext{ cm}$ ; drip emitter: $2 ext{ L/hr}$ ; irrigation: $2-3 ext{ L/m^2/day}$ ; storage: $7-8^{ ing ext{C}}$ , up to $45-60 ext{ days}$ .
Lettuce: transplant spacing $45 ext{ cm} imes 20-30 ext{ cm}$ ; harvest: $40-70 ext{ days}$ (head types) or $40-60 ext{ days}$ (leaf types); storage at near 0°C with high RH 90–95%.
Tomato: determinate vs indeterminate; drip irrigation; N-P-K management with fertigation; maturity indices: breaker, pink, red; typical Bangladesh yield around $50-70 ext{ t/ha}$ ; temperature for color development around $21-24^{ ing ext{C}}$ .
Turnip: root diameter target $5-7.5 ext{ cm}$ ; yield $200-300 ext{ q/ha}$ ; Asiatic types tolerate warmer conditions than European types.
Carrot: seed sowing on ridges; seed rate $5-6 ext{ kg/ha}$ ; harvest at $100-120 ext{ days}$ ; storage: 0–4.4°C, RH 93–98% for up to 6 months.
Radish: sowing window in cool seasons; half to full dose FYM; harvest in $25-60 ext{ days}$ ; storage up to 2 months in cold storage.