৪৯তম বিসিএস ⎯ কৃষিবিজ্ঞান [৮০১]

Location: Situated in the wet and humid areas. Chittagong Hill Tracts, Sylhet, Chittagong and Cox’s Bazar. Dumur, Gamar, Chapalish, Jarul
Characteristics
- Forest is rich in diversified types of plants.
- Plant of this forest are tall unto 46-60 m in height.
- Canopy of trees arranged in different layers.
- The average annual rainfall ranges from 380-500 cm.
- The forest contains at least 600 species of plants
- Forests are evergreen and do not shed all their leaves at once, so they appear green throughout the year.

Moist Deciduous Forests বা পর্ণমোচী আর্দ্র বন শুকনো মৌসুমে (dry season) গাছের পাতা ঝরিয়ে ফেলে, যাতে পানি কম খরচ হয়।
বর্ষায় ও আর্দ্র মৌসুমে এরা আবার ঘন সবুজ হয়ে ওঠে।
Characteristics
- Most dominant tree is the Sal tree (Shorea robusta) and 90% area of this forest is covered with the Sal trees and height 20-25 m.
- The trees shed their leaves during the long dry season (Winter) to conserve water. It is culled "bare" or "deciduous" forest.
- In this forest, there are some raised lands and some low lying areas which lying are termed as ‘Chala’ and ‘Baid’, respectively.

সুন্দরবনের নামই এসেছে প্রধান বৃক্ষ সুন্দরী (Heritiera fomes) থেকে।

সুন্দরী গাছ লবণাক্ত পানির সাথে মানিয়ে নিতে পারে এবং সুন্দরবনের সর্বাধিক বিস্তৃত ও প্রভাবশালী প্রজাতি।
Characteristics
- The main species of this forest is Sunduri (Heritiera fomes), due the abundance of this species, this forest is also
known as Sundarban.
- Sundarban is the largest Mangrove forest all over the world.
- The soil is highly saline and it remains wet due to inundation of low lying areas for two times every day.
- The forest is about 2 m above the sea level.
- Most of the trees have stilt roots  and propagated by viviparous germination.
- Almost all the plants growing in the forest are salt tolerant and evergreen.

অতিরিক্ত ঝুম চাষ (Shifting cultivation) করলে—

বনভূমি কেটে ফেলা হয় → forest cover কমে যায়
ঢালু জমি খালি হয়ে পড়ে → soil erosion বৃদ্ধি পায়
মাটির উর্বরতা দ্রুত নষ্ট হয়
জীববৈচিত্র্যও কমে যায়

Shifting Cultivation
- Land is cleared by cutting and burning vegetation.
- Crops are grown for 2–3 years until soil fertility declines.
- Land is then left fallow for several years to recover.
- Practiced in hilly, forested, and less fertile areas.
Jhum cultivation – Same as Shifting cultivation. Its regional name
used in Northeast India and Bangladesh (Chattogram Hill Tracts).
Rice, Maize, Sesame, Cotton, Vegetables

চা পাতার fermentation (অক্সিডেশন প্রক্রিয়া) চলাকালে—

Pectase → পেকটিন ভেঙে আঠালো পদার্থ তৈরি করে।
Polyphenol oxidase → ক্যাটেচিনসহ Polyphenol কে অক্সিডাইজ করে, যার ফলে চায়ের রং, স্বাদ ও ঘ্রাণ তৈরি হয়।

Forage alley cropping-এ সারি করে fodder trees/shrubs (যেমন Leucaena, Gliricidia) লাগানো হয়।

মাঝের ফাঁকা জায়গায় (alleys) চাষ করা হয় forage/grass crops, যা মূলত পশুখাদ্য (livestock feed) হিসেবে ব্যবহৃত হয়।
Forage Alley Cropping: rows of fodder trees/ shurbs are planted at intervals, and livestock feed crops (forage, grasses, or
legumes) are grown in the alleys between the rows.
Forage-cum-Mulch Alley Cropping: Rows of fodder trees or shrubs are planted at intervals, and annual crops are grown in the alleys. Combines fodder production + soil fertility improvement + crop yield.
Multistoried Tree Garden: trees, shrubs, and crops of different heights are grown together in layers or tiers to utilize vertical
space efficiently.

Opium poppy (Papaver somniferum) → Morphine, Codeine, Heroin
Coca plant (Erythroxylum coca) → Cocaine
Cannabis / Hemp (Cannabis sativa) → THC (Tetrahydrocannabinol), Hashish, Marijuana
Datura (Datura stramonium) → Atropine, Scopolamine (hallucinogenic in high doses)
Khat (Catha edulis) → Cathinone (stimulant)

চা পাতার withering পর্যায়ে:

Caffeine এর পরিমাণ বৃদ্ধি পায়
অ্যামিনো অ্যাসিড প্রোটিন থেকে ভেঙে বের হয়
জৈব অ্যাসিড, চিনি, ক্লোরোফিলের পরিবর্তন ঘটে
কোষঝিল্লির পারমিয়াবিলিটি বাড়ে

Alley cropping হলো একটি agroforestry system, যেখানে—

সারি করে গাছ/ঝোপ লাগানো হয় 
সেই সারির মাঝের ফাঁকা জায়গায় (alleys) বিভিন্ন ফসল জন্মানো হয়
Alley cropping is an agroforestry system in which rows of trees or shrubs (Eucalyptus, Acacia) are planted at regular
intervals (called alleys) and agricultural crops ((Maize, wheat, millet, pulses, vegetables, and sometimes paddy)) are grown
in the spaces between these rows.
- Trees may be leguminous (nitrogen-fixing) or non-leguminous.
- Provides short-term crop yield + long-term tree products.

Cotton ginning = তুলার আঁশ (fiber) কে বীজ (seed) থেকে আলাদা করার প্রক্রিয়া।

মূল উদ্দেশ্য: আঁশকে বীজ থেকে আলাদা করে সুন্দর, বাণিজ্যিকভাবে ব্যবহারযোগ্য তুলা তৈরি করা।
এটি মেশিনে বা হাতেও করা যায়, তবে আধুনিকভাবে ginning machine ব্যবহার করা হয়।

Narcotic plants are those that produce alkaloids and other psychoactive compounds affecting the central nervous
system. They are important both medicinally and economically, but also have social and legal concerns. 
Example
Opium poppy (Papaver somniferum) → Morphine, Codeine, Heroin
Coca plant (Erythroxylum coca) → Cocaine

Shifting Cultivation
- Land is cleared by cutting and burning vegetation.
- Crops are grown for 2–3 years until soil fertility declines.
- Land is then left fallow for several years to recover.
- Practiced in hilly, forested, and less fertile areas.

Coir হলো একটি natural fiber যা নারকেল-এর খোসা (husk) থেকে সংগ্রহ করা হয়। এটি শক্ত, durability বেশি এবং সাধারণত রশি, মাদুর, ব্রাশ, mattress ইত্যাদিতে ব্যবহার হয়।

Alley cropping-এ সাধারণত Nitrogen-fixing trees/shrubs (যেমন Leucaena, Gliricidia) লাগানো হয় কারণ—

এরা মাটিতে নাইট্রোজেন সরবরাহ করে → ফসলের বৃদ্ধিতে সহায়ক
ফসলের মাঝখানে (alleys) ভালো উপযোগী পরিবেশ তৈরি করে

Coagulation and stimulants is used for rubber processing.
Coagulation:
- Is a process by which rubber is separated from suspended latex
- Formic acid, Acetic acid, Flurosilic acid, Potassium alum is used for coagulation
- Anti-coagulation NaOH, Ammonia, Formaldehyde
 Stimulants
- The chemical which used to accelerate the flow of the latex is called stimulant.
- Some stimulants are used Ethylene, Ethapon, Acetylene,Cetrims etc.

SALT (Sloping Agriculture Land Technology)-এ soil fertility বজায় রাখতে সাধারণত crop rotation করা হয়।

বিভিন্ন ফসল পালাক্রমে চাষ করা হয় → মাটির উপাদানসমূহ পুনঃস্থাপন হয়
এক ধরনের ফসল বারবার চাষ করলে মাটি উর্বরতা হারায় → mono-cropping এ সমস্যা দেখা দেয়

To maintain and restore soil fertility:
১) Nitrogen-Fixing Hedgerows:
২) Crop Rotation:

In rubber tapping, ethylene is commonly used as a stimulant to increase latex yield.
It works by stimulating latex flow in the tapped rubber trees.
Ethephon is an ethylene-releasing compound. When applied to the bark (tapping panel) of the rubber tree, the chemical decomposes within the plant tissue to release ethylene gas.

The "tanning" of proteins in tea, which refers to the binding of protein molecules and often leads to their precipitation or the formation of a dark color, is primarily caused by polyphenols (specifically, a group of polyphenols called tannins).
During tea processing, especially withering and drying, tannins are formed.
Tannins are a type of polyphenol that react with proteins, leading to tanning of proteins.

Boundary planting or bund planting involves planting trees or shrubs along the boundaries or edges of fields.
Purposes:

Prevent soil erosion
Act as windbreaks
Protect crops from external damage
Provide additional resources (fruit, fodder, timber)

Tea বা অন্য plant products drying করার সময় volatile compounds (যেমন essential oils, aromatic compounds) evaporate করে।
এই compounds মূলত aroma এবং flavor এর জন্য দায়ী।
অন্যান্য প্রভাব:

Colour – বেশি oxidized polyphenols দ্বারা affected হয়, volatiles এর কারণে নয়।
Texture – moisture loss বা structural changes দ্বারা পরিবর্তিত হয়।
Caffeine content – drying এ প্রায় stable থাকে, কমে না।
তাহলে, volatile compounds loss mainly **aroma কমিয়ে দেয়।

SALT (Sloping Agricultural Land Technology) method এ contour bunds along strips তৈরি করা হয়।
Early harvesting crops সাধারণত middle two rows of every third strip এ লাগানো হয় যাতে:

Soil erosion কমানো যায়
Nutrient recycling সহজ হয়
Crop growth optimize করা যায়

Steps of SALT Model
1. Making an A-frame
2. Locate the contour lines for growing hedgerows
3. Land preparation along the contour lines
4. Seed sowing and planting of cutting/ seedling in the soil
along the contour line
5. Prepare the land of each alternate alley or strip
6. Plant permanent crops on every third strips
7. Plant early harvesting crops in the middle two rows of
every third strips
8. Trim down hedgerows regularly
9. Practice crop rotation
10. Maintenance of green terraces

Biofuel production এর জন্য mainly high oil-yielding plants ব্যবহার করা হয়।
উদাহরণ: Jatropha, Palm oil – এগুলো থেকে biodiesel বানানো যায়।

Biodiesel হলো একটি renewable, biodegradable fuel যা মূলত vegetable oils বা animal fats থেকে তৈরি করা হয়।

Source: Oil plants: Jatropha, Palm, Soybean, Mustard, Coconut

Uses: Diesel engine fuel হিসাবে ব্যবহার
Fossil fuel এর alternative

Manufacturing of Green Tea (Orthodox)
Streaming of fresh leaf at a pressure of 80 PSI in a roaster
for 4-5 minutes.
- Immediate cooling of steamed leaf by immersing in ice cold water or spraying water over the leaf.
- Removal of surface water by blowing air over the bed of leaf for 15-20 minutes.
- Rolling of the surface dried leaves sequence of 10 min without pressure, 5 min light pressure ,10 minutes medium
pressure; 5 minutes ball breaking and 15 minutes hard pressure.
- Sun drying of rolled leaf in a conventional dryer at 104°C for 35-40 minutes to a moisture content of 2-3%.

Economic Importance of Fiber Plants
Textiles: Cotton, jute, flax → clothing, ropes, bags
- Industrial Use: Jute → gunny bags, carpets; Coir → mats, brushes
- Paper & Pulp: Bamboo, jute sticks → paper industry
- Foreign Exchange: Cotton and jute are major export crops
for countries like Bangladesh, India, Egypt
- Employment: Provides large-scale employment in agriculture and textile industries

Agri-silviculture হলো একটি ধরনের agroforestry system।
এখানে মূলত কৃষি ফসল (Crops) এবং বনজ বৃক্ষ (Forest trees) একসাথে লাগানো হয়।
Purpose:

Soil fertility maintain করা
Erosion control করা
Shade, wind protection এবং timber/fruit production পাওয়া

Conventional forestry → big forests, govt managed, Large government or private forest lands
Social forestry → community trees for social & environmental benefits, Marginal lands, degraded lands, community lands
Agroforestry → farmers mix crops + trees on their land for multiple benefits, Croplands, homesteads, grazing
lands, sloping lands

জরায়ুজ অঙ্কুরোদগম (Viviparous Germination): এটি এক ধরনের অঙ্কুরোদগম প্রক্রিয়া যেখানে বীজ মাতৃগাছে থাকা অবস্থায়ই অঙ্কুরিত হয়। অর্থাৎ, বীজ মাটি বা জলে পড়ার আগেই তার মধ্যে থাকা ভ্রূণ বড় হয়ে চারাগাছে পরিণত হতে শুরু করে।
Characteristics of Mangrove or Tidal forest
- The main species of this forest is Sunduri (Heritiera fomes), due the abundance of this species, this forest is also
known as Sundarban.
- Sundarban is the largest Mangrove forest all over the world.
- The soil is highly saline and it remains wet due to inundation of low lying areas for two times every day.
- The forest is about 2 m above the sea level.
- Most of the trees have stilt roots (?ঠস মূল) and propagated by viviparous germination (জরায়ুজ অ?ুেরাদগম).

Narcotic plants are those that produce alkaloids and other psychoactive compounds affecting the central nervous system. They are important both medicinally and economically, but also have social and legal concerns.
Narcotic plants produce alkaloids and other psychoactive compounds that affect the central nervous system (CNS).

Examples:: Opium poppy → Morphine, Codeine
Coca plant → Cocaine
Cannabis → THC

A simple, low-cost agroforestry system designed to prevent soil erosion and improve crop yields on sloping or hilly land.
- It involves planting rows of nitrogen-fixing trees and shrubs along contour lines to create a living barrier, with crops grown in the alleys between these rows.
- The system was developed in the Philippines Sloping Agricultural Land Technology (SALT)
Advantages of SALT
- Prevents soil erosion
- Improves soil fertility and productivity
- Conserves water
- Provide fodder for livestock
- Regulates microclimate
- Promotes sustainable agriculture
- Increase bio-diversity

Green tea processing এ drying step-এর পরে target moisture content রাখা হয় 2–3% এর মধ্যে।
Purpose:

Prevent microbial growth
Ensure long shelf life
Maintain quality, flavor, and color

If the moisture content is 1–2% – too low, leaves brittle

Natural rubber হলো একটি polymer of isoprene (C₅H₈)।
Structure: (C₅H₈)n, যেখানে n হলো repeating units।

Other info of rubber
- Rubber is a hydrocarbon which is colorless, tasteless and elastic
- Contains 92-94% hydrocarbon, 3% resin, 2% protein
- Long chain of isopropane
- 99% of world rubber production from Hevea brasiliensis species, family Euphorbiaceae . It produce quality latex but production is very low.

Evergreen forests এ year-round leaf fall এবং decomposition হয়, ফলে soil organic matter খুব high থাকে। Forests are evergreen and do not shed all their leaves at
once, so they appear green throughout the year.
Characteristics:

Moist, nutrient-rich soil
Thick humus layer
Supports high biodiversity

Aroma in tea comes from oxidation products formed during fermentation (oxidation) step.
Black tea undergoes full fermentation, leading to:

Formation of theaflavins and thearubigins
Development of rich aroma and dark color
More oxidation → more aromatic compounds → black tea has strongest aroma.

Multistoried tree garden system এ different height এর trees and shrubs একসাথে লাগানো হয়।
এটি সাধারণত homestead areas এ practice করা হয়, যেখানে:

Fruits, vegetables, fuelwood, fodder একসাথে পাওয়া যায়
Space utilization efficient হয়
Soil conservation হয়

Natural rubber মূলত Hevea brasiliensis থেকে আসে।

Native to Amazon rainforest, now widely cultivated in Southeast Asia (India, Thailand, Malaysia)
Latex tapped from the bark of the tree
Used for tires, industrial products, gloves, etc.

Sundarbans হলো world’s largest mangrove forest, এবং এটি Bangladesh–India border এ অবস্থিত।
Geographically, এটি Ganges–Brahmaputra–Meghna (GBM) delta তে।