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পৃষ্ঠাসমূহ

CROPS AND CROPPING,CROPPING SEASONS ,PLANT GROWTH AND DEVELOPMENT,

CROPS AND CROPPING

Crop:

It is very difficult to give a precise definition of crop but it has some characteristics-

i. Crop must be cultivated species

ii. It must have economic value

Crops are aggregation of individual plants grown on a particular location usually of the same species or variety and have some economic value.

Agronomic Crops / Field Crops:

The crops, which are grown together or collectively with less intensive care, compared to horticultural crops (with intensive core) and harvested in bulk.

Classification of crops:

Classification is an acceptable product of scientific studies and is obviously based on well-defined characteristics or concepts that separate one group from another.

Crops are grouped into there main classes according to the range of cultivation. They are-

a) Gender Crop:

Crop plants that are grown on a small scale with intensive care in gardens such as kitchen gardens, flower gardens and background gardens e.i. onion, brinjal, banana, okra, mango, jackfruits, rose, tuberose, etc.


b) Plantation Crops :

Crop plants that are grown on a larger scale on estates. They are permanent in nature (need not be replanted after each harvest) be harvesting continues for a prolonged period from a single planting e.g. tea, coffee, cocoa, rubber etc.

c) Crop plants that are grown together or collectively on a vast scale with less intensive care and harvested in bulk, e.g. rice, wheat, maize etc.

Among these there classes agronomy deals with field crops only.

Agronomic Classification of Crops :

a) On the basis of use, agronomic crops are as follows-

i. Cereals :

Cereals are the cultivated grasses grown for their edible starchy grains under graminal family. In general, the longer grains used as staple food are cereals such as rice, wheat, maize, barley etc. (One seeded fruit known as caryopsis).

ii. Millets :

Millets are the small grained cereals and they have a single cover (due to fusion of testa paricorp) such as cheena, kaon, basra, etc.

iii. Oil seeds :

Crop seeds that are rich in fatty acids, which are used to extract vegetable oil to meet various requirements e.g. mustard, rape, rai, sesame, sunflower, castor, linseed, groundnut, soybean, etc.


iv. Pulses :

Seeds of liguminous crop used as food. On splitting they produce dal which are rich in protein such as lentil, gram, grass pea, black gram, pea, cow pea, arhor etc.

v. Fiber Crops :

Crop plants grown for fiber yield. Fiber may be obtained from seed such as cotton; stem or bark such as jute, mesta, sumhemp, kenat; leaf such as pineapple.

vi. Sugar Yielding Crops :

Crops grown for production of sugar and starch e.g. sugar cane, sugar beet, potato, sweet potato, etc.

vii. Nareotic Crops :

Crop plants or their products that are used for stimulating, numbing, drowsing or relishing effects such as tobacca, ganja, poppy etc.

viii. Beverage Crops :

Products of crops used for mild, agreeable and stimulating liquors meant for drinking such as tea, coffee, cocoa etc.

ix. Fodder Crops :

Crop plants or their products which are utilized as feed for animals e.g. maize, Napier grass, cow-pea etc.

x. Green manuring Crops :

The crop plant which is growth to be incorporated into the soil to increase the dertility of the soil e.g. Dhaincha, sunnhemp, cowpea, etc.

b) On the basis of cultural requirement agronomic crops are as follows-

A. According to suitability of topogrophy

i. High land crops

They cannot tolerate water stagnation e.g. Arhar, groundnut, sunnhemp, maize, bajra cotton, sesame, napier etc.

ii Medium land crops :

They require sufficient soil moisture but can not tolerate water stagnation e.g. Jute, Patato, Suger cane, Upland rice, Wheat, Black gram, Burley, Mustard etc.

iii. Low Land Crops :

They require an abundant supply of water and can stand prolonged water logged conditions. e.g. Rice, dhanha, para grass and jute (Capsular’s)

B. According to the suitability of the textural groups of soils-

i. Crops of sandy to sandy loan soils :

Sugar-beet, green gram, black gram, sunflower, jowar, bajra.

ii. Crops of silty to silty loan soils :

Jute, sugarcane, maize, cotton, mustard, tobacco, peas, pigeon pea, cow pea etc.

iii. Crops of clay to clay loan soils :

Rice, wheat, barley, linseed, lentil, chick pea etc.

C. According to the tolerance to the problem soils :

i. Crops tolerance to acidic soils

e.g. wet-rice, mustard

ii. Crops tolerance to saline soils

e.g. wheat, bajra, jowar, barley

iii. Crops tolerance to alkaline soils

e.g. Barley, cotton, chick pea, peas, groundnut, maize

iv. Crops tolerance to water logged soils

e.g. wet-rice, dhancha, para grass, napier grass

v. Crops tolerance to soil erosions

e.g. groundnut, black gram

D. According to tillage requirements

i. Crops requiring preparatory tillage

e.g. Sugarcane, rice, tobacco, maize

ii. Crops that may not requiring preparatory tillage

e.g. Black gram, para grass, cow-pea.

E. According to the depth of root system

i. Shallow-rooted crops: Rice, patato

ii. Moderately-deep-rooted crops: wheat, groundnut tobacco, barley, chick pea, cow- pea.

iii. Deep rooted crops : Maize, cotton, jowar, sugar beet.

iv. very deep-rooted crops: Sugar cane, sat-flower.

F. According to the tolerance to harardous weather conditions :

i. Frost tolerant crops : Sugar beet, wheat

ii. Cold tolerant crops : Mustard, potato

iii. Drought tolerant crops : Bajra, jowar, barley, cotton, sesame.

G. According to the method of sowing or planting :

i. Direct seeded crops :

Upland rice, wheat, mustard, maize, jowar, bajra, groundnut, peas, grams, etc.

ii. Planted crops :

Sugar cane, potato, sweet potato, napier, para grass.

iii. Transplanted crops :

(After raising seedlings in the nursery)

Transplanted rice, tobacco, bajra etc.

H. According to the length of field duration :

i. very short duration (up to 75 days ) crops

e.g. Green gram, beet, maize

ii. Short duration ( 75 to 100 days ) crops

e.g. Uplard rice, sunnhemp, sunflower, potato (early)

iii. Medium duration ( 100 to 125 days ) crops

e.g. wheat, jowar, bajra, barley, groundnut, soybean, sesame, tobacco (rustica) boro rice, jute.

iv. Long duration ( 125 – 150 days ) crops

e.g. Mustard, tobacco ( tobacum), Kharif rice, mesta, cotton, etc.

v. Very long duration ( 150 days ) crops

e.g. Sugar cane, sugar beet, pigeon pea, napier, para grass.

Special purpose classification of crops :

Crop plants which are grown with the intention of serving purposes in addition to obtaining yield or to meet a particular purpose are grouped into special purposes are grouped into special purpose crops.

1. Catch crops / Emergency crops / Contingent crops :

These are crops cultivated to ‘catch’ the forth coming season. They are generally of very short duration quick growing, harvestable or useable at any time of their field duration e.g. green gram, black gram cow pea, bajra etc.


2. Restorative crops :

The crops which provide a good harvest along with enrichment or restoration or amelioration of the soil such, such as legumes. They fixed atmospheric nitrogen in root nodules, shed their leaves during ripening and thus restore soil conditions.

3. Exhaustive crops :

The crop-plants which on growing leave the field exhausted because of more aggressive nature, e.g. sesame, linseed, maize.

4. Paira crops :

These are crop plants which are sown a few days or week before the harvesting of standing nature crop, e.g. black gram (paira crop) in aus paddy, grass pea ( paira crop) in Aman paddy, paira crops in succession may constitute relay cropping.

5. Smother crops :

The crop plants are able to smother or suppress the population and growth of weed by providing suffocation ( curtailing movement of air ) and obscuration ( of the incidental radiation ) by their dense foliage, e.g. parley, mustard, cow pea.

6. Cover crops :

These crop plants are able to protect the soil surface from erosion ( wind, water or both ) through their ground covering foliage, e.g. groundnut, black gram, grass pea, para grass.

7. Nurse crops :

These crop plants help in the nourishment of other crops by providing shade and acting as climbing sticks such as rai in peas, jowar in cow pea, Glyricidia, Crotalaria in tea.


8. Barrier crops :

These crop plants help to protect another crop e.g. safflower in gram.

9. Brake crops :

These crops are grown to break the continuity of the agro-ecological situation of the field under multiple cropping systems, fir instance rice-rice, rice-wheat, rice-maize breaks the continuity of a large number of pest (weed, insect, pathogens) due to variations in host ranges and changing of agro-ecological situation.

10. Trap crops :

These crop plants are grown to trap soil borne harmful biotic agents such as parasitic weeds, Orobanche and stria that are trapped by solanaceous and sorghum crops.

11. Mulch crops :

These crop plants are grown to conserve soil moisture by their thick and multilayered foliage and self-seeding nature e.g. cow-pea, Atylosia.

12. Sod or turf crops :

These crop plants belong to the grass family and have sod type tillers with matted foliage and root close to the soil surface, e.g. marvel grass, Digilria sanguinalis , Cyrodon Dactylon.

13. Cash crops :

These crop plants are grown for sale to earn hard cash. e.g. Jute, tobacco, cotton and sugarcane.

14. Cole crops :

These crop plants are essentially cold weather crops belonging to the cruciferal family capable of with standing considerable frost such as cabbage, cauliflower, Brussels sprouts.

15. Leaf crops :

These crop plants are grown to harvest leaves for economic yield e.g. tobacco, spinach, basella.

16. Erosion restricting crops :

These crop plants are grown to restrict soil erosion. e.g. marvel grass, groundnut, Atylosia.

“ Crop is a plant or a group of plants that are cultivated with proper care and management for getting raw materials for sustaining the life of human being and livestock.”

CROPPING SEASONS

Seasons for Agricultural Crops :

Different annual crops are grown in different seasons of the year. Crops are grouped under the season in which are their major field duration.

A. Kharif season :

The season starts in mid March ( 16 March) and continues up to mid October (15 October). Crop plants grown during this season are known as Kharif crops e.g. rice, maize, groundnut. These crops require warm-wet weather during their major period of growth and shorter day-length for flowering.

Kharif season is again divided into Kharif-I (16 March to 30 June) and Kharif-II (01 July to 15 October) season.

B. Robi season :

The season starts in mid October ( 16 October ) and continues up to mid March ( 15 March). Crop plants grown during this season are known as Rabi crops. e.g. wheat, mustard, basley, potato, peas, linseed, lemtil, cabbage, caul, flower. They require cold-dry weather for their major growth period and longer day-length for flowering.

Comparative characteristics of Kharif and Rabi Seasons :

Kharif-I

Kharif-II

Rabi

Duration : 16 March to 30 June

Duration : 01 July to 15 October

Duration: 16 October to 15 March

Intensity of rainfall is medium and rain starts in the mid of the season.

The whole season is more or use rainy

Intensity of rainfall is very law and there is some rain at the beginning of the season.

There is possibility of hailstorm

Possibility of hailstorm is less.

Possibility of hailstorm is minimum

Temperature is high

Temperature is high

Temperature is low

Sky is cloudy, mainly in the late season

The sky is cloudy

Clear and cloud free sunny day. But little cloud in early season.

Day length increases with advancement of season.

Length of day and night is almost equal

Day length decreases with the advancement of the season.

Atmospheric humidity is moderate.

Atmospheric humidity is high

Atmospheric humidity is low

Major crops are, aus rice, jute, groundnut, maize soybean

Major crops are aman rice, maize sunflower, soybean

Major crops are boro rice, potato tobacco, mustard, groundnut pulses, wheat etc.

N.B. : Chaitra to 15 Ashar 16 Ashar to Arswin Kartik-Falgun

Seasons for Rice Crop :

Three seasons viz, aus, aman and boro are noticed with respect to rice cultivation.

1. Aus season :

The word ‘aus’ has been derived from the sansicrit ashu meaning quick or early. The season designates the cultivation of rice varieties which are planted in mid March-April and harvested in mid June-July.

e.g. Local aus varities : Dular, dharial, hashikalmi, shita, pabira

High yielding aus varieties : Nizami (BR 20), niamat (BR 21)

Rahmat (BR 24), Shraboni (BR 26)

2. Aman season :

The word aman has been derived from Arabic meaning safety which indicates stability of the crop. The season designates the cultivation of rice varieties which are planted in mid July and harvested in mid November-December. e.g.

Local aman varieties : Lalishail, nizershail, jhingashail, pajam, rajashail.

HYV (aman) : Brrishail, Binashail, Dulabhog (BR5), Kiron (BR22), Dishari (BR23).

3. Boro season :

Boro rice refers to the rice grown in submerged land lower in elevation. The season designates the cultivation of rice varieties which are planted in Novermber-December and harvested in March-April. e.g.Local boro varieties : Tepi boro, khoya boro

HYV (boro) : BR 17 (hashi), BR 18 (Shahjalal), BR 19 (mongal), BRRI dhan 28,

BRRI dhan 29 etc.

This seasonal classification is not a universal one. It only indicates the period of the year when a particular crop has been grown. Some crops overlap the seasons such as jute which may be sown in February-March and harvested and thermo-sensitive crop varieties may be grown thought the year providing irrigation. e.g.

rice variety BR3 (biplob), maize, groundnut. Again, some long duration temporary crops such as sugar-cane, cotton, pigeon pea etc. do not follow the regular pattern except that low temperatures in winter provide a triggering factor contributing towards the maturity of the crops.

PLANT GROWTH AND DEVELOPMENT

The dictionary meanings of growth are many: the advancement towards or attainment of full size or maturity; development; is a gradual increase in size. Growth refers to cell division (increase in number) and cell enlargement (increase in size). Both the process are irreversible. In other words, growth is an irreversible increase in mass, length, or height, surface area, or volume of plant body. From agronomic point of view, growth means an increase in dry matter.

Growth = Vt-Vo and growth rate =

Vt-Vo

t

where, Vt = Volume at end of time, t and

Vo = Orginal volume at time zero

Growth = St – So

Where ,

St = surface area at end of time t, So = Orginal surface area

Growth = Lt-Lo

Again growth = Wt-Wo

Where,

Lt = Length at end of time, t

Lo = Orginal length

Wt = Weight at end of time, t

Wo = Orginal weight

According to Blackman

W 1 = Wo, ert

Where,

W1 = Final size (weight, height, etc). after time. t.

Wo = Initial size at the beginning of the time period

r = The rate at which plant substance is laid down during time, t.

(relative growth rate)

e = Base of natural logarithms.

Development :

Development is a combination of growth and differentiation. The process of growth and differentiation of individual cell into tissues and organs are called development.

[ The process of specialization of newly formed calls and their transformation into different types of tissues or organs is known as differentiation.]

* Development refers to one or more complex processes after completion of which plant moves towards maturity.

* Development of a plant from germination to maturity can be considered as a series of discrete processes each identified by a process of change in the structure, size or mass of specific organs.

Growth

Development

a. Growth is a quantitative aspect of development

a. Differentiation is a qualitative aspect of development.

b. Growth is a continuous process.

b. Development is a discrete process.

c. Growth can be measured by number, quantity, volume and area.

c. Development is measured interims of time

e.g. if a development process require 4 days (e.g. germination to complete, after two days, it can be said that 50% of the process has been completed.

PATTERNS OF GROWTH

The growth of most plants follows a similar pattern, generally sigmoid in shape. A relatively slow growth rate characterizes early or seedling growth. The rate of growth increases as the plant becomes larger, is greatest just before or in early stages of flowering, and then decreases as the plant matures. The slow growth rate of seedlings relative larger plants may be attributed to the relatively small number of calls that can divide, the small leaf area available for light interception and photosynthesis, and perhaps to the relatively large percentage of photosynthate going to roots. As plants increase in size, larger meristematic regions (areas of call division) per plant exist, and more leaves are present to act as photosynthetic energy sources. Thus each plant is capable of capturing and utilizing more energy as it increases in size. The decline in growth rate near maturity may be attributed to several factors. Many species have determinate growth characteristics; that is, vegetative growth cases prior to or con-current with reproductive growth. In species, such as corn or small grains, the formation of fruit signals an end to growth of other plant parts. Even in species such as cotton where vegetative and reproductive growth occur simultaneously, the onset of reproduction reduces vegetative growth rates.

As plants become older a large portion of the plant structure becomes inactive. Lower leaves may become heavily shaded or non photosynthetic due to senescence. Leaves may fall from the plant, representing loss of dry weight. Large portions of the plant may be comprised of stem or other tissue reactively low in metabolic activity and therefore not contributing to growth. In addition, competition from neighboring plants for water, nutrients, and light may cause a reduction in growth rates when plants in crop stands become large.

** Fig. Dry weight accumulation patterns for a hypothetical plant and its parts.