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During the 19^th century various hypotheses were advanced about the origin of earth. These hypotheses can be grouped into two general classes:

1. Monistic hypotheses: The pioneers of this hypotheses believed that only one mass or body was responsible for the creation of the solar system. The representative of this theory is Nebular hypothesis. The advocates of this hypothesis were Kant and Laplace.

2. Dualistic hypotheses: The advocates of this hypothesis believed that two separate masses or bodies were responsible for the creation of the solar system. The representatives of this hypothesis are Planetesimal hypothesis and Tidal hypothesis. The pioneer of Planetesimal hypothesis was the great English scientist T. C. Chamberlain. The Tidal hypothesis was advocated by another English geographer named James Jeans.

Rock

A rock may be defined as “an aggregate of one or more minerals”. An aggregate of single mineral calcite gives rise to crystalline limestone. Granite is a combination of several minerals. Most rocks are hard and compact as granite and basalt, but some are loose and feebly aggregated as sandstone. Rocks possess certain characteristics such as structure, colour, specific gravity, cleavage and mineralogical make-up by which we can identify the rocks and also distinguish one from the other.

Mineral

A mineral is defined as “a natural substance, usually inorganic, having a definite chemical composition and commonly a definite molecular arrangement which is usually expressed in geometric form”.

Rocks and minerals formed under a very high temperature and pressure, when exposed to atmospheric conditions of low pressure and low temperature, they become unstable and weather. Soils are formed from rocks through the intermediate stage of formation of regolith (parent material) which is the resultant of weathering.

Soil formation takes place in two consecutive stages:

1. The weathering of rocks into regolith

2. The formation of true soil from regolith

The evolution of true soil from regolith takes place by the combined action of soil forming factors and processes. The first step is accomplished by weathering (disintegration and decomposition) and the second is associated with the action of soil forming factors which are known as pedogenic factors.

The pedogenic processes are dynamic and extremely complex involving several chemical and biological reactions, usually operating simultaneously in a given area. One process may counteract another, or two different processes may work in tandem to achieve the same result. Different processes or combination of processes operate under varying natural environments. The combined interaction of various soil forming factors under different environmental conditions set a furtherance to certain recognized soil forming processes. Pedogenic processes include:

There are over 100,000 different types of soil in the world, each with its own set of characteristics. If any soil is dug deep, one can see that it is made of layers, or horizons. The horizons together form a soil profile. Each profile tells a story about the life of a soil.

The development of soil profile is a constructive process where in disintegrated materials resulting from weathering of rocks and minerals get converted into a soil body. Soil Individual or Polypedon is a natural unit of soil that differs from its adjoining unit on the landscape in one or more properties. In modern soil taxonomy, polypedon is the unit of soil mapping. Apedon is the smallest volume recognizable in nature that can be called “a soil”.

Soil classification, or soil taxonomy as it is called, is grouping of soils in an orderly and logical manner based on soil properties (differentiating characters) for the purpose of studying and identifying them. The following are the purpose of soil classification:

To organize our knowledge of soils

To bring out and understand the relationships among the soils

To remember the properties of soils

To learn new relationships and principles in different soil groups

Physical properties of a soil greatly influence plant growth. The plant support, root penetration, drainage, aeration, retention of moisture and availability of plant nutrients are all linked with the physical condition ofthe soil. The physical properties of a soil which depend on the amount, size, shape, arrangement and mineral composition of its particles, also influence its chemical and biological behaviour.

Soil Structure Defined

Soil structure is defined as the arrangement of individual soil particles with respect to each other into a pattern. Structure describes the gross, over-all arrangement ofthe soil solids. In other words, soil structure is the ‘architecture’ of a soil.

Soils are composed of structural units, called “peds”. The peds consist of many individual particles, bound together by cementing agents like organic matter, clay and hydrous oxides of iron and aluminium. However, the strength of the bonds, the size and shape of the peds and the proportion of the soil particles involved in the peds differ considerably among soils.

Soil Consistence Defined

Soil consistence is the strength with which soil materials are held together or the resistance of soils to deformation and rupture. Soil consistence is measured for wet, moist and dry soil samples. For wet soils, it is expressed in terms of both stickiness and plasticity. Stickiness is the ability of soil materials to adhere to other objects. Plasticity is the ability of the soil materials to change shape continuously under a constant pressure and to retain the impressed shape when the pressure is removed. Soil consistence may be estimated in the field using simple tests or may be measured more accurately in the laboratory.

Soil Density

The density of a soil, as any other matter, is its mass per unit volume. However, in case of soil, because of its unique nature, the density can be expressed by two terms, viz., bulk density and particle density. Soil density is typically expressed in mega gram per cubic metre (Mg m^-3) which is numerically equal to g cm^-3.

Soil colour is the most obvious characteristic of soil. It has no direct effect on plant growth; however, it has indirect effect through temperature, moisture. Soil colour can indicate the climatic conditions under which it has developed and can be related to its parent material. It can also reflect upon its age, and the temperature and moisture characteristics of the climate. Thus, cooler regions tend to have grayish to black topsoils, due to the accumulation of humus. In moist warm regions, soils tend to be more yellowish-brown to red. Arid soils tend to be light in color (due to low organic content) and primarily express the color of their mineral content. Practically all colours occur in soils - white, red, brown, gray, yellow, black, etc. Predominantly soil colours are not pure, but mixtures. Frequently two or three colours occur, called as “mottling”.

15.1. Soil Temperature

Soil temperature affects plant growth directly; influences soil moisture, aeration, structure, microbial activity, decomposition of plant residues and availability of plant nutrients. Intermediate temperatures, near optimum for each crop, are the desirable temperatures for crop growth. Extreme temperatures are undesirable, lest crop growth would be retarded and weeds and germs may be favoured. Moderate daily variations are desirable as they lead to soil moisture distribution and aeration.

15.1.1. Factors Affecting Soil Temperature

The mean annual soil temperature is about 1°C higher than the mean annual air temperature. Soil temperature is influenced mainly by climatic conditions. The factors which affect the transfer of heat through atmosphere from the Sun also affect the soil temperature. The following are the factors that affect soil temperature:

Water is the elixir of life. It is required for the evapo-transpiration of growing plants. Water acts as a solvent and, together with dissolved nutrients, makes up soil solution from which plant roots derive nutrients. Soil water content controls soil air and soil temperature.

16.1. Forces of Water Retention

The forces responsible for water retention in soils are adhesion and cohesion. Adhesion refers to the attraction of solid surfaces for water. Cohesion refers to the attraction of water molecules for each other.

The force with which the soil particles retain water is defined in terms of pF scale (Schofield, 1935). pF is defined as “the logarithm to the base 10 of the numerical value of the negative pressure of soil moisture expressed in centimetres of water.”

The phenomena related to the retention and movement of water in soils, its uptake and translocation in plants and its loss to the atmosphere are all energy related. The more strongly water is held in the soil, the greater is its energy. It means that if water is to be removed from a moist soil, work has to be done against the adsorptive forces. The water movement is always from a zone where the free energy of water is high (standing water table) to one where the free energy is low (a dry soil). This is called soil water energy concept.

17.1. Soil Water Potential

The free energy of soil solids for water is influenced by:

i) Matric force: the attraction of the soil solids for water (adsorption) which markedly reduces the free energy (movement) of the adsorbed water molecules.

Water can move in the liquid and gaseous phases:

1. Liquid water

i) Saturated flow: Most pores are filled with water; water in this condition is tension free

ii) Unsaturated flow: Pores are partially filled with air; the water is under tension.

2. Water vapour

i) Diffusion: Water vapour moves by diffusion as a result of vapour pressure differences (partial pressure)

ii) Mass flow: Water vapour flows in a mass with other gases of the system in response to differences in total pressure.

Soil Colloids

A colloidal system is a two-phase heterogenous system in which one material in a very finely divided state is dispersed through the second phase. Solid in liquid (dispersion of clay in water) and liquid in gas (fog or clouds in atmosphere) are examples. The clay fraction of the soil contains particles less than 0.002 mm in size. Particles less than 0.001 mm size possess colloidal properties and are known as soil colloids.

Structure of Crystalline Clays

Soil clay minerals are of two types: crystalline and amorphous. Crystalline clays are made up of sheets of octahedra and tetrahedra of O and OH. Clays with alternating sheets of aluminium octahedra and silicon tetrahedra, are called, “1:1 clays” or “diphormic clays”. A sheet of octahedra is sandwiched between two sheets of tetrahedra in 2:1 clays which are called as, “triphormic clays”.

The building blocks of clay crystals are called “unit cells”. The geometry of octahedra has 3 voids in each half unit cell, equivalent to 6 negative valences. In order to nullify these 6 negative valences, 6 positive valences are needed. The 6 negative valences can be nullified by 3 divalent cations, one each in the three voids, or by 2 trivalent cations, leaving the third void empty. When trivalent cations such as Fe³+ and Al³+ fill two of the three voids, the clays are called, “dioctahedral clays”. When three divalent cations such as Fe , Mg and Mn fill up all the three voids, such clays are called, “trioctahedral clays”.

Ion Exchange Defined

By ion exchange is meant “the reversible process by which cations and anions are exchanged between solid and liquid phases, and between solid phases, if in close contact with each other”. For exchange of cations the term “base exchange” is exclusively used.

Soil Reaction

Soil reaction is an indication of the acidity or basicity of the soil and is measured in pH units. The pH scale ranges from 0 to 14, with 7.0 as neutral point. From pH 7 to 0, soil is increasingly acidic. From pH 7 to 14, soil is increasingly alkaline.

Pure H₂O ionizes to a very small degree, though to a measurable extent, so that it has the following equilibrium: both H+ and OH^- are in concentrations of 10^-7 moles L^-1.

Electrical conductivity (EC) is the ability of a material to transmit electrical current. In the soil, the EC is the ability of the soil solution to carry an electrical current and is a measure of the total amount of soluble salts present in the soil. Pure water is a poor conductor of electricity and increases in soluble salts water result in proportional increases in the conductivity.

23.1. Sources of Soluble Salts in Soil

The soluble salts in soils consist mostly of the cations sodium, calcium, and magnesium and the anions chloride and sulfate. Constituents that ordinarily occur only in minor amounts are the cation potassium and the anions bicarbonate, carbonate, and nitrate. The original and, to some extent, the direct source of all the salt constituents are the primary minerals found in soils and in the exposed rocks of the earth’s crust.

While the mean chlorine and sulfur content of the earth’s crust is 0.05 and 0.06 percent, respectively, sodium, calcium, and magnesium each occur in the range of 2 or 3 percent. During the process of chemical weathering, which involves hydrolysis, hydration, solution, oxidation, and carbonation, these constituents are gradually released and made soluble. When carbon-di-oxide, of atmospheric or biological origin, dissolves in water, bicarbonate ions are formed. Water containing carbon-di-oxide is an active chemical weathering agent that releases appreciable quantities of the cation constituents as the bicarbonates. The concentrations of carbonate and bicarbonate ions are a function of the pH of the solution. Appreciable amounts of carbonate ions can be present only at pH values of 9.5 or higher.

Soil organic matter (SOM) is one of the most complex materials existing in nature. Besides the organic constituents in undecayed plant and animal tissues, SOM contains both living and dead microbial cells, microbially synthesized compounds and an unending array of derivatives of these materials produced as the result of microbial activity. Soil organic matter contains most of the naturally occurring organic compounds. Some components of SOM are undoubtedly unique to the soil environment, particularly those involving inorganic-organic complexes.

The Carbon Cycle

The element that serves as a corner stone for cell structure is carbon. Plant tissues and microbial cells contain approximately 40 to 50% of C on dry weight basis. Yet, the ultimate source is the CO₂ of the atmosphere. The CO₂ is converted into organic C by the action of photoautotrophic organisms (higher plants and green algae). It has been estimated that the vegetation on earth’s surface consume some 1.3 x 10¹⁴ kg of CO₂ per annum which is about V₂₀ of the total CO₂ supply of the atmosphere or ¹/₁₀₀₀ of that in the ocean. Soil carbon constitutes the largest terrestrial pool of carbon.

The synthesis of humic substances is the least understood and the most intriguing aspect of humus chemistry. Studies on this subject are of enduring and continued research. Several pathways have been identified for the formation of humic substances during the decay of plant and animal remains in soil, the main ones being shown in Fig. 26.1.

To millions of different organisms around the world, soil is the habitat. A handful of soil can contain billions of soil micro-organisms. One gram of a fertile soil can harbour up to one billion bacteria. Only 5% of what is produced by green plants is consumed by animals, but 95% is consumed by microorganisms. Soil organisms are generally grouped into microfauna/microorganisms and macrofauna. The main soil microorganisms are bacteria, fungi, and protozoa. The macro-fauna includes oligochaeta, arthropods, mollusks and nematodes. These organisms play an essential role in soil formation and soil environment.

27.1. Bacteria

Bacteria are the major single-celled microorganisms in the soil ecosystem that are responsible for many important processes. There are many different types of bacteria and most of them are aerobic, requiring oxygen from the soil atmosphere. However, there are bacteria that live without oxygen and other types can live both with and without oxygen. The growth of these bacteria is limited by the food that is available in the soil. They decompose plant materials as well as other organisms’ wastes that contain plant nutrients in an unusable form and convert them into a form that can be used by plants. One such essential nutrient that is converted by bacteria is nitrogen. Nitrogen-fixing bacteria are able to use the nitrogen (N₂) that exists in the atmosphere and convert it through cellular processes into ammonia (NH₃). Nitrifying bacteria mix ammonia with water to create ammonium ion (NH₄+) and nitrate (NO₃^-), which can be used by other organisms.

Although plants can be grown to maturity in aerated nutrient solutions and other media, virtually all land plants, including those on which we depend for food, fibre and fuel, grow in soil. The soil has three-fold function to perform with respect to crop growth: physical, chemical and biological.

Soil pollution indicates the presence in the soil of any chemical or substance out of place and/or present at an abnormally higher concentration so as to adversely affect any non-targeted organism. Soil pollution often cannot be visually perceived or directly assessed, thus rendering it a latent danger. The Status of the World’s Soil Resources Report identified soil pollution as one of the main soil threats affecting global soils and the ecosystems services provided by them. Concerns about soil pollution are growing in every region. Recently, the United Nations Environmental Assembly (UNEA-3) adopted a resolution calling for accelerated actions and collaboration to address and manage soil pollution. This consensus, achieved by more than 170 countries, is a clear sign of the global relevance of soil pollution and of the willingness of these countries to develop concrete solutions to address the causes and impacts of this major threat.

29.1. Sources of Soil Pollution

The main anthropogenic sources of soil pollution are the chemicals used in or produced as byproducts of industrial activities, domestic, livestock and municipal wastes (including wastewater), agrochemicals, and petroleum- derived products. These chemicals are released to the environment accidentally, for example from oil spills or leaching from landfills, or intentionally, as is the case with the use of fertilizers and pesticides, irrigation with untreated wastewater, or land application of sewage sludge. Soil pollution also results from atmospheric deposition from smelting, transportation, pesticide applications and combustion of many substances as well as radionuclide fallouts from atmospheric weapons testing and nuclear accidents. New concerns are being raised about emerging pollutants such as pharmaceuticals, endocrine disruptors, hormones and toxins, among others, and biological pollutants, such as micropollutants in soils, which include bacteria and viruses.

Soils play a vital role in the health of ecosystems in the world. Soils connect with air, water, rocks and organisms and are responsible for a multitude of functions in the global ecosystem services. These functions include providing habitat for most living things, air composition and quality, temperature regulation, carbon and nutrient cycling, water cycling and quality, and natural waste recycling. Mankind cannot survive without these soil functions.

30.1. Habitat

Soils are the environment in which plants grow. They provide heat, nutrients and water to nurture plants to maturity. These plants, together with other plants and organisms, create ecosystems. These plants then provide valuable habitat and food sources for animals, bacteria and other things. Ecosystems depend on the soil and soils determine the nature and kind of ecosystems.

Soil quality is the capacity of the soil to function, within its natural or managed ecosystems, to sustain plant and animal productivity, maintain or enhance water and air quality, support human and animal health and habitation. This is not limited to agriculture, though most work and evaluation has occurred on agricultural lands.

Soil health refers to the condition of the soil and its potential to sustain biological functions, maintain environmental quality and promote plant and animal health. Healthy soils are the key to food security and sustainable future. They support sustainable food production, mitigate and adapt to climate changes, filter water, enhance resilience to floods and droughts and so much more.

India is endowed with varied types of soils and this could be attributed varied relief features, landforms, climatic realms and vegetation types in the subcontinent. In ancient times, soils used to be classified in India into fertile and sterile soils. Later, the inherent characteristics and external features of soils such as texture and colour, were used to classify the soils. Based on texture, soil types were identified as sandy, clayey, loam, etc. In terms of colour, they were red, yellow, black, etc.

Scientific surveys of soils in India have been conducted by various agencies since independence. All India Soil Survey Organization, established in 1956, carried out detailed soil surveys in the catchment areas of major river valley projects like the Damodar Valley. Later, the National Bureau of Soil Survey and the Land Use Planning (NBSSLUP) ofthe Indian Council of Agricultural Research, established in 1976, made extensive studies on Indian soils and classified them as per the USDA SoilTaxonomy

Horticulture deals with the art, science, business and technology of cultivation and management of horticultural plants. The word Horticulture is derived from two Latin words viz. ‘Hortus’ (means garden) and ‘Culture’ (means growing). Horticulture is an aesthetic science that deals with cultivation of fruit, vegetable, spice, plantation, medicinal, aromatic and flower crops. There is a vast therapeutic use of horticulture wherein gardening and aroma therapy are used to deal with new age maladies like depression and various addictions.

In ancient times, huge gardening spaces to grow large number of fruits, vegetables and flowers were available and these areas were demarcated with the help of high walls. This enclosed area was referred to as garden. This led to the term garden culture. The land area is decreasing due to industrialization and population growth, at the same time, there is a drastic increase in demand for horticultural produce. To meet the increased demand for horticultural produce and to cope up with the space constraints, multitier cropping systems, vertical gardening and other intensive cultivation practices are being resorted to. Hence, horticulture may also be described as the “Practice of growing and manipulating plants in a relatively intensive manner”.

Presently, fruits, vegetables, flowers and ornamentals are grown not only within the home premises, but also in large quantities on a commercial scale. In other words, many horticultural crops throughout the world are grown primarily as business enterprises. Thus, horticulture has two aspects in general i.e., the amateur and the professional. In addition, with the establishment of horticultural experiment stations as an integral part of colleges and universities, comparatively a large amount of scientific information on the behaviour and cultivation of horticultural plants and products is freely available. This information or literature, constitutes the science of horticulture, and the application of this scientific information constitutes the “Technology of Horticulture.” Thus, present day horticulture may be defined as the science and technology of production, processing and merchandising of fruits, vegetables, flowers and ornamentals where each crop has its own science and technology. Consequently, horticulture may appear differently to different people. To a teacher, professor, research scientist, extension official and landscape architect, it is an applied science and a profession, while to a commercial producer, wholesaler, a retailer of horticultural products, or to the manufacturers or seller of horticultural products, it is a business. It is also a fascinating hobby for connoisscur.

Horticulture is a wide field and includes a great variety and diversity of crops. In general, these crops are classified as follows:

1. Crops grown for the food and/or vitamin and mineral content, for e.g., apple and sweet potato.

2. Crops grown for their beverage properties, for e.g., tea and coffee.

3. Crops grown to beautify the environment, for e.g., the grasses of the well planned lawn.

4. Crops grown to express sentiments, for e.g., cut roses, jasmine.

5. Crops grown for perfume for e.g., rose, jasmine.

6. Crops grown for spices for e.g., pepper, nutmeg.

The Horticultural crops show wider adaptation and therefore exact delineation of the agro-climatic areas specific to each crops is not possible, except for the typical temperate and tropical species. However, our country can be broadly divided into seven zones for horticultural crops as indicated below:

1. Temperate Northern Region

Comprising of states of Jammu & Kashmir, Himachal Pradesh, Hilly areas of Uttar Pradesh and West Bengal. Temperate fruits, cool season vegetables are the important horticultural crops in the zone.

2. North Western Arid Region

Comprising ofthe entire Rajasthan state, Gujarat and parts ofPunjab & Haryana. Arid fruit crops like ber, pomegranate, amla, date palm, wood apple and seed spices like coriander, cumin, fennel occupy major area in this zone.

3. North Eastern Sub-tropical Humid Region

Comprising of states and union territories like Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland and Tripura. Fruit crops like banana, pineapple, citrus, jack besides plantation crops like tea and large cardamom are also grown here.

The Government of India has established boards for important crops. The boards are statutory bodies which help in guiding the production and export. The main objectives for setting up the boards are -

To monitor and promote the export of primary items.

To empower the producers by providing trainings and close guidance.

To conduct research to improve the commodity, e.g. Central Coffee Research Institute, Coir Research Institute etc.

To advise the government on policy matters such as price fixing, fixing quota for export and signing trade agreements.

To promote the commodity by opening offices and outlets in India and abroad.

To showcase the commodity by participating in trade fairs and exhibitions.

A number of tools, implements and machineries are used in cultivation of horticultural crops to make every operation easy and efficient. There are a number of operations involved in cultivation of horticultural crops, like making of nursery, propagation of plant material, field ploughing, breaking of clods, levelling, making bunds, sowing and planting, plant protection, training, pruning, harvesting, lawn mowing etc. All these operations are physically taxing and cannot be carried out efficiently without proper tools, implements and machineries. Following are some important tools -

1. Bill hook: To cut and remove big sized unwanted branches of trees.

2. Buckets and plastic pots: used in the orchard for spraying, transport water, carry harvested produce etc.

3. Budding and grafting knife: The budding and grafting operations in propagation of many horticultural plants are carried out using budding and grafting knife.

4. Country plough: Used in field preparation for ploughing the soil, incorporation of organic manures into the soil at the time of last ploughing, summer ploughing in conserving of soil moisture.

5. Crow bar: Used to loosen the soil, digging and deepening the pits and channels.

6. Dibbler: Used to make holes and sow the seeds in the nursery as well as in the main field.

7. Digging fork: It is of a great use in harvesting the tuber crops without damaging the produce.

The performance of plants is affected by the soil in which it grows and climate and micro climate of its surroundings.

Impact of soil

The soil provides anchorage, nutrients and water for plant growth. Soil fertility status, structure and texture influence the plant growth and productivity.

Classification of soil

On the basis of the organic and inorganic contents and particle size and texture, the soils have been classified. The inorganic matter in the soil constitutes of varying amount of sand, silt and clay, on the basis of which the soils are classified as follows.

Sandy soil

These soils have coarse textured and large pore spaces, have poor water holding capacity. Retention of nutrients in this soil is very poor. This type of soil is suitable for precocious crops. Sandy soils initiate rapid root growth, hence good as propagating medium. Since sandy soils has low in nutrient content, supplementation of adequate nutrition is imperative to achieve good plant growth.

Nutrient management is one of the key aspects that ensure good quality produce in optimum quantity. Nutrient availability influences growth and productivity of crops. Sixteen elements are recognized as essential nutrients for growth and development of plants. These essential elements are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, sulphur, iron, zinc, manganese, copper, boron, molybdenum and chlorine. While carbon, hydrogen and oxygen are derived from air, soil and water, other elements are taken by the plant roots from the soil, according to the requirement of the plant. The soil contains these elements in varying quantities depending on the origin of the soil. According to the quantity of requirement of these elements by plants for its various growth processes,the elements are classified into different categories.

Major nutrients or primary nutrients - These are required by plants in large quantities because they are involved in all the processes of plant growth and development. Major nutrients are nitrogen, phosphorus and potassium.

Secondary nutrients - These are required by plants in relatively smaller quantities for growth and development. Secondary nutrients are magnesium and sulphur.

Micro nutrients - As the name suggests, these are required by plants in minor quantities for their physiological processes. These elements are iron, zinc, manganese, copper, boron, molybdenum and chlorine.

Each of the plant nutrients has a definite quantitive role and specific function in the physiological processes of plants. If any of the essential element is deficient or absent in the soil sysem, the plant growth is affected negatively and this is reflected as inferior quality produce. On the contrary, if a nutrient is excess in the soil system, it hinders in absorption of other nutrients and also may itself be toxic. Hence to get the required growth, quality and quantity of the produce, optimum availability of all the nutrients should be ensured.

Water is an extremely essential component in plant growth and development. It is of utmost importance for photosynthesis, cell division, cell growth / elongation, respiration, nutrient uptake, mineral utilization and much other metabolic process, which directly affect the quantity and quality of the produce. Hence quantity and quality of water play a vital role in performance of a crop. A well distributed water supply, throughout the growth of plant is essential. Rainfall is the major source of water for the crops. Rainfall recharges the surface water resources such as rivers, streams and ponds and also the ground water resources like wells.

Different crops are grown in a field. Any plant growing in a place where it is not desired competing with the main crops, has to be weeded out and such plants are called ‘weed’.

Effect of weed menace The weeds

Reduce crop yield and production efficiency. It competes with the main economical crop for space, water and nutrients.

Reduce crop quality.

Hamper intercultural operations.

Reduce crop quality.

Obstruct the flow of water in the irrigation channels.

Exert allelopathic effect on crops.

Harbour insect and pests, which affect the main crop of interest.

Increase the cost of production.

Plant propagation techniques refer to the methods by which the plants are multiplied and increased in number.

Methods of Propagation

i) Sexual Method of Propagation - Seeds are used as propagating material.

ii) Asexual Methods of Propagation - Plant parts, other than seeds are used for plant propagation.

Pot mixture is the media, used in the pots for propagation of nursery plants. It is the combination of different materials in a particular proportion to create better environment for rooting, growth and development of plants.

The most commonly used ingredients to make potting mixture areas follows

An orchard is the place where different kinds of fruit crops are grown in large scale. An orchard is a long-term investment and needs lot of planning and expertise. The orchard crops are generally trees, which ultimately have a large spread, so when they are planted, the distance between plants and rows is kept keeping in mind the final spread of the tree. So, before the trees attain their full growth, some suitable crops which are of short duration, like vegetables, flowers, spices and herbs are grown as intercrops.

Fruit trees are perennial, may be tropical, sub tropical and temperate types and thus require proper environmental conditions and suitable management practices for their successful growth.

Training and pruning of horticultural crops is very important practice to obtain a strong frame work of tree and sustained productivity. It is necessary to understand the various terms used to make the subject more comprehendible.

Crotch: It is the angle made by the scaffold limb to the trunk or the secondary branch to the scaffold limb.

Head: The point on the trunk from which first branch arises.

Leader: It is the main stem growing from ground level up to the tip dominating all other branches.

Low head trees: Trees in which scaffold branches arise within 60-70 cm height from the ground level.

High head trees: Trees in which the scaffold branch arise 120 cm above the trunk.

Scaffold branches: The main branches arising from the head are known as scaffold branches.

The types of crops and the practices used to grow them and the sequence in which they are grown altogether refers to cropping system. It comprises of all components required for the crop production and their relationships with the environment. Traditionally the cropping systems aim at maximizing the per unit area productivity, which can be done by growing improved high yielding varieties, by adequate and scientific crop management practices and by increasing cropping intensities with the help of different cropping patterns.

In today’s world cropping system should produce more, at the same time the practices should be ecologically and environmentally sustainable. There should be efficient utilization of land and water. It should be designed to conserve soil, soil moisture and improve soil resilience.

The term growth refers to an irreversible increase in size and weight of the plant. It normally reflects an increase in protoplasm, which may occur through increase in size of the cell and number of cells. Hence, the process of cell elongation and cell division provides the basis for growth. Cell division and enlargement are complicated processes involving synthesis of many organic compounds such as protein, cellulose and nucleic acid, besides the physical force required, which results in cell enlargement. The growth of the whole plant is compartmentalized into areas called ‘meristem’ where cell division and cell elongation are localized. The meristem cells such as shoot apex, root apex, cambium and the intercalary zones undergo repeated mitosis resulting in replication of DNA and nuclear material and finally the cell mass increases. Adjacent to this area of meristematic activity is the region of cell elongation, which phases in to the region of differentiation and maturation.

The increase in protoplasm (occurring in cell division and elongation) is brought about through a series of events in which water, carbon - di-oxide and inorganic salts are transformed into living materials. These events include (a) photosynthesis (production of carbohydrates) (b) nutrient absorption and translocation (uptake of water, nitrogen and other mineral elements) and (3) anabolism (synthesis of various materials produced in plant from the carbon fragments produced by photosynthesis and from the inorganic nutrients and water absorbed from the soil). The energy required for all these processes is provided by a catabolic process viz., respiration (degradation of sugars and fats to release energy). The net balance of anabolism and catabolism results in growth of the plant.

Plant growth regulators are defined as chemicals other than nutrients and vitamins which regulate (or) modify the physiological process ofthe plant. A plant hormones or phytohormones are chemical substances which are naturally produced by plant in specific organs and are translocated from site of synthesis to the site of action. They bring about specific physiological response, even in very low concentration. The quantity of synthesis of these hormones differ from plant to plant, plant internal and external factors. They are readily absorbed and these chemicals move rapidly through the tissues when applied to different parts of the plant. A plant growth hormone may be termed as a plant growth regulator, but not vice - versa, since other than natural plant hormones, plant growth regulators are synthetically manufactured chemicals.

Plant growth regulators have a diverse chemical composition. Based on the general response the chemical mediates in the plant system, they are classified as growthpromoters and growth inhibitors/retardants. However, a particular growth regulator may be growth promoter at a lower concentration and growth inhibitor at higher concentration.

Greenhouses are frames or inflated structures covered with a transparent or translucent material in which crops can be grown under partially controlled or totally controlled conditions of atleast. It is large enough to permit persons to work within, to carry out cultural operations. Greenhouse cultivation as well as other modes of controlled environment cultivation has been evolved to create favourable microclimate, for the crop production all through the year or during off season, when the produce is highly priced and remunerative. Green house is a broader term of protected structures which includes different types of structures according to the need. Green houses vary in size and complexity from small home or hobby structures to large commercial units, from solar green house to sophisticated environment controlled ones.

GAP stands for “Good Agricultural Practices” which are used for production of safe agricultural produce which has zero microbial load on it and inside it. It is important for the producer to be acquainted with GAP.

Good Agricultural Practice of horticultural crops are intended to apply to the growing and processing of all produce as traded and used in the European Union. Hence, they apply to the production of all plant materials used in the food, feed and medicinal industries. They also apply to all methods of production including organic production in accordance with the European Union regulations.

The farmers involved in the cultivation of horticultural produce should ensure that the there is no damage to the existing wild life and the biodiversity in the farms which are maintained. It is advisable to regulate wild gathering by a specific guideline.

The main aim of GAP guidelines is to ensure that the produce meets the demand of the consumer and is of high quality standard.

It is therefore, important that they are produced hygienically, in order to reduce microbiological load to a minimum. They are produced with care, so that negative effect on plants in the course of cultivation, processing and storage is limited.

All participants in the production process are required to comply with these guidelines voluntarily and to develop practical measures to achieve it.

Organic cultivation is a deep rooted cultivation tradition, which had been practiced in many parts of the world, before the advent of the practice of use of chemicals.

After the green revolution there has been exponential usage of chemicals in agriculture, right from planting to harvesting. Chemicals are used in the form of nutrient inputs or for plant protection against pests, diseases, weeds and keeping deficiencies at bay. Nevertheless, after the awareness regarding the detrimental effect of chemicals on soil, climate and human health, there has been a lot of contemplation on substituting the chemicals with the organic alternatives. Growing crops using organic inputs is known as ‘organic cultivation’. Organic cultivation is a sustainable form of cultivation where a proper balance is maintained and management of plant nutrition, pests, weeds and diseases is done in a sustainable manner, keeping the soil microflora intact and active. It does not release any chemical gases in the atmosphere, does not make the soil acidic and the soil does not lose its structure and texture. Contrary to chemical farming, where over a time period, the soil quality, texture and structure is lost, in organic practices, the soil texture, quality and structure improves over time, the plants become strong and the quality of the produce is improved. Other than organic inputs, organic farming relies on some sustainable practices like using native germplasm, crop rotations with legumes, green manuring, mulching, inter cropping, mixed cropping, incorporation of farm and animal waste compost. These simple age old practices build to organic content in the soil and elevate the soil’s efficiency to make nutrients and water to the plants. The soil microflora and earthworms become biologically active, efficient and exponentially proliferate. The goal of organic cultivation is to get maximum produce from the soil in such a manner that the soil, air and water are clean and protected.