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Plant absorbs large number of elements from the soil and other sources during their growth and development. But all these elements are not essential for plant growth. Seventeen mineral elements are known to be essential for the growth and development of all plants. A list of essential nutrients, their source and forms by which they are absorbed by plants are presented in Table 1.1.

Except carbon (C), hydrogen (H) and oxygen (O), all the other nutrients are obtained by plants largely from soils, fertilizers or manures. It has been seen that the number of nutrients obtained from soil is about 5 times the number of nutrients obtained from air and water. However, most of the plant tissue, in general, from 74 to 99.5% is made up of C, H and O i.e. nutrients obtained from air and water and only 0.5 to 26% of the plant tissue is synthesized from soil constituents. In ordinary (normal) conditions of agriculture, except drought, C, O and H are not limited for plant growth. It is the remaining 14 elements from soil that are usually limiting plant development and hence considerable emphasis is placed on the improvement of soil in respect of greater availability of these 14 nutrients. It may be borne in mind that all nutrients are essential for all crops even though their requirements differ from crop to crop and even among varieties of a given crop. Secondly, all nutrients are equally essential regardless of amounts required. For example, to produce one tonne of grain, wheat may absorb 25, 9, 33, 3.7, 5.3 and 4.7 kg of nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca) and magnesium (Mg), respectively and 56, 624, 70, 24, 48 and 2 g of zinc (Zn), iron (Fe), manganese (Mn), copper (Cu), boron (B) and molybdenum (Mo), respectively. If the crop (any crop) does not get the smallest amounts of micronutrients needed, it cannot make the best use of abundant NPK.

According to Liebig’s Law of minimum which he enunciated in 1855, the growth of a plant is limited by that nutrient which is in shortest supply. This law in fact lays the ground rules for balanced crop nutrition.

Soil acidity is a major constraint for crop production. The production of acid in soils is a natural process, especially in the high rainfall areas. The removal of basic cations especially Ca and Mg, by leaching and erosion results in their replacement by acidic cations, H, Al and Fe on cation exchange sites and in the soil solution, which are in dynamic equilibrium with each other. Soils, that develop from weathered granite are likely to be more acidic than those developed from shale or limestone. Organic matter decay produces H+ in soils, which also contribute to soil acidity. Intensive cropping and use of hybrid & high yielding crop varieties remove large quantities of basic elements essential for their growth i.e. Ca, Mg and K & deplete the soils. Rate of acidification is also accelerated by  faulty fertilizer (especially Nitrogen) management practices.

13.1 Exchange Capacity

Soil colloidal particles carry both negative and positive charges on their surface which attract and hold equivalent amount of oppositely charged ions to their surface. The total number of negative charges present on a given mass of soil or capacity of a given mass of soil to exchange cations or total number of cation held by a given mass of soil is termed as cation exchange capacity (CEC). Similarly, the capacity of a soil to retain anions is known as anion exchange capacity (AEC). The ion exchange capacity of a soil depends upon the type and amount of colloidal particle (clay and organic matter) present in the soil. Ion exchange capacity (CEC / AEC) is expressed as milliequivalent ion (cation / anion, respectively) per 100 g of soil (meq / 100g). It is also expressed as centimoles of charge (positive / negative) per kg of soil [cmol (±) / kg]. Meq / 100g = cmol (±) / kg of soil.

20.1 Exchange Capacity

Soil colloidal particles carry both negative and positive charges on their surface which attract and hold equivalent amount of oppositely charged ions to their surface. The total number of negative charges present on a given mass of soil or capacity of a given mass of soil to exchange cations or total number of cation held by a given mass of soil is termed as cation exchange capacity (CEC). Similarly, the capacity of a soil to retain anions is known as anion exchange capacity (AEC). The ion exchange capacity of a soil depends upon the type and amount of colloidal particle (clay and organic matter) present in the soil. Ion exchange capacity (CEC/AEC) is expressed as milliequivalent ion (cation/ anion, respectively) per 100 g of soil (meq/100g). It is also expressed as centimoles of charge (positive/negative) per kg of soil [cmol (±) / kg]. Meq/ 100g = cmol (±) / kg of soil.

20.1.1 Determination of Cation Exchange Capacity of Soil Principle

Soil is first saturated with normal ammonium acetate (pH 7.0). Excess ammonium (NH₄⁺) ions and displaced cations are then removed by washing with alcohol. The amount of NH₄⁺ ions retained by the soil is measured by steam distillation of NH₄-saturated soil with MgO. During distillation evolved ammonia is absorbed in a boric acid solution as ammonium borate and the amount ammonium borate formed is determined by titration with standard sulphuric acid in presence of mixed indicator.

Cation Exchange of Clay Minerals in Soil

The term “clay mineral” refers to phyllosilicate minerals and to minerals which impart plasticity to clay and which harden upon drying or firing. Clay minerals are layer silicates that are formed usually as products of chemical weathering of other silicate minerals at the earth’s surface. Clay minerals in soil play a significant role in exchanging cations, which are positively charged ions, and in regulating soil fertility and nutrient availability. Cation exchange capacity (CEC) is a measure of a soil’s ability to exchange cations and is influenced by the type, abundance, and charge properties of clay minerals in the soil. Clay minerals have a high CEC due to the presence of charged surfaces (silanol and alumoxane groups) that can exchange cations with the soil solution. The most common cations exchanged by clay minerals are hydrogen (H+), calcium (Ca2+), magnesium (Mg2+), potassium (K+), and sodium (Na+). When a soil solution comes into contact with clay minerals, cations in the soil solution are adsorbed or attracted to the charged surfaces of the clay particles.

The exchange of ions (cations or anions) are important phenomena in soil for the growth and nutrition of the crops. The oppositely charged ions are being adsorbed by the clay colloids which are subjected to be released or exchanged reversibly from the soil solution. The participating ions in the exchange process are called exchangeable or counter ions. The activity of ions depends on the pH of the soil. Hence, factors like, soil texture, organic matter, concentration of ions could govern the ion exchange phenomena in soil.

6.0 Ion Exchange

Ion exchange is a reversible process where exchange of ions are possible between the two electrolytes or between an electrolyte solution and a complex. The ion exchange processes help in purification, separation, and decontamination of aqueous and other ion-containing solutions. The ion-exchange resins (functionalized porous or gel polymer), zeolites, montmorillonite, clay and soil humus are considered as typical ion exchangers which are either cation exchangers [exchanging positively charged ions (cations)], or anion exchangers [which can exchange negatively charged ions (anions)].

8.1. What is an ion exchange reaction and its application in soil system

Ion exchange is a reversible chemical reaction between two substances, either between two electrolytes or between an electrolyte solution and a solid complex as well as between two solid phases (if in close contact with each other), where ions of equal charge may be interchanged in equivalent proportion.

Organic colloids and inorganic micelles (clays) are sites of ion exchange. Soil contains silicate clay minerals which exhibit charges due to isomorphous substitution as well as due to the pH dependant charges for ionisation of hydrogen and hydroxide functional groups. Organic matter present in soil also contributes to the pH dependent charges due to the presence of various active functional groups. Thus, the organic and inorganic colloids present in soil bear positive or negative charges. Electric charge on soil particles is neutralized by equivalent amount of oppositely charged exchangeable counter ions, held by coulomb forces and van der Waals forces. Ca⁺², Mg⁺², H⁺, K⁺, Na⁺, NH₄ ⁺, Al⁺³, Fe⁺³, Fe⁺², Mn⁺², etc. are the common cations present in soil where Ca⁺² serves as the dominant ion. However, Na⁺ and Al(OH)₂ ⁺ are the dominant cations found in the exchangeable phase in strong alkali and strong acid soils, respectively. SO₄ ^- 2, Cl^-, HCO₃ ^-1, NO₃ ^- etc. are the most common anions found in soil to neutralize positively charged soil colloids.

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.

Artificial brainpower (Artificial Intelligence) is quite possibly of the quickest developing innovation in this cutting edge world. Artificial intelligence is presently broadly utilized in different enterprises going from the improvement of mechanical technology to the observing of natural issues. Computer based intelligence innovation has evident extensions in medical services gadgets, self driving vehicles, satellite imaging, scene planning, Climate change checking, also medical services frameworks. Artificial intelligence has heightened the improvement of mechanical technology across the globe that has made the life very simpler and added to a greatly improved existence of prosperity. Artificial intelligence interceded robot of a few areas including farming will create great quality items with more positive effects on Climate. Artificial intelligence utilizes various Smart sensors that cycle information progressively with higher precision. Consequently, Artificial intelligence has upgraded the presentation of any gadget to a few folds with more prominent reasonableness and Precision in their results. Computer based intelligence with Smart sensors has lead to the improvement of a cutting edge innovation called as Internet of Things (IoT). IoT is center of remote frameworks and Artificial intelligence manages information progressively and creates suitable results. This innovation has been taken on in pretty much every area of science and examination. IoT based advanced advancements can possibly create inventive models for improved creation of buyer items including agro-items.
Agriculture is fundamental piece of people local area. It is overhauled with time to increment rural production. Present day advancements has additionally been utilized in farming, agriculture, also ranger service for better observing of plant development, sicknesses, and bug populace. Artificial intelligence and IoT have various expanding extensions in farming to settle different issues such as soil conditions, Climate status, bother discovery, assurance of collecting time, etc. Likewise computer based intelligence and IoT offers fantastic extensions for continuous observation of temperature, dampness, contamination, soil quality, water content, radiation, and others. Brilliant

Introduction

It is a well known fact that agricultural pests cause substantial crop losses throughout the world. In the past farmers had to manage this problem to secure their basic subsistence needs, and as a response, the farmers practiced and developed cultural and mechanical pest control based on trial and error. Over a period of time, these practices have become a part of their production management system. The first known chemical control dates back to 2,500 years. From the late 1800s to 1940s, the main insecticidal compounds used were oils, soaps and resins, plant-derived poisons and inorganic compounds. The chemical age began in the 1940s with the discovery of dichloro diphenyl trichloroethane (insecticide), ferbam (fungicide), and 2, 4-D (herbicide) (Arneson and Losey, 1997). In 1940s and 1950s, pesticides were thought to be the final word in pest control and their introduction contributed substantially to raising agricultural productivity in many regions of the world. Since then, pesticides have become an integral component of many intensive agricultural systems. Repeated applications of pesticides lead to resistance in the pest (Beaument, 1993). This resistance results in the increased application of pesticides and to the collapse of the agricultural systems characterized by highly resistant pests, with no natural enemies left to control them. Pesticides have been found to causeacute and chronic human health problems, contamination of groundwater, surface water, atmospheric contamination, and negative effects on non-target organisms (Mullen, 1995). Concerns about the negative effects of pesticides led to research and promotion of alternative pest control practices – Integrated Pest Control or simply IPC. This new concept called Integrated Pest Control (IPC) and later Integrated Pest Management (IPM) was stimulated by symposia organized by the Food and Agriculture Organization (FAO) of the United Nations in 1966. IPM made a paradigm shift in the philosophy of pest control, from pest eradication to pest management. Instead of single tactic control, emphasis was placed on the use of a combination of available tactics in a compatible manner aimed at providing cheap, long term sustainability with minimum of harmful side effect and controls the pest at ETL level.

Iron Toxic Soils

Lowland rice is being cultivated on approximately 128 million hectares of either irrigated or rainfed land out of which 100 million hectares suffer due to nutrient deficiency or toxicities. Among the toxicities, iron toxicity is well recognized as a nutritional disorder in low land rice production. Iron toxicity is a syndrome of disorder associated with high concentration of Fe²⁺ in soil solution. A wide range of soil types show iron toxicity problem including acid sulphate soils, acid clay soils, peat soil and valley bottom soil. During monsoon rains in the wet season, soluble iron (Fe²⁺) migrate to the surface and its iron content increases to subtoxic or toxic levels.

In rolling topography and with heavy monsoon downpour there is considerable lateral flow of iron containing water from the adjacent uplands to mid – and low lands. This increases the iron content to toxic levels. Poorly drained sandy soils in valleys receiving interflow water from adjacent uplands with laterite horizon (Plinthudults) showed iron toxicity in Srilanka and Kerala and Odisha in India. These soil groups come under the taxonomic orders Alfisols, Ultisols and Oxisols occurring in association with Entisols and Inceptisols. The iron concentration (Fe²⁺) in soil solution that affect low land rice yield ranges from 10 to > 2000 mg L^-1 Iron toxicity induced yield reduction which is associated with poor nutrients . status (deficiency of P, K and Zn) and H₂S toxicities.

Water is one of the most critical resources in horticultural production, directly influencing plant growth, flowering, fruit development, and quality. This chapter introduces principles of irrigation scheduling, water requirements, soil–water relationships, and efficient water application. Surface, sprinkler, drip, micro-irrigation, fertigation, and other modern systems are discussed in relation to crop type and environmental conditions. The chapter emphasizes irrigation efficiency, root-zone moisture management, water quality, salinity, drainage, and conservation. Proper irrigation scheduling reduces water losses and prevents both drought stress and excessive wetness. Modern technologies such as sensors, automated irrigation, and precision fertigation are also considered important tools for sustainable horticultural water management.

5.1. Irrigation requirement of field crops

6.1. Quality of irrigation water

Asia per capita water availability has fallen by around 80 per cent during last five decades.

Suitability of waters for a specific purpose depends on the types and amounts of dissolved salts.

Some of the dissolved ions such as NO₃ are useful for crops.

Water required for irrigation of cropped land is being degraded in terms of quantity and quality due to fast increasing demand for its use. Furthermore, the soil quality and crop productivity is linked to the quality of the water available for irrigation. In general, evaluation of irrigation water quality should focus on salt content, sodium concentration, the occurrence of nutrients and trace elements, alkalinity, acidity, and hardness of the water.

Introduction

Irrigated agriculture is dependent on an adequate water supply of usable quality. The water quality used for irrigation is essential for the yield of crops, maintenance of soil productivity, and protection of the environment as well. The quality of irrigation water is defined with respect to its effect on plant growth, soil properties, soil biological equilibrium, and irrigation technology. Conceptually, water quality refers to the characteristics of a water supply that will influence its suitability for a specific use, i.e. how well the quality meets the needs of the user. Specific uses have different quality needs and one water supply is considered more acceptable (of better quality) if it produces better results or causes fewer problems than an alternative water supply. For example, good quality river water which can be used successfully for irrigation may be unacceptable for municipal use without treatment to remove its sediment load. Similarly, snowmelt water of excellent quality for municipal use may be too corrosive for industrial use without treatment to reduce its corrosion potential.

Technical Term            Definition

Infiltration                    Infiltration is movement of water from the surface into the soil or ground.

The capacity of soil to function as a vital living system, within ecosystem and land use boundaries, to sustain plant and animal production, maintain or 

enhance water and air quality, and promote plant and animal health (Doran and

Zeiss, 2000). A healthy soil may function is as follows:

• Sustain biological activity, diversity, and productivity

• Regulate, store of nutrients and cycle water and, decompose organic

matter

• Filtering and buffering, degrading, mineralizing, immobilizing, and

detoxifying organic and inorganic materials

• Inactivate toxic compounds, suppress pathogens, protect water quality,

and enhance catchment soil health.

8.1. Kisan Credit Card (KCC)

Credit scheme introduced in August 1998 by Indian Banks.

Prepared by NABARD on recommendations of R.V.Gupta committee to provide term loans and agricultural needs.

KCC holders are covered under personal accident insurance up to Rs.50,000 for death and permanent disability and up to Rs.25,000 for other risk.

Premium is borne by both bank and borrower in a 2:1 ratio.

Validity period is five years with an option to extend for up to three more years.