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Fish excrete Ammonia, is a byproduct from protein metabolism and bacteria break down organic waste such as discarded food, faeces, dead planktons, sewage, and so on. When ammonia is unionized form (NH3) is extremely dangerous; yet when ammonia ionized form (NH4 +) it is harmless; both forms are known as total ammonia. Fish suffering from ammonia toxicity often”become lethargic and frequently emerge near the surface gasping for oxygen. common effects of ammonia in the range >0.1mg/l include Gill damage, breakdown of mucous-producing membranes, “sub-lethal” effects like reduced growth, poor (FC) feed conversion, and reduced disease resistance at concentrations lower than lethal concentrations, osmoregulatory imbalance, and kidney failure.
Principle
When Ammonia react with alkaline Nessler reagent (K2HgI4 or 2KI + HgI2) it produces a yellowish-brown coloured compound. Pretreatment with ZnSO4 and NaOH precipitates Ca, Mg, Fe and sulphide, which form turbidity and apparent colour. Addition of ethylene diamine tetraacetic acid, EDTA (before nessler’s reagent) or Rochelle salt solution prevents precipitation of residual Ca and Mg in presence of the alkaline Nesslers’s reagent.

Nitrite (NO2-) is formed in waters by oxidation of ammonia compounds (by aerobic nitrifying bacteria, e.g. Nitrosomonas) or by reduction of nitrate (by facultative anaerobic denitrifying bacteria, e.g. Pseudomonas). Such oxidation and reduction may occur in wastewater treatment plants, water distribution system, and natural waters. As an intermediate stage in nitrogen cycle, it is unstable. Very high nitrite levels are usually associated with waters having unsatisfactory microbiological activity.
Principle (Colorimetric method)
When nitrite (NO2 -) as nitrous acid (HNO2) mixes with sulfanilamide in an acidic environment (pH 2-2.5), a diazonium salt is created. This salt then combines with N-(1-naphthyl)-ethylenediamine dihydrochloride (NED dihydrochloride) to make a vivid pinkish red azo-dye. The amount of nitrite in the sample directly correlates with the colour that is created. At 543 nm, the colour follows Beer’s law up to 180 µg/L with a 1 cm light path. By diluting a sample, a higher nitrite concentration can be determined. Sulfanilamide + HNO2 + HCl ? Diazonium salt + H2O.
Diazonium salt + NED-dihydrochloride ? Red colouredazo dye

The most oxidizable form of nitrogen is nitrate nitrogen (NO3 -N), which is found in minimal amounts in surface waters but can reach considerable concentrations in some aquifers. An essential plant nutrient, nitrate also contributes to eutrophication in receiving water bodies.
Principle
Nitrate reacts with phenol disulphonic acid and produces a nitro-derivative which in alkaline solution develops yellow colour due to rearrangement of its structure. The yellow colour follows Beer’s law and is proportional to the concentration of nitrate present in the sample. Ultraviolet (UV) technique measures the absorbance of nitrate at 220 nm, which is suitable for screening uncontaminated water (low in organic matter). A second measurement made at 275 nm, may be used to correct the nitrate value (because 275 nm is not absorbed by nitrate, but absorbed by other matter). The nitrate calibration curve follows Beer’s law up to 11mg NO3 -N /L.
Reagents
1. Stock nitrate solution (1ml=100 µg NO3 -N): Dry potassium nitrate (KNO3) in an oven at 105 oC for 24 h. Take 360.9 mg potassium nitrate and dissolve in distilled water and dilute to 500 ml. Preserve it with adding 1 ml of chloroform in per 500 ml stock nitrate solution. This solution will stable for at least 6 months.
2. Intermediate nitrate solution (1 ml = 10µg NO3 -N): Take 100 ml of stock nitrate solution and dilute it to 1000 ml of distilled water. This solution can be preserve by adding 2 ml of chloroform per 1000 ml. This Intermediate nitrate solution will stable for at least 6 months.
3. Hydrochloric acid (HCL) solution, 1N: Take 83 ml of hydrochloric acid and dilute it to 1000 ml of distilled water

Phosphorus is nearly exclusive found as phosphates in waters and wastewater and it categorised in to: a) orthophosphate, (b) organically bound phosphate and (c) condensed phosphates. Theses all three forms of phosphorus occur in solution, in the body of aquatic organisms through food chain. All the forms of phosphorous, whether dissolved or particulate are converted to inorganic forms (phosphate) after digestion of sample. Various methods use for the digestion of the sample including use of perchloric acid, H2SO4- K2SO4, H2SO4- HNO3 etc. The H2SO4- HNO3 digestion technique is discussed here.
Reagents
1. Phenolphthalein indicator
2. Conc. sulphuric acid (H2SO4)
3. Conc. nitric acid (HNO3)
4. Sodium hydroxide (NaOH), 1 N: Dissolve take 40 g of NaOH in 1000 ml of distilled water
Procedure
Digestion
1. Take 50 ml of sample in a Kjeldahl flask
2. Add 1 ml H2SO4 and 5 ml HNO3
3. Once the HNO completely removed, digest the sample on a hot plate until the volume approaches 5 ml. Then, keep heating the solution until it loses colour (you may also heat it in a beaker covered with a watch glass to prevent excessive evaporation).

Sulfate can have harmful effects on aquatic life in freshwaters, sulfate cause osmotic stress or specific ion toxicity in aquatic organisms, especially in soft waters where Ca2+ and Mg2+ concentrations are low. Egg fertilization and early embryonic development were the most sensitive developmental stages of whitefish to sulfate (Karjalainen et al., 2021).
Sulphate (SO4 2-) may be estimated by either turbidimetric or gravimetric methods (APHA, 1995)
1. Turbidimetric method is more applicable in the range of 1- 40 mg Sulphate (SO4 2-)/ L
2. Gravimetric method is suitable if the concentration of Sulphate (SO4 2-) is above 10 mg/ L
Turbidimetric Method (Range 1 - 40 mg/L of sulphate) Principle
Sulphate ion (SO4 2-) precipitated with barium chloride (BaCl2) in an acetic acid medium in order to form crystals of barium sulphate (BaSO4).
BaCl2 + SO4 2-+ BaSO4 (precipitate)
The formation of these crystals is increased in the presence of an acetic acid solution containing sodium acetate, potassium nitrate, acetic acid and magnesium chloride. The suspended barium sulphate (BaSO4) is measured by spectrophotometer and concentration of sulphate (SO4 2-) is determined by comparison of the reading with a standard curve. Minimum detectable concentration is approximately 1 mg (SO4 2-) / L.

The total plate count (TPC) is also called the Bacterial plate count (BPC), aerobic plate count, standard plate count (SPC), total viable count (TVC) or mesophilic count represents the number of colony forming units (CFU) per g (or per mL) of growing microorganisms such as bacteria, yeast and mold on a nonspecific solid bacteriological growth medium under the specified conditions. Temperature, incubating time, medium type, and any other conditions used in the enumeration varies upon reference standards and laboratory objectives. Laboratories participating in the program choose their own routine conditions.
Principle
Usually direct count of too many bacteria in a sample is difficult but the bacterial colonies may be used as a measure of the bacterial cells in the known serially dilution and plated out on an agar surface in such a way that single isolated bacteria form visible isolated colonies. However, colony-forming unit might actually consist of a chain of bacteria rather than a single bacterium if the organism often develops various cell configurations, such chains. Furthermore, a portion of the bacteria might be grouped together. Thus, typically refer to the process of using the plate count technique as a means of estimating the number of colony forming units (CFUs) in that known solution. Then further this figure use to extrapolate the total amount of CFUs present in the original sample.

Laboratory pipettes are classified by their method of liquid transfer. There are two types of pipette one is plastic which is made up of polystyrene and are essentially disposable and second one is glass pipettes are very resistant to chemicals. Glass pipette can be used frequently by washing, sterilising and dry heat sterilisation is also available. Some of the common types of pipettes are using in laboratory such as serological, volumetric, micropipettes, multichannel, and Pasteur pipettes. Serological and graduated pipettes are used for transferring various volumes, while micropipettes and volumetric types of pipettes are only considered for precise measurement and transfer. Multichannel pipettes are used for dispensing into multiple wells, and Pasteur pipettes are simple for transferring small amounts.
1. Serological Pipettes
• Also known as graduated pipettes, made of glass or transparent polystyrene they are calibrated with markings to measure and dispense varying volumes.
• Appropriate for cell culture applications, transferring liquids and mixing.
2. Multichannel Pipettes
• It is design to transfer multiple samples at once, often used for 96 well plates or pcr tubes.
• It can be manual or automated, with multiple heads for faster dispensing.
3. Volumetric Pipettes
• It is designed to supply for single and particular volume of liquid.
• Marked by single graduation for an exact volume, such as 1, 5, 10, 25, and 50 mL.
• Used in chemical reactions and analysis where accuracy is crucial.

Irrigation: definition and objectives; Importance: Function of water for plant growth, water resources and irrigation development for different crops in India.
Introduction
The effect of supplemental water application as irrigation for crop production at its needs during rainless period is well established throughout the world. The plant has life, so it requires water for growth and development to give us proper quality and good yield. Water is required for metabolic activities including solubilization, absorption and translocation on the way of biochemical processes in photosynthesis, transpiration and respiration. India with 2.4% of the world’s total area has 16% of the world’s population; but has only 4% of the total available fresh water. This clearly indicates the need for water resource development, conservation, and optimum use.
Importance of irrigation water management
The importance of irrigation in the world is well stated “Irrigation in many countries including India is an age-old art–as old as civilization – but for the whole world it is a modern science–science of survival”. The pressure of survival and the need for additional food supplies are necessitating a rapid expansion of irrigation throughout the world including India. Production and productivity of agricultural lands is primarily dependent upon the availability of irrigation water to crops. Expansion of irrigation has paid rich dividends in India. fter independence, production registered nearly 4.52 times increase from around 50.8 million tons in 1950-51 to about 230 million tons in 2007-08. This has been mainly attributed to three factors viz., high yielding cereals, expansion of area under irrigation and fertilizer use. Irrigation may be considered as the major factor of modern intensive agriculture as it aids in efficient use of costly fertilizers and other inputs besides meeting crop water needs.

Water Resources: Classifications of water: Groundwater, surface water and Virtual Water; Conjunctive use of water in agriculture; Water resources in different states and Stakeholders of water use.
Introduction
Despite fact that more than two-third of the earth’s surface is covered with water, currently, near about 450 million people in 29 countries are facing severe water shortage and at least 20 percent more water would be required to feed additional 3 billion populations by 2025. About 97.5 percent of ocean-sea water is not available due to its salinity and 2.49 percent is locked up in ice and only 0.01 percent is technologically available and economically accessible water either from surface or ground water sources for human uses. So water saving technologies developed so far is very pertinent to propagate amongst the users. Water is an essential natural resource for sustaining the environment and supporting life where the agriculture is the major user of water resource. Water is an indispensable for sustainable agricultural growth and development. Previously, rainfed agriculture was associated primarily with conservational land treatments to check soil erosion and land degradation.But in the areas of medium to heavy rainfall, there is ample scope of tapping excess rain water through suitable water harvesting structures constructed for this purpose for its subsequent uses as irrigation or to apply lifesaving irrigation to the crops which should also come under the purview of water management for crop production. Although there is a difference in the objectives of water management where there is abundant availability of water from continuous flow connected with perennial sources or lakes and rivers and that of from restricted or limited supply from collection of excess rain through water harvesting structures.The former is associated with to obtain as much as yield of crop per unit area under water application and later is associated with increasing productivityof crop per unit of water application even under rainwater recycling and its effective management for the purpose of irrigation. Hence, both the rainwater and irrigation water are considered to be equally important to context of

Soil physical properties
The physical properties of soil, particularly its mechanical behavior, significantly impact its suitability for plant growth. Factors like plant support, root penetration, drainage, aeration, moisture retention, and nutrient availability are all influenced by the soil’s physical condition. These properties also affect the soil’s chemical and biological activities.
A soil’s physical properties are determined by the quantity, size, shape, arrangement, and mineral composition of its particles, as well as its organic matter content and pore spaces.
Important Physical Properties of Soils
1. Soil Texture
2. Soil Structure
3. Surface Area
4. Soil Density
5. Soil Porosity
6. Soil Color
7. Soil Consistence
Soil Texture
Definition
Soil texture refers to the relative proportions of different-sized particles, specifically the percentage by weight of sand, silt, and clay. It’s a fundamental soil property that is difficult to alter. Soil textural determinations typically exclude particles larger than 2 mm in diameter (stones and gravels). While larger particles can affect land management and tillage, they contribute minimally to water-holding capacity (WHC) and nutrient storage/supply.

Different kinds of soil water and soil water movement; Water in relation to plant growth and crop production; Soil texture, structure, infiltration and permeability; Bulk density and particle density of the soil; Concept and theories of water retention in soils; Consumptive use and ET; Soil moisture characteristics curves; Different losses of water (seepage and run off) and Soil moisture measurement, stress and plant growth
Soil-Water-Plant Relationships and Irrigation Scheduling Concepts
A good understanding of soil-water-plant relationships is the foundation for understanding irrigation concepts.
Water reaches the soil through irrigation, precipitation, or from groundwater drawn up into the root zone through “capillary action”. To be available to plants, it must be held by the soil strongly enough so it is not lost to gravity before the plant gets it, but not so strongly that the plant cannot extract it from the soil. At the same time, the roots must have sufficient aeration to function properly.
Roots are responsible for obtaining almost all of the plant’s water and nutrients. These substances move through the soil during and after irrigation/fertigation and rainfall. In addition, root systems are continually growing and branching to seek out water and nutrients. Root hairs are very fine structures that extend at right angles to the roots. Water and nutrients predominantly enter the root system via specialized cells near the tips of root hairs.
The xylem is the cellular pathway through the plant that transports water from the roots to the leaves for use in photosynthesis and to cool the plant by evaporation. The process by which water vapour is released to the atmosphere by the leaves and other parts of a living plant, resulting in evaporative cooling, is called transpiration. The xylem also transports water and nutrients to other parts of the plant. In a living plant, the xylem is completely filled with water, just as the veins and arteries of the human circulatory system are filled with blood. The plant needs a continual replacement of water lost through transpiration to keep the xylem full of water, and of course, this has to be accomplished without an organ analogous to a human heart. Tomato plants

Water budgeting and its importance, methods of soil moisture estimation, evapo-transpiration and crop water requirement and effective rainfall Water budgeting and its importance, irrigation scheduling approaches
Water budgeting
Allocation of the water receipt including anticipated within the crop period and its detailed account of expenditure for efficient and profitable farm management is called as water budgeting.
Water budgeting may be for an irrigation system planned by irrigation engineers; may be for a canal or for an area (block) or may be for a farm according to the need and plan by responsible persons who plan the irrigation efficiency.
Importance of water budgeting
Efficient utilization of available recourse (water) for bringing more area under irrigation:
1. To increase the productivity of a region / farm.
2. To increase cropping intensity of a region / farm
3. To tide over some dry-spells
4. To reduce excess irrigation and losses caused thereby
5. To avoid run off losses
Irrigation scheduling
Irrigation scheduling is defined as frequency with which water is to be applied based on needs of the crop and nature of the soil.
Irrigation scheduling is nothing but number of irrigations & their frequency required to meet the crop water requirement.

Introduction
India is the seventh largest having 329.73 million ha of geographical area and second most populous country having more than a billion population in the world. There is no other substitute other than to use every square inch of land and every drop of water effectively and efficiently. Though there was markedly increase in annual food grain production from 51 (1950-51) million tones t0 206 million tones (2000-01), still the death on hunger is visualized.
The demand for food is increasing with ever-increasing population growth rate. So there is no option other than to increase food production. There is very little or no scope of horizontal expansion due to land limitation, the question of vertical expansion is the only way to fit with the situation. Genetically improved crop variety, hybrids, mechanized agriculture, higher rate of fertilizers and chemicals application may give one or two more green revolution, but the question lies how far it can sustain greenness?
Adoption of improved crop cultivars, cropping system, increasing cropping intensities, precision farming can hold good to get out of this situation where whole system is to be considered.
The cropping intensities in the states like Assam, Bihar, MP, Orissa, UP and West Bengal are 137.7, 137.8, 125.6, 154.6, 148.6 and 159.6 percent, respectively (FAI,1994-95). This indicated that a vast majority of lands remain fallow during dry season due to lack of proper technologies, which are under rainfed conditions, neglected. Except West Bengal, more than half of the arable land remains fallow during rainless period. Increasing cropping intensities in rainfed uplands is not easily achievable but there is great potential of intensification of cropping in rainfed lowland by utilizing natural resources and conserved residual moisture. Pulses like black gram, green gram, lentil, lathyrus, chick pea and oilseeds like linseed, groundnut, rapeseed could not only increase the cropping intensities but also come forward to increase national productivity.

Rice farming under different subsystems of lowland ecology
1. Rainfed lowland with limited water at seeding and excess water at later growth stages: In rainfed lowland areas, the rice is direct seeded in dry soil in April-May before onset of monsoon (June) and seeds germinate with the showers received after sowing. Drought at the seedling stage kills seedlings and results in poor stand establishment. Furthermore, heavy rains in catchment areas of river basins result in water logging and flooding at late growth stages. The water hinders tillering and results in poor panicle number less than 200/m2 as against 350 /m2 of high yielding rice cultivars.
2. Rainfed lowlands with limited/excess water at transplanting and excess water at later stages: When on-set of the monsoon is delayed, transplanting delayed because the farmer has to wait for adequate rains for land preparation. Monsoon rain submerges the transplanted crop, resulting in poor stand. In some areas, the land gets inundated before transplanting and farmers generally transplant aged and tall seedlings to keep the plant parts above the water. Plant survival in deeper water depends on rise in water level and on the elongation ability and submergence tolerance of the plant. Varieties that elongate fast develop weak culms and may lodge when the water level recedes. In this situation tillering is poor and panicle per unit area are less.
3. Assured irrigated areas with excess water during crop growth due to poorly drained condition: Rice grown in the river deltaic areas of Krishna, Godavari and Indo-Gangetic rivers suffer from water stagnation even though some areas are having irrigation facilities. Heavy rains in the catchment cause flooding and stagnation in rice fields because of congested drainage or lack of drainage caused by topographically saucer-shaped land. These conditions develop during peak monsoon (July-September). The late planted crops, being at an early stage of growth, suffersfro water stagnation. In these areas, transplanting early in the season is necessary for plants to grow enough to escape submergence.

Irrigation Scheduling: Approaches and Advantages
Efficient irrigation scheduling aims to optimize crop yields while maximizing water use efficiency and minimizing soil damage. This involves determining the correct timing and amount of water to apply for each irrigation event. Several criteria can be used for scheduling irrigations, broadly classified into climatological, soil water regime, and plant-based approaches. The most suitable criterion depends on specific soil, plant, climate, and management factors.
Climatological Approach
Under conditions where soil water is readily available, the potential rate of water loss from a crop primarily depends on the atmosphere’s evaporative demand. This approach uses potential evapotranspiration (PET) or cumulative pan evaporation (CPE) over short periods as an index for irrigation scheduling.
Penman (1948) defined PET as the water transpired by a short, uniformly green crop completely covering the ground and never lacking water. He also noted that PET is generally a fraction of pan evaporation under the same conditions. PET can be estimated using various techniques, including lysimeters, energy balance calculations, aerodynamic approaches, and empirical formulas. Based on PET or crop water use rates over short periods, irrigation can be conveniently scheduled. Lysimeters isolate the crop root zone, allowing accurate determination of water balance components by controlling and measuring difficult-to-assess processes.
Soil Water Regime Approach
This approach uses the available soil water held between field capacity and the permanent wilting point in the effective crop root zone as a guide for irrigation scheduling. Soil moisture tension, which reflects how tightly water is held by soil particles, can also serve as an indicator.

Surface: border strip, furrow, basin and check basin
Sub-surface
Micro-irrigation: drip, sprinkler; Pichter and bottle
Definition of Irrigation Method
Application of irrigation water to cropped field by different types of layouts is called as irrigation methods. The methods of irrigation initially might have been started to check the over flow of water from one field to another. But today, it has become necessary to save the water by proper methods to arrest run-off loss, percolation loss, evaporation loss etc., and to optimize the crop water need. Hence, irrigation method can be defined as the way in which the water is applied to the cropped field without much application and other losses, with an objective of applying water effectively to facilitate better environment for crop growth.
Factors Influencing Irrigation Methods
Soil type: The soil physical properties such as texture, structure, porosity, infiltration rate, etc. influence the selection of irrigation methods. Heavy texture soil restricts water movement than light texture soil wherein water move freely to deeper sections due to high porosity. Single grain structure soil allows water freely to move downward compared to other structures
Soil depth: If soil is shallow which holds less water, leveling and forming bunds etc. to hold? Maximum water is to increase the irrigation interval. Similarly if the soil is deep, it holds more water and needs longer irrigation interval. Accordingly, the irrigation methods can be selected.
Topography of land: In undulating topography, it is very difficult to adopt normal methods of irrigation. The slope of the land also decides the methods to be adopted. If the land is more sloppy, basin method cannot be used. In this condition strip method can be used. For undulating topography instead of strip or basin method, sprinkler or drip methods can be used.

Irrigation Efficiency
Irrigation water is an expansive input and has to be used very efficiently. The main losses that occur during irrigation of fields as conveyance, run off, seepage and deep percolation; Irrigation efficiency can be increased by reducing these losses. Uneven spreading and inadequate filling of root zone are the other causes for low irrigation efficiency. Irrigation efficiency at the field level can be increased by selecting suitable method of irrigation, adequate land preparation and engaging an efficient irrigator. At the project level, it can be increased by proper conveyance and distribution system. Irrigation efficiency is the ratio usually expressed as percent of the volume of irrigation water transpired by plants, plus that evaporate from the soil, plus that necessary to regulate the salt concentration in the soil solution and that used by plants in building plant tissue to total volume of water diverted, stored or pumped for irrigation.
Wt+Ws-RsEi=×100Wi
Where,
Ei = Irrigation efficiency (percent)
Wt = the volume of irrigation water / unit area of land transpired by plants, evaporation from the soil during the crop period.
Ws = the volume of irrigation water per unit area of land to regulate the salt Content of soil solution.

Water Quantity and Measurement: The amount of water to be applied and its measurement are crucial aspects of irrigation management. There are various methods and tools used to measure and control the flow of water, including:
1. Parshall flume
2. Orifice
3. Weirs
4. Water meter
5. Float method
6. V-Notch
Methods of Soil Moisture Measurement
The measurement of soil moisture is essential to determine when to irrigate, the amount of water needed, to evaluate evapotranspiration, and to monitor soil matric potential. Soil moisture is measured in two ways: direct and indirect methods.
Direct Methods
1. Gravimetric method: The gravimetric method is a standard method for measuring soil water content directly. It involves collecting soil samples from the field and determining their moist and dry weights. The mass water content is then calculated as the ratio of the weight loss in drying to the dry weight of the soil sample. This method is accurate but time-consuming and requires laboratory equipment.
2. Spirit burning method: The spirit burning method is a direct method for measuring soil moisture in the field. Soil moisture is evaporated by adding alcohol and igniting it. The time taken for the soil to dry is then used to calculate the soil moisture content. This method is quick and easy but can be affected by soil temperature and organic matter content.

Soil moisture stress in relation to crop and development of crop
Agronomic methods are supported with mechanical measures where land slope exceeds permissible limits and runoff gains erosive velocities. The following boxes explain the nature of agronomic measures which are essential in inter-bunded or terraced areas. These practices enhance the utility value of all kinds of mechanical structures.
1. Contour Tillage: All agricultural operations such as ridging, ploughing, harrowing, sowing, trenching, etc., are recommended to be done on the contour wherever possible or at least generally across the direction of the slope where holdings are very small. Even though the operation is very simple, it plays a major role in retarding the process of soil erosion through runoff. It also conserves soil, and due to increased time of concentration, more rainwater seeps through the soil profile to recharge ground water. Summer ploughing leaves the soil highly absorbent of initial rains.
2. Dead furrows: When all tillage operations are complete, it is advisable to leave a deep dead furrow at every 10 m interval. This should remain in position until the crop is harvested. Dead furrows aid in reducing the runoff velocity and they also conserve water.
3. Organic Matter: Indian soils are very poor in organic matter, especially in drought-prone areas: This can be improved by leaving the crop residue in situ (on the fields). Adding organic manures such as farmyard manure and compost every year as basal application to the soil improves the physical condition of the soil considerably.
Soil-Air, Soil-Temperature, and Soil-Moisture relationships are well balanced with the presence of organic matter. Organic matter improves the activities of soil microorganisms and also provides the much needed micro plant nutrients of all kinds, besides nitrogen, phosphorus and potash. Addition of large amounts of chemical fertilizers to dryland crops should be discouraged as it damages the soil due to:

Water Quality Parameters
Irrigation water contains impurities in varying concentration. The suitability of irrigation water mainly depends up on the amount and type of salts present in the water. The main soluble constituents are calcium, magnesium, sodium as cations and chloride, sulphate, bicarbonates as anions. The other ions present in minute quantities are boron, selenium, molybdenum and fluorine which are harmful to animals fed on plants grown with excess of these ions.
Quality of irrigation water is judged with three parameters
1. Total salt concentration
2. Sodium absorption
3. Bicarbonate and boron content.
Total Salt Concentration
Salt content of irrigation water is measured as electrical conductivity (EC). Conventionally, water containing total dissolved salts to the extent of more than 1.5m mhos /cm has been classified as saline. Saline waters are those which have sodium chloride as predominant salt. Brackish water is one that is contaminated with acid, bases, salts or organic matter, whereas saline water contains mainly dissolved salts, Based on EC irrigation water is classified as below.