Agronomy: Irrigation and Water Management

• Agronomy is derived from the Greek words "Agros" (field) and "Nomos" (to manage).

Irrigation

• Irrigation is the artificial application of water to soil or agricultural fields, supplementing rainfall in dry areas or during inadequate rainfall periods.
• Irrigation helps agricultural crops and plants grow by maintaining the required water amount, suppressing weed growth in fields, and preventing soil consolidation.
• Irrigation is the process of supplying water to crops by artificial means from sources like rivers, tanks, ponds, or underground water, using canals, wells, and tube-wells.

Need for Irrigation

• Irrigation enhances overall productivity.
• It taps into the soil's potential for production.
• It reduces dependence on monsoons and rain-fed agriculture.
• Irrigation enhances production by enabling multiple crops within a year.

Well and Tube Well Irrigation

• Wells are commonly found in U.P., Bihar, and Tamil Nadu and come in various types: shallow, deep, tube, and artesian.
• Water from shallow wells is unreliable during dry months due to declining water levels, whereas deep wells provide a more consistent year-round water supply.
• Most of peninsular India is unsuitable for well irrigation due to its uneven surface, rocky structure, and lack of groundwater.
• Large dry tracts of Rajasthan, along with parts of Punjab, Haryana, and Gujarat, use wells for irrigation.
• Some regions of Uttar Pradesh have brackish underground water unsuitable for irrigation and human consumption.
• Uttar Pradesh has the largest area under well irrigation, accounting for 23% of the country's total.
• Following Uttar Pradesh, Rajasthan (10%), Punjab (8%), Madhya Pradesh (7.9%), Gujarat (7.3%), and Bihar (6.2%) have significant areas under well irrigation.
• A tube well is a deeper well that lifts water using a pumping set powered by an electric motor or diesel engine.
• Tube-wells can be set up near agricultural areas where groundwater is available and electricity-powered deep tube wells can irrigate larger areas (about 400 hectares) more than surface wells (half hectares).
• Tube wells are commonly used in U.P., Haryana, Punjab, Bihar, and Gujarat.

Merits of Well Irrigation

• Well irrigation is the simplest, cheapest, and most independent irrigation source, used as needed.
• Well water contains chemicals like nitrate, chloride, and sulphate, which enrich the soil.
• It is more reliable than surface water during droughts.
• Demerits: Only a limited area can be irrigated and groundwater levels may drop, reducing water availability during droughts.
• Tube wells can deplete groundwater in neighboring areas, rendering the ground dry and unsuitable for agriculture.

Canal Irrigation

• Canals effectively irrigate areas with low relief, deep fertile soils, perennial water sources, and extensive command areas.
• Canal irrigation is mainly concentrated in the northern plains of India, especially Uttar Pradesh, Haryana, and Punjab.
• Digging canals in rocky and uneven terrain is challenging and uneconomical.
• Canals are rare in the peninsular plateau, but coastal and delta regions in South India have some canals.
• Inundation canals divert water from rivers without any regulating system and primarily provide irrigation during the rainy season when rivers flood.
• Perennial canals are taken off from perennial rivers using a barrage across the river; most canals in India are perennial and provide irrigation as needed, protecting crops from drought and increasing farm yields.
• Demerits: Canals may overflow during the rainy season, causing floods, and are best suited for plain areas.

Tank Irrigation

• A tank is created by building a small bund of earth or stones across a stream to impound water for irrigation and other purposes.
• Tanks are an important irrigation source in the Karnataka Plateau, MP, Maharashtra, Odisha, Kerala Bundelkhand area of UP, Rajasthan, and Gujarat.
• Tanks are mainly natural, have lower construction costs, and longer lifespans; many tanks also support fishing, which adds to food resources and farmer income.
• Demerits: Many tanks may dry up in the dry season, impeding irrigation, and water extraction from tanks can be strenuous and costly.

Drip Irrigation

• Drip irrigation applies water near plant roots through emitters or drippers at a slow rate that ranges from 2-20 liters per hour to maintain optimal soil moisture with frequent irrigations.
• Drip irrigation is the most efficient method and can be used for various crops, especially vegetables, orchards, flowers, and plantations.
• Fertilizer and nutrient loss is minimized due to localized application and reduced leaching.
• Field leveling is unnecessary, recycled non-potable water can be used, water application efficiency increases, and soil erosion and weed growth are reduced.
• Demerits: High initial costs and potential for clogging, leading to wasted water, time, and harvest if not installed correctly.

Sprinkler Irrigation

• In sprinkler irrigation, water is sprayed into the air to fall on the ground like rainfall, using pressure through small orifices or nozzles.
• Sprinkler irrigation is appropriate for shallow soils and uneven land.
• Almost all crops, except paddy and jute are suitable for sprinkler irrigation, including dry crops, vegetables, flowering crops, orchards, and plantation crops such as tea and coffee.
• It can be used for all soil types except heavy clay, saves water, increases yield, and saves land.
• Demerits: Higher initial costs and poor distribution and application efficiency under high wind conditions and high temperatures.

Other Types of Irrigation

• Furrow Irrigation: Trenches, or furrows, are dug between crop rows, and water is flowed down them to seep vertically and horizontally, refilling the soil reservoir.
• One difficulty of furrow irrigation is ensuring uniform water dispersion, and another issue is the potential for water loss due to runoff.

Border Method

• Borders are made by dividing a field into strips separated by ridges; strips are generally leveled in width and may or may not have a slope along the length.
• An irrigation channel runs along the upper end of the borders, with water diverted from the channel into the strips, flowing slowly towards the lower end, wetting the soil.
• Extra water is removed through a collecting drain at the strip.
• This method is suited to fields with soil that efficiently absorbs water.

Check Basin

• This runs water into level plots surrounded by small ridges; the plot length is generally less than three times its width.
• The main channel is aligned along the field's upper end, and checks are made on either side of the lateral channels.

Surge Irrigation

• Surge irrigation is a type of furrow irrigation where water supply is pulsed on and off in planned time periods.
• Wetting and drying cycles reduce infiltration rates, enabling faster advance rates and more uniform distribution than continuous flow.

Ditch Irrigation

• This traditional method involves digging ditches and planting seedlings in rows, where canals or furrows are placed between rows and siphon tubes move water from the main ditch to the canals.

Sub Irrigation or Seepage Irrigation

• In this water is delivered to the plant root zone from below the soil surface and absorbed upwards, with any excess collected for reuse.
• The advantages of this method are water and nutrient conservation, and labor-saving.
• The outfitting cost is relatively high, and potential problems include the chance of increased disease presence in recycled water.

Sprinklers

• WaterSprinklers water with pressure to any soil or crop surface in the a thin spray resembling rainfall.
• The system consists of sprinkler heads or nozzles on risers in lateral lines, connected to a pumping unit.
• The rate of water spray can be adjusted, mimicking natural rainfall, and can be used for most crops except rice and jute and on most soils except heavy clay soils; also suited to fields with steep slopes or irregular topography.
• If soil erosion is a risk, sprinkler irrigation can be used alongside contour bunding, terracing, mulching and strip cropping, which makes it suitable for undulating topography and sandy soils.
• It saves 25-50% of water for different crops and has a discharge rate greater than 1000 l/hr with water use efficiency as high as 60%, greater than surface irrigation.
• It has the potential to increase irrigated area by 40% with the same water amount versus surface methods, saves 40-60% in labor, and can protect crops from frost and high temperatures.

Drip Irrigation

• This applies water slowly, drop by drop, directly to the crop's root zone.
• Also called trickle irrigation, it is most popular in areas facing water scarcity and salt-related issues.
• It introduced in Israel and involves the precise and slow water application via emitters along water lines.
• It is incredibly efficient in water usage by reducing deep percolation and surface evaporation losses.
• It is best for areas with water scarcity, marginal water quality, undulating or steep topography, restricted soil depth, high labor costs, and high crop value.
• It has water savings of 50-70% compared to surface methods.
• Fertilizer or chemical amendments can be efficiently applied, and it is typically done at a discharge rate of 1-4 lit/hr at 2.5 kg/cm² pressure, supporting both fertilization and herbicide application.
• Most suitable for widely spaced crops, orchard trees, and greenhouses (protected cultivation of vegetables and flowers).

Typhoon System of Drip Irrigation

• This is a sugarcane modified drip, where a specific water depth is maintained during certain growth stages.

Benefits of Irrigation

• Increases agricultural productivity.
• Diversifies crop range.
• Supports cultivation of cash crops.
• Makes yields stable and reliable, reducing fluctuations.
• Guarantees consistent cultivation.
• Reduces regional disparities and enables multiple cropping patterns.

Ill Effects of Irrigation

• Excessive and unscientific irrigation leads to depletion of ground water table, e.g. Punjab.
• Irrigation may cause salinity, water logging, and soil degradation.
• Salinization on irrigated land is a primary cause of land loss in production, as well as a prominent environmental setback from irrigation.
• Waterlogging and salinization are common issues with surface irrigation, primarily due to poor drainage and over-irrigation.
• Waterlogging causes salts to concentrate in the plant's rooting zone, drawn from lower soil layers and Alkalization, a buildup of sodium, is a harmful type of salinization that is hard to correct.

Potential Environmental Impacts of Irrigation Development

• Waterlogging, water borne and water-related diseases are also potential downsides.
• Such diseases, including malaria, proliferate in irrigation waters, alongside agrochemical related health risks, poor water quality and increased population pressure.
• Damming rivers to make lake-like environments radically alters river hydrology and limnology, affecting the timing of flow, water quality, quantity, aquatic life, and sedimentation in the basins.
• The influence region stretches from the reservoir to the estuary, coast, and offshore zone.
• Construction impacts, dust, erosion, and disposal problems are direct environmental effects, while impounding water and changing river flow have the largest impacts.
• Socio-economic impact of large dam construction leads to resettlement of displaced peoples being a substantial issue which can cause community breakdowns and unrest, as well as malnutrition.

Terminology

• Nominal Duty: The ratio of the area to be irrigated, relative to the mean supply discharge during the base period.
• Kor Watering: The initial watering is known as Kor watering with a specific depth during a Kor period and Crop water requirements are not uniform throughout this base period
• Palco: Initial irrigation before sowing for seed germination and seedling establishment.
• Crop Period: Crop duration in days from sowing to maturity.
• Base Period: Duration of crop in days from irrigation for preparatory cultivation to the final irrigation.
• Delta (Δ): Represents the total depth of water (cm) needed by the crop.

Irrigation Efficiencies

• Surface canal conveyance: 40-50%.
• Surface well conveyance: 60-70%
• Sprinkler conveyance: 100%.
• Drip conveyance: 100%.
• Surface application: 60-70%.
• Sprinkler application: 70-80%.
• Drip application: 90%.
• Surface evaporation losses: 30-40%.
• Sprinkler evaporation losses: 30-40%.
• Drip evaporation losses: 20-25%.
• Surface overall: 30-35%.
• Sprinkler overall: 50-60%.
• Drip overall: 80-90%.
• Duty of Water (D): It is ratio between crop area irrigated and the water amount applied, typically described by the letter D.
• Cumec Day: A days worth of water flow at one cumec which is equal to 8.64 ha-m.
• Rostering System: The process of irrigation water distribution (also called rotational or warabandi irrigation).
• Irrigation efficiencies (%) depends on irrigation methods using water efficiently (kg/ha-mm) and this depends on field water use efficiency which is the crop yield over the amount of water and drip systems are the most accurate
• Physiologic, consumptive, or root zone efficineies vary depending on the technique

Agro Meteorology

• The atmosphere is a colorless, tasteless, odorless gas mix surrounding Earth, up to around 1600 km with 99% of total mass within 40 km.

Atmospheric Composition

• Nitrogen: 78.088% volume, 75.527% weight.
• Oxygen: 20.948% volume, 23.143% weight.
• Argon: 0.930% volume, 1.282% weight.
• Carbon Dioxide: 0.033% volume, 0.045% weight.
• Other Gases: Traces.

Atmospheric Structure

• Troposphere: Lower atmospheric layer, 8-18 km height, varying with latitude, denser at the equator, comprising 85% of atmospheric mass, hosting weather events, separated from the stratosphere by tropopause.
• Stratosphere: Layer of atmosphere above tropopause spanning 8-50 km, cloudless and warmer with peak ozone concentration (ozonosphere) between 20-25 km.
• A property of ozone is that it absorbs ultra violet rays, making an ozonosphere to absorb Ultra Violet rays.
• Mesosphere: Layer above the stratosphere, separated via a narrow stratopause.
• Thermosphere: Outermost layer above mesopause, with lower ionosphere for long-distance communication, warm due to ozone's UV absorption, reflecting radio waves.

Solar Radiation

• It is the energy transmission from source to the other without a medium.
• The sun provides 99.9% of all the Earth's energy and emits 1.94 cal/cm²/min, i.e. called the solar constant.
• The amount of solar energy one sq centimeter recieves at the boundary is called solar constant.
• Radiation is energy transmitted without a medium.
• Conduction is heat moved through touching matter and heat spreads until the temperatures are the same.
• Heat is transmitted through molecule movement, is critical in the earth processes, like boiling water.

Net Radiation

• The difference between incoming and outgoing solar radiation from the earth.
• Absorptivity: The ratio of electromagnetic radian power.
• Reflectivity: Represents the energy reflected and indicated as a percentage.
• The transmittance ratio describes how much radiation is transmitted through the crop area.
• Albedo: Ratio of reflected-to-incident radiation, specifically for fields, snow, and leaves; High on white surfaces, 75 to 95% for snow.
• Total radiation types like UV, photosynthetically active, or near-Infrared depend on the fraction of total radiation.

More Atmospheric Properties

• Lapse Rate: Measures vertical temperature decrease and gradients, typically 6.5°C per kilometer.
• Adiabatic Lapse Rate: Rate of temperature alteration with air motion, constant at 10° C/km for dry air.
• Inversion: A temperature increase, instead of decrease, at certain altitudes.
• Humidity: A measure of air moisture that impacts crops, pests, health, where higher humidity reduces radiative cooling.
• High relative humidity aids crop survival under soil stress, enhances leaf growth, reduces evaporation and plant transpiration, and influences the outbreak of diseases and pests, relative to absolute humidity.

Humidity Types

• Absolute humidity measures moisture weight or volume.
• Specific humidity measures vapour weight and air weight(g/kg).
• Relative humidity measures vapour saturation on temp and pressure.

Evaporation

• Water is supplied into the atmosphere via evaporation from plants, soil or water bodies.
• Weather Bureau is used to measure evaporation, and has the evaporation that can be measure with pan and screen.

Monsoon

• Monsoon originates from "season" in Arabic.
• South -West monsoon starts from June in south India (Kerala), spreading 30 km/hour, deemed India's 'Grand period'.
• North -east monsoon effects southern states (AP & TN), or called retreated monsoon.
• River with Utilizes more flows: Ganga.

Rainfall

• Winter rains have 12 MhaM (3%) .
• Pre-monsoons 52 MhaM (13%).
• South West Monsoons 296 MhaM (74%).
• North East monsoons 40 MhaM (10).

Rainfall Type

• Convectional Rains occur as warmed ground makes air rise and cool at a rate of almost 1°C per kilometer which then enables saturation, so cloud formating results in more precipitation.
• Orographic Rains happen mountains force uplift of ocean-origin air upward which cools, forms clouds, and results in precipitation, meaning high-intensity processes occur on the windward mountain side.
• Cyclone precipitation happens when vertical lifting occurs between differing air temperatures.

Artificial rain/Cloud seeding

• Using foreign material seeding to create cloud precipitation using Silver iodide (AgI) or dry ice.
• The precipitation is determined by rainfall levels depending on days and year.
• Standard Rain level is > 2.5 mm, and crop rain is >5 mm.

Instruments for measuring various factors

• Various weather factors can be continuously measured with instruments like sunlight, velocity, evaporation, or temp.
• Ground measurements are taken with various instruments.

Units of Measurement

• Temperature: °C.
• Vapour Pressure: Mm of Hg.
• Relative Humidity: Percentage (%).
• Wind Direction: Degree (0 t0 360°).
• Wind spree: Km hr-¹.
• Rainfall and Evaporation: Mm day-¹.
• Bright sunshine duration: Hrs.
• Cloud Cover: Okta (0 to 8).
• Atmospheric Pressure: Milli bars/mm of Hg/Pascals.

Types of Weather Forecasting

• Used to determine how sky and sunlight conditions relate different levels percentage (Cloudiness, sun, etc)
• Forecasters consider Synoptic or Statistics to make methods.

Agro Ecosystems of India

• Agro systems differ by regions: Arid, Rain-fed, Irrigated, or Coastal with the Area varying for all of land types.
• Each land has its special type: Severe water deficits, occasional water, cyclones.

Influence of Climate on crops

• Solar radiation influences plant types and is categorized into for Photosynthetic, Photo periodic and Thermal effects using energy that helps growth.
• The life of spectral plants depend on solar exposure

Light

• The plants respond between 300 nm and 700 nm wavelengths.
• Plants without sunlight is are considered etiolated.
• Sunlight impacts plant physiology and categorizes plants into short-term, long term and etc types.
• Tropical crops are short-day plants.

Temperature

• Temperature affects growth of long-day and tropical crops that are barley or wheat.
• Cool plants thrive at 30-38°C, 0-5°C or 25-30°C.
• Warm ones grow at 45-50°, 15-20° C and 30-38° C.
• Heat for growth in days is described max temp, min temp and bottom level:

Dry land Agriculture

• Rain dependant for crops of any kind.

Dry area farming categories

• It is grouped into three levels:
  • Dry farming is < 750mm with water season lasting less than 75 days
  • Dry-land farming over 750 MM and 120 days long
  • Rain fed with 1150 mm where excess water needs disposal

Arid regions

• Arid zones have moisture index with Precipitation below and 74 days lasting.
• Semi-arid zones is -33.3 with water possible to conserve for 119 days
• Region covers 135.8 million

Drought types

• Tropics covers 3.17 which are rajisthan and other south regions
• Temperate are j and k
• Semiad cover south coastal Andhra Karnataka Maharashtra
• Semiad cold areas over j and k.
• Drought is classified if the water is two times more deficient
• Atmospheric describes how water gets to the crops

Classification of drought

• The levels differ depending on duration of effects.
• Permanaent effects desert agriculture and season effects climate.
• Drought happens based on rainfall and the regions will change.
• Invisible crops happen with borderline rain.
• Meteor effects are determined area by long time of rain and temperature
• Agricultural is usually a soil water level over crops that get worse and is gradual.

Mid-season drought

• This occurs due to long wait between new moisture that will is insufficient.

Late season drought

• Early rains and water stress that is near maturity

Physiological drought

• No water or low amounts of from high concentration levels in soil.
• Ant-transpirants help the water levels
• There are two types:
  • Those the stop stoma
  • Help reduce leaf exposure
• Growth enhancers help to change to make growth

Crop Adaptation for Dry Growing Conditions

• The plants need to be able to leave, and have less resistance to drought which is stress.
• Efficiency should be more resistant and more resistant to dehydration
• The water needs to go up

Tiliage

• Tillage: Soil management that will determine when growth of the crop happens.

Tilth

• Means weather will allow plant growth and germination and also moisture levels are optimal.
• Objectives of tillage are to make seedbed great, aerate soil, and to make soil ready to plant seed.
• No hard soil or other issues like pathogens.

Disadvantages of tillage

• Soil moisture makes no desired effect for germination
• Operations hasten oxidation and breaks soil bonds