Irrigation is the artificial application of water to partially meet the crop evapotranspiration requirement when rainfall is insufficient.

Transpiration constitutes nearly 99% of the total water uptake in evapotranspiration.

In BBF system, beds are 120–150 cm wide with about 0.5% slope for proper drainage. Beds are raised about 15 cm and furrows are 45 cm wide.

Wheat requires about 650–800 mm of water, which is much lower than sugarcane (1500–2500 mm) and rice (1500 mm).

Well-aerated soils have Eh of about 400–700 mV. In waterlogged conditions, Eh decreases sharply to around –250 to –300 mV due to anaerobic conditions.

For crops like maize and wheat, irrigation is recommended when 25% of available soil moisture is depleted. Drought-resistant crops can tolerate up to 50% depletion.

Wheat contains 11–12% protein, mainly gluten, which gives elasticity to dough.

Sub-surface drainage is designed to reduce the groundwater table below the root zone. This prevents waterlogging and creates favorable conditions for plant growth.

In waterlogged rice fields, SO₄²⁻ is reduced to sulphide and further to hydrogen sulphide (H₂S), which causes ‘Akiochi’ due to its toxicity.

Tensiometers are sensitive up to about 0.85 bars of soil moisture tension. They are suitable for low tension ranges, especially near field capacity.

Poaceae (grass family) includes cereals and fodder grasses like napier grass.

Oven-dry soil corresponds to a pF value of 7.0, indicating extremely high soil moisture tension (about 10,000 atm/bars equivalent).

In cold cloud seeding, silver iodide (AgI) or dry ice is used as nuclei to induce precipitation. It helps in forming ice crystals in cold clouds.

The IW/CPE ratio acts as a soil moisture stress index. A lower ratio indicates greater moisture stress on the crop.

Sprinkler irrigation can save 25–50% water compared to conventional methods and is suitable for sandy soils and undulating topography.

Water logging occurs when all soil pores (macro and micro) are filled with water, reducing aeration and adversely affecting plant growth.

As per CRIDA classification, shallow ploughing is 5–6 cm, medium is 15–20 cm, and deep ploughing is 25–30 cm.

The Arabian Sea branch contributes about 770 mm rainfall (around 80% of SW monsoon rainfall), while the Bay of Bengal branch contributes about 340 mm.

The Penman method (1950) is used to estimate evaporation from free water surfaces and evapotranspiration.

At UWP, wilting is complete and the plant dies. Soil moisture tension can be as high as –60 bars, indicating extremely dry soil conditions.

1 ha cm = 100,000 litres (10⁵ litres). This unit is commonly used to measure irrigation water volume in agriculture.

The concept of PET was introduced by Thornthwaite in 1948.

Furrow irrigation is suitable for most soils except sandy soils with very high infiltration rates, as excessive percolation losses occur.

Water attains maximum density at 4°C. This is a unique property of water and is important in environmental and agricultural sciences

Briggs and Shantz (1912) proposed the concept of PWP and used dwarf sunflower as an indicator plant to determine permanent wilting.

In sub-surface irrigation, water is applied through underground pipelines into field ditches. It is commonly followed in Western countries.

Coconut contains about 60% oil, which is the highest among the listed field crops.

Surge irrigation involves intermittent (ON–OFF) water application under gravity flow, reducing deep percolation and runoff losses (generally not exceeding 20%).

pH, introduced by SPL Sorenson (1909), is defined as the negative logarithm of hydrogen ion activity. Its scale ranges from 0 to 14 (7 = neutral).

The neutron moisture meter measures soil moisture by detecting the number of hydrogen nuclei present in a unit volume of soil, which correlates with water content.

At PWP (15 bars tension), the corresponding pF value is about 4.18. This represents the logarithm of the suction head in cm of water.

Long-range forecasting refers to predictions for more than 10 days. It is useful for planning cropping patterns and monsoon predictions.

As per the page, discharge per dripper is generally 1–8 liters per hour, operating at 1.5–2.5 kg/cm² pressure. This ensures slow and efficient water delivery.

Infiltration is the entry of water from the soil surface into the soil profile and occurs in unsaturated soil. It is different from percolation, which happens in saturated soil.

PET occurs when soil moisture is not limiting and the ground is fully covered with actively growing vegetation.

Drip irrigation applies water slowly and precisely in drops through emitters placed along delivery lines. It directly targets the root zone, minimizing losses due to evaporation and deep percolation.

El Niño causes a rise in ocean temperature starting from the coast of Peru. It adversely affects the Indian monsoon, often resulting in dry weather and drought conditions.

Available water is the portion of capillary water held between Field Capacity (about –0.3 bar) and Permanent Wilting Point (–15 bars), which plants can utilize.

Western Disturbances are active from December to March, bringing rainfall to north and central India. This rainfall is highly beneficial for Rabi crops and is locally called “Mavath” in Rajasthan.

Furrow method is mainly used for row crops and vegetables. It is suitable where infiltration rate is about 0.5–2.5 cm/hour and slope ranges from 0.2–0.5%.

Percolation is the downward movement of water through saturated or nearly saturated soil under the influence of gravity. It mainly occurs after infiltration when soil becomes saturated.

The South-West monsoon normally arrives at the Kerala coast around 1st June every year and covers most parts of India by mid-July.

Leaching refers to the downward movement of nutrients and salts along with water from the root zone. It may reduce soil fertility if excessive.

Sugarcane has the highest irrigated area (93%) among the listed crops, indicating its high dependence on assured irrigation.

Sprinkler irrigation is ideal for undulating lands, steep slopes, and irregular topography where surface irrigation is difficult.

Watershed classification is based on area. A micro watershed covers 100–1000 ha, while a mini watershed covers 10–100 ha.

Border strip irrigation is suitable for soils with a slope of 0.5–1% and works well on medium to heavy textured soils.

At PWP, soil moisture tension is about –15 bars (≈15 atmospheres). At this stage, plants cannot extract water and remain permanently wilted unless water is added.

Crop water use efficiency is the ratio of crop yield (Y) to evapotranspiration (ET), i.e., WUE = Y/ET.

At field capacity, gravitational water has drained away. Large pores are filled with air while small (micro) pores hold water, making it the upper limit of available water for plants.

The North-East monsoon begins around 15 October and is commonly called the “Retreating monsoon.” It mainly affects southern states like Tamil Nadu and Andhra Pradesh.

Surface irrigation is the most widely practiced method in India due to its simplicity and suitability under traditional farming systems.

The South-West monsoon is called the “Grand period” of rainfall in India and contributes more than 75% of the total annual rainfall.

Check-basin is commonly used for close growing crops such as wheat, groundnut, and pearl millet. It is suitable for relatively level fields.

Rice has the highest IW/CPE ratio of 1.2 among the listed crops, indicating higher water requirement compared to others like wheat (0.9) and safflower (0.4).

Finger millet has the highest WUE (13.4 kg/ha mm), whereas rice has the lowest (3.7 kg/ha mm).

Drip irrigation has an irrigation efficiency of about 90%, significantly higher than surface methods. It also saves 50–70% water in scarcity areas.

At PWP, soil moisture tension is about –15 bars (≈15 atmospheres). At this stage, plants cannot extract water and remain permanently wilted unless water is added.

Nipping (removal of terminal bud) is practiced in gram and cotton to encourage branching

Saturation capacity occurs when all soil pores are filled with water at zero bars tension. It is also called maximum water holding capacity.