Irrigation Scheduling Calendar — Plan Every Watering Day for Your Crop

Stop Guessing When to Irrigate — Use Science to Schedule Every Drop

Most farmers irrigate by habit. Every three days. Every Tuesday and Friday. When the soil looks dry. When the neighbour turns on his pump. This guesswork approach has two equally damaging failure modes: irrigating too often drowns roots, wastes water, and promotes disease; irrigating too rarely stresses the crop at critical growth stages and silently kills yield — often before any visible wilting appears.

The most successful farms in the world — from the drip-irrigated vineyards of California to the sugarcane fields of Maharashtra to the pepper farms of Spain — share one practice: they follow a science-based irrigation schedule. They know exactly how much water their crop needs each day, how many days the soil can store it, and precisely when to turn the pump on.

Our free Irrigation Scheduling Calculator brings that same precision to any farm, anywhere in the world. Enter your crop, soil type, and irrigation system — and get a complete 30-day irrigation calendar, pump run hours, water volumes, and a full seasonal water budget, all ready to print and post at your pump house.

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Why Irrigation Scheduling Matters More Than You Think

The Hidden Cost of Poor Timing

Water stress does not announce itself loudly. A crop that receives water every five days when it actually needs it every three does not immediately wilt — but its stomata close during the stress period, photosynthesis slows, flower drop increases, and fruit size decreases. By the time wilting is visible, yield loss has already accumulated silently over weeks.

Conversely, over-irrigation creates a waterlogged root zone where oxygen is driven out of the soil. Roots suffocate, uptake of nitrogen and potassium collapses, and fungal diseases like Phytophthora and Pythium find ideal conditions. Yield suffers — and the excess water was paid for, pumped, and wasted.

Research from multiple countries consistently shows that precise irrigation scheduling increases yield by 10–25% compared to calendar-based or appearance-based scheduling, while simultaneously reducing water use by 20–40%. The pump runs less. The electricity bill drops. The crop performs better. Every metric improves when you schedule correctly.

Agriculture Is the World’s Biggest Water User

Agriculture accounts for approximately 70% of all freshwater withdrawals globally. In India, that figure exceeds 85%. As groundwater tables fall across Punjab, Rajasthan, Maharashtra, Andhra Pradesh, and agricultural regions worldwide, every litre saved through better scheduling extends the life of the aquifer and reduces pumping costs for every farmer who depends on it.

Irrigation scheduling is not just good agronomy — it is essential water stewardship. And it costs nothing to do correctly once you understand the numbers.

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The Science Behind Irrigation Scheduling

Understanding how the calculator works helps you use it more effectively and adapt it to your specific field conditions.

Crop Evapotranspiration (ETc) — How Thirsty Is Your Crop?

The foundation of every irrigation schedule is ETc — Crop Evapotranspiration — the combined water lost from the soil surface through evaporation and from the plant through transpiration each day.

ETc is calculated as:

ETc = ETo × Kc

Where ETo is the Reference Evapotranspiration — the water demand calculated from local weather conditions (temperature, humidity, wind speed, and solar radiation) — and Kc is the Crop Coefficient, a factor that adjusts the reference value for each specific crop and growth stage.

In practice, most farmers use locally published ETc tables that combine both values for common crops and seasons. Our calculator uses typical peak-season ETc values for each crop that you can adjust for your local conditions.

Typical ETc Values (mm/day, peak growing season):

Crop	ETc Range (mm/day)
Tomato	4.5 – 6.5
Chili / Capsicum	3.5 – 5.5
Onion	3.0 – 5.0
Potato	4.0 – 6.0
Watermelon / Melon	4.5 – 7.0
Wheat	4.0 – 6.0
Maize / Corn	4.5 – 6.5
Rice (Paddy)	5.5 – 8.0
Cotton	4.0 – 6.0
Sugarcane	4.5 – 7.0
Banana	4.0 – 6.0
Grape	3.0 – 5.0
Soybean	3.5 – 5.5
Strawberry	3.0 – 4.5

Higher ETc means more water lost per day — which means shorter irrigation intervals, especially in light sandy soils that cannot store much between events.

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Soil Water Holding Capacity — Your Underground Reservoir

The soil acts as a reservoir between irrigation events. Understanding its capacity is the key to knowing how often you need to irrigate.

Available Water Capacity (AWC) is the amount of water a soil holds that is actually available to plant roots — the difference between field capacity (maximum water holding after drainage) and the permanent wilting point (where plants can no longer extract water). It is expressed in millimetres of water per metre of soil depth.

Soil Type	AWC (mm / metre)	Typical Irrigation Interval
Sandy	50 – 70	Every 1 – 2 days
Sandy Loam	80 – 100	Every 2 – 3 days
Loam	110 – 150	Every 3 – 5 days
Clay Loam	140 – 180	Every 5 – 7 days
Clay	180 – 220	Every 7 – 10 days

A farmer with clay loam soil can irrigate far less frequently than one with sandy soil — and use far less total water across the season — even growing the same crop under the same weather. Knowing your soil type is as important as knowing your crop’s water need.

Root Zone Depth — Only What the Roots Can Reach Matters

Only the water stored in the active root zone is available to the plant. An onion crop with 35 cm roots can only access water in the top third of a metre. A grape vine with 1.2 m roots accesses a much larger soil reservoir and can go much longer between irrigations.

Crop	Effective Root Depth
Onion, Lettuce, Spinach	0.3 – 0.4 m
Strawberry	0.3 – 0.4 m
Potato	0.4 – 0.6 m
Tomato, Chili, Eggplant	0.5 – 0.7 m
Wheat, Rice	0.5 – 0.7 m
Maize, Cotton, Soybean	0.6 – 0.9 m
Sugarcane, Banana	0.6 – 0.8 m
Grape, Pomegranate	0.8 – 1.2 m
Mango, Coconut	1.0 – 2.0 m

Multiplying root zone depth by AWC per metre gives the total water storage capacity of the root zone — the effective size of your soil reservoir.

Management Allowed Depletion (MAD) — How Dry Before You Water?

You should never wait until the soil is completely dry before irrigating — plant stress begins well before visible wilting. Management Allowed Depletion (MAD) is the safe fraction of available water that can be used before the next irrigation without causing plant stress.

• MAD 40% — used for shallow-rooted vegetables (onion, lettuce, strawberry) and crops highly sensitive to water stress
• MAD 50% — the standard for most vegetable crops (tomato, chili, capsicum, eggplant, brinjal)
• MAD 55–60% — suitable for field crops (wheat, maize, soybean) and trees with deeper roots

Readily Available Water (RAW) = AWC × Root Depth × MAD

This is the volume of water the crop can comfortably use between irrigations. Dividing RAW by the daily ETc gives you the optimal irrigation interval in days.

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How the Irrigation Interval Is Calculated — A Real Example

Let’s walk through a complete calculation so you can see exactly what the calculator is doing:

Crop: Tomato
Soil: Loam (AWC = 130 mm/m)
Root depth: 0.6 m
MAD: 50%
ETc: 5.5 mm/day
Irrigation system: Drip (90% efficiency)
Field area: 1 hectare
Pump flow rate: 9,000 LPH (9 m³/hr)

Step 1 — Total water in root zone: 130 mm/m × 0.6 m = 78 mm

Step 2 — Readily Available Water (RAW): 78 mm × 50% MAD = 39 mm

Step 3 — Irrigation interval: 39 mm ÷ 5.5 mm/day = 7.1 days → irrigate every 7 days

Step 4 — Net irrigation depth per event: 39 mm (to replace the depleted water)

Step 5 — Gross depth (accounting for system efficiency): 39 ÷ 0.90 = 43.3 mm gross depth to apply

Step 6 — Water volume per event: 0.0433 m × 10,000 m² = 433 m³ (4,33,000 litres) per irrigation

Step 7 — Pump run time: 433 m³ ÷ 9 m³/hr = 48 hours of pump running per event

This is the exact science our calculator automates. You just enter your numbers — the tool does all seven steps and generates a complete 30-day calendar showing which specific dates to irrigate, which to rest, and how long to run your pump each time.

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Irrigation System Efficiency — Why Your Choice of System Changes Everything

Not all the water that leaves your pump reaches the crop root zone where it is needed. Losses occur through evaporation, wind drift, surface runoff, and deep percolation below the root zone. Irrigation efficiency measures what fraction of the applied water is actually used productively by the crop.

Irrigation System	Efficiency	Notes
Subsurface Drip	90 – 98%	Highest efficiency — water delivered directly below soil surface
Surface Drip Irrigation	85 – 95%	Best choice for most vegetables and fruit crops
Micro Sprinkler	80 – 90%	Excellent for orchards, wide-spaced crops
Overhead Sprinkler	70 – 80%	Wind and midday evaporation cause significant losses
Furrow / Surface Irrigation	50 – 65%	Deep percolation and tailwater runoff are major loss sources
Flood / Basin Irrigation	40 – 55%	Lowest efficiency — large volumes required for same crop need

A farmer switching from flood irrigation (50% efficiency) to drip irrigation (90% efficiency) for the same crop immediately cuts gross water consumption nearly in half. The same pump, running half as many hours, delivers the same crop outcome. For most vegetable and fruit crops, the capital cost of a drip system is recovered within one to three seasons through water and electricity savings alone.

The calculator automatically adjusts all computed water volumes for your system’s efficiency, so every number you see represents what you actually need to apply at the pump — not just the theoretical plant requirement.

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Seasonal Water Budget — Know Before You Sow

Before the season begins, every farmer should calculate the total water volume their crop will need from planting to harvest. This single number determines:

• Whether your borewell or water source has sufficient yield to supply the crop
• How large your farm pond or storage tank needs to be
• Whether you need to plan for supplementary water purchase
• Your approximate electricity bill for pumping across the season

Seasonal Water Calculation:

Seasonal Volume (m³) = (ETc − Effective Rainfall) ÷ Efficiency × Field Area (m²) × Crop Duration (days) ÷ 1000

Example — 1 hectare of cotton, 180-day season:

• ETc: 5.0 mm/day
• Effective rainfall credit: 1.5 mm/day
• Net irrigation need: 3.5 mm/day
• Gross depth at 85% efficiency: 3.5 ÷ 0.85 = 4.12 mm/day
• Daily volume: 4.12 mm × 10,000 m² ÷ 1000 = 41.2 m³/day
• Seasonal total: 41.2 × 180 = 7,416 m³ (74.16 lakh litres)

For a borewell yielding 3 m³/hr, supplying this crop requires 7,416 ÷ 3 = 2,472 hours of pump running across 180 days — approximately 13.7 hours per day. If the borewell yields only 1.5 m³/hr, this crop cannot be supplied without a storage pond or a second water source. Knowing this before planting prevents a very expensive mid-season crisis.

Our Water Requirement tab calculates all of this automatically, with breakdowns by day, week, month, and full season.

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Critical Growth Stages — Never Miss an Irrigation at These Points

Some growth stages are so sensitive to water stress that missing a single irrigation event causes irreversible yield loss. These are the stages where your schedule must be followed without exception.

Germination and Seedling Establishment

Seedlings have almost no root depth and no ability to access deep soil moisture. A single dry day can kill a seedling outright or cause severe stunting from which the plant never fully recovers. Irrigate lightly and frequently — every 1–2 days — until the root system is established at 3–4 weeks after sowing or transplanting.

Flowering

Flower drop is one of the most damaging and time-sensitive consequences of water stress. Water deficit during the 5–7 days around anthesis (pollen release and fertilisation) causes flowers to abort and fall from the plant. In tomato, capsicum, cotton, and maize, this translates directly into empty fruit clusters and unfilled cobs. No amount of subsequent irrigation will restore the dropped flowers. Never skip or delay an irrigation during the flowering window.

Fruit Set and Early Fruit Expansion

The first 2–3 weeks after fruit set determines the maximum cell number — and therefore the maximum potential size — of each fruit. Water stress during this window causes small, misshapen fruits that will never grow to full size regardless of how well they are irrigated later. Blossom end rot in tomato and tip burn in lettuce both occur at this stage, driven by inadequate water uptake disrupting calcium transport within the plant.

Grain Fill in Cereals and Legumes

For wheat, maize, soybean, and sunflower, the grain fill period is both the most water-demanding and the most yield-sensitive stage of the entire season. Water stress during grain fill reduces grain weight, produces chalky or chaffy grains, causes premature maturity, and directly reduces oil content in oilseed crops. Keep your schedule tight during this window — it is worth more than any other irrigation of the season.

Tuber and Bulb Development

Underground storage organs — potato tubers, onion bulbs, garlic cloves — require remarkably consistent moisture throughout their development. Irregular irrigation during bulbing causes cracking and hollow heart in potato, double bulbing in onion, and reduced size and storability in all root and bulb crops. Maintain regular irrigation right up to the final two weeks before harvest, when a slight drying-off is beneficial for skin set and curing.

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Month-by-Month Irrigation Planning

A good irrigation schedule accounts for seasonal variation in ETc — crops need more water in hot, dry months and less in cool or humid periods. ETc is highest at peak crop growth during hot, windy weather, and lowest at establishment and late season.

Example Monthly ETc Pattern — Tomato Crop, Maharashtra, India:

Month	ETo (mm/day)	Crop Stage	ETc (mm/day)	Interval (Loam)
October (planting)	4.5	Initial	2.7	14 days
November (vegetative)	4.2	Development	3.8	10 days
December (flowering)	3.8	Mid-season	4.4	9 days
January (fruiting)	4.2	Mid-season	4.8	8 days
February (peak harvest)	5.0	Mid-season	5.75	7 days
March (final harvest)	5.8	Late season	4.6	8 days

This shows why a fixed schedule throughout the season is never optimal — the required interval changes from 14 days at planting to 7 days at peak growth, then relaxes again at the end. Our calculator lets you re-run the schedule at each growth stage and print a fresh calendar as the crop develops.

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Irrigation Timing — What Time of Day to Water

Even with a perfectly calculated interval and volume, poor timing within the day wastes water and can damage crops. Here is the definitive guide to daily irrigation timing:

Time of Day	Suitability	Reason
Early morning (5:00 – 8:00 AM)	✅ Best for all systems	Lowest evaporation, calm wind, cool air — water reaches roots efficiently
Mid-morning (8:00 – 11:00 AM)	🟡 Acceptable	Rising evaporation and wind — small losses but workable
Midday (11:00 AM – 3:00 PM)	❌ Avoid for sprinkler and flood	Evaporation losses up to 35–40% in summer heat
Afternoon (3:00 – 6:00 PM)	🟡 Acceptable for drip	Cooling temperatures reduce losses
Evening (6:00 – 8:00 PM)	🟡 Acceptable	Good for drip; avoid overhead — wet foliage overnight promotes disease
Night (8:00 PM – 5:00 AM)	🟡 Drip: fine / Sprinkler: avoid	Drip is unaffected; overhead at night creates foliar disease risk

For drip irrigation systems, timing matters considerably less because water is applied at soil level and evaporation from the emitter zone is minimal regardless of the hour. However, scheduling drip fertigation in the early morning is still preferred — it delivers nutrients to the root zone during peak photosynthesis hours.

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Irrigation Scheduling for Common Crops

Tomato

Tomato has moderate to high water requirement and is acutely sensitive to both water stress and waterlogging. On loam soil, the standard drip irrigation interval is 4–7 days depending on the season, with daily drip runs of 30–60 minutes on high-density plantings. Critical stages are flowering, fruit set, and the rapid fruit expansion phase.

Reduce irrigation to 60–70% ETc in the final 2–3 weeks before harvest — this increases fruit dry matter, sugar content (Brix), and post-harvest shelf life without causing stress-related quality problems.

Wheat

Wheat in northern India and similar climates typically receives 4–6 planned irrigations across the 130–150 day season:

• Crown Root Initiation (CRI): 20–25 days after sowing — the single most critical irrigation of the season
• Tillering: 40–45 days
• Jointing / Stem elongation: 60–65 days
• Heading / Ear emergence: 80–85 days
• Grain filling: 100–105 days
• Dough stage: 115–120 days (in dry years only)

Skipping CRI irrigation reduces tiller number significantly and suppresses the yield potential for the entire season. Skipping grain fill irrigation directly reduces grain weight and protein content.

Rice (Paddy)

Rice has the highest water requirement of any major food crop — 900–1,200 mm across a typical 120-day season under traditional flood management. The field is maintained under 5–8 cm of standing water throughout the vegetative period, with drainage 10–14 days before harvest.

Alternate Wetting and Drying (AWD) is a proven water-saving technique adopted widely in Bangladesh, the Philippines, and parts of India. The field is allowed to dry until the water table drops 15–20 cm below the soil surface (measured using a simple perforated pipe inserted in the field), then re-flooded. AWD reduces water use by 25–40% with minimal yield loss when managed correctly.

Drip-Irrigated Vegetables

For high-value vegetables grown under drip systems — tomato, capsicum, cucumber, brinjal, bitter gourd — irrigation and fertigation scheduling are inseparable. The most productive approach:

• Irrigate daily or on alternate days to maintain the root zone near field capacity at all times
• Apply water-soluble fertilisers through the drip system at each irrigation event, in small daily doses rather than large weekly applications
• Adjust irrigation run time based on daily ETc — use a local weather station, ET app, or model data
• Install a tensiometer at 20–25 cm depth in the bed to verify your schedule: irrigate when the tensiometer reads 20–35 centibars (loam), 15–25 centibars (sandy loam)

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Common Irrigation Scheduling Mistakes — and How to Fix Them

Mistake 1: Using a fixed calendar throughout the entire season ETc changes significantly as the season progresses and weather changes. A correct interval in November will seriously under-irrigate the same crop in February. Recalculate and adjust your calendar every 3–4 weeks.

Mistake 2: Running the pump for the same duration every day regardless of need Especially common with drip systems — farmers run drip for a fixed time daily (e.g., 3 hours every morning) without considering whether the soil actually needs it. This leads to waterlogging, shallow root development, excess fertigation loss, and root disease. Use your calculated volume and interval, not a fixed clock.

Mistake 3: Ignoring effective rainfall A 25 mm rain event replaces 4–5 days of drip irrigation for a loam-soil vegetable crop. Farmers who keep running their drip schedule after a significant rainfall event over-irrigate, waste fertiliser, and create anaerobic root conditions. When significant rain falls, push your next irrigation date forward by the number of days’ equivalent water received.

Mistake 4: Irrigating all crops on the same schedule Different crops in adjacent fields have very different ETc values, root depths, and MAD tolerances. An onion crop needs irrigation every 2–3 days during bulbing; a neighbouring pomegranate orchard may only need water every 10–12 days. Running both on the same schedule serves neither well.

Mistake 5: Ignoring pump run time calculations Knowing the interval is only half the schedule. A farmer who knows to irrigate every 7 days but runs the pump for 3 hours instead of the correct 48 hours applies only a fraction of the required water — the soil appears irrigated on the surface but the root zone remains dry. Always calculate the required volume and the pump run time together.

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How to Use the Irrigation Scheduling Calculator

The tool has three functional tabs and one reference tab:

Tab 1 — Irrigation Schedule (30-Day Calendar)

1. Select your crop — ETc is auto-filled for the selected crop at peak season
2. Enter your field area — choose your unit (acre, hectare, m², guntha)
3. Select your soil type — AWC and MAD are auto-filled; adjust if you know your specific values
4. Select your irrigation system — efficiency is applied automatically
5. Enter root zone depth — the default is suitable for most vegetable crops; adjust for orchards and trees
6. Enter your pump flow rate — in LPH, LPM, m³/hr, or GPM
7. Set your start date and schedule duration
8. Click Generate Irrigation Schedule to get your complete calendar, water volumes, and pump hours
9. Click Print / Save Schedule to generate a printable PDF report — ideal to post at the pump house or share with farm workers

Tab 2 — Seasonal Water Requirement

Enter crop, field area, ETc, crop duration, effective monthly rainfall, and system efficiency to get a complete water budget — daily, weekly, monthly, and seasonal volumes, with per-hectare and per-acre breakdowns.

Tab 3 — Interval Calculator

Enter only ETc, soil type, root depth, and rainfall to quickly find the optimal days between irrigations and the depth of each irrigation event — a fast reference without needing to set up a full calendar.

Tab 4 — Crop Reference

A comprehensive reference table of ETc values, soil water capacities, irrigation system efficiencies, and timing best practices for all major crops.

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Frequently Asked Questions (FAQ)

Q. How do I find the ETc value for my crop and location? Your local agricultural university extension, Krishi Vigyan Kendra (KVK), state department of agriculture, or district agro-meteorology station will have published seasonal ETc data for your region. Alternatively, the FAO AQUASTAT database and tools like FAO’s CROPWAT software provide ETc data for most locations globally. For quick planning, use the auto-filled values in our calculator as a starting point and adjust based on local advice.

Q. My borewell flow rate is very low. Can I still irrigate on this schedule? Yes — but you may need to run the pump for more hours or use a storage tank to accumulate water between pump runs. Calculate your required volume per event from the tool, then divide by your pump flow rate to find required pump hours. If the pump hours exceed 18–20 hours per day, you may need a supplementary water source, a larger pump, or to reduce your irrigated area.

Q. How does the calculator account for rainfall? In the Interval Calculator tab, you can enter effective daily rainfall to reduce the net depletion rate and extend the irrigation interval. In the Water Requirement tab, enter your effective monthly rainfall to reduce the gross seasonal water need. For the calendar, manually push your next irrigation date forward after a significant rain event.

Q. What is effective rainfall? Effective rainfall is the portion of actual rainfall that remains in the root zone and is available to the crop. It is typically 70–80% of actual rainfall in loam soils — the remainder is lost to runoff and deep percolation below the root zone. A simple approximation: effective rainfall = actual rainfall × 0.75.

Q. Can I use this calculator for drip fertigation scheduling? Yes — use the calculated irrigation volume and interval as the base for your fertigation schedule. The water volume per event determines how much fertiliser solution your drip system applies. Cross-reference with our Fertiliser and Fertigation Calculator (Tool 8) to combine both into a complete nutrition and irrigation plan for your crop.

Q. How often should I recalculate my schedule? Recalculate every 3–4 weeks, or whenever you move from one growth stage to the next. ETc changes significantly between vegetative, flowering, and fruiting stages — especially for vegetable crops where the Kc can shift from 0.6 at establishment to 1.15 at peak growth.

Q. Is this calculator suitable for greenhouse and polyhouse crops? Yes, with one important adjustment: greenhouse crops are not exposed to outdoor wind and receive no rainfall, so ETo inside a greenhouse is typically 50–70% of outdoor ETo. Multiply the auto-filled ETc by 0.6–0.7 for polyhouse-grown crops with good ventilation, or by 0.5 for closed greenhouses with climate control. Root zone depth and soil parameters remain the same.

Q. What is Alternate Wetting and Drying (AWD) for rice, and can this tool help with it? AWD is a water-saving rice irrigation technique where the field is allowed to dry to 15–20 cm below the soil surface between irrigations. The Interval Calculator tab can estimate the AWD irrigation interval for rice by entering the appropriate root depth and available water parameters. For standard AWD, check the water level in a perforated field tube every 2–3 days and irrigate when it drops to the threshold — this field monitoring cannot be replaced by calculation alone, but the calculator gives you the framework.

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Conclusion

Irrigation scheduling is the single most impactful agronomic practice available to farmers using any type of water supply — borewell, canal, pond, or rainwater harvest. A correctly scheduled crop receives exactly the water it needs, exactly when it needs it. Nothing is wasted. No stress is inflicted. Every litre is productive.

The barrier to good scheduling has never been knowledge — the science is well understood. The barrier has been the effort required to calculate intervals, volumes, and pump times for a specific combination of crop, soil, and system. Our Irrigation Scheduling Calendar eliminates that barrier entirely.

Enter your field details once. Generate your 30-day calendar. Print it. Pin it at the pump. Follow it. Adjust it after rain. Regenerate it when the crop enters its next growth stage.

Water less. Grow more. Save every drop.

Whether you are managing a half-acre drip-irrigated tomato plot in Maharashtra, a 50-acre wheat field under canal irrigation in Punjab, a banana plantation under micro-sprinklers in Tamil Nadu, or a mixed vegetable farm anywhere in the world — this tool gives you the numbers to irrigate with confidence, precision, and purpose.

💧 Schedule scientifically. Irrigate precisely. Grow profitably.

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Explore More Free Agricultural Calculators:

• Drip Irrigation Layout Calculator — Pipe lengths, dripper spacing & total discharge
• Water Tank & Farm Pond Capacity Calculator — Plan your on-farm water storage
• Evapotranspiration (ET) Calculator — Daily crop water requirement from weather data
• Borewell Yield Estimator — Measure and verify your groundwater supply
• Fertiliser & Fertigation Calculator — Combine nutrition and irrigation planning
• Crop Spacing & Plant Population Calculator — Optimise plant density for your field
• Rainwater Harvesting Calculator — Capture roof and field runoff for irrigation

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References: FAO Irrigation and Drainage Paper No. 56 — Crop Evapotranspiration (Allen et al., 1998) | FAO Irrigation and Drainage Paper No. 33 — Yield Response to Water (Doorenbos & Kassam) | ICAR — Water Management in Drip Irrigation Systems | Indian Council of Agricultural Research — Package of Practices for Crop Production | International Rice Research Institute (IRRI) — Alternate Wetting and Drying Guidelines

This calculator is for planning and educational purposes. Actual irrigation requirements vary with local weather, soil variability, crop variety, and management. Always cross-reference with local agro-meteorological data and field soil moisture monitoring for precision scheduling.