Reviewed August 2026 against USDA NASS Crop Production, USDA ERS irrigation statistics, and University of Nebraska–Lincoln Extension G1367.

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A fully irrigated soybean crop uses 20 to 26 inches of water across the season, and demand peaks at 0.32 inches per day during late flowering and early pod development (R2–R3), reaching about 0.5 inches on a hot, windy day in late July or August — figures published by University of Nebraska–Lincoln Extension in G1367 (revised December 2012). About 65% of that season total is consumed after flowering starts, which is why when you irrigate decides the yield outcome more than how much you pump. And the payoff is measurable: US irrigated soybean yields have run at roughly 1.21 times non-irrigated yields since 2000.

This page gives you the per-day and per-stage numbers, the soil-depletion trigger that tells you to start a pass, a calculator you can run against your own soil, and the delivery-system efficiencies that decide how many inches you pump to put one inch in the root zone.

What this guide covers

Soybean Irrigation Requirements: Season Total and Per Day

Two numbers govern soybean irrigation. The first is seasonal evapotranspiration — the 20 to 26 inches in UNL G1367, which NC State Extension’s North Carolina Soybean Production Guide puts at “can exceed 25 inches” under Southeast conditions. The second is the daily rate, because that is what empties your soil profile between passes.

Run the arithmetic that a search for “soybean crop irrigation per day” is really asking for: at 0.30 inches per day with no rain, a soybean field consumes 2.1 inches in a week. Very few Midwest or Mid-South profiles hold that much plant-available water in the top two feet, which is why July rain gaps of ten days show up directly in the combine monitor.

UNL G1367 also gives the number most growers actually want — effective irrigation by reproductive stage on deep medium- and fine-textured soils. It totals about 10.5 inches, and it accumulates as follows.

How Irrigation Increases Crop Yield — the Mechanism and the Number

Soybean yield is built from pods per plant, seeds per pod and seed size, and all three are set during the reproductive window. That window is also when the crop draws most of its water: UNL G1367 attributes about 65% of season-long use to the reproductive stages, NC State reports more than 60% between R1 and R6, and Clemson’s Science for Success write-up puts roughly 60% between R3 and R6. Three independent extension programmes converge on the same shape.

Remove the water deficit in that window and you keep pods that would otherwise abort. The scale of the effect is documented at national level in farmdoc daily’s analysis by Irwin, Hubbs and Good (3 May 2017), covering 1960–2016: the ratio of irrigated to non-irrigated soybean yield settled near 1.21 after 2000, and irrigated yields trended upward at 0.44 bushels per acre per year against 0.41 for non-irrigated. Mississippi State’s on-farm work is blunter still — irrigated soybean yields exceeded non-irrigated by 20% to 79% across three years of Delta trials.

Two cautions. Irrigation cannot rescue a crop that is short of nodulation, potassium or stand, and over-application in a poorly drained field costs yield rather than buying it. NC State notes that roughly 70% of soybean water uptake comes from the top 12 inches of soil, so a shallow, well-timed refill beats a heavy soak that pushes water past the roots.

Soybean Production in the United States, and Where Irrigation Sits

USDA’s National Agricultural Statistics Service put 2025 US soybean production at 4.26 billion bushels, down 3% from 2024, on 80.4 million harvested acres, with a record national average yield of 53.0 bushels per acre — released in the Crop Production 2025 Summary on 12 January 2026. Illinois, Indiana and Nebraska each averaged 54.0 bushels; Arkansas and Mississippi averaged 51.0. NASS refreshes this in the annual summary each January and revises in the Small Grains and Crop Production series through the year.

Irrigation is a minority practice on US soybeans but a heavily concentrated one. USDA’s Economic Research Service reports 54.9 million acres of irrigated crop and pastureland in the 2022 Census of Agriculture, of which soybeans accounted for about 9 million irrigated acres — second only to corn. Farms with irrigation generated more than 50% of total US crop sales from under 17% of harvested cropland. Nebraska alone carries 8 million irrigated acres, 14.5% of the national total, and farmdoc puts irrigated soybean acreage in Arkansas and Nebraska at about 2.5 million acres each.

That concentration is why groundwater matters to soybean economics. ERS attributes 47% of US freshwater withdrawals in 2010–2020 to irrigation, with 55% of irrigation water drawn from groundwater in the 2023 Irrigation and Water Management Survey. In the Mississippi Delta, Mississippi State’s MAFES reports the Mississippi River Valley alluvial aquifer losing about 300,000 acre-feet per year, with roughly 70% of Delta acres furrow irrigated. Soybeans also feed a growing crush and biofuel feedstock demand, which keeps pressure on those acres.

The Depletion Trigger: a Scheduling Method That Does Not Expire

Prices, varieties and forecasts change. The soil-water balance does not. This is the spine of soybean irrigation scheduling and it will read the same in five years.

1. Establish plant-available water capacity. Pull the value for your soil series from USDA-NRCS Web Soil Survey. It is normally expressed in inches of available water per foot of soil.
2. Set the managed root depth. UNL G1367 manages the top 2 feet through R2 and the top 3 feet from R3 to R6 on deep medium and fine-textured soils.
3. Set the allowable depletion. UNL G1367 specifies no more than 50% depletion in that profile. Clemson’s Science for Success guidance for sensor-based scheduling recommends triggering at 25% to 50% maximum allowable depletion. Use 25–35% on coarse sands, 50% on silt loams and clays.
4. Track the daily draw-down. Subtract crop water use each day and add effective rainfall — the checkbook method. At R3 use 0.30 in/day when hot and windy, 0.25 in/day otherwise, per the table above.
5. Convert net inches to gross inches. Divide the deficit by your system’s application efficiency before you set run time.
6. Stop at R6.5. Clemson’s guidance is to hold adequate soil moisture through R6.5; water applied past that point buys little seed weight.

Verify the assumptions with a soil probe rather than trusting the ledger blindly. MAFES found soil-moisture sensors alone can eliminate at least one irrigation per season — on a 0.30-inch-per-day crop that single skipped pass is real water and real diesel.

Calculator: Days to Trigger and Inches to Refill

Enter your own soil and system numbers; the defaults are the UNL G1367 reproductive-stage values, not a stand-in for your field.

Assumptions: a uniform profile, a full starting profile, no effective rainfall during the interval, and 27,154 gallons per acre-inch. It excludes rainfall, runoff, deep percolation, salinity leaching requirements, pumping cost, well capacity limits and any cap on how fast your system can apply water. Well capacity, not soil, is the binding constraint on many High Plains fields.

Furrow, Pivot and Soybean Drip Irrigation Compared

Application efficiency decides how many inches leave the well to put one inch in the root zone. Kansas State irrigation engineers Freddie Lamm and Todd Trooien, in their review of a decade of subsurface drip research (1 October 1999), use 85% application efficiency for sprinkler and 65% for furrow, and report that subsurface drip reduced net irrigation needs by about 25% — a 35% to 55% saving against sprinkler and furrow systems in their comparisons.

On soybean drip irrigation specifically: SDI wins on odd-shaped, small or hilly fields where a pivot cannot turn, and on high-value rotations that can amortise the pipe. Lamm and Trooien noted that in 1998 only 9,500 of Kansas's roughly 3 million irrigated acres used microirrigation, growing about 1,320 acres a year since 1989 — a useful reminder that adoption has been slow because the capital case is genuinely tight, not because the agronomy fails. Get a current installed quote for your field geometry rather than a per-acre rule of thumb.

Pumping cost tracks the gross inches, not the net. Nebraska Extension's fuel-source comparison (20 April 2007) works the example at 140 feet of lift and 40 psi discharge, requiring 26.5 water horsepower-hours per acre-inch, with the Nebraska Pump Plant Performance Criteria benchmark for diesel at 12.5 water hp-hours per gallon. Their worked example found a typical installation burning 30% more energy than the benchmark — pump-plant testing is often a cheaper win than new hardware.

Get real-time crop and irrigation monitoring on your phone:

Soybean Precision Irrigation and Production Technology

Precision irrigation means varying water in space and time instead of treating a field as one uniform block. Three layers do the work, and they stack.

• Soil-moisture sensors convert the depletion trigger from a ledger estimate into a measurement. MAFES reports sensor packages spanning $200 to several thousand dollars and projected savings of up to $20 per acre. Place them at the depths you are managing — 12, 24 and 36 inches — because NC State's finding that about 70% of uptake comes from the top foot means a single deep probe will mislead you.
• Scheduling software and flow control turn measurement into run time. MAFES credits its irrigation scheduling tools with 30% to 40% reductions in water use.
• Satellite crop monitoring shows which parts of the field are drawing down first, at a cost per acre that scales to whole farms. That is what Farmonaut's soybean irrigation coverage and its multispectral index layers are built for: spotting the sand streak that runs short three days before the rest of the pivot circle does.

The direction of travel across US irrigation is clear in the ERS series: pressurised systems rose from 37% of Western irrigated acres in 1984 (14.7 million acres) to 74% in 2023 (29 million acres), and average application fell from more than 2 acre-feet per acre in 1979 to just over 1.5 acre-feet per acre by 2022. Soybean growers who have not moved on scheduling are being outrun by their neighbours on the same aquifer.

For teams running many fields, Farmonaut's satellite and weather feeds are available programmatically via the Farmonaut API with developer documentation, so pivot controllers and farm-management systems can consume field-level indices directly. Cooperatives and agribusinesses managing large soybean portfolios use Farmonaut's large-scale farm management platform; irrigation and harvest logistics run through fleet management tools.

Buyers in the crush and renewable-fuel channels increasingly ask for field-level provenance and water-use evidence. Blockchain-based product traceability and satellite carbon footprinting attach that record to the load rather than to a spreadsheet, and satellite verification is also used to speed crop loan and insurance assessment.

How to Verify Every Figure on This Page

• National and state yield, acreage and production: USDA NASS Quick Stats (quickstats.nass.usda.gov) holds series from 1870 to the present and is the authoritative source behind the January annual summary. The Crop Production 2025 Summary cited above was released 12 January 2026.
• Irrigated acres and water applied by crop: the Irrigation and Water Management Survey follows the Census of Agriculture every five years. The 2023 survey results were published in November 2024; the next survey falls in 2028.
• Crop water use for your county: most land-grant universities publish daily reference ET. Nebraska, Kansas, Arkansas and Mississippi all run public networks. Multiply reference ET by the soybean crop coefficient for the stage.
• Soil available water capacity: USDA-NRCS Web Soil Survey, by map unit, for your exact field boundary.

FAQ: Soybean Irrigation

How much water does a soybean crop need per day?

Peak use is 0.32 inches per day at late flowering and early pod development (R2–R3) per UNL Extension G1367, with 0.20–0.30 in/day across the flowering-to-pod-fill window in NC State's Table 10-1, and single-day extremes near 0.5 inches on hot, windy days.

What are total soybean irrigation requirements for a season?

20 to 26 inches of total crop water use (UNL G1367); NC State reports it can exceed 25 inches. Irrigation supplies only the shortfall after rainfall. UNL's reproductive-stage schedule totals about 10.5 inches of effective irrigation: 3 inches at R1–R2, 3 inches at R3–R4 and 4.5 inches at R5–R6.

How does irrigation increase crop yield?

By removing water deficit during the stages that set pod and seed number — the stages that consume 60–65% of seasonal water. Nationally, farmdoc daily found irrigated soybean yields at about 1.21 times non-irrigated after 2000; Mississippi State's Delta trials measured gains of 20–79% over three years.

Is drip irrigation worth it for soybeans?

Kansas State reports subsurface drip cutting net irrigation about 25%, a 35–55% saving versus sprinkler and furrow, but the system must last 10–15 years to compete economically with a full-size centre pivot. It fits irregular, small or hilly fields where a pivot cannot cover the ground; on a square quarter-section a pivot covering 130 of 160 acres is usually the cheaper path.

How much of US soybean production is irrigated?

USDA ERS records about 9 million irrigated soybean acres in the 2022 Census of Agriculture, against 80.4 million harvested acres nationally in 2025 — roughly one acre in nine, concentrated in Nebraska, Arkansas and the Mississippi Delta.

The Short Version

Soybeans need 20–26 inches of water, take 60–65% of it after flowering starts, and peak at 0.32 inches a day. Manage the top three feet from R3, refill at 50% depletion or earlier, divide net inches by application efficiency to set run time, and stop at R6.5. Do that and you are chasing the 1.21× irrigated-to-dryland yield ratio that USDA-derived data has shown since 2000 — with numbers you can re-check in NASS Quick Stats and your own soil survey whenever they move.