Tips For Adjusting Nebraska Irrigation During Dry Springs

Nebraska growers regularly face variable spring moisture. Dry springs present a particular challenge because they shape planting decisions, early crop development, and the timing and intensity of irrigation demand later in the season. This article provides practical, field-tested guidance for adjusting irrigation strategy during dry springs in Nebraska. It focuses on soil monitoring, scheduling, system adjustments, crop-stage priorities, and long-term adaptations that conserve water while protecting yield and profitability.

Read the Field First: Soil and Root Zone Assessment

Before changing irrigation strategy, take an accurate inventory of soil moisture and root development in each field. Decisions based on visual cues alone are risky; use objective measurements whenever possible.

• Walk representative areas of each field and use a soil probe or shovel to inspect moisture in the top 12, 24, and 36 inches.
• Use simple tools: a hand auger or probe, tensiometers in the root zone, or portable capacitance (TDR) sensors. If available, install a soil moisture sensor at 6″, 12″, 24″, and 36″ depths.
• Estimate effective root depth by digging and examining root distribution. Many Nebraska-grown corn roots reach 3 feet under good conditions; soybeans commonly explore 2-3 feet. Root depth matters because it defines the available water reservoir you can draw on before irrigation becomes critical.

Know Your Soil Water Holding Capacity and Depletion Thresholds

Adjusting irrigation depends on how much plant-available water the soil holds and how much can be depleted before yield loss.

• Typical plant-available water (PAW) ranges by texture (inches of available water per foot of soil):
• Sandy soils: 0.5 to 1.2 inches per foot.
• Loamy soils: 1.5 to 2.5 inches per foot.
• Clayey soils: 2.0 to 3.0 inches per foot.
• Choose an allowable depletion fraction based on crop and growth stage. Common guidance:
• Vegetative stages: 40 to 60 percent of PAW can be safely depleted.
• Pre- and post-flowering (reproductive stages): reduce allowable depletion to 30 to 40 percent for crops like corn and soybean.
• Example calculation: corn with a 3-ft effective root zone on a loam at 1.8 in/ft equals 5.4 inches of PAW. If you use a 50% depletion rule, allowable depletion is 2.7 inches. If daily crop evapotranspiration (ETc) is 0.3 in/day, irrigation interval = 2.7 / 0.3 9 days.

Use Evapotranspiration and Weather Data for Scheduling

ET-based scheduling is the most defensible approach in a dry spring.

• Track reference evapotranspiration (ETo) from the nearest reliable station or on-farm weather sensors. Multiply ETo by crop coefficient (Kc) to estimate crop ET (ETc).
• Typical crop coefficients (Kc) change over the season. For example, corn Kc values might be roughly 0.3 early vegetative, 1.05 at peak, then decline during grain fill. Use local extension or published tables for accurate Kc values.
• Schedule irrigation to refill the root zone before the crop reaches the chosen depletion fraction. In dry springs, prioritize fields and retain flexibility to irrigate high-value or stress-sensitive acres first.

Prioritize Crops and Fields During Shortages

When water is limited, not every field can be irrigated to full evapotranspiration. Make data-driven triage decisions.

• Prioritize high-value crops (corn at reproductive stage), irrigated fields with high yield potential, and fields with high water holding capacity.
• Delay or reduce irrigation on fields with shallow soils, lower fertility, or late-planted fields with lower yield potential.
• Use partial-season irrigation or deficit irrigation strategies on more tolerant crops (sorghum, sunflower) or fields planned for lower inputs.

Adjust Applications and System Operation

Changing how and when water is applied can stretch supplies and improve uniformity.

• Application depth per irrigation: aim to replace the depleted portion of the root zone. For many pivots and soils, applying 0.5 to 1.25 inches per event is practical. Avoid very large single applications that cause runoff or deep percolation losses.
• Increase application frequency on coarse-textured soils. Sands have low PAW, so smaller, more frequent irrigations maintain moisture without exceeding field capacity.
• Check and maintain uniformity. Low coefficient of uniformity (CU) wastes water and exacerbates stress in parts of the field. Calibrate nozzles, replace worn parts, and correct uneven pressure along center pivots.
• Consider variable-rate irrigation (VRI) if available. VRI allows targeting wetter parts of the field or conserving water on marginal zones.
• Manage pumping to save energy and water. Avoid excessive pressure drops, check pump efficiency, and fix leaks. Monitor application rate and runtime to match measured needs.

Deficit and Strategic Irrigation: Where You Can Save Water with Little Yield Loss

Deficit irrigation deliberately applies less water than full crop ET during non-critical stages to conserve water for critical periods.

• Corn: protect the reproductive period. Water stress during silking and early grain fill (around pollination to early R3) causes the largest yield loss. You can accept moderate deficits during early vegetative stages if root development is adequate.
• Soybean: flowering and pod fill stages are most critical. Moderate water stress during vegetative stages is tolerable but avoid stress at R1-R5.
• Alfalfa: maintain moisture to support regrowth between cuttings; avoid severe deficits before harvest.
• Use a calendar or soil-based strategy to conserve water early, then shift water to maintain soil moisture at or just above the critical depletion fraction during flowering and grain fill.

Short-Term Management Actions to Take Early in a Dry Spring

Take these steps now to improve water-use efficiency and reduce stress risk as the season progresses.

• Calibrate your irrigation system, check uniformity, and replace damaged nozzles or sprinklers.
• Install or verify soil moisture sensors or tensiometers and use them for real-time decisions.
• Review crop varieties and hybrids: if early-season moisture is poor, switching to shorter-season or drought-tolerant hybrids can reduce peak water demand later.
• Delay or minimize spring tillage. Conservation tillage and residue reduce soil evaporation and preserve moisture.
• Manage fertility carefully. Avoid over-application of nitrogen that promotes excessive vegetative growth and water demand under limited water.

Long-Term Adjustments to Increase Resilience

Dry springs will continue to occur. Investments and changes that reduce vulnerability pay dividends over multiple seasons.

• Increase soil organic matter through cover crops, reduced tillage, and crop rotations. Higher soil organic matter increases PAW and improves infiltration.
• Implement variable-rate irrigation and precision agriculture tools to match water to plant needs spatially.
• Consider cropping shifts on marginal irrigated acres to lower-water crops or partial-season dairying/hay systems that tolerate less water.
• Improve irrigation infrastructure: convert from low-efficiency surface systems to center pivots with modern nozzles, or add subsurface drip irrigation for high-value vegetables or specialty crops.
• Evaluate pump and energy efficiency. Replacing old pumps and motors can reduce energy cost per acre-inch and enable more flexible water delivery.

Practical Checklist for the Next Dry Spring

• Measure soil moisture in multiple depths and fields now.
• Confirm effective root depths for each crop and use that to compute PAW.
• Set depletion thresholds by crop growth stage (more conservative near reproductive stages).
• Calibrate irrigation systems and check uniformity.
• Prioritize fields for irrigation based on crop, stage, and soil capacity.
• Use ET or sensor-based scheduling to time applications and avoid over-watering.
• Apply smaller, more frequent irrigations on sandy soils; larger, less frequent applications on heavier soils.
• Maintain pumps and pipelines to avoid energy and water waste.
• Consider deficit irrigation strategies that protect reproductive stages.

Final Takeaways and Practical Recommendations

Dry springs require a combination of quick tactical moves and longer-term strategic changes. In the short term, monitor soil moisture, focus water where it will protect yield the most, and adjust application depth and frequency to soil texture. Use ET and root-zone science to schedule irrigations so you refill before critical depletion levels are reached, especially ahead of flowering and grain fill. Improve system uniformity and pump efficiency to avoid wasting water that could be used elsewhere.
Over the long run, build soil organic matter, adopt precision irrigation tools, and consider crop and hybrid choices that lower peak water demand. By combining sound measurements, conservative depletion thresholds during critical stages, and operational improvements, Nebraska growers can navigate dry springs with minimized yield loss and better stewardship of water resources.