Types Of Irrigation Suitable For South Dakota Farms

The decision to irrigate, and the choice of system, depends on climate, soils, water availability, crop type, and farm economics. South Dakota spans a range of climatic and soil conditions: eastern counties generally receive more precipitation and have deeper loess and glacial soils, while western counties are drier with sandy or shallow soils. This article reviews irrigation systems that work well in South Dakota, compares strengths and limitations, and offers practical guidance on selection, sizing, management, and maintenance.

Climate, Soils, and Water Sources: What Drives System Choice

South Dakota’s irrigation needs are driven by three basic factors: precipitation pattern and evapotranspiration (ET), soil texture and infiltration, and available water supply.

Precipitation and ET

Annual precipitation varies widely across the state, roughly 14 to 28 inches per year. The growing season is short to moderate, but hot summer weather can produce high daily ET rates during peak corn and soybean growth. Irrigation is most valuable in western and central South Dakota, and in drier years in the east.

Soils and Infiltration

Soils range from loamy, water-holding types in the east to sandy, fast-draining soils in the west. Infiltration rates drive whether you can apply large volumes quickly (as with sprinklers) or must apply slowly to avoid runoff (as with drip or reduced-rate sprinkler applications).

Water sources and legal considerations

Water sources include alluvial wells, deeper bedrock wells, and surface water from reservoirs and irrigation districts. Well depth, static water level, sustainable yield, and water permitting are crucial. South Dakota requires water use registration and varying rules by county for high-capacity wells; check local state and county requirements before planning.

Overview of Irrigation Systems Suitable for South Dakota

Several irrigation systems are commonly used in South Dakota. Each system has specific operational needs and economic profiles.

Center Pivot Irrigation

Center pivot is the dominant irrigated acreage in many parts of South Dakota.

• How it works: A rotating pipeline on wheeled towers distributes water with sprinklers along its length.
• Advantages: High field efficiency (60-85 percent effective application depending on management), mechanized operation, good uniformity with correct nozzle selection and maintenance, and adaptability to large, circular fields.
• Variants: Conventional sprinklers, Low Energy Precision Application (LEPA) and low-pressure sprinklers. LEPA places water at or near the canopy to reduce evaporation losses.
• Design parameters: Typical pivots are 400 to 1,400 feet in radius (1/4 to 1/2 mile diameters). Flow rates vary from 400 to 1,200 gallons per minute (gpm) depending on span, nozzle sizes, and application depth. Pump horsepower commonly ranges from 30 to 400 HP depending on flow and lift.
• Practical points: Ensure uniformity by managing pressure (typically 20-50 psi at sprinklers depending on nozzle type), maintaining towers, and calibrating application depths (0.1 to 0.5 inches per pass depending on crop need). Consider LEPA for sandy soils or areas with limited water to increase efficiency.

Lateral Move / Linear Move Systems

• How it works: A linear pipeline moves across rectangular fields delivering uniform irrigation.
• Advantages: Better for rectangular fields where pivot circles waste ground. Comparable efficiencies to pivots.
• Considerations: Requires straight runs and typically more labor or automation for turning around and repositioning.

Drip and Subsurface Drip Irrigation (SDI)

• How it works: Water is delivered slowly at the root zone through drip tapes or subsurface buried lines.
• Advantages: Highest application efficiency (up to 90 percent), low evaporation and runoff, precise management of root-zone moisture and fertigation.
• Best uses: High-value crops (vegetables, small fruits, specialty forage), replanting tree or vine orchards, and saline conditions where leaching can be controlled more precisely.
• Constraints in South Dakota: Risk of freeze-thaw damage, emitter clogging by fine sediments or biological growth, need for filtration and chemical treatment, and upfront tubing costs. SDI is less common for broadacre corn and soybeans unless water is very limited or crop value justifies cost.
• Design tips: Use filters sized to 120 mesh or finer for drip systems; include pressure regulation and air/vacuum relief. Bury drip at 6-12 inches for SDI in annual crops to protect from UV and mechanical damage.

Surface Irrigation (Furrow and Flood)

• How it works: Gravity distributes water across level or graded fields using furrows, borders, or corrugations.
• Advantages: Low capital cost for small setups, simple equipment, and effective on flat fields with fine-textured soils.
• Limitations: Lower efficiency (30-60 percent), high labor requirements, and need for precise land leveling. Tailwater recovery and reuse systems can improve efficiency.
• Where practical: Sandwiched by irrigation districts or where cheap surface water is available and topography is flat.

Solid-Set Sprinkler and Traveling Gun

• Solid-set: Fixed sprinklers with pipes placed permanently or seasonally. Good for small fields, greenhouses, or orchards.
• Traveling gun: High-output portable gun systems that move across a field. Useful for temporary irrigation or irregular fields, but less efficient and high-wind sensitive.

Choosing a System: Criteria and Sizing

System selection must match water availability, soil infiltration, crop, and budget.

Assess water availability first

• Determine sustainable supply: well yield (gpm), permit limits, and surface water hours.
• Calculate crop water need: peak daily ET for corn in mid-summer can exceed 0.25 to 0.30 inch/day. Multiply by crop coefficients and area to get daily volume.
• Example: A 160-acre pivot irrigating corn needing 1.0 inch/week requires about 435,600 gallons/week, roughly 4,000 gpm-hours per week. Match pump capacity and reservoir storage accordingly.

Soil infiltration and application rate

• Match application rate to infiltration rate to avoid runoff. Sandy soils may accept high rates but need frequent smaller applications because of high percolation. Clay soils require reduced rates to avoid ponding.

Field shape and farm scale

• Large circular or near-circular fields favor center pivots.
• Rectangular fields may favor lateral systems, solid-set, or multiple pivots.
• Small or fragmented acreage may favor solid-set sprinklers, drip, or furrow depending on crop.

Economic analysis

• Compare capital cost, operating cost (fuel/electricity for pumps, maintenance), and yield benefit.
• Rule of thumb: pivots often pay back through yield increases for row crops in areas with reliable water; drip and SDI require higher crop value to justify cost.

Management and Scheduling Practices

Optimal outcomes require good scheduling and maintenance.

Irrigation scheduling

• Use soil moisture probes (TDR or capacitance probes) and reference ET data with crop coefficients (Kc) to compute net irrigation need.
• Aim to refill the root zone before crop stress but avoid over-irrigation that reduces oxygen and increases disease risk.
• Common scheduling frequency: every 5-10 days depending on soil texture and crop stage; more frequent for sandy soils and young plants.

Fertigation and salinity control

• Fertigation can improve nutrient use efficiency, especially with drip systems. Monitor EC (electrical conductivity) and leach salts if necessary, particularly where groundwater quality is marginal.

Maintenance essentials

• Pivots: gearboxes, check bracing, swath control, nozzle wear, and pressure regulators.
• Pumps: regular seals, motor bearings, and electrical inspections.
• Drip systems: filters, regular flushing, and chemical treatments to control biological fouling.
• Winterization: drain lines and protect pumps and valves from freeze damage.

Practical Recommendations by Region and Crop

• Eastern South Dakota (higher rainfall, deeper soils): Consider limited irrigation with pivots or reduced-rate sprinklers to complement rainfall. Pivots with precision control (variable-rate irrigation) can target drier zones.
• Central and Western South Dakota (drier): Full irrigation with center pivots or lateral systems is common for corn and hay. LEPA can conserve water and improve efficiency.
• Specialty crops and high-value vegetables: Drip or SDI is preferable for precise moisture control and fertigation despite higher initial cost.
• For small-acreage livestock hay producers: traveling guns or hand-move systems may be cost-effective if only occasional irrigation is needed.

Key Takeaways and Practical Steps

• Assess water supply and soil infiltration first; these two factors will often rule out or favor particular systems.
• For broadacre row crops, center pivots (including LEPA) are the most practical and widely used option in South Dakota.
• Drip and SDI offer the highest efficiency but require strong filtration, regular maintenance, and are best for high-value crops or water-limited situations.
• Surface irrigation can be economical where topography and soils permit, but expect lower efficiency and higher water demand.
• Use soil moisture monitoring and ET-based scheduling to avoid under- or over-irrigation and to protect water quality.
• Budget for pump capacity, energy costs, and maintenance when sizing a system; a system that cannot deliver the needed gpm reliably will underperform.
• Investigate available cost-share programs, irrigation districts, and local extension guidance to optimize system choice and access technical assistance.

Selecting the right irrigation system for a South Dakota farm requires balancing agronomic needs, hydrology, and economics. With careful planning, proper design, and disciplined management, irrigation can reliably boost yields, stabilize production risk, and increase farm profitability across the diverse landscapes of South Dakota.