Best Soil Moisture Sensors for Row Crops in 2026

If you're scheduling irrigation based on calendar days or gut feel, you're almost certainly over-watering some fields and under-watering others. University of Nebraska research found that calendar-based irrigation scheduling over-applies water by an average of 30% compared to sensor-guided scheduling — and on a 500-acre irrigated corn operation, that translates to $8,000-15,000 in unnecessary pumping costs every season, before you factor in the environmental cost of leaching nutrients below the root zone.

Soil moisture sensors are the foundation of data-driven irrigation management, and as we detail in our comprehensive guide to precision agriculture, they're one of the highest-ROI precision ag investments available to row crop farmers. The technology has matured significantly — sensors are more accurate, more durable, and more affordable than they were five years ago, and wireless connectivity has eliminated the data retrieval problem that made early systems impractical. Here's how the leading systems compare and which makes sense for your operation.

How Soil Moisture Sensors Work: The Technology Behind the Reading

Understanding the measurement technology helps you evaluate sensor accuracy and choose the right system for your soil type.

Capacitance sensors (also called FDR — Frequency Domain Reflectometry) measure the dielectric constant of the soil, which changes with water content. They're the most common technology in modern agricultural sensors because they're accurate across a wide range of soil types, respond quickly to moisture changes, and are relatively inexpensive to manufacture. The Sentek Drill & Drop, CropX, and AquaSpy systems all use capacitance technology. Accuracy is typically ±2-3% volumetric water content (VWC) in calibrated conditions.

Tensiometers measure soil water tension (how hard the plant has to work to extract water) rather than volumetric water content. The Irrometer Watermark is the most widely used tensiometer in agriculture. Tension-based readings are often more directly relevant to plant stress than VWC readings, but tensiometers require more maintenance (periodic refilling) and can lose accuracy in very dry or very wet conditions.

TDR sensors (Time Domain Reflectometry) are the most accurate technology but also the most expensive. They're primarily used in research applications and high-value specialty crop operations. For most row crop operations, the accuracy premium doesn't justify the cost.

For corn and soybeans, capacitance sensors offer the best combination of accuracy, durability, and cost. The key calibration consideration is that capacitance sensors need to be calibrated for your specific soil texture — a sensor calibrated for sandy loam will read incorrectly in heavy clay. Most commercial systems offer soil-type calibration in their software, but it's worth verifying with a gravimetric sample when you first install.

Top Soil Moisture Sensor Systems for Row Crops

CropX: Best for Integrated AI Recommendations

CropX combines soil moisture sensing with an AI-driven irrigation recommendation engine that accounts for weather forecasts, crop growth stage, and historical field data. The system uses a proprietary sensor design that installs with a simple push-in installation (no digging required) and communicates via cellular to the CropX cloud platform.

Specs: Multi-depth sensing at 4, 8, 16, and 24 inches. Cellular connectivity with no gateway required. Battery life of 3-5 years. Compatible with major pivot controllers.

Cost: Approximately $400-600 per sensor node. For a 500-acre operation, 4-6 nodes is typical, putting system cost at $1,600-3,600 before installation.

Performance: A 2024 Kansas State University trial found CropX-guided irrigation reduced water applications by 24% on corn with no yield difference compared to calendar-based scheduling. The AI recommendation engine is the differentiator — instead of just showing you a moisture reading, it tells you when to irrigate and how much to apply.

Best for: Operations of 300+ acres that want a complete decision-support system rather than raw data. The AI layer is most valuable when you're managing multiple fields with different soil types.

Sentek Drill & Drop: Best for Accuracy and Flexibility

Sentek's Drill & Drop is the workhorse of commercial soil moisture monitoring — widely used in research, specialty crops, and row crops globally. The system uses a drill-installed tube that houses multiple capacitance sensors at user-defined depths, giving you a continuous profile of soil moisture from surface to deep root zone.

Specs: Configurable sensor depths at 10cm intervals. Available in 30cm, 60cm, 90cm, and 120cm lengths. Connects to Sentek's EnviroSCAN data logger or third-party loggers via SDI-12 protocol.

Cost: $600-1,200 per installation depending on depth and data logger. Higher upfront cost than CropX but longer service life (10+ years with proper maintenance).

Performance: Sentek sensors are consistently rated among the most accurate in independent comparisons. The SDI-12 output makes them compatible with virtually any data platform, giving you flexibility to integrate with your existing farm management software.

Best for: Operations that want maximum accuracy and data flexibility, or that are already using a farm data platform like Climate FieldView or Granular and want to feed sensor data into it.

Irrometer Watermark: Best Budget Option

The Irrometer Watermark is the most widely installed soil moisture sensor in American agriculture — simple, durable, and inexpensive. It measures soil water tension in centibars (cb), with readings from 0 (saturated) to 200 cb (very dry). For corn, irrigation is typically triggered at 50-75 cb in the primary root zone.

Cost: $15-30 per sensor. A complete monitoring station with 3 sensors at different depths and a wireless data logger runs $200-400.

Performance: Watermark sensors are less accurate than capacitance sensors in very dry or very wet conditions, but they're accurate enough for practical irrigation scheduling in the 30-100 cb range where most irrigation decisions are made. University of Missouri extension research found Watermark-guided irrigation performed comparably to more expensive capacitance systems for corn irrigation scheduling.

Best for: Smaller operations (under 300 acres) or farmers new to soil moisture monitoring who want to learn the technology before investing in a more expensive system. Also excellent as supplemental sensors to fill coverage gaps in a larger system.

AquaSpy: Best for Large-Scale Operations

AquaSpy uses a unique 47-inch probe that provides continuous moisture readings every 4 inches from surface to 47 inches deep — the most complete soil profile picture available in a single installation. The system is designed for large irrigated operations and integrates directly with pivot automation systems.

Cost: $800-1,200 per probe installed. Higher per-unit cost but fewer probes needed per field due to the deep profile coverage.

Best for: Large irrigated operations (1,000+ acres) with deep-rooted crops where deep water use and drainage monitoring are important management decisions.

Installation Strategy: Where and How Deep to Place Sensors

Sensor placement is as important as sensor selection. A well-placed inexpensive sensor will outperform a poorly placed expensive one.

Field selection: Instrument your most representative fields first — the fields that are closest to your average soil type and topography. Avoid placing sensors in field corners, near waterways, or in areas with known soil variability. Once you've calibrated your irrigation decisions against sensor data in representative fields, you can extrapolate to similar fields with fewer sensors.

Within-field placement: Place sensors in the middle of the field, away from edges. In fields with significant soil variability (visible from yield maps or soil EC surveys), place sensors in both the high-productivity and low-productivity zones to understand how they respond differently to rainfall and irrigation.

Depth strategy: For corn and soybeans, the standard three-depth installation covers the critical zones:

6 inches: Surface zone. Critical for monitoring germination conditions and tracking how quickly rainfall infiltrates.
12-18 inches: Primary root zone. This is your irrigation trigger depth — when this zone drops below your threshold, it's time to irrigate.
24-36 inches: Deep zone. Monitors drainage (if this zone is consistently wet, you may have drainage issues) and tracks deep water use in drought conditions.

Replication: One sensor node per field is the minimum. For fields over 160 acres or fields with significant soil variability, two nodes in contrasting soil zones gives you much better decision-making data.

Setting Irrigation Thresholds: Translating Readings to Decisions

The most common mistake with soil moisture sensors is installing them without establishing clear decision thresholds. Raw data without decision rules is just noise.

For corn using capacitance sensors (VWC readings):

Field capacity (no irrigation needed): 30-35% VWC in silt loam, 20-25% in sandy loam
Irrigation trigger (time to irrigate): 50% depletion of plant-available water — approximately 22-26% VWC in silt loam, 14-18% in sandy loam
Stress threshold (irrigate immediately): 60-70% depletion — below 20% VWC in silt loam

For tensiometer-based systems (Watermark):

Irrigation trigger for corn: 50-75 cb in the primary root zone (12-18 inches)
Irrigation trigger for soybeans: 40-60 cb during pod fill (R3-R6 growth stages)
Post-rain reset: Wait for readings to drop below 20 cb before considering the next irrigation

Your local university extension service will have soil-type-specific thresholds for your region. Iowa State, University of Nebraska, and Kansas State all publish free irrigation scheduling guides with sensor-based thresholds for corn and soybeans.

Key Takeaways

Capacitance sensors (CropX, Sentek) offer the best accuracy for row crops; tensiometers (Watermark) are a cost-effective entry point.
Install sensors at three depths: 6 inches (surface), 12-18 inches (irrigation trigger zone), and 24-36 inches (deep monitoring).
CropX is the best choice for operations wanting AI-driven irrigation recommendations; Sentek Drill & Drop for maximum accuracy and data flexibility; Irrometer Watermark for budget-conscious entry.
A 500-acre irrigated corn operation can expect $8,000-15,000 in annual water and energy savings from sensor-guided irrigation — typically recovering system costs in the first season.
Sensor placement and decision thresholds matter as much as sensor selection. Instrument representative fields first and establish clear irrigation trigger values before the season starts.

Frequently Asked Questions

What is the best soil moisture sensor for corn and soybeans?

For most row crop operations, capacitance-based sensors like the Sentek Drill & Drop or CropX offer the best balance of accuracy, durability, and cost. CropX adds an AI recommendation layer that tells you when and how much to irrigate rather than just showing raw data. For budget-conscious operations, the Irrometer Watermark at $15-30 per sensor performs comparably for practical irrigation scheduling decisions.

How deep should soil moisture sensors be installed in row crops?

Install sensors at three depths: 6 inches (surface zone, critical for germination monitoring), 12-18 inches (primary root zone, your main irrigation trigger depth), and 24-36 inches (deep zone, monitors drainage and deep water use). The 12-18 inch reading is the most actionable for day-to-day irrigation decisions.

How much do soil moisture sensors cost?

Entry-level single-depth sensors start around $50-150 per unit. Multi-depth wireless systems with cloud connectivity range from $300-800 per node. For a 500-acre operation, a complete system with 4-6 monitoring nodes typically costs $2,000-5,000 installed. Most operations recover this cost in the first season through reduced water and energy costs.

Can soil moisture sensors work with my existing irrigation system?

Most modern soil moisture sensor systems integrate with existing center pivot and drip irrigation controllers. CropX and Sentek offer direct integrations with Valley, Lindsay, and Reinke pivot controllers. Older systems may require a simple relay interface costing $100-300. The SDI-12 output standard supported by Sentek and most research-grade sensors is compatible with virtually any modern data logger or farm management platform.

What is the ROI on soil moisture sensors for row crops?

University of Nebraska extension research found that soil moisture-guided irrigation reduced water applications by an average of 22% on corn without yield penalty. On a 500-acre irrigated corn operation at $40 per acre-inch of water, a 22% reduction saves approximately $8,800-12,000 per season — well above the $2,000-5,000 system cost. The ROI is highest on sandy soils with high irrigation frequency and lowest on heavy clay soils with infrequent irrigation needs.