Improving water and nitrogen use efficiency using soil moisture monitoring to improve irrigation management

Final Report for LNE12-314

Project Type: Research and Education
Funds awarded in 2012: $210,666.00
Projected End Date: 12/31/2015
Region: Northeast
State: Delaware
Project Leader:
James Adkins
University of Delaware
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Project Information

Summary:

Cropland irrigation has been gradually increasing in the Mid-Atlantic as a means to overcome the low moisture holding capacity of sandy soils and as a way to stabilize yields in better soils.  While cheap and affective tools to measure soil moisture levels have been commercially available since the early 1950’s, farmers still tend to rely on estimated crop water use curves, soil feel and past experience to schedule their irrigation applications.

Recent advances in soil moisture monitoring equipment have made it economically feasible for irrigated grain producers to utilize this technology to improve yields and utilize water more efficiently. This demonstration project quantifies the costs, both in equipment and labor, to implement soil moisture monitoring for scheduling irrigation in addition to accessing the usable value to farmers.  An infield network of 4 monitoring stations with three soil moisture probes (6”, 12” and 18” depths) were installed on 50 different irrigated fields.  The infield network was connected via cell modem to a commercial website where each producer could access their real-time soil moisture data via any web enabled device.   All of the equipment was provided, installed, maintained and removed free of charge to the farmer in exchange for feedback on the value of the information to their operation.

Overall the farmers liked having access to the soil moisture data but the cost of equipment coupled with the unavoidable time investment required for installation, maintenance and data interpretation outweighed the benefits.  Soil moisture monitoring systems still have significant potential for high value specialty crop producers and in areas with very little rainfall.  For agronomic crop production in the Mid-Atlantic there is an opportunity for independent crop consultants to provide moisture monitoring as a service however the time investment is simply too high for a vast majority of farmers to undertake on their own.

Introduction:

According to the 2007 USDA census of agriculture, Delaware had approximately 105,000 acres of irrigated farm land. A 2010 University of Delaware project to identify the scope of irrigation in the state generated a graphic information system (GIS) layer that located each center pivot in the state. The GIS layer noted 2026 center pivots covering 113,000 acres in the state.  The relatively flat topography and sandy soils tend to be ideal candidates for the center pivot type irrigation that is employed on over 85% of the irrigated acreage. Despite the higher level of management required when irrigation is used, many growers still rely on some vague assumptions and instinct to schedule irrigations.  While irrigation improves yields and reduces the risk of crop failure, the environmental cost of mismanagement can be sizable.  Over-irrigation reduces yields, leaches fertilizer, and wastes water and energy. Under-irrigation reduces nitrogen and water use efficiency, and depresses yields.

Currently, the most widespread method to schedule irrigation is based on evapotranspiration (ET). In Delaware, producers determine the daily reference ET provided by the Delaware Environmental Observing System’s network of 32 weather stations (www.deos.udel.edu).  The next step is to determine a crop coefficient. Crop coefficients correct reference ET for the plant growth and rooting stage and is different for each crop. Reference ET is then multiplied by the crop coefficient resulting in an estimate of how much water was used each day. The daily water use is recorded manually or by using a spreadsheet and combined with a record of rainfall and applied irrigation to provide “checkbook” type water balance (Cal-Poly 2004).

Evapotranspiration is not a perfect science.  Many assumptions are required to reach the daily water use figure, any one of which could cause an under or over estimation of crop water use.  Crop coefficients do not account for changes in population, variety, compaction or prior stresses. The root zone ranges that determine how much rain can be stored are often significantly biased causing poor estimates of the current soil moisture levels.  Further complicating ET scheduling is the requirement of irrigation system calibration. Through an ongoing cooperative agreement between the Natural Resource Conservation Service and UD, more than 400 center pivot irrigation systems covering approximately 25,000 acres have been evaluated for uniformity, efficiency and application rate. Over 50% of the systems tested in this program applied less than 80% of the water estimated by the system manufacturer’s calibration chart.  Despite these shortcomings, no other irrigation scheduling method has exceeded the ET based checkbook method in adoption.

Despite limited adoption of evapotranspiration (ET) rates to schedule irrigations, many irrigators still rely on solely on instinct.  In many cases, irrigators use the qualitative and unreliable hand-feel method to estimate soil moisture.  Many producers have purchased tensiometers to measure soil tension with the intention of using them to supplement the checkbook method of scheduling.  Unfortunately, due to the high maintenance requirements and the grower’s tendency to only read the instrument once a week, most tensiometers are sitting in a box unused.

In a winter of 2010 survey, Delaware growers indicated that they would like to know the moisture content of their soil for making irrigation decisions, but the equipment has to be maintenance free and require very little time to determine whether to irrigate or not.

There are four major hurdles to improving irrigation management in Delaware:

  • Awareness by the growers of the current mismanagement.
  • Adoption of sensor based quantitative soil moisture measurement.
  • Timely recording and analysis of the soil moisture data.
  • Utilization of the soil moisture status to make adjustments to the irrigation schedule.

A project was conducted in Sussex County, Delaware in 2009-2011 to gather information on local corn water needs, evaluate the efficacy of local grower irrigation strategies, and to educate growers on irrigation management (Whaley et al. 2010).  In this project, Watermark soil moisture sensors were installed in center pivot irrigated corn fields of 3 growers.  UD personnel periodically visited each site to download data (approximately twice per week) and the historical soil moisture levels were emailed to the participant. Approximately half way through the growing season each grower was asked if they used the data to adjust their irrigation schedule; all responded “no”.  However, the technician that normally downloaded the data was on vacation the following week and no data was downloaded.  By day 3 of his vacation each participant had called, requesting a soil moisture update. In follow-up interviews post season, each grower indicated that initially they did not trust the equipment as they felt they were excellent irrigators, however, the soil moisture data showed otherwise. Once comfortable that the data was accurate and reliable, they began adjust their irrigation schedule and looked forward to confirming that their decision to irrigate was correct, their timing was accurate and the application rate was appropriate.  By the end of the season they had become very reliant on the periodic updates and felt that crop yields were improved as a result of using the equipment.

Based on the data collected throughout the growing season, all of the participating growers realized that inadequacies existed in their current strategy.  As a result of this project, 2 of the participating growers adopted moisture sensing technologies into their irrigation scheduling program for the 2011 season. The results of the 2009 & 2010 project were presented to a group of 175 irrigated farmers at the 2011 Delaware Ag Week educational sessions.  Despite widespread interest generated at the meeting, and multiple follow up phone calls from growers wanting more information, only 1 new producer adopted the technology for the 2011 season.

For the 2010 and 2011 growing seasons, the 3 soil moisture systems initially purchased in 2009, were used at 6 new cooperating farms.  At the conclusion, each responded similarly to the earlier cooperators and 2 indicated that they would be purchasing similar equipment to use for the 2012 season. Over the 3 year project duration, each of the 9 participants felt that the monitoring soil moisture levels enabled them to better manage their irrigation enabling more efficient water use and improving yields. Of the 5 producers that have either purchased soil moisture equipment or indicated that they plan to for 2012 season, all but 1 indicated that they would not have made the investment without the equipment demonstration on their farm that quantified the deficiencies in traditional irrigation management techniques.

The 2009-2011 pilot projects demonstrated that:

  • Growers liked the results of soil moisture monitoring but they required considerable hand holding to be comfortable enough to trust data to manage their irrigation.
  • Despite multiple publications and extension presentations on the topic, growers do not recognize the inadequacies of the current irrigation management techniques.
  • Convincing irrigated farmers to invest in soil moisture monitoring equipment will require a one on one demonstration of how the technology fits into their operation.

The results and benefits of the 2009-2011 pilot projects were shared with the USDA Natural Resources Conservation Service, the Delaware Department of Agriculture and Delaware Department of Natural Resources in hopes of generating support for a cost share program to encourage the adoption of soil moisture equipment. Both state agencies declined, siting lack of funding and the fact that the new Environment Protection Agency (EPA) Watershed Implementation Plan (WIP) gives states nutrient load reduction credits only for acres irrigated regardless of the management.  NRCS currently requires participants in the Irrigation Management cost share program (449) to use a soil moisture monitoring device, but only a basic device designed to supplement an ET schedule.  Several efforts have been made to encourage the creation of a cost share program for soil moisture monitoring equipment through NRCS, however no progress has been made.

This project will expand upon earlier efforts to encourage the adoption of soil moisture monitoring equipment by adding 20 monitoring stations.  These will be demonstrated with a total of 60 producers over the course of the 3 year project.

Performance Target:
  1. Twenty irrigated corn and soybean producers will be selected by the project team for the demonstration of the field monitoring equipment. (May (2013)
  2. Four Hundred growers will receive invitations to attend irrigation workshops at Delaware Ag Week. (November 2013)
  3. Two hundred and fifty producers with center pivot irrigation will attend irrigation management workshops that discuss the findings of the 2012 field research/demonstration. (December 2013 – January 2014)
  4. Twenty new producers will be selected by the project team for the demonstration of the field monitoring equipment based on interest they expressed at the winter meetings. (May 2014 & 2015)
  5. Four Hundred growers will receive invitations to attend irrigation workshops at Delaware Ag Week. (November 2014 & 2015)
  6. Two hundred producers per year with center pivot irrigation will attend irrigation management workshops that discuss the findings of the 2014 & 2015 field research. (December 2014 – January 2015)
  7. Forty-five growers representing nine thousand acres will adopt soil moisture monitoring to manage irrigation. (2015 growing season)

 

Thirty-four irrigators representing sixty nine hundred acres will improve their irrigation scheduling on 6,900 acres of corn to improve yields by 15 bu/acre ($621,000/year) and increase nitrogen use efficiency from 1 lb applied per harvested bushel to 0.95 lbs/bu. An additional 14 irrigators will improve soybean irrigation on 2800 acres by 5 bu/acre ($182,000 per year)

Twelve irrigators will reduce their overall irrigation application by two inches per year over twenty-five hundred acres, resulting in a five percent increase in yield (approximately $110,000/year), $20 per acre reduction in pumping costs ($50,000/year) and 135 million gallons in conserved water.

Cooperators

Click linked name(s) to expand
  • Phillip Sylvester
  • Dr. Cory Whaley
  • Scott Wright

Research

Materials and methods:

This project will improve and expand the ongoing effort to educate farmers about the current mismanagement of irrigation, demonstrate technology to improve management deficiencies, and quantify the environmental and financial benefits of adopting soil moisture sensors.  The on-farm demonstration of soil moisture monitoring equipment to manage irrigation will be conducted on 20 farms per season. The monitoring systems will be installed and maintained by the project coordinators with no labor required by the cooperator other than to observe and react to the data provided.  Each system will consist of 4 soil moisture monitoring stations per field with one station located in both the lighest/highest soil type and the heaviest/lowest soil.  The other 2 stations will be placed in the most predominate soil.  A station consists of 3 soil moisture sensors placed at 6″, 12″ and 18″ below the surface and the data is wirelessly transmitted back to a central logger approximately 10-15 times per day.  The Irrometer Watermark 950R data logging system located at each farm will be upgraded to include a cell modem that will automatically post soil moisture reports online through the manufacturer’s online report system.  Soil moisture data will be available in real-time to each cooperator via a computer internet connection or smartphone. Immediate access to soil moisture levels will greatly improve the irrigation schedule as the participants will not have to drive to the field with a laptop and manually download data (a 20-30 min process). Online data access will also permit the project team to view the statistics of how often the grower checks the data, and fix problem sensors without long periods of data loss.

All participants will be verbally surveyed prior to the demonstration to quantify their typical fertilizer rates, planting populations, irrigation schedule and crop yield.  Furthermore, the project team will meet one on one a minimum of twice throughout the season to discuss problems and address any concerns. Finally, the participants will be verbally surveyed at the conclusion of the season to record any irrigation schedule changes made with the soil moisture data, crop yield and overall satisfaction with the equipment.

After year 1, a statewide irrigation meeting will be held to train growers on irrigation management and determine interested cooperators. Follow up sessions will be held in each county to describe the details of managing irrigation using soil moisture sensing, description of how the equipment is used and how to interpret the results. Additional guidance will be available to each cooperator via the participating county agents. Following each season, a group meeting for all cooperators will be held to discuss the problems encountered during implementation and lessons learned. Finally, all results will be presented in county, state, and regional meetings at the project conclusion in addition to publication in print and on the internet.

Research results and discussion:

This project began with identifying the 20 cooperators for year one of the demonstrations.  An overview of the project goals was presented at the January 2013 Delaware Ag Week in Harrington, DE and approximately 25 farmers approached the project leaders with a desire to participate.  20 cooperators, representing 11,340 irrigated acres were selected and the pre-project surveys of their irrigation methods were conducted.  In the later years of the project,  it was determined that these initial cooperators were the top notch irrigators that were already contemplating purchasing soil moisture monitoring equipment after the challenges they faced in the extremely dry 2012 growing season.

The initial grower meetings went smoothly and the growers were excited about the project.   As the equipment was installed the participating farmers, and the project coordinators became very frustrated with the failure rate of the equipment.   After time it was learned that the antenna seals were incorrectly installed and would allow water to enter the box and affect the circuitry.  Once this issue was rectified the failure rate was reduced, but the equipment was still too unreliable.  There were concerns that the cell modems providing communication to the web reporting service would not have adequate signal strength in remote areas to transmit the data.  Fortunately due to the low bandwidth required the modems were functional at all 54 sites tested over the 3 years. 

The 2013 growing season was very wet and required very little irrigation for corn (the primary crop tested).  This wet season gave the participants a false sense of security regarding their irrigation management skills as any failures tended to be masked by the regular rain events.  The data from the northern (Kent County DE) sites were erratic verses the southern sites.  Initially, this condition was blamed on the heavier soil containing more silt and clay than the sandy soils located in Sussex County.  In 2015 it was determined that while simply boring an undersized hole and press fitting the Watermark sensors was adequate in sands, in heavier soil types an oversized hole was required with the sensor being installed into a slurry of the spoils to ensure good soil-sensor contact.

The initial cooperators (2013) tended to be very tech savvy and had little problem accessing the data with only 3 of the 20 requiring one on one consultation.  This would not be the case in subsequent seasons.  Nearly all of the first year participants expressed disappointment in not being able to use the equipment another year as the wet growing season limited the value of their experience.

Due to a failed modem, 19 farmers representing 8,940 irrigated acres participated in year two. 2014 proved to be an ideal growing season in Delaware with timely and adequate rainfall and low heat stress levels.  In many cases dryland corn yields were on par with typical irrigated yields, thus minimizing the importance of irrigation for the 2014 season.

Unfortunately, during the driest and most critical crop stage for corn (July 4th weekend), the reporting website was down and no one was able to access the data for 4 days.  The website issues were easy to repair, but all of the employees at the hosting site were off for the holiday and unaware of the issue.

6 cooperators reported that they looked at the data every day and another 2 stated every other day.  5 growers looked at the data once per week and the remaining 6 either did not look at the data at all or had connection/equipment problems. 

As the field technicians became more familiar with the maintenance and operation of this equipment, the failure rate was greatly reduced.  The extra steps taken to minimize moisture in the boxes and new sensor installation techniques for fine textured soils significantly improved reliability.  Despite the expanded efforts 5 systems were unable to be fielded in the final year.

The remaining 15 systems were installed with growers representing only 3,680 irrigated acres in 2015.  This final season tended to include much smaller operations with considerable less comfort with technology.  It appeared as though many of the larger operations had already begun to discount the value of this technology by this point and declined to participate.

In 2015 many of the cooperators simply didn’t care enough to look at the soil moisture data on the web despite the sometimes excessive hand holding.  Additionally the relatively timely rainfall gave the growers a high sense of security that the crop would be fine without micromanaging irrigation.

Overall each of the three project years lacked the challenging weather conditions during the growing season that would benefit from the soil moisture data.  With regular rainfall, an irrigation schedule that applies too little water will not dry to the point that the sensors would display a problem.  Likewise, problems with irrigation system uniformity or calibration will not appear as the soil profile is continually refilled with rain.  These back to back to back easy years for irrigation managers coupled with the high failure rate of the equipment left most of the cooperators with the sense that the value to their operation wasn’t worth the time investment or the equipment cost.

Milestones

  1. Twenty irrigated corn and soybean producers will be selected by the project team for the demonstration of the field monitoring equipment. (May 2013)
    1. Milestone achieved April 2013, 2014, 2015. Only nineteen producers participated in 2014, and fifteen in 2015 due to equipment failures and the inability to repair an obsolete system.
  1. Each cooperator will be trained on a one on one basis to access their soil moisture status via the internet, analyze the data and modify their irrigation schedule to address crop needs. Growers will become proficient in interpreting soil moisture data into irrigation recommendations through frequent communication with the research team in the form of site visits, phone, and email contact.  (May – Aug 2013)
    1. Milestone achieved April – September 2013, 2014, 2015
  1. Four Hundred growers will receive invitations to attend irrigation workshops at Delaware Ag Week. (November 2013)
    1. Over five hundred invitations to attend the irrigation session at Delaware Ag Week 2014 were sent the week of December 1, 2013 in addition to print advertising in the Delmarva Farmer and multiple internet/social media links.
  1. Two hundred and fifty producers with center pivot irrigation will attend irrigation management workshops that discuss the findings of the 2013 field research/demonstration. (December 2013 – January 2014)
    1. While an irrigation management session will be held at Delaware Ag Week on January 14th, 2014, the result of the 2013 field research/demonstration will not be presented due to the extraordinarily wet growing season. The 2013 season was so extremely wet that very little irrigation was needed, in fact saturated soil severely limited corn yields by anywhere from ten to thirty five percent for many of the cooperators.  This was a very atypical year and the soil moisture equipment was of little to no use to the cooperators.
  1. Twenty new producers will be selected by the project team for the demonstration of the field monitoring equipment based on interest they expressed at the winter meetings. (May 2014 & 2015)
    1. 19 producers were selected in March of 2014 to participate in the monitoring project for the upcoming summer.
    2. 15 producers were selected in March of 2015 to participate in the monitoring project for the upcoming summer.
  1. Four Hundred growers will receive invitations to attend irrigation workshops at Delaware Ag Week. (November 2014 & 2015)
    1. Over six hundred invitations to the irrigation presentation at Delaware Ag Week 2015 were sent in addition to print and internet advertising.
    2. Over eight hundred invitations to the irrigation presentation at Delaware Ag Week 2016 were sent the week of December 8, 2014 in addition to print and internet advertising.
  1. Two hundred producers per year with center pivot irrigation will attend irrigation management workshops that discuss the findings of the 2013 & 2014 field research. (December 2014 – January 2015)
    1. The Irrigation Session at Delaware Ag Week was held January 15th, 2015 where the results from the 2013 and 2014 season were presented. Attendance for this session was two hundred and eight farmers.
    2. A presentation entitled “Practical Challenges with Soil Moisture Sensing: Results of Field Demonstration” was presented in the Agronomy Session of Delaware Ag Week on January 14, 2016. One hundred and fifty seven farmers were in attendance
  2. Forty-five growers representing nine thousand acres will adopt soil moisture monitoring to manage irrigation. (2015 growing season).
    1. None of the cooperators in this project adopted soil moisture monitoring due to cost, reliability and time. In fact one grower that was using this technology has since terminated his use of soil moisture in favor of Evapotranspiration models.

Thirty-four irrigators representing sixty nine hundred acres will improve their irrigation scheduling on 6,900 acres of corn to improve yields by 15 bu/acre ($621,000/year) and increase nitrogen use efficiency from 1 lb applied per harvested bushel to 0.95 lbs/bu. An additional 14 irrigators will improve soybean irrigation on 2800 acres by 5 bu/acre ($182,000 per year)

  1. In 2013, 20 irrigators representing 11,304 irrigated corn acres have participated in this project, with only 1 reporting an increase in yield as a result of participating. Most growers saw their irrigated yields drop due to an overly wet growing season.
  2. In 2014, 19 irrigators representing 8,940 irrigated corn acres have participated in this project, with only 2 reporting an increase in yield as a result of participating. Most growers indicated that the high dryland and irrigated yields for this season were primarily the result of mild temperatures and timely rainfall.
  3. In 2015, 15 irrigators representing 3,680 irrigated corn acres have participated in this project, with only 3 reporting an increase in yield as a result of participating. Most growers indicated that the relatively mild season minimized the need for irrigation.

Twelve of these thirty four irrigators will reduce their overall irrigation application by two inches per year over twenty-five hundred acres, resulting in a five percent increase in yield (approximately $110,000/year), $20 per acre reduction in pumping costs ($50,000/year) and 135 million gallons in conserved water.

  1. All twenty cooperators reported a reduction in applied irrigation of over ten inches this season as a result of repeated rainfall. The sensors had virtually no effect on the irrigation schedule in the 2013 season.
  2. Two of 2014 cooperators indicated that they applied less water using the sensor data. Five cooperators said they used more water and five more stated they used the same amount. The other seven participants didn’t look at the data, didn’t trust the data or couldn’t figure out how to access the website.
  3. In 2015, only two cooperators indicated that they used less water using the sensor data. Three cooperators said they used more water and three more stated they used the same amount. The other six participants didn’t look at the data, didn’t trust the data or couldn’t figure out how to access the website.

 

 

Participation Summary

Education

Educational approach:

The data gleaned from this project was presented to farmers at the following extension meetings:

  • Delaware Ag Week 2015 – January 15, 2015 – Harrington, DE
    • Irrigation Management Session
  • Basic Irrigation Management – February 20, 2015 – Hebron, MD
    • 30 minute segment on using soil moisture monitoring
  • Axis Seed Field Day – August 24, 2015 – Willin Farms, Seaford, DE
    • Soil Moisture Sensing for Irrigation Scheduling, James Adkins
  • VA Water Resources Conference – October 28th, 2015 – Richmond, VA
    • Irrigation in the Mid-Atlantic
  • Delaware Ag Week 2016 – January 14th, 2016 – Harrington, DE
    • Practical Challenges with Soil Moisture Sensing; Results of Field Demonstration
  • Virginia Grain and Soybean Conference – February 16th, 2016 – Williamsburg, VA
    • Irrigation Scheduling for Agronomic Crops; James Adkins
  • UD Wheat Field Day – May 26, 2016 – UD Warrington Irrigation Research Farm
    • Irrigation Management Techniques for Wheat; James Adkins
No milestones

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

In the 2013 post season survey, 6 of the 20 cooperators responded that they plan to purchase soil moisture equipment to help them manage their irrigation in the 2014 season.  Another 11 responded that they might purchase the equipment if it is affordable and reliable.  Only 3 farmers responded that they would not consider purchasing any soil moisture equipment. 

While 16 of the participating farmers saw similar or reduced yields from previous years, all of those attributed the yield reduction to excessive rainfall and nitrogen loss.  Despite the poor crop year, 8 farmers responded that they planned to make changes to their irrigation schedule as a result of this project.   Overall, when asked what could be done to improve this project 17 of the 20 participants responded with “nothing”, the other 3 answered “keep the equipment working”, “calibrate the irrigation system”, and “need more help setting up the web service” (it should be noted that this cooperator did not own a computer or smart phone and traveled to the local library to view his data online). 

The overall feeling of the 2013 cooperators was that they wished they could use the equipment again so they can experience firsthand how to implement soil moisture into their irrigation schedule in a more representative season

In the 2014 post season survey, 3 of the 19 cooperators responded that they plan to purchase soil moisture equipment to help them manage their irrigation in the 2015 season. Another 7 responded that they might purchase the equipment if it is affordable and reliable. 8 farmers answered that they would not consider purchasing any soil moisture equipment.

While all 19 of the participating farmers saw increased yields, 15 of those attributed the yield increase to weather. Only 4 responded that improved management and cooperation with UD played a role in the yield increases. 8 farmers responded that they plan to make changes to their irrigation schedule as a result of this project. Overall, when asked what could be done to improve this project 8 participants responded with “nothing”; 4 answered “keep the equipment working or find better equipment”, and 4 replied “setting up the web service/ assemble a quick start guide” (it should be noted that we gave each cooperator a guide but many never read it).

The overall feeling of the 2014 cooperators was that they felt that the soil moisture monitoring added value to their operation and made the irrigation decisions less guesswork and more science based. Everyone had major concerns about the reliability, longevity and cost of the equipment. Most felt that the biggest hurdle to using soil moisture equipment is the 8 – 12 man hours required to install and setup the network during an already high work load period. One farmer commented that he thought the soil moisture monitoring should be a service provided by the University.

In the 2015 post season survey, 2 of the 15 cooperators responded that they plan to purchase soil moisture equipment to help them manage their irrigation in the 2015 season. Another 3 responded that they might purchase the equipment if it is affordable and reliable. 8 farmers answered that they would not consider purchasing any soil moisture equipment.

While 3 of the 15 participants indicated that they saw increased yields, none attributed the yield increase to refined management with the sensors.  Most of the cooperators used the soil moisture system to test their own method of scheduling.  Unfortunately, the mild summer likely exaggerated the adequacy of their methods.  6 farmers responded that they plan to make changes to their irrigation schedule as a result of this project. Overall, when asked what could be done to improve this project 11 participants responded with “nothing” and 1 recommended that a better explanation of how to read the graphs was needed.

The 2015 cooperators felt that they already do a good job irrigating using personal experience and the time required to install and maintain the equipment plus the initial cost would not bring adequate value to their operation.  

Overall, a total of 11 cooperators stated that they intended to purchase soil moisture equipment after participating in the project.  In a follow-up phone interview in the spring of 2016, none of the 11 had purchased any soil moisture equipment.  When asked why nothing was purchased the cooperators almost unanimously stated that they didn’t have the time to manage and maintain the system and they would still consider purchasing if a cheaper, more reliable and easier to use option became available. 

Perhaps the only positive impact from conducting this project were the 12 cooperators that stated that they planned to change their irrigation management practices as a result of what they had learned from the monitoring system.  In most cases growers observed that they needed to irrigate more frequently in smaller amounts and gained some understanding of the relationship between application timing and soil moisture content. Unfortunately, the large investment in equipment and labor prevents this system from being a feasible educational tool.  Four farmers felt that saw yield increases resulting from their participation and acknowledged in the final 2016 interview that the increases were likely a result of the crop year rather than equipment.

The primary benefit to the farmer from this project is that despite the multitude of national efforts to push adoption, with the current equipment available, soil moisture monitoring is not a realistic tool for farmers in the Mid-Atlantic.  This is a marked difference from the experiences found in semi-arid regions of the country, however the basis for irrigation is slightly different than in the humid region.  Irrigation in the plains typically compensate for the limited and sporadic rainfall while the Mid Atlantic typically irrigates to address the low soil moisture holding capacity.  In the humid region regular rainfall during the growing season tends to “reset” the available water balance and often can compensate for deficits in irrigation scheduling.

Economic Analysis

Ongoing research projects on corn irrigation timing and amounts has shown that over irrigation has little if any negative affect on crop yield.  This information coupled with the fact that the application cost per acre averages from $3 – $6 per inch of irrigation applied means that it is cheaper for a farmer to apply an extra inch or two of water than invest in the equipment at an average of $13.50 per acre plus $9/acre of labor (calculated using a 5 year equipment life, 50 acre field and labor at $25/hr).

It is nearly impossible to quantify any economic benefit resulting from this project as the growers simply did not adopt the practice or make significant adjustments to their current management practices.

Farmer Adoption

Despite 11 of the participants stating that they planned to purchase soil moisture monitoring equipment in post season interviews, zero followed through and actually purchased the equipment.  Informal interviews of the participants indicated that growers felt they were already doing a good job of scheduling and that the one year of sensor data they gleaned from this project helped to refine their traditional scheduling methods. 

In the final year of this project (2015) a private company began marketing a soil moisture monitoring and irrigation recommendation service.  Participation with the service also saw limited adoption due to the cost to participate.   The one grain farmer that was using his own soil moisture monitoring equipment prior to this project has since abandoned the equipment due to high maintenance costs (both in time and material) and the sense that similar yield could be obtained with other methods.  Several vegetable growers are using manually read tensiometers and Watermark sensors to schedule drip irrigation and occasionally pivots, however those farmers were using these methods for several years prior to this project. 

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

The three years of cooperator research (2013 – 2015) were all relatively mild growing seasons with regular rain events during the critical corn growing periods.  As a result, dryland corn yields were some of the best on record and any deficiencies in irrigation scheduling were masked by rainfall.  In a dry season grower reliance on soil conditions would be significantly higher as the typical scheduling methods (ET model and personal experience) tend to break down with extended dry periods.  Semi arid regions of the country and high value specialty crop grown under plastic mulch have the greatest potential to benefit from soil moisture monitoring.

The following steps should be taken to fully evaluate soil moisture monitoring as a effective tool to schedule irrigation in the humid region:

  1. Locate a RELIABLE, cost effective soil moisture recording system.
  2. Minimize manual labor during installation and removal.
  3. Develop simple methods to analyze data and trigger irrigation
  4. Evaluate the feasibility of of equipment during a dry season and with poorly calibrated irrigation systems.

 

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.