Identifying Stacked Conservation Practices that Optimize Water Use in Agriculture

Progress report for SW19-909

Project Type: Research and Education
Funds awarded in 2019: $349,977.00
Projected End Date: 06/30/2022
Grant Recipients: Utah State University; Brigham Young University; Brigham Young University-Idaho; University of Idaho
Region: Western
State: Utah
Principal Investigator:
Matt Yost
Utah State University
Niel Allen
Utah State University
Dr. Earl Creech
Utah State University
Neil Hansen
Brigham Young University
Matthew Heaton
Brigham Young University
Ross Spackman
Brigham Young University-Idaho
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Project Information


Concerns about water scarcity are mounting due to rapid urban growth, depleting groundwater supplies, and drought resulting from less and more variable snowpack in the western United States. These concerns are apparent in several areas of Idaho and Utah where water shortages are already common. We propose collaborations with several stakeholders to answer these three critical research questions: (1) Which combinations of irrigation and crop management practices result in the optimal use of limited water supplies for the best yield and profit outcomes for producers? (2) Which water conservation practices are and could be used by producers? and (3) How can their barriers to adoption be overcome?

            To address these research questions, we propose expanding ongoing work to: i) conduct on-farm and research station experiments to identify how individual and ‘stacked’ water conservation practices (irrigation, crop genetics, and crop management) optimize water use and increase crop profit at three sites in Utah (Logan, Cedar City, and Vernal) and three in Idaho (Pocatello, Rexburg, and Twin Falls); and ii) conduct statewide and local surveys of major irrigators in Idaho and Utah to quantify adoption rates of water conservation practices, barriers to adoption, and impacts of the proposed work. This work will be focused on pivot irrigation which comprises most of the sprinkler irrigation in Utah and Idaho. Dynamic outreach components will include interactive field days at the six research sites, presentations and publications through Idaho and Utah Extension and professional associations, and new curriculum and training for students at six Universities.  

            The anticipated project outcomes in the Western Region include:

1.      Over 300 stakeholders will engage in discussions and demonstrations of water conservation research at six field days;

2.      Over 1,000 stakeholders will be educated on practices to optimize their water use during various Extension and professional presentations;

3.      Producers, agricultural professionals, and others will have access to timely information about practices that optimize water use through at least 3 Extension publications and 3 journal articles;

4.      Over 2,000 producers will have the opportunity to share their experience with water conservation through surveys; and

5.      Students from six universities will have access to new water conservation curriculum and hands-on training.

            Producing and disseminating results on the suites of practices that economically and feasibly optimize water should lead to greater acceptance and use of these practices. Preliminary studies by investigators have shown that some combinations reduce irrigation and energy use without impacting yield. Annual diversion of water could be reduced by 100,000’s of acre-feet if advanced practices were implemented by just half of the irrigators in Idaho and Utah. These outcomes would also assist producers and other stakeholders involved in proposing, creating, and administering cost-share or water bank programs to help conserve water. Furthermore, we expect these trials will provide the foundation for years of valuable information concerning ideal short- and long-term water conservation practices, and should spur further funding and support from the state and federal agencies where water conservation and optimization is a high priority.

Project Objectives:
  1. Identify combinations of six (irrigation system, rate, and schedule coupled with crop type, crop genetics, and tillage) water conservation practices with the greatest ability to optimize water and energy use. Years 1-3.
  2. Expand variable-rate irrigation research to provide dynamic irrigation prescriptions based on soils and yield to improve water and energy use efficiencies. Years 1-3.
  3. Determine producer’s attitudes, acceptance rates, and barriers to adoption of water conservation practices in order to better adapt and target Extension and outreach efforts. Year 2.
  4. Deliver dynamic educational products and training on water and energy optimization through Extension and coordinated outreach to increase awareness and adoption of proven water optimization practices. Year 2 and Year 3.


Click linked name(s) to expand
  • Ryan Christensen - Producer
  • Steve Hanberg - Producer
  • Brent Hunter - Producer
  • Howard Neibling (Educator)
  • Jason Westover - Producer


  1. Suites of six (irrigation system, rate, and schedule coupled with crop type, crop genetics, and tillage) water conservation practices will increase the ability to optimize water and energy use in forage and grain cropping systems in the Intermountain West.
  2. Variable-rate irrigation based on in-field dynamic irrigation prescriptions will improve water and energy use efficiencies.
  3. Quantifying producer’s attitudes, acceptance rates, and barriers to adoption of water conservation practices will assist in more adaptable and targeted Extension and outreach efforts.
Materials and methods:

Objective 1: Identify combinations of six water conservation practices with the greatest ability to optimize water and energy use.

The experiment started in the 2019 growing season close to the south portion of the Utah State University farm on a Greenson loam. The experiment will be done with three crop types – corn, safflower, and alfalfa. The corn will be grown in a corn-corn-wheat rotation with the focus mainly on the corn. A completely randomized block design with a split-split treatment is the experimental design with the blocks being replicated three times with eight treatments being randomly assigned within each replication. The five irritation technologies and four rates are assigned to strips for each group of three treatment replication blocks. For each of the technologies, four rates are assigned – 100% of the rate, 75% of the rate (a 25% reduction), 50% of the rate (a 50% reduction), and a 50% partial rate. The 50% partial rate is a rate designed to irrigate 50% of the rate but more focused during critical growing periods of the crop. The 100% rate was determined by the season’s water schedule placed by the water district with the plans of using the soil moisture sensors to help decide the rate. However, there were some issues with the sensors. The different soil management practices being studied are conventional tillage, no-till, cover crop, conventional tillage/ cover crop, and no-till/ cover crop. Among the different soil management treatments, conventional genetics, and drought tolerant genetic seed are planted. A soil additive called Aquadrive is added to certain plots as well to see how a soil water additive effect the water holding capabilities of the soil, which would allow for more available water to the plants.

In late April 2019, field preparation and planting began at the Logan location with the plots of safflower planted first in cultivated soil conventionally tilled to a depth of 7.6 cm for an even planting bed at a rate of 28 kg ha-1. During the same time as safflower planting, the oats were planted in the area of the field that would soon be the alfalfa trial to give a rotational break since the field being used was originally an alfalfa field. Planting was not the only fieldwork going on at the site as 24 soil moisture systems to monitor moisture for the season at different depths throughout the different trials.

The soil moisture system used for the Logan site was chosen to be the Acclima Inc system, a cloud-based system. The moisture sensors were buried at four depths – 0.3 m, 0.6 m, 0.9 m, and 1.8 m. The sensors are time domain reflectometry (TDR) type. Eight sensor stations were installed into each of the main blocks of corn acreage, alternate crop acreage, and alfalfa acreage. This system was meant to be used as a basis for monitoring water moisture to irrigate more efficiently through irrigating based on need. This did not occur, though, since the sensors did not upload to the cloud at all during the season. Data has not been extracted yet as the Acclima representative helping with the case has suggested no data is extracted until an update is ready for each of the sensors.

Due to the ongoing issues with the Acclima sensors and loggers, the Vernal and Cedar City sites will have Meter sensors installed at three depths. The Meter sensors have been used at various other sites for other projects, proving to have reliability and ease of use. Unlike the Acclima sensors, the probes for the Meter are easier to install with less groundwork needed, thus disturbing less of the site.

Corn planting occurred in June 2019 due to an overly wet early spring. The plots were predetermined in size to be 9.5 m north to south by 6.1 meters west to east, making them eight 76.2 cm wide rows. The only exceptions were the plots in the LESA span that were five rows wide due to a length restriction of the lateral. The 4.6 m wide planter (type, dealer, location) ran north to south during planting at a seeding rate of 88,980 plants per ha at 5.1 cm deep. The two seed types planted were DKC 5120 as the drought tolerant variety and DKC 5084 as the non-drought variety as hybrid genetics of Roundup Ready were chosen for both varieties for easy of weed control. No soil management practices were implemented during the 2019 growing season because the field had already been manured and tilled before the study was initiated in early 2019.

The alfalfa trial was planted on the southern portion of the field in late August at a rate of 10.9 kg per acre. The plots of drought tolerant Ladak II alfalfa were placed on predetermined sides of the soil moisture probes (type, dealer, location) at dimensions of 9.5 × 239 m. The remainder of the field was planted in the conventional crop genetics at the same rate. Due to the late planting after the oats, alfalfa cuttings will not be collected for the project until the 2020 season to give crop time to establish.  

Irrigation occurred from June until late September, with a total of 33 cm applied to the corn in 2019 in the 100% rate treatments. Only irrigating 33 cm of water to receive the yield acquired during harvest is typically unheard of until one considers the overly wet spring and late summer rains, giving a total of 46 cm of rain from January to early October when the corn was harvested. Although the study was to have a 50% rate and a 50% partial rate applied in different spans, the 50% partial became more of a 75% partial rate and will be monitored more closely for the coming seasons. The 75% rate spans received 24.75 cm of irrigation, while the 75% partial spans received 26 cm. The 50% rate spans received 16.5 cm of irrigation. The alfalfa was irrigated twice, each time receiving 2.5 cm for germination purposes.

Harvest began for the corn the last week of September, where 546 plots of 560 were harvest as the last 14 got cut off by the eight-row chopper (type, dealer, location). A two-row pull behind chopper (type, dealer, location) was used to harvest the plots with a pull-behind weigh wagon taking the bulk wagon while a student walked along outside the machinery taking samples and their weights. The sample weights collected in the field were taken to the Greenville dryers and left in until the moisture was taken off. After a month, the samples were weighed to record their moisture weights and ground to 1 mm for future nutrient analyses.

In late October, the safflower was harvested with the Almaco plot combine (type, dealer, location) by removing the alleyways first. A total of 60 bulk samples were taken from the field, weighed, taken to have small samples cleaned, and placed in the Greenville dryer room. Three samples were taken from each irrigation type and rate combination from the northern, central, and southern portion of the plot to get the variation within the plots.

A similar set of trials are in progress for the 2020 growing season in Vernal, Utah to gather data in different geography and climate of the state. The Logan trial will be running again with more soil management practices implemented into the plots as well as having alfalfa available to be harvested. The alternative crop at the Logan site has been discussed to be a possible hemp variety trial under overhead irrigation to give answers to the heated topic of Utah hemp production. As for the Vernal site’s alternative crop, teff will be the alternative crop in 2020. This experiment is still on track to be established in Cedar City for the 2021 growing season.

Objective 2: Expand variable-rate irrigation research to provide dynamic irrigation prescriptions based on soils and yield to improve water and energy use efficiencies.

The pilot VRI study that was initiated on an Idaho field in 2016 showed a 25% irrigation water savings, reduced variation but similar total yield compared to those expected under uniform irrigation. 

To expand the existing pilot study, three VRI research and demonstration sites are being established across Southern Idaho (Twin Falls, Pocatello, and Rexburg). The Pocatello, ID location will expand on the pilot study and will be led by our producer representative, who utilizes a VRI system on a field in a potato-wheat rotation. 

Here are reports for each of the three sites:

Rexburg: In 2019, a wheat field in Rexburg Idaho was chosen for VRI research. Soil samples were collected on April 29th just after planting, May 30th, June 25th, and August 29th, just after harvest. Sample locations were 66 points based two superimposed grids to have samples that were spaced at a range of sampling intervals. Field-moist soil samples were collected using augers driven into the soil with a jack hammer and stored in plastic bags. Samples were weighed, dried at 105o for 24 hours and re-weighed. From these wet and dry weights volumetric water content (VWC) values were determined. These were interpolated (kriged) to a 5m grid then values for the four measurement times were averaged.  

       A k-means clustering algorithm was used in SPSS to group the average VWC data into 2-7 zones. The largest break of slope in the mean squared errors (Figure 2) was for 3 zones so 3 zones was assumed to be optimal.  The 3-zone VWC map (Figure 7) was used to compare with 3-zone maps produced using other inexpensive variables.

       Inexpensive variables included yield data from a yield monitor, normalized difference vegetation index (NDVI) from LandSat 8 imagery (June and July 2014-2019), elevation (collected from the GPS on the yield monitor) and derived topographic attributes such as slope, aspect and topographic wetness index (TWI).  These datasets were kriged to the same 5m grid that as the VWC data and were used individually and in different combinations to create more 3-zone maps using k-means clustering. The percentage agreement between the different 3-zone maps was determined.

The pivot requires upgraded VRI equipment, which is currently being installed in preparation for implementing uniform and VRI irrigation treatments for spring wheat in 2020. Soil moisture sensing stations are also being installed this week.


Twin Falls: The VRI project is located under a single-span VRI pivot at the University of Idaho Kimberly Research and Extension Center. The field site is on a hillside of eroded. The upslope half of the pivot is approximately 3% slope of eroded Portneuf silt loam soil. Low infiltration rates and excessive surface runoff due to surface seal formation are serious issues. The lower half of the pivot is approximately 1% slope Portneuf silt loam with relatively deep topsoil resulting from deposition of topsoil eroded upslope. This portion of the field has less tendency for surface seal formation and runoff issues. Crop productivity is also higher than for the more sloping portion of the pivot.

A two-zone VRI map under development based on crop yield and post-harvest soil water content from 16 plots each of malting barley, winter wheat and alfalfa. In 2019, plots were arranged so that equal numbers of plots of each crop were located in each quadrant of the pivot. In 2019, all plots received the same irrigation and fertility applications. Crop yield varied considerably, based on location on the hillside for each of the 3 crops. Part of the difference appears to be due to overall fertility / soil tilth conditions and part due to differences in water available for crop growth due to infiltration / runoff differences with slope position. End-of-season soil water content was measured for each of the 48 plots at 6-inch depth increments to 5 feet. Plots on the top (more sloping and eroded) half of the field had a noticeably lower post-harvest water content, more visual indications of crop water stress during the growing season, and lower crop yields relative to the lower slop, non-eroded portion of the field. Data from 2019 is being used to develop VRI prescriptions for testing during the 2020 growing season for spring wheat. 

Grace: The field site is near Grace, Idaho and winter wheat (Triticum aestivum L.) was growing in 2019. The field was equipped with a variable rate irrigation (VRI) system. 100 soil samples were collected to compute volumetric water content (VWC) on April 23, May 30, June 25, and September 5 of 2019. Beginning sampling was at spring green-up, and the final sampling was shortly after harvest. In this study, the data from May 30th were focused on. Five irrigation zones were created and managed from soil sensors with sensor location installed in each zone. Soil sensors collected VWC and irrigation was applied to reach field capacity. A large portion of the west side of the field had ponding due to snow melt early in the season so wheat was replanted in spring, causing a late growth in this area compared to the rest of the field. The yield monitor and GPS in the combine collected spatially referenced yield data. LandSat 8 and Sentinel 2 imagery was obtained from USGS to calculate normalized difference vegetative index (NDVI) and normalized difference red edge (NDRE) and then correlated with soil sampling data. All data was kriged to the same 5 meter grid. Best subset regression was performed using a subset of 15 points (3 per management zone). Estimated VWC using the regression equation was compared with kriged VWC measurements and the root means square error (RMSE) was calculated. SpaceStat and ArcPro were used for all spatial and statistical analysis.

Objective 3: Determine producer’s attitudes, acceptance rates, and barriers to adoption of water conservation practices in order to better adapt and target Extension and outreach efforts.

Three nearly identical online 8-page surveys were developed in 2019 for corn, potatoes, and small grains. The questions were developed to ask Idaho and Utah growers how they manage irrigation and nitrogen needs. Questions were formulated to ask in an order of finding out the scope of the production, planting populations, fertilization plans, and irrigations plans. For the N fertilizer section, growers are asked questions relating to the time of year of application, rate of application, application practices, and application source. The irrigation questions are similar in nature, asking about irrigation type, scheduling, amounts, and frequencies. For both areas, growers are questioned about advanced practices such as variable rate applications. The last few questions of each crop survey for both nitrogen fertilizer and irrigation question growers on how they would handle a price increase of each of the inputs. This will allow us to assess both irrigation and nitrogen 4R adoptions and barriers. The survey has been emailed to about 7,000 growers in Utah and Idaho. We currently have about 200 responses and will continue to send reminders to try and increase the completion rates. If results are not satisfactory, we plan to send a mail version of the two surveys to increase the response rate. Surveys will be summarized and results published.   



Research results and discussion:

Objective 1:

The first harvest of corn for the Logan location resulted in 546 plot samples, giving an introduction into how the first few factors yielded. Overall, there were no statistically significant differences in water optimization between drought tolerant and non-drought tolerant corn genetics. The addition of the soil additive Aquadrive did not allow for plants to use water any more efficiently. The largest statistical differences were seen in the factors of the Irrigation Rate, while the technology showed no differences. For the water efficiency among the rates, the 50% rate maintained yield while double water efficiency compared to the other rates.

Energy use has not been investigated currently as there is a wait on the data. The soil sensors used at the Logan location had connectivity issues during the season and are currently in storage before they are updated to the newest software, and the data is transferred from the devices. When the data is able to be extracted from the nodes, the data will be analyzed to check the energy use going forward.  

Soil samples were taken before planting began but have not been sent off due to some mislabeling and getting caught up in the fieldwork of the summer and early autumn. All the corn samples from the initial harvest were ground up and have started to be run at the Analytical lab to get the nutrient data for the samples. After spending some time at the lab, it was determined the samples are slightly too dry and will need to be exposed to open air for a few days before the analysis can be run on them, slowing down the process. When the data comes back from both the soil samples and the corn samples, an analysis of the nitrogen use can be started.

Objective 2:

The visible atmospherically resistant index (VARI), green leaf index (GLI), Normalized green red difference index (NGRDI) and Normalized difference vegetation index (NDVI) extracted from drone imagery at several spatial resolutions were compared with leaf area index values (LAI) measured on the ground. The values that correlated best with LAI were the 1×1 m and 2×2 m VARI index data for Grace, ID and Rexburg, ID (r= 0.44 and 0.45), respectively. The R2 values from aspatial regression were quite low and reflected these correlation coefficients. 

A GWR of LAI and VARI was performed for Rexburg and Grace and yielded correlation coefficients of r= 0.98 and 0.99, respectively for the estimated LAI derived from VARI and actual LAI. This shows that the correlation and regression coefficients between LAI and VARI change locally and estimates are more reliable when these local relationships are taken into account. While generally in the field, high values of LAI coincided with high values of VARI, the bi-variate local Moran’s I tests showed that there were areas with significant clusters where there were low values of LAI and high values of VARI (pale blue) and high values of LAI with low values of VARI (pink). The moving correlation maps from GWR show where the correlations between LAI and VARI change from positive (red) to negative (blue). For Rexburg, LAI and VARI were negatively correlated predominantly on west facing slopes (map of aspect not shown). For Grace, the areas with negative correlations between LAI and VARI were partially on a west-facing but also on relatively flat areas above the ridge. The potential reasons for negative correlations between LAI and VARI being associated with certain topography and aspects need to be investigated in the future. It may be that these topographic features distort the light received by the camera on the drone and that the imagery needs correcting for them.

 Objective 3:

Surveys are still being administered and have been deployed out to growers of Utah and Idaho to determine their current irrigation and nitrogen practices in corn, potatoes, and small grains. The surveys are going to be deployed via an online service to get as many responses as possible. As a supplement, paper versions of the survey will be sent via the mail. The survey has already been reformatted to be sent by mail. In addition, surveys were advertised and available at all major Extension and related events in Idaho and Utah including the Utah Hay Symposium (February 2020) and the Idaho Hay and Forage Conference (February 2020). Results will be compiled after about a month of the surveys being distributed.

Research conclusions:

Objective 1:

2019 was a relatively wet growing season. This likely diluted impacts of our water stress treatments. Irrigation rate had the largest impact on yield, suggesting that rate adjustments may have greater potential to optimize water use than other approaches tested. Results need to be confirmed in more environments. In 2020 at Logan, additional soil management practices (no-tillage and cover crops) and crops (alfalfa and sorghum-sudangrass) will be tested. A second site will also be established in Vernal, Utah. Both of these studies will be repeated in 2021, along with the addition of a third site in Cedar City, Utah.

Objective 2:

This analysis has shown good potential for VIs based on visible band images for predicting LAI. The high correlations between LAI and LAI estimated from VARI using GWR show that GWR shows better potential for predicting LAI from imagery than simple linear regression as the correlations and regression coefficients change spatially throughout both fields. Here, all the ground LAI data were used in the prediction as well as the imagery data. Future work should investigate prediction using GWR, imagery and a minimal sub-sample of the ground data. The potential improvement of predictions by including other variables such as patterns of past yield and topographic attributes in regression should also be investigated. Once accurate estimates of LAI are obtained they can be converted to crop coefficients (Kc) for use in ET modelling and determining how irrigation requirements vary spatially within fields.

Objective 3:

Results will be compiled and summarized when surveys are completed.

Participation Summary
4 Farmers participating in research


Educational approach:

Education materials will be created by the team for use in undergraduate agronomy/irrigation coursework at six university campuses (BYU, BYU-I, USU, USU-Vernal, UOI, and SUU). This would be one of the first coordinated efforts like this in Western states to concentrate training on water conservation in agriculture for current and upcoming generations of producers and ag professionals. This will include powerpoint presentations and videos based on results from objectives 1-3. This training would also include a coordinated field trip during the summer of 2021 where students from multiple institutions would spend a week together touring and discussing the experiments in this proposal to gain firsthand experience in multiple technics related to water management in agricultural systems. We have begun preparations for this new applied water conservation course that will be co-taught by multiple universities during the summer of 2021. This includes organizing and requesting approvals for a new course at each university, and developing the assignments, field trips, group projects, and activities. 

Educational & Outreach Activities

15 Consultations
5 Curricula, factsheets or educational tools
1 Journal articles
4 Published press articles, newsletters
4 Tours
25 Webinars / talks / presentations
3 Workshop field days

Participation Summary

400 Farmers
200 Ag professionals participated
Education/outreach description:

Ojectives, design, methods, and preliminary results of this project have been presented and published in many Extension, farm press, and professional settings. This included about 20 separate presentations at Extension crop schools and other related meetings in Utah. It also included a news highlight of this work by the American Society of Agronomy, along with 5 professional presentations by scientists and/or graduate students at regional and national professional meetings. 

Five factsheets that drew on efforts and experience gained in this project and focused on water conservation were developed in 2019-2020. Some of these stemmed directly from training priorities that were identified at our training event we held in Wellsville, UT as a part of objective 1 and 4. 

We hosted three separate trainings for irrigation professionals, crop advisors, and conservation planners (NRCS and Utah Department of Agriculture, and Utah Association of Conservation Districts) in 2020 with a total of 120 participants.

Due to his involvement with this and other related projects, Dr. Yost was invited to write a journal article on 75 years of applied water conservation efforts for a special edition of the Journal of Soil and Water Conservation. The article has been accepted with revision and will be resubmitted within a month.   

Learning Outcomes

150 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas taught:
  • Irrigation maintenance and irrigation scheduling
Key changes:
  • 84% of the 183 participants who completed evaluations for the crop events indicated that they had gained knowledge about advanced techniques for irrigation scheduling. 63% indicated that they planned to use the information to improve their management.

Project Outcomes

116 Farmers intend/plan to change their practice(s)
7 Grants received that built upon this project
7 New working collaborations
Project outcomes:

In this first year, we have concentrated heavily on training and strengthening ties with the agricultural and conservation industries and organizations in Utah and Idaho. We hosted three brand new separate events for irrigation professionals, crop advisors, and conservation staff from NRCS and state agencies/organization. These events were highly successful, built trust between Extension and other stakeholders, provided effective and in-depth training on water and soil conservation, and are leading to new collaborations, grants, and coordination. Similar events and field days will be held in 2020 and 2021 with focus on educating farmers. 

We have educated other researchers and practitioners by presenting initial results at several regional and national professional meetings. 

Results are still preliminary, but we are beginning to identify the most ideal ways to improve water optimization and soil conservation in forage and grain field crops in Utah and Idaho. This information will help improve production, profit, sustainability, and well-being of farmers in Utah, Idaho, and the greater Intermountain West. 

Success stories:

We hosted a training for irrigation professionals at our research and demonstration site in Wellsville, UT in August 2019. This is the first time this type of meeting has been held in Utah. Attendees who completed evaluations indicated the event was educational, needed, and would facilitate improved irrigation advising in Utah and southern Idaho. As Dr. Yost was collecting evaluations, he noticed that one of the irrigation dealers had written that an irrigation package was installed incorrectly on one of their grower’s pivots. Incorrect installations can cost growers thousands and sometimes millions of lost crop income over the lifespan of an irrigation package. 


This project is in its first year so many of the results are preliminary and are not ready to be turned into recommendations. 

We have learned important lessons in the first year. Many lessons learned about mobile drip irrigation and variable frequency drives were recently published as USU Extension fact sheets. Filtration is critical for successful irrigation with mobile drip irrigation.

We are beginning to identify conditions where variable-rate irrigation (VRI) might be feasible and economic. These appear to be where water requirements are highly variable, as caused by variable soils, variable yield, or variations in field conditions.   

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.