Alabama Irrigation Management Program
June 14, 2020
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Alabama Precision Ag Extension Program Brings Demonstrations of Irrigation Technology to Your Farm
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Ten demonstration sites of best irrigation practices have been established by the ACES and Auburn University Precision Agriculture Extension program. The goal of this program is to increase awareness on the agronomic and economic benefits of implementing these practices and to train farmers and consultants on use of technologies for better irrigation water management. The demonstration sites are located at Posey Farm, Bridgeforth Farm, E. V. Smith Research Station (Plot 101 and Plot 501), and L. C. Farms (Sod Farm, Bellwood, and Sunday's). We are currently evaluating and demonstrating three different commercially available soil moisture sensors (AquaSpyTM, Trellis, Acclima), two irrigation scheduling smartphone Apps (https://smartirrigationapps.org/), and a crop growth simulation modeling-based irrigation scheduling decision support system (FieldNet AdvisorTM). Variable rate irrigation is also demonstrated at five of the ten sites. This newsletter is not endorsing any specific company or product.
This report covers the period June 1st to 7th, 2020. The sites planted with corn in Geneva are at the Blister growth stage. Frequent rain events were received that week and then irrigation was not required. On average the corn crop was using 0.25 inches per day. The site at E. V. Smith research station planted with corn was at the V12 growth stage. Irrigation was applied three times towards the end of the week. Dry conditions were observed in Tanner and Town Creek, Alabama. Corn at those sites was at the V10 and V8 growth stages respectively. Although irrigation was required farmers decided to wait for the expected rainfall towards the end of this reported period. The soil sensors installed at various locations within the fields in Town Creek, Tanner and Shorter Alabama shows within-field differences in soil water content which validates the recommendation of variable rate irrigation.
Every week we will share with you a brief report per demonstration site with information of weather conditions and irrigation decisions supported by use of technology. If you would like to subscribe to this newsletter, please send an email to Dr. Brenda Ortiz, Professor and Precision Agriculture Extension Specialist. bortiz@auburn.edu
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Reports |
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Reporting Period: June 8th to June 14th (Week 9 after planting)
Location: Town Creek, Alabama / Farm: Posey Field
weekly weather conditions
Temperatures were fairly constant again this week at an average daily temperature of roughly 75 °F. The field experienced moderate rainfall early in the week, with 0.24 in on 6/8 and 0.45 in on 6/9, for a cumulative 0.69 in of rain this week.
Study field – location of sensors
Changes in rainfall, svapotranspiration, soil water conditions, irrigation
Crop evapotranspiration values (dashed green line - ET Crop) – the amount of water used by the corn – climbed early in the week before leveling out around 0.2 in/day. The average ET Crop for this week was 0.15 in/day and the total ET Crop for the week was 1.02 in. The striped blue “Past Recom. Irrig.” bar represents irrigation recommendations generated from Trellis sensor data throughout the week. All values in the graph above come from Location 2 in the field. These past recommended irrigation values are included in the graph to show the relationship between rainfall/irrigation and current recommended irrigation values. For example, the 0.94 in of recommended irrigation on the 8th was quickly offset by the rain on the 8th and 9th. On 6/13, the farmer irrigated 0.64 in, while the past recommended irrigation was about 1.1 in. This difference in recommended vs prescribed irrigation led to a continued need for irrigation on 6/14. The solid blue “Recom. Irrig.” bar continues to represent the most recent recommended irrigation value at Location 2.
Changes in soil moisture levels
This week’s soil moisture graph shows a steady decrease in soil moisture in both locations (2 and 5) throughout the week. Due to the irrigation applied on the 13th, moisture levels increased in Location 2. This change was not observed at Location 5. This may indicate an error on the pivot, which could lead to irrigation not being applied in this location. We are currently investigating this issue. Soil water depletion reached 35% on the day before irrigation (6/13) based on Trellis sensor at Location 2, and irrigation replenished water to near field capacity.
Daily changes in soil moisture – AquaSpy sensor data – sensor locations 2 (left) and 5 (right)
 
The screenshots above are from the AgSpy Mobile app and show available moisture changes at Locations 2 and 5. The clearest takeaway from this graph is the stark difference in moisture between the two sensors. Location 2 (on the left) is safely withing the healthy bounds for corn growth (green band) while Location 5 (on the right) is well below the optimal moisture levels. As mentioned before, there is a high chance that the pivot did not apply water in this location. This would explain the fact that there was no spike in soil available moisture on the day of irrigation for Location 5. The downslopes in the moisture data show the corn uptaking water during the day and the plateaus show the decreased uptake of water by the corn during the night. Note that the long flat line at the beginning of this week is due to a temporary sensor outage.
Daily change in soil water tension – Trellis sensor data – location 2
 
The screenshot above is from the Trellis app and shows the difference in soil moisture at varying depths. As a general rule, soils closer to the surface will dry out quicker due to evaporation and crop water uptake while soils farther from the surface will dry out much slower. As the corn matures throughout the season, we will be able to see the 24” depth lose moisture more quickly due to increased root uptake. The large spike this week is from the irrigation event on the 13th. It is worth noting that this irrigation brought the 6” depth to field capacity but did not manage to greatly increase moisture levels for deeper soils. Further, we can see that the 24” soil depth is beginning to see dips in moisture level. This indicates that roots have started to form and uptake water at this depth.
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Reporting Period: June 8th to June 14th
Location: Bridgeforth – Week 11 after planting
Weekly weather conditions
The maximum temperature of the week was 90 oF and the minimum temperature was 59.7 oF. The average temperature of the week was 75.7 oF. Also, a rainfall event of 0.97 in was recorded on 6/8 of 0.37 in.
Within-field variability - soil moisture
Changes in rainfall, evapotranspiration, soil water conditions, irrigation
The corn is at the V12 growth stage. A clear progression of Corn evapotranspiration (ET Crop) was observed during the week. This was because the crop is growing fast and increasing daily water demand. Daily ET crop averaged 0.17 inches, totaling 1.17 in. As mentioned in the last week, sensor 5 is located at the highest point in the field, while Sensor 4 is in a valley, explaining why sensor 5 dries out fester when compared with sensor 4. The recommended irrigation was 0.8 in for sensor 4 and 1.32 in for sensor 5. Even though the farmer irrigated a flat rate of 0.6 in through the field on the same day, the irrigation did not meet the recommended irrigation by the sensors. It explains why on 6/14 the recommended irrigation for sensor 4 and 5 was still very high (0.9 in for sensor 4 and 1.37 in for sensor 5).
Soil water depletion recorded by Trellis sensors were very responsive to daily crop water uptake (increase on depletion) and the irrigation event (decrease of depletion) on 6/11. AquaSpy sensor did not responded well to changes in water levels, and the available moisture values were fairly the same during the week. We are investigating these issues and there is a high chance that the sensor was not well installed, and air gaps between the sensor and the surrounding soil is preventing from collecting reliable data.
Trellis sensors (Watermark ®) – locations 4 & 5
 
The screenshot below shows the change in soil tension from Trellis sensors 4 (left) and 5 (right). Sensors were responsive to rainfall on 6/8 and irrigation on 6/11 for sensor 4 and on 6/12 on sensor 5. This is explained by the fact that pivot takes about 2 days to complete full rotation, so there is a delay when the sensors responds to irrigation. For sensor 5, the 24 in depth sensor (brown line) showed higher changes on soil tension values when compared to the same sensor depth for sensor 4. It confirms that on highest points of the field, the soil dries out faster, and the root system reaches deeper soil layers to find water.
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Reporting Period: June 8th to June 14th (Week 11 after planting)
Location: Shorter, Alabama / Farm: E.V. Smith Research Station / Field: Plot 501
Weekly weather conditions
Temperatures remained fairly constant, with the average temperature for the week around 76 OF. Some rain was recorded at the beginning of the week, totaling 1.09 in from 6/8 to 6/10.
Study field and demonstration location
Changes in rainfall, evapotranspiration, soil water conditions, irrigation
The green dashed line shows crop evapotranspiration (ET Crop) which averaged 0.21 in/day, and the total ET Crop for the week was 1.45 in. Weekly total rainfall was 1.09 inches. The small rainfall that occurred on 6/8 (0.1 in) was not enough to replenish crop water demand (recommend irrigation of 0.6 in using Acclima sensors. The recommendation was maintained for the next day, but the rainfall event of 1 in that occurred from 6/9 to 6/10 dropped the recommended irrigation to 0 in. The lack of rainfall and the fast plant water uptake from 6/11 to 6/14 contributed to a recommended irrigation of 1 in by 6/14.
The graph above shows that water depletion measured by an Acclima sensor within the 24” inches soil depth was around 10% at the start of the week. This reading went down to around 0% by 6/11 due to rainfall event that occurred in the beginning of the week. The dry conditions from 6/11 to 6/14 increased water depletion to 20% by 6/14. Similar results were observed for the AquaSpy sensor, with available moisture values reaching 50% on 6/14. The data from the sensors are invaluable to identify the progression the soil water depletion as plants uptake water.
Daily changes in soil water - AquaSpy sensor
The graph above shows daily changes in soil moisture recorded by an AquaSpy sensor. The moisture level line went below the green zone on 6/14, indicating that irrigation is required. As mention before, a 1 in irrigation was applied on 6/15 to prevent from water deficit.
The graph above shows daily changes in available moisture recorded by an AquaSpy sensor at the 8, 12, 20, and 24 inches depth. The increase in moisture, represented by the peaks on the graph, are results of rainfall. Daily crop water uptake can clearly be seen from 6/11 to 6/14. On 6/14, the values were about 0.13 in/d lower when compared to previous days (average of 0.35 in/d on 6/11 and 6/12). These data show how that, as soil water depletion levels increases, daily plant water uptake decreased due to water deficit. Irrigation must be prescribed to prevent from plant water stress and yield losses.
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Reporting Period: June 8th to June 14th (Week 11 after planting)
Location: Shorter, Alabama / Farm: E.V. Smith Research Station / Field: Plot 101
Weekly weather conditions
Temperatures remained fairly constant, with the average temperature for the week around 76 OF. Some rain was recorded at the beginning of the week, totaling 1.09 in from 6/8 to 6/10.
Changes in rainfall, evapotranspiration, soil water conditions, irrigation
The green dashed line shows crop evapotranspiration (ET Crop) which averaged 0.21 in/day, with peak of 0.25 in on 6/13, and the total ET Crop for the week 11 was 1.45 in. Recommended irrigation using Acclima sensors was 0.19 in by 6/8, and 0.07 in on 6/9, but rainfall was sufficient to meet this crop water demand. By the 14th, after three days without rainfall, Acclima sensors recommended irrigation of 0.72 inches.
The graph above shows that water depletion measured by an Acclima sensor within the 24” inches soil depth was around 0% until 6/12. This reading went up to about 10% by the 14th. AquaSpy available moisture increased from around 66% on 6/9 to 100% on the 6/10 (measured up to 40” soil depth). Over the following days available moisture fell back to 50% on the 14th, showing the fast water uptake from plants. No irrigation was applied this week, but a 1 in irrigation was scheduled to be applied on 6/15 to prevent from water deficit.
Daily changes in soil water - AquaSpy sensor
The graph above shows daily changes in soil moisture recorded by an AquaSpy sensor. The incremental drops in soil moisture from 6/11 until the end of the week comes from daily crop uptake (step pattern). The three peaks on the graph correspond to soil moisture increase due to the rainfall events on the 8th through the 10th.
The graph above shows the soil moisture levels (in volumetric water content) for the week from Acclima sensors. The rainfall that occurred from 6/8 to 6/10 increased soil level to above field capacity. This fact was favored because irrigation was applied on the week before. The sensors installed at 6 and 12 in soil depth had higher soil moisture levels drops when compared to sensors installed at 24 in. It suggests that most of the root system is currently located at 0-12 in soil depth profile. As the root system continues growing and reaches the sensor located at 24 in depth, the soil moisture levels changes will be like those sensors located at 6 and 12 in depth.
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Reporting Period: June 8th to June 14th (Week 13 after planting)
Location: Samson, Alabama / Farm: L.C. Farm / Field: Sod Farm Middle
Weekly weather conditions
The highest temperature for the week was 91.5 oF on 6/14 and the lowest temperature was around 64 oF on 6/11. The weekly average temperature was around 80 oF. Two rainfall events were recorded this week for a total of 1.5 inches.
Field location and sensor installation location
The figure above shows with a yellow dot the location where Acclima and AquaSpy Sensors were installed.
Changes in rainfall, evapotranspiration, soil water conditions, irrigation
The total rainfall occurred early in the week 13 (0.5 in on 6/8 and 1 in on 6/9) replenished soil water level to field capacity and no irrigation was needed in the beginning of the week 13. By the end of the week, recommended irrigation based on Acclima sensor was 1 in, and farmer irrigated 1 in. Total crop evapotranspiration (ET Crop) for the week was 1.39 inches and the average daily ET Crop was 0.20 (green dashed line).
The graphic above compares crop evapotranspiration estimated by the SmartIrrigation Corn App (green dotted line) and calculated ET Crop based on Kc (1.1 for week 13) using weather station data (green dashed line). Corn app ETc Crop was similar to calculated ETc Crop based on Kc. The highest daily ETc crop ocurred on 6/12 (0.24 in/day) for both the corn app ETc Crop and for the calculated ET Crop.
The graph above shows daily changes on soil moisture levels measured by the AquaSpy, depletion values for Acclima sensor, and water deficit for Corn App. Rainfall that occurred on 6/8 and 6/7 kept the soil at highest soil water levels/ The blue line from AquaSpy shows that soil water depletion within a soil depth of 0-24 inches started increasing after 6/10. AquaSpy data shows that on 6/13, the soil moisture level has dropped to 77% with respect to the Full Point. For the same day, the soil depletion estimated with Acclima TDR soil sensors was estimated at 43%, and Corn App reached water deficit of 31%. The rainfall event of 1.5 in that occurred on 6/8 and 6/9 increased available moisture to 100%, and depletion values and water deficit were reduced to 0%.
Daily changes in soil water
The figure above shows daily changes of soil moisture content recorded by an AquaSpy sensor. At the beginning of the week, on 6/8, a rain event of 0.50 in was recorded, and was followed by another 1.0 in of rain on 6/9. These two rainfall events resulted in an increase of soil moisture content above the Full point (100% moisture of Field Capacity). Daily plant water uptake (represented by the step pattern from 6/10 to 6/13) decreased available moisture below the optimum zone (green band). Irrigation that occurred between 6/13 and 6/14 increase of soil available moisture back to full point. Available moisture would most likely reach 0% (refilling point) if irrigation was not applied. In that scenario, irrigation was key to prevent plants from water stress that would certainly reflect on yield losses.
The graph above shows daily soil moisture level (in volumetric water content) changes during week 13 after planting (Early Dent stage). Greater soil water depletion levels were observed at 6 in soil depth (red line) compare to 12 in soil depth (blue line) and 24 in soil depth (green line). Daily soil water uptake was 0.46 in/day on 6/12 and 0.32 on 6/13. These values are in line with the expected daily water uptake estimated on week 12 of > 0.3 in/day. Rainfall that occurred on 6/8 and 6/9, and irrigation on 6/14 were captured by all three sensors (spike on the graphics). This time of the growing season is characterized by the highest crop water demand, and daily water uptake is expected to be as high as 0.3 in/day. 1 in of irrigation is expected to occur every 3-4 days.
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Reporting Period: June 8th to June 14th (Week 14 after planting)
Location: Bellwood, Alabama / Farm: L.C. Farm / Field: Bellwood
The temperature this week stayed fairly constant with average temperatures remaining around 78.4°F. The Max Temperature of the week was 90.1°F and the minimum temperature was 66°F. From 6/8 to 6/10 there was an accumulated rainfall 1.4 in.
Demonstration location
Changes in rainfall, evapotranspiration, soil water conditions, irrigation
Corn is at peak of crop water use. The daily crop evapotranspiration values (suggested by the Corn App https://smartirrigationapps.org/) average 0.21 in/day, totaling 1.47 in during the week 14 after planting. Rainfall that occurred early in the week was higher than daily crop evapotranspiration.
Water deficit was 0% from 6/8 to 6/11, which was caused by the rainfall that occurred in the beginning of the week. Because of the dry weather conditions from 6/11 to 6/14, it was observed a progressing of water deficit from the Corn App. By 6/14, water deficit reached about 30%. The recommended irrigation for June 14th was 0.77 Inches (Corn App screenshot below).
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Reporting Period: June 8th to June 14th (Week 13 after planting)
Location: Samson AL / Farm: L .C Farm / Field: Sunday’s
Weekly weather conditions
The highest temperature for the week was 91.5 oF on 6/14 and the lowest temperature was around 64 oF on 6/11. The weekly average temperature was around 76 oF. Three rainfall events were recorded this week for a total of 1.5 inches.
Changes in rainfall, evapotranspiration, soil water conditions, irrigation
Most of rainfall occurred at the beginning of the week 13, with 0.64 in on 6/8, 0.72 in on 6/9, and 0.14 in on 6/10. Total week estimated crop evapotranspiration (green dashed line – ET crop) was 1.26 in and the daily average crop evapotranspiration was 0.18 in.
The graph above compares crop evapotranspiration estimated by the Smart Irrigation Corn App and the values reported by the weather stations and a crop coefficient (Kc) of 1.10. Both Corn App and weather station based ETc crop were similar, with highest values of 0.25 in/day observed on 6/12.
The graph above from the SmartIrrigaiton Corn App (https://smartirrigationapps.org/) shows that on 6/14. There was a soil water deficit of 21%, which represented an irrigation recommendation of 0.7 in by the end of the week 13. Farmer started irrigation on 6/15.
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Guidelines for Installation of Soil Sensors
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Data from soil sensors can be used to support irrigation scheduling decisions. Over- or under-irrigation could be minimized by using sensors to monitor changes on soil moisture conditions and/or canopy temperature. Proper installation of soil sensors can guarantee accurate and reliable data throughout the growing season.
Click here to read our blog with guidelines for soil sensor installation.
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Acknowledgments |
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The preparation of this newsletter is the result of a team effort from members of the Alabama Precision Ag Extension team and cooperating farmers. Thank you Guilherme Morata, Bruno Lena, Hunter Whatley, Kyle Stewart, Megan Thurmond, Pierce Massey, Barrett Mason, Tyler Stephenson, Mailson Oliveira, Luan Oliveira, Mary Herron, Luca Bondesan, Greg Pate and Dr. Brenda Ortiz.
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Support for this program provided by the institutions below
     
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