Alabama Irrigation Management Program
August 11, 2021

This report covers the period August 3^rd to 9^th, 2021. The weather was dry for all demonstration sites and very little rainfall was observed. Peanut and Cotton crops growing in South Alabama are at the peak of crop water use. Peanuts planted in South Alabama on mid-May and growing on sandy soils are filling and adding pods. The peanut crop at this growth stage is using 0.29 inches per day. Cotton fields locating in South and Central Alabama are at the white and pink flowering stage. The cotton crop at this growth stage is using 0.23 inches per day. Corn fields in South and Central Alabama are reaching physiological maturity. The site planted with corn in Shorter are at late Dent growth stage and very close to Black Layer growth stage. After the last irrigation on 9/3, irrigation is no longer needed in this site. The soybean planted in North Alabama and peanut in the Southeast are at peak of water demand and are using from 0.20-0.26 inches per day. Irrigation is key to prevent stress from soil water deficit. 

This report will provide a quick glance on weather conditions, crop growth, crop water use and how different irrigation tools could support irrigation decisions.

The goal of this on-farm irrigation 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, Clark Farm, Lazenby Farm, E. V. Smith Research Station (Plot Corn and Cotton), L. C. Farms (Sod Farm), McKenzie Farm, Wiregrass Research Station, and Atmore, Alabama. We are currently evaluating and demonstrating three different commercially available soil moisture sensors (AquaSpy^TM, Trellis), three irrigation scheduling smartphone Apps found at https://smartirrigationapps.org/ or irrigatorpro.org, and a crop growth simulation modeling-based irrigation scheduling decision support system (FieldNet Advisor^TM). This newsletter is not endorsing any specific company or product. 

Reporting Period: August 3^rd to August 9^th (Week 15 after planting)
Location: Shorter, Alabama / Farm: E.V. Smith Research Station  

 
Study Field – Demonstration Area - Location of Sensors


 
Weekly Weather Conditions

 

• Average temperature: 81.6 ⁰F.
• Accumulated rainfall: 0.22 in.

 
Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation

• Average of daily crop water demand: 0.15 in/day
• Accumulated crop water demand for the week: 1.02 in
• Total irrigation recommendation: 0.54 in on 8/3 in and 0.7 in on 7/26.
• Highlights: The weather for the week was dry. Plants are approaching maturity and a daily decline of daily crop water demand is expected to occur. An irrigation of 0.75 in was applied on 8/3 and that was the last one of the growing season. Even though at Dent growth stage plants still required water, the last irrigation was enough to replenish the soil back to field capacity and enough to be available to the plants until it reaches maturity (Black Layer growth stage).
• Highlights: This season was considered wet season for corn at the Central Region of Alabama. Only three irrigations events occurred - one after side dressing nitrogen application and two during the peak of water demand. This irrigated corn is expected to yield around 200-230 bu/ac even though rainfall delayed planting.

 
Daily Changes in Volumetric Water Content – Acclima Sensor Data

   

• Data interpretation: soil volumetric water content is given at three soil depths: 6 (red line), 12 (blue line), and 24 in (green line). The higher the volumetric water content, the higher the available water for the plants. Volumetric water content decreases due to crop water demand (step patten represented by the black arrows) and increases due to irrigation or rainfall.
• Highlight: The irrigation event occurred on 8/3 was captured by the three soil sensors with the increased volumetric water content values. Daily crop water demand (represented by the step patter – arrows) slowly decreased from 8/4 to 8/9, suggesting that the crop water demand is approaching physiological maturity.

 
Corn App report


Highlights: At the end of week 15 after planting, the Corn App was suggesting 34% water level deficit, meaning that there is still plenty water available for the plants as they approach full physiological maturity. Therefore, irrigation is no longer necessary.

 
Study Field – Demonstration Area - Location of Sensors


  
Weekly Weather Conditions

 

• Average temperature: 81.6 ⁰F.
• Accumulated rainfall: 0.14 in.

 Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation

• Average of daily crop water demand: 0.18 in/day
• Accumulated crop water demand for the week: 1.25 in
• Total irrigation recommendation: 2 in
• Highlights: Cotton is approaching peak of water demand and crop water demand is expected to increase daily. The dry weather and the lack of irrigation reported in this week reflected on high recommended irrigation on 8/9 (2 in). Although this soil can hold about 3.5 in of water up to 24 in of soil depth, this soil is not able to receive this total amount of irrigation at once without experiencing runoff. Therefore, irrigation should start soon but it should be split in 3 or more application to prevent runoff.

Daily Changes in Volumetric Water Content – Acclima Sensor Data

• Data interpretation: soil volumetric water content is given at three soil depths 8 (red line), 16 (blue line), and 24 in (green line). The higher the volumetric water content, the higher the available water for the plants. Volumetric water content decreases due to crop water demand (step patten represented by the black arrows) and increases due to irrigation or rainfall.
• Highlight: Because neither rainfall nor irrigation occurred this week, the only change in volumetric water content was due to crop water demand. This is represented by the step pattern observed in the graphic (black arrow). Note that the majority of changes occurred at the soil sensor located at 8 in of soil depth, with very little changes observed at 16 and 24 in soil depth. This is explained by the fact that cotton root system is still shallow and changes in the 16 and 24 in soil depth is expected to occur as the roots growth deeper and starts to withdraw water from deeper soil layers.

 
 
Daily Changes in Available Moisture – AquaSpy Sensor Data

 

• Data interpretation: soil moisture (black solid lines) represents the amount of water collected up to 48 in soil depth. For irrigation purposes, soil moisture should be kept within the green zone, and irrigation should return soil moisture to full point (field capacity).
• Highlights 1: Crop water demand was captured by the sensor and is represented by the black arrows. This week was dry and the available moisture went from above the green zone (plenty water for the plants) to the bottom of the green zone (soil water is becoming less available). It suggests that the crop used all freely available water in the soil and is approaching the water stress range. It is important, therefore, that irrigation starts to prevent from water stress.

 
Cotton App Report

• Highlights 1: The SmartIrrigation Cotton App reported a water deficit of 29% and an irrigation recommendation of 1.5 in at the end of week 12 after planting.

Reporting Period: August 3^rd to August 9^th (Week 15 after planting)
Location: Courtland, Alabama / Farm: Paul Clark


 
Study Field – Demonstration Area - Location of Sensors


 
Weekly Weather Conditions

• Average temperature: 74.8 ⁰F.
• Accumulated rainfall: 0.05 in.

 
Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation

• Average of daily crop water demand: 0.24 in/day
• Accumulated crop water demand for the week: 1.7 in
• Soybean irrigation recommendation: 3.74 in on 7/26.
• Highlights: This week was dry with very little rainfall observed. Because farmer did not irrigate, the recommended irrigation rate was high (3.74 in) by the end of week 15 after planting. Farmer should irrigate to prevent soil water deficit building up and to prevent higher water deficit.

 
Daily Changes in Available Moisture – AquaSpy Sensor Data

 

• Data interpretation: soil moisture (black solid lines) represents the amount of water collected up to 48 in soil depth. For irrigation purposes, soil moisture should be kept within the green zone, and irrigation should return soil moisture to full point (field capacity).
• Highlights: Available moisture indicated by the AquaSpy Sensor on 8/2 was reaching the upper boundary of optimal water conditions for the plant (green band) indicating no need for irrigation several days this week. The lack of rainfall from 8/2 to 8/9 decreased available moisture until half of the green band, indicating that no irrigation was still required during week 15 after planting. This decreased is represented by the daily crop water demand – blue arrows representing the step pattern.

Soybean App Report



Highlights: The SmartIrrigation Soybean App is reporting 34% soil water deficit and a recommended irrigation of 3.74 in.

 
Study Field – Location of Sensors



Weekly Weather Conditions

• Average Temperature: 80 ᵒF
• Accumulated Rainfall: 0.46 inches

Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation

• Average Daily Crop Water Demand: 0.29 in/day
• Accumulated Crop Water Demand: 2.03 in
• Highlights: Peanut is at peak of water demand and there is a high amount of soil water uptake. Although an accumulated rainfall of 0.46 in was registered during middle of the week, the soil sensors were recommending 1.35 inches on 08/06. The farmer applied 0.4 inches on 08/07 and 08/09. The rainfall and both irrigation events were not enough to meet crop water use.

 
Daily Change in Soil Water Tension – Trellis Sensor Data – Location 3

• Data Interpretation: When dealing with soil water tension, lower values (less negative) represent wet conditions and high values (more negative) represent dry conditions. In the example above, soil water tension was measured at 8 (blue line), 16 (pink line), and 24 in soil depth (brown line) using soil water tension sensors. The oscillation observed on each color line (each soil depth), indicate daily changes in soil water. Those oscillations indicate crop water uptake by the crop roots. The blue top line, soil sensor data at 8 inches depth, decreased very rapidly between 08/03 to 08/06 compared to the other depths which indicate a greater rate of crop water uptake. As the soil tension values go down (become more negative), the lower soil water.
• Highlights: The soil water tension data from the depths of 8, 16, and 24 inches was used to estimate irrigation timing and rate. On 08/07, 1.34 inches were recommended.

Irrigator Pro Report

• Daily Water Use (DWU) - 0.29 in/day
• Available water content (AWC) by 08/06 was 0.22 in in
• Highlights - Irrigator Pro App for the treatment area indicates that the available water content was below the daily crop water use now of 0.29 inches. For this week, Irrigator Pro recommended irrigation almost every day in order to meet crop water use.

   
FieldNET Advisor^TM Report

• Highlights - FieldNET irrigation tool on the treatment area recommended that irrigation should start by August 8^th, 2021. There was an agreement between the irrigation recommendation between IrrigationPro and FieldNetadvisor.

Reporting Period: August 3^rd to August 9^th (Week 13 after planting)
Location: Samson, Alabama / Farm: Jim Lewey / Field: MZ4


 
Study Field – Demonstration Area - Location of Sensors


 
Weekly weather conditions

• Average Temperature: 81.6 °F
• Accumulated Rainfall: 0.00 in

 
Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation

• Average of daily crop water demand: 0.29 in/day
• Accumulated crop water demand for the week: 2.03 inches
• Total irrigation recommendation: 0.91 in on 8/5, and 1.32 in on 8/9
• Farmer irrigation was 0.5 in on 8/5
• Highlights: The farmer’s irrigation was not enough to satisfy the sensor bases recommended irrigation on 8/5. Because irrigation was behind the amount required, at the end of the week 13 after planting (8/9), recommended irrigation was 1.32 in. Applying this irrigation depth at once could impose runoff, therefore, farmer might have to split the irrigation in two events to avoid runoff.

 
Daily Changes in Soil Water - AquaSpy Sensor  

   
                                                        

• Data interpretation: soil moisture (black solid lines) represents the amount of water collected up to 48 in soil depth. For irrigation purposes, soil moisture should be kept within the green zone, and irrigation should return soil moisture to full point (field capacity). The black line of average moisture was close to field capacity, then no irrigation was required.
• Highlights: Because no rainfall occurred in the week and farmer irrigated a smaller rate (spike on the graph on 8/4) than what was recommended by the sensor, available moisture was low and is about to fall out of the green band at the end of week 13 after planting. The daily crop water uptake is represented by the step pattern (blue arrows). If weather continues on the current pattern, an irrigation recommendation will  happen within the next day.

Irrigator Pro Report

• Daily Water Use (DWU) - 0.29 in/day
• Available water content (AWC) – 0.00 in
• Highlights: Irrigator Pro shows growth stage at Pod Fill, Addition, & Maturation and development starting on 7/18 and ending on 8/18, along with irrigation recommendations this week.
• Highlights: All available tool that can be used for irrigation scheduling was recommending irrigation at the end of the week.

Reporting Period: August 3^rd to August 9th (Week 12 after planting)
Location: Auburn, Alabama / Farm: Lazenby-Harvey / Field: Location 9


 
Study Field – Demonstration Area - Location of Sensors


 
Weekly weather conditions

• Average Temperature: 78.49 °F
• Accumulated Rainfall: 0.00 in.

 
Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation


 

•  Average of daily crop water demand: 0.21 in/day
• Accumulated crop water demand for the week: 1.47 in.
• Total irrigation recommended: 0.22 in on 8/31 and 1.01 in on 8/9 to bring the soil water level back to field capacity.
• Highlights: Even though on 8/3, irrigation was being recommended 0.22 in and 1.01 on 8/9 by the Trellis sensor, the farmer did not irrigate. In this week 12, after planting, no rainfall event occurred. Hence the evapotranspiration increases significantly around 0.79 in. Because the irrigation requirement is still little, the farmer did not irrigate this week. However, there is a high chance that irrigation will be required within 2-3 days if no rainfall is observed at this field.

 
Daily Changes in Soil Water - AquaSpy Sensor

• Data interpretation: soil moisture (black solid lines) represents the amount of water collected up to 48 in soil depth. For irrigation purposes, soil moisture should be kept within the green zone, and irrigation should return soil moisture to full point (blue line) which is field capacity.
• Highlights: Available moisture was kept within the optimum soil water level (green band) during most of the week 12 after planting. This suggests that irrigation was not required yet. No irrigation was recommended during this week. If no rainfall is registered for the next 2-3 days, an irrigation will be required to prevent water deficit.

 
Irrigator Pro App Report

• Highlights: Irrigator Pro App recommended irrigation on 8/9 and reported the current growth stage as Pod Addition and Development for this location.

Reporting Period: August 3^rd to August 9^th (Week 6 after planting)
Location: Town Creek, Alabama / Farm: Posey’s Farm


 
Study Field – Demonstration Area - Location of Sensors


 
Weekly Weather Conditions

 

• Average temperature: 76 ⁰F.
• Accumulated rainfall: 0.05 in.

 
Changes in Rainfall, Evapotranspiration, Soil Water Conditions, Irrigation

• Average of daily crop water demand: 0.13 in/day
• Accumulated crop water demand for the week: 0.91 in
• Total irrigation recommendation: 0.92 in on 8/9.
• Highlights: The soybean is still in early development and daily crop water demand is low. In the beginning of the week (8/3), sensor-based irrigation recommendation was 0.3 in and it increased to 0.91 in by the end of the week (8/9). This increment in irrigation recommendation was because of neither rainfall nor irrigation occurred in this field. Crop water demand is expected to increase as plant approach peak of development.

 
Daily Changes in Volumetric Water Content – Acclima Sensor Data

• Data interpretation: soil volumetric water content is given at three soil depths 8 (red line), 16 (blue line), and 24 in (green line). The higher the volumetric water content, the higher the available water for the plants. Volumetric water content decreases due to crop water demand (step patten represented by the black arrows) and increases due to irrigation or rainfall.
• Highlight: Because plants are still in early growth development, crop water demand was only recorded at the sensor located at 8 in soil depth. This is represented by the daily step pattern in the graphic (black arrows). As plants progress towards the peak of water demand, the root system will grow deeper and crop water uptake will be also recorded by the soil sensors installed at 16 and 24 in soil depth.

 
Daily Changes in Available Moisture – AquaSpy Sensor Data

 

• Data interpretation: soil moisture (black solid lines) represents the amount of water collected up to 48 in soil depth. For irrigation purposes, soil moisture should be kept within the green zone, and irrigation should return soil moisture to full point (field capacity).
• Highlights 1: At the biggening of the week available moisture was above full point and was as available to plants. At the end of the week, however, available moisture dropped below the green zone, suggesting the irrigation should be initiated. If farmers do not irrigate, plants might experience water stress. Crop water demand is represented by the step pattern in the graphic (black arrow).

 
Soybean App Report

• Highlights 1: SmartIrrigation Cotton App was reporting 12% water deficit and a suggested irrigation of 0.39 in by the end of week 6 after planting.

Guidelines for Installation of Soil Sensors

Operation & Maintenance Problems of Center Pivot Irrigation