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United States Department of Agriculture

Agricultural Research Service

Research Project: Development of Sustainable Water Management Technologies for Humid Regions

Location: Crop Production Systems Research

2012 Annual Report

1a. Objectives (from AD-416):
Objective 1. Develop novel sensing technologies to determine crop water status and improve irrigation scheduling. Sub-objective 1.1. Implement wireless sensing systems to measure soil water content and temperature; Sub-objective 1.2. Develop a 3D plant morphometer to monitor plant morphological responses to water stress; Sub-objective 1.3. Measure water use and develop crop coefficient functions for corn and soybean for use in irrigation scheduling models; Sub-objective 1.4. Develop low-cost wireless monitoring systems for measuring soil moisture and agronomic parameters using open-source components; Sub-objective 1.5. Develop and adapt technologies for evaporation-based instruments that can be readily used by farm managers to assist in scheduling irrigation; and Sub-objective 1.6. Evaluate switchgrass water productivity in the Mid-South. Objective 2. Quantify the potential for and conditions under which site-specific irrigation and nutrient applications can address spatially varying field conditions and crop requirements. Sub-objective 2.1. Develop a method to improve surface-irrigation applications by reducing spatially varying field conditions using site-specific information; and Sub-objective 2.2. Implement a plant health sensing system and remote sensing technology for site-specific nutrient application.

1b. Approach (from AD-416):
To complete Objective 1, wireless sensor networks will be deployed and evaluated to measure soil water status for irrigation scheduling. Soil water sensors will be calibrated for predominant soils in Mississippi Delta region. A 3D plant morphometer will be developed to allow real-time, in-situ, non-destructive measurement of the morphological characteristics of bush-type plants. Field evaluation of the morphometer will be conducted and data collected will be analyzed to identify relationships between plant morphological characteristics and evaporative demand and soil moisture availability. Crop water use will be measured using electronic load cell-based weighing lysimeters. The measurements will be used to develop crop coefficient functions for corn and soybean. Low-cost wireless monitoring and control systems will be developed for measuring soil moisture and agronomic parameters. A University of Georgia (UGA) Evaporation-based Accumulator for Sprinkler-enhanced Yield (EASY) Pan will be set up in fields along with soil water sensors. The sensors and pan water levels will be read daily and composite soil water potentials will be calculated for each station. Experiments will be conducted to evaluate water productivity of the switchgrass as an energy crop. To complete Objective 2, a standard tractor 3-point quick-hitch will be modified to allow real-time control of the vertical movement of the hitch. Performance of the modified real time kinematic (RTK) global positioning system (GPS) - controlled hitch in improving surface-irrigation application will be field tested. An improved plant health sensing system equipped with multispectral and ultrasonic sensors will be designed and fabricated for diagnosing plant health conditions. Experiments will be conducted in a cotton field with water and nitrogen (N) treatments. Relationships among canopy spectral reflectance, plant height, soil moisture, leaf N, yield, and fiber quality will be examined for site-specific water and nutrient management.

3. Progress Report:
A wireless sensor network (WSN) was deployed to measure soil moisture in a research farm. The WSN included 48 sensors, 16 dataloggers, and wireless devices. The sensors were installed underground at depths of 6”, 12” and 24”. Soil moisture was measured by the sensor at one hour interval and the data were wirelessly transferred via cellular communication network onto internet so that users can access the data online. Soil moisture data were collected under various irrigation rates in fields planted to soybean, corn, and cotton. Soil temperature data were also collected along with soil moisture. Six 72”x72”x28” wood compartments were built in a greenhouse. Six different types of soil were filled in the compartments for evaluating effect of soil type on the response of soil moisture sensors. A 3D plant morphometer was designed to non-destructively measure plant morphological characteristics for diagnosing plant water stress. In the design, ultrasonic and optical sensors were combined with data acquisition system to scan plant canopy in three dimensions. A touch screen was used as an interface between the morphometer and users. Visual Basic was employed as program language for data collection and processing. Ultrasonic sensors and electronic components for development of the morphometer were purchased. A 4-span center pivot irrigation system capable of variable rate irrigation and mobile monitor/control was installed in a research farm. With this system, one experiment was completed which involved variable-rate water application and variable timing of irrigations to study water use of soybeans. Daily weather data were collected and used to estimate evapotranspiration for input to water-balance, irrigation scheduling models. Soil moisture sensors and automated datalogging equipment were installed, and moisture data were collected and monitored to evaluate water use. An evaporation pan was installed for scheduling irrigation of soybeans and modified with a fine mesh screen to limit evaporation and provide for the relatively high water holding capacity of the Dundee very fine sandy loam soil. Data obtained from both Watermark sensors and Decagon EC-5 soil moisture sensors are analyzed to provide points from which to calibrate and adjust pan sensitivity as required at various soybean growth stages. An 8-ac field was selected as experimental field for switchgrass water-use study. The field was prepared using a laser-land-leveling system for furrow irrigation practice. A pond was reconstructed for storage of catfish waste water. Equipment, including a water pump and engine, were purchased for the experiments. Experimental plots were set up for irrigation treatments, with Alamo switchgrass planted in July, 2012. A real time kinematic (RTK) global positioning system (GPS) receiver was installed on a tractor and tested for spatial accuracy. A prototype 3-point tractor hitch was designed which would allow vertical movement of a hitch-mounted implement. The hitch was designed to move vertically up and down in response to the tractor's RTK GPS signal. Hydraulic cylinders will be controlled to enable up and down movement of the implement.

4. Accomplishments
1. Wireless sensor network to monitor soil moisture. In recent years, producers in the Mid-South have become increasingly reliant on supplemental irrigation to ensure adequate yields and reduce risks of production, but very few use any irrigation scheduling aids. There is a need to provide technical tools to producers for appropriate management of irrigation in the region. Wireless sensor network (WSN) offers the capability of providing continuous, real-time, in-situ measurements under a variety of operating conditions. ARS scientists in Crop Production Systems Research Unit at Stoneville, MS, used a WSN in a cotton field to monitor soil water status for irrigation under humid conditions. Soil water data were measured and collected using the WSN. Results indicated that the soil water sensors were able to measure the soil water status, and the measurements recorded by the systems reflected general trends of soil water change during the growing season. Sensor measurements indicated that there was an effect of soil texture on available water capacity.

2. Inexpensive data loggers. Cost is one critical factor for wide adoption of new technologies in agriculture. ARS scientists in Crop Production Systems Research Unit at Stoneville, MS, designed inexpensive, automated measurement and datalogging devices using open-source hardware and software components. Approximately 150 dataloggers were fabricated and deployed to monitor soil-moisture status for crop water-use and irrigation-scheduling research projects. Devices were also designed and fabricated to monitor plant height using ultrasonic sensors and plant canopy temperature using infrared thermometer modules. Sensors and datalogging devices were installed in 13 fields to support a variety of research projects under soybeans, corn, and cotton in collaboration with researchers in ARS, Mississippi State University, Arkansas State University, and International Maize and Wheat Improvement Center (CIMMYT).

3. Plant height mapping. Cotton plant requires proper amount of nitrogen (N) for desirable growth. In conventional N management systems, N fertilizer is uniformly applied across a field. However, due to spatial variability of soil in the field, plants in some parts of the field may need more N while the plants in other parts need much less. It is desired to diagnose N status of plants in individual locations within the field and site-specifically apply appropriate amount of N that the plants need. Plant height can be used as an indicator of plant health status and yield potential. ARS scientists in Crop Production Systems Research Unit at Stoneville, MS, developed and used a plant height measurement system to map cotton plant height across a field. Plant height was measured using an ultrasonic sensor to scan plant canopy while spatial information was collected by the system from a global positioning system (GPS) receiver. A plant height map of the field was created. The variation of plant height could be easily identified on the map, and it compared favorably to visible field conditions. Plant height and cotton yield had a fairly close relationship. Irrigation had significant effect on plant height, leaf-blade N content, and yield. When cotton plant was not under N stress, correlation between leaf-blade N content and plant height was very weak. On-the-go measurement and mapping of plant height could be a useful tool in diagnosis of plant growth conditions and decision making for site-specific crop management.

Last Modified: 06/22/2017
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