Francis J. Pierce

Performance Assessment of Wireless Sensor Networks in Agricultural Settings

Wireless Sensor Network (WSN) utilizes radios operating primarily in the 900 MHz and 2.4 GHz frequency bands. In general, as frequency increases, bandwidth increases allowing for higher data rates but power requirements are also higher and transmission distance is considerably shorter. In general, depending on the operating environment, significant signal loss can occur at these frequencies particularly when the radios require line-of-sight for optimal performance, with 2.4 GHz more susceptible than 900 MHz. For agricultural applications, WSN must be able to operate in a range of environments, from bare fields to orchards, from flat to complex topography, and over a range of weather conditions, all of which affect radio performance. However, there are limited data on radio performance as affected by agricultural setting and no standard tests are available for quantifying WSN performance in agricultural applications. Using a low powered, 10 mW 900 MHz frequency hopping spread spectrum radio, we developed a range of tests intended to quantify the performance of agricultural WSN in fields, vineyards, and orchards over a range of crop and weather conditions. Performance data include different metrics of radio performance such as packet delivery and signal strength along with power consumption tests under different supply strategies. This paper evaluates the extent to which various tests can be used to quantify WSN performance and how WSN perform under various cropping systems.

Instrumentation and Control for Wireless Sensor Network for Automated Irrigation

An in-field sensor-based irrigation system is of benefit to producers in efficient water management. A distributed wireless sensor network eliminates difficulties to wire sensor stations across the field and reduces maintenance cost. Implementing wireless sensor-based irrigation system is challenging on seamless integration of sensing, control, and data communication. An automated sensor-based irrigation system was developed for an integrated wireless in-field sensor network and automated variable rate irrigation. Field conditions were real-time monitored sitespecifically by in-field sensor stations distributed across the field. Each sensor station measured soil moisture, soil temperature, and air temperature, while one weather station recorded precipitation, wind speed and direction, air temperature, relative humidity, and solar radiation. Sensors and a data logger were self-powered by a solar panel and sensory data was periodically sampled and wirelessly transmitted to a base station about 700 m away from the sensor stations. A host computer received and real-time displayed field data without interference. This paper describes details of the design and construction of wireless communication, hardware used, and the costs and benefits of the control system.

A Remote Irrigation Monitoring and Control System for continuous move systems. Part A: description and development

Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology that performed well for on-site control but were very expensive to add remote, real-time monitoring and control aspects that have been made possible by wireless sensor networks and the Internet. A new approach to the monitoring and control of continuous move irrigation systems is described. This system uses a Single Board Computer (SBC) using the Linux operating system to control solenoids connected to individual or groups of nozzles based on prescribed application maps. The main control box houses the SBC connected to a sensor network radio, a GPS (Global Positioning System) unit, and an Ethernet radio creating a wireless connection to a remote server. A C-software control program resides on the SBC to control the on/off time for each nozzle group using a “time on” application map developed remotely. The SBC also interfaces with the sensor network radio to record measurements from sensors on the irrigation system and in the field that monitor performance and soil and crop conditions. The SBC automatically populates a remote database on the server in real time and provides software applications to monitor and control the irrigation system through the Internet.

Spatial analysis of soybean yield in relation to soil texture, soil fertility and soybean cyst nematode

The objective of this work was to study the spatial distribution of the soybean cyst nematode (SCN), Heterodera glycines Ichinohe, in relation to soil fertility (pH, P+, K+, Ca2+, Mg2+ ), and soybean yield spatial patterns in relation to SCN, soil texture and soil fertility. SCN was positively cross-correlated with soil pH within a range of 60-130 m, and negatively cross-correlated with Ca2+ up to a range of 110 m in Field B; the correlation was weaker in Field A. Yield was negatively correlated with SCN. Yield was strongly cross-correlated with soil texture (r(sand)= –0.89, r(clay) = 0.84), soil pH (r = –0.60), and Ca2+ (r = 0.60) in Field B (range = 130-140 m). We conclude that management zone delineation would be an appropriate strategy to overcome yield losses in fields where soil properties and SCN densities appear spatially structured and where SCN and unfavourable soil conditions pose a strong influence on yield spatial variability.

Automation: The Future of Weed Control in Cropping Systems

Technology is rapidly advancing in all areas of society, including agriculture. In both conventional and organic systems, there is a need to apply technology beyond our current approach to improve the efficiency and economics of management. Weeds, in particular, have been part of cropping systems for centuries often being ranked as the number one production cost. Now, public demand for a sustainably grown product has created economic incentives for producers to improve their practices, yet the development of advanced weed control tools beyond biotech has lagged behind. An opportunity has been created for engineers and weed scientists to pool their knowledge and work together to fill the gap in managing weeds in crops. Never before has there been such pressure to produce more with less in order to sustain our economies and environments. This book is the first to provide a radically new approach to weed management that could change cropping systems both now and in the future.

Software Design for Wireless In-field Sensor-based Irrigation Management

A wireless in-field sensor-based irrigation management system is of benefit to producers in efficient water management, but implementing sensor-based irrigation control and monitoring is challenging in sensor fusion and data interface. Wireless in-field sensing and control software was developed for user-friendly interface of an integrated wireless in-field sensor network and automated variable rate irrigation. In-field sensory data was periodically sampled and remotely transmitted to a computer. Variable rate irrigation was controlled by the computer that reads information about field condition and GPS positions of sprinklers and transmits control signals to an irrigation controller via real-time wireless communication. This paper describes details of the software design using graphic user interface for wireless control and monitoring of a variable rate irrigation system.

The relationship between soybean cyst nematode seasonal population dynamics and soil texture

The soybean cyst nematode (SCN), Heterodera glycines Ichinohe, cyst population densities at planting and at harvest have been related to soil texture but the seasonal mechanisms by which these correlations are established are less well known. The purpose of this work was to analyse the relationship of SCN life stages and reproductive potential (number of eggs per cyst) with soil texture. Cyst population density was positively correlated with sand and negatively correlated with clay and silt percentage in the soil within the ranges of 45-80% sand, 8-23% clay, and 8-43% silt in one field, but not in the other at five sampling times. The relationship between soil texture and juvenile stages in roots was weak. The stable relationship between SCN spatial and seasonal population dynamics and soil properties provides further support for potential delineation of management zones in SCN infested fields with a wide range of soil textures.

Compensating inherent linear move water application errors using a variable rate irrigation system

Continuous move irrigation systems such as linear move and center pivot irrigate unevenly when applying conventional uniform water rates due to the towers/motors stop/advance pattern. The effect of the gear drive/cart movement pattern on linear move water application is larger on the first two spans, which introduces errors on site-specific irrigation. Therefore, the objectives of this study were to model the linear move irrigation system cart movement and to develop an algorithm to compensate for unintended variable irrigation (application errors). The cart advance/movement modeling considered terrain attributes, average nozzle travel speed, and high frequency DGPS (differential global positioning system) cart positioning readings. This paper describes the use of an irrigation monitoring and control system, DGPS, GIS, and statistical analysis utilized in the modeling and compensation processes. The irrigation monitoring and control system was composed of a single board computer, a relay board controller, DGPS, electric solenoid valves, wireless ethernet bridge units, high frequency spread spectrum radios, as well as in-line and in-field sensor networks. This technology allowed for continuous, real-time data acquisition and irrigation system management through the internet. This study has shown that irrigation application errors were reduced from over 20% to around 5%, in the subsequent irrigation event.

A Remote-Real-Time Continuous Move Irrigation Control and Monitoring System

Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology that did a good job of on-site control but were expensive to add remote, real-time monitoring and control aspects made possible by wireless sensor networks and the Internet. A new approach to control and monitoring continuous move irrigation systems is described. This system uses a Single Board Computer (SBC) using the Linux operating system to control solenoids connected to individual or groups of nozzles based on prescribed application maps. The main control box houses the SBC connected to a sensor network radio, a GPS unit, and an Ethernet radio creating a wireless connection to a remote server. A C-software control program resides on the SBC to control the on/off time for each nozzle group using a “time on” application map developed remotely. The SBC also interfaces with the sensor network radio to record sensors on the irrigation system monitoring performance and in the field monitoring irrigation soil and crop conditions. The SBC automatically populates a remote data base on a server in real time and provides software applications to monitor and control the irrigation system from the Internet.

Evaluation of Wireless Control for Variable Rate Irrigation

Development of a variable rate irrigation control system allows producers to maximize water efficiency, while minimizing the effects on their productivity. This research evaluated the performance of an irrigation system for variable rate water application with real-time wireless control and monitoring. A self-propelled linear sprinkler system with a program logic controller (PLC) was wirelessly interfaced with a base computer located 700 m away by using Bluetooth radio modules. GUI-based user-friendly software was developed to receive GPS locations of the irrigation cart and send control signals to sprinklers every second either automatically or manually. The base computer received geo-referenced positional information of the irrigation cart from a differential global positioning system (DGPS) and sent control signals to execute 30 solenoid valves via real-time wireless communication. Individual control for all 30 sprinkler nozzle banks was identified and the performance of the four selected banks was quantified with measurement of water collected by catch cans that were uniformly distributed on soil surface across the field. Catch can readings compared to irrigation amount showed about 200 ml difference of water between two irrigation patterns and no significant transition differences on both GPS-based automatic and GUI-based user’s irrigation controls at wind speed of 9-20 km/h. The benefit of the real-time wireless irrigation system will extend to a closed-loop control for automated irrigation system with in-field sensing feedback of plant and soil conditions.