R. Troy Peters

Automatic irrigation scheduling of apple trees using theoretical crop water stress index with an innovative dynamic threshold

We developed an irrigation algorithm relying on a theoretical stress index (i.e. CWSI).A new, variable threshold for the CWSI was developed.Irrigation water was automatically delivered to the plots of apple trees.There was a high correlation between midday CWSI and stem water potential.The algorithm avoided over irrigation on humid, cool, and overcast days. An adaptive scheduling algorithm relying on a theoretical crop water stress index (CWSI) was developed to automatically irrigate apple trees. Unlike the traditional CWSI algorithm where the threshold is a constant value, in the present approach the threshold is dynamically determined by following the CWSI trend. A previous work on the energy budget analysis of a single apple leaf provided the base for calculating lower and upper boundaries of CWSI. To test the feasibility of the algorithm, it was applied to the thermal and meteorological data collected during the 2007 and 2008 growing seasons. A computer-based wireless control system was also developed to automatically schedule irrigations in three plots of apple trees in the 2013 growing season. In a small scale field experiment, two treatments were compared: (1) automatic irrigation using the new algorithm (CWSI-DT) and (2) irrigation scheduling based on weekly readings of neutron probe (NP). The soil water deficit under the CWSI-DT treatment was maintained within the well-watered range with no signs of over or under irrigation. This was better than the results in the NP treatment where there were occasions of under irrigation. Midday canopy and air temperature difference ( Δ T m ) exhibited a close agreement with midday stem water potential ( Ψ stem ; R2=0.63, p < 0.01 ). Normalizing Δ T m in the form of CWSI resulted in a much higher correlation between midday CWSI and midday Ψ stem (R2=0.91, p < 0.0001 ) suggesting CWSI as a reliable indicator of apple trees water status. The automatic control system running the new CWSI-DT algorithm was able to avoid over-irrigation under humid and cool weather conditions, and adapted itself to the changing conditions of the apple trees. The results of this study were promising in terms of using ground-based thermal sensing for automatic irrigation scheduling of sparse, discontinuous apple trees.

Design of Zero Slope Microirrigation Laterals: Effect of the Friction Factor Variation

AbstractMicroirrigation has become quite a common practice in agricultural production in various parts of the world. To achieve the optimum (hydraulic and economic) system performance, designers are often faced with the problem of designing a maximum lateral length which results in a desired coefficient of uniformity (CU) or an allowable pressure head variation (δH). Previous theoretical design approaches are usually based on a constant Darcy–Weisbach (DW) friction factor along the lateral and this assumption can lead to substantial errors. In the research reported in this paper, a new analytical design approach does not require the constant DW assumption for zero-slope laterals while it still takes into account the emitter exponent and the effect of minor friction losses caused by emitters. Assuming a constant friction factor along the lateral might result in errors up to 14% in the calculation of the maximum lateral length. Conversely, the maximum relative error caused by the application of the proposed...

Complete Center Pivot Automation Using the Temperature-Time Threshold Method of Irrigation Scheduling.

It has been shown that the temperature-time threshold (TTT) method of automatic irrigation scheduling is a viable alternative to traditional soil water based irrigation scheduling in the Southern High Plains. The TTT method involves using infrared thermocouples (IRTCs) to remotely examine crop canopy temperatures over the course of a day. If a threshold canopy temperature is exceeded for a predetermined threshold time an irrigation event is scheduled. Applying this method using IRTCs mounted on self propelled irrigation systems such as center pivots or linear moves presents special challenges. First, it necessitates a method of estimating the diurnal canopy temperature dynamics using only a one-time-of-day canopy temperature measurement. Secondly, it requires a method of automatically collecting and analyzing the canopy temperature data and controlling the moving irrigation system based on the data analysis. A method of determining the diurnal canopy temperature curve using a one-time-of-day temperature measurement and a reference temperature curve was developed. The mean absolute error from calculated to observed was approximately 0.5° C from 0800 h to 2200 h. An array of 16 IRTCs were connected to a datalogger and mounted on a three tower center pivot. A separate array of IRTCs was located in stationary positions in the field and also connected to a datalogger. Two different spread spectrum (900 MHz) radios were connected to a desktop computer located nearby that queried both dataloggers, and got pivot status information and send commands to the center pivot control panel. Using scheduled data collection intervals, this computer was able to collect the data, analyze it, determine need for an irrigation event, and issue control commands thus completely automating the center pivot.

Evaluation of yield quantity and quality of two oil crops in the promotion of sustained deficit irrigation in the Pacific Northwest, USA

Agriculture, as the main user of available fresh water in the Pacific Northwest, faces persistent pressure to be efficient. The intent is to maximize the water use efficiency of crops by minimizing the amount of water used for production by reducing irrigation levels and minimizing water losses. This study evaluated the impacts of reduced, sustained deficit irrigation water management on two specialty oil crops, mint and canola. The study evaluated the yield parameters of native spearmint (Mentha Spicata) and two varieties of canola (Rapier and Athena) over two seasons for the impact of sustained deficit irrigation on the quantity and quality of yields and yield characteristics. Sustained deficit irrigation is shown to be adaptable to water constraints for canola and spearmint with potentials to stabilize farm returns by potentially raising the unit price of the oils and byproducts. With this scenario increased price offers, due to improved quality coupled with production cost savings would create a production niche to sustain the Pacific Northwest spearmint and canola farming systems.

Economical thermal-RGB imaging system for monitoring agricultural crops

Developed was an imagery-based crop monitoring system integrating thermal and RGB imaging modules.Developed were custom image-processing algorithms to calculate canopy coverage and sunlit leaves surface temperature.Imagers were field tested successfully on modified pivot systems irrigating mint crop. In this study, a low-cost thermal-RGB imager was developed for use in agricultural crop monitoring applications. It is weatherproof, and has a geo-referencing capability along with a power management panel that allows unattended field deployment of the systems for crop monitoring over extended period of time. The imager is made up of single-board Linux-based computer integrated with RGB and thermal imaging modules. The imager can be configured as FTP server to allow data transfer to/from a client computer. Developed was also the custom image-processing algorithm which overlays, aligns thermal and RGB images, and mask for the thermal image to remove the soil background and shaded leaves. The algorithm outputs are the average temperature of sunlit leaves and canopy coverage. Prior to field validation, the performance of ten thermal modules and four fully assembled RGB-thermal imagers were assessed under laboratory conditions. In the spring of 2017, two imagers were mounted on a center pivot retrofitted with Medium Elevation Spray Application (MESA) and Low Elevation Spray Application (LESA) systems in a mint field near Toppenish, WA. The thermal modules showed an accuracy of 2.4C on average over a range of 050C of a blackbody target. Although accurate for larger canopies, the imperfect alignment of RGB and thermal images introduced significant errors in the calculations of sunlit leaves surface temperature in images with small canopy coverage. Further investigations revealed that the first peak of thermal image relative frequency histogram could be a more accurate representative of sunlit leaf surface temperature. Overall, the amended image-processing algorithm was able to successfully extract canopy surface temperature and percent canopy cover from a wide range of images captured during the crop growing season. The current design of imager allows for creating a network of imaging units in the field to obtain real-time surface temperature data from plant canopies. The system has the potential to be used for creating evapotranspiration and prescription maps in real-time, and irrigation scheduling.

Advancing Water Use Efficiency in Vineyards with Sub-surface Micro-irrigation Techniques

Abstract. This poster presentation describes methods employed to increase water use efficiency in grapevines via micro-irrigation delivered sub-surface at depths ranging from 30 – 120 cm. The irrigation delivery system uses 1.27 cm (id) diameter PVC tubes inserted vertically into pre-drilled holes placed 45 cm either side of the vine trunk and in line with the dripline. A barbed connector with attached 15 cm length of 0.63 cm diameter tubing attached to a fixed rate drip emitter (2 L/hr) beneath a center drilled PVC cap secures the system in place and prevents exposure of the dripper to either atmosphere or soil. Plant root growth in response to wetting zone is quantified by periodic digital photography via a clear hard acrylic mini-rhizotron and camera system controlled by a laptop computer. Plant water stress is monitored by pressure bomb and auto-porometer, and compared to digital imagery obtained from a thermal sensing camera mounted on an unmanned aerial vehicle (UAV). While this technique is currently being used only for research to quantify physiological responses of the vine and its root system, its potential use in mature vineyards may permit more water efficient irrigation while reducing weeds and disease issues, as well as avoiding root pruning during installation and lessening problems from burrowing rodents impacting buried lines or clogging of emitters from contact with the soil. Published results are anticipated by 2017.

Subsurface Drip Irrigation: Status of the Technology in 2010 Freddie

Subsurface drip irrigation (SDI) although a much smaller fraction of the microirrigated land area than surface drip irrigation is growing at a much faster rate, and is the subject of considerable research and educational efforts in the United States. This paper will discuss the growth in SDI, highlight some of the research and extension efforts, and point out some of the challenges to SDI adoption and some of the future opportunities for SDI.

An Artificial Dry Reference Surface for Predicting Canopy Temperature Dynamics from a Moving Irrigation System

Elevated crop canopy temperatures are a useful indicator of water stress. Single-time-of-day canopy temperatures of large field areas can be detected by infrared thermometers (IRTs) mounted on center pivots or lateral move irrigation systems. Determining canopy temperatures at other times of day from these measurements requires a method of estimating diurnal canopy temperature dynamics due to changing environmental conditions from a one time-of-day measurement. This has been shown to be possible by using canopy temperature dynamics measured with an IRT in a stationary reference location in another part of the field to scale the one time-of-day measurement. It has also been shown that the water stress condition of the reference location has little effect on the errors of the predicted canopy temperatures. It would simplify instrumentation and programming if the reference temperature dynamics could be collected from a location other than the field, such as on the moving irrigation system itself. An artificial dry reference surface was tested to determine whether it could be used as the reference surface to capture the canopy temperature dynamics. The surface consisted of a large artificial plant leaf, cut to fit and mounted in a cross-stitch hoop. This was located in a stationary position next to the field being studied. The temperatures of the artificial reference surface were measured with IRTs mounted both above and below it. Canopy temperature dynamics predicted from one time-of-day measurements using the artificial dry reference surface were compared to those predicted using living and transpiring canopy temperature measurements in a stationary location in the field. The absolute mean errors of the predicted diurnal curve from the actual measured curves were compared. The errors when using the artificial dry reference surface were significantly worse than those of the living crop. These errors were possibly due to the fact that the artificial dry reference surface was not located amongst the living canopy. Future experiments need to be done with the artificial dry reference surface located on the moving irrigation system but near or amongst the living canopy.

Mechanized Irrigation System Positioning Using Two Inexpensive GPS Receivers

Precision irrigation or chemigation using mechanized irrigation systems such as center pivots or lateral moves requires accurate and real-time knowledge of the irrigation systems field location. A GPS receiver mounted on a center pivot or lateral move has the potential to increase the accuracy of these position estimates. Differentially corrected GPS receivers have become more affordable (less than

Automation of a Center Pivot Using the Temperature-Time- Threshold Method of Irrigation Scheduling

200 US) and it has become more feasible to use them for reporting field position of mechanized irrigation systems. Although these low-cost differentially corrected receivers have been shown to have accuracies of 95% less than 2.1 meters in previous experiments in the panhandle of Texas, the remaining 5% of the reported points gave errors greater than 6 meters. These errors are large enough to present problems for site-specific irrigation. It was hypothesized that the errors from an additional GPS receiver in a known, stationary location could be used to correct the positioning estimates of the receiver mounted on a moving irrigation system and thereby improve the accuracy sufficiently for use with precision irrigation or chemigation. This was tested by placing two similar low-cost receivers in stationary locations and correlating the errors in the North- South and East-West directions. The r2 values of the linear regression lines were very small, showing that almost no correlation existed between the errors of these two receivers. This demonstrated that the integration of an additional, stationary low-cost GPS receiver will not significantly improve positioning estimates of GPS receivers mounted on moving irrigation systems.