Rodrigo S. Zandonadi

Reducing Pesticide Over-Application with Map-Based Automatic Boom Section Control on Agricultural Sprayers

The use of precision agriculture technologies such as automatic guidance and map-based automatic boom section control on agricultural sprayers has increased substantially over the past few years. The purpose of these systems is to decrease pesticide application inaccuracy by reducing pass-to-pass overlaps or by turning boom sections off when the boom passes over previously covered areas or beyond field boundaries. The objectives of this study were to compare areas treated by a sprayer before and after the addition of an automatic boom section control system and determine if there was a relationship between field shape factors, specifically perimeter-to-area (P/A) ratio, and pesticide over-application. Coverage files were downloaded from a self-propelled agricultural sprayer with a 24.8 m boom divided into five manually controlled sections. Prior to the subsequent cropping season, automatic boom section control (seven sections) was installed on the sprayer. Application inaccuracy was calculated for the 21 study fields by comparing the actual sprayed area (based on boom section control state: on/off) versus the total projected field area. A comparison between the average percent over-application from fields during season one (12.4%) and season two (6.2%) revealed a significant reduction in off-target application. This reduction represents savings to agricultural producers, potentially justifying the purchase and implementation of this technology. Further analysis indicated an increasing trend in over-application for manual and automatic boom section control as the P/A ratio increased for the study fields. Over-application increased at a greater rate with manual boom section control, which suggests that as field inclusions (grassed waterways or other obstacles) increase, automatic boom section control will provide a greater opportunity for producers to reduce these errors.

A Computational Tool for Estimating Off-Target Application Areas in Agricultural Fields

A computational method for estimating off-target application areas based on the machine-controlled section width and the field shape was developed and implemented in software with a graphical user interface written in the MatLab environment. The program, which is called the Field Coverage Analysis Tool (FieldCAT), includes three modules: data import, data preparation, and coverage analysis. Nine field boundaries were evaluated to test the software using controlled section widths from 0.5 to 27 m and various swath orientations. The estimated off-target application area from the widest section width varied from 9% to 24% depending on the shape and size of the field boundary and was reduced to less than 1% with the smallest section width. The simulated results were also compared to actual field data from 25 different fields. The FieldCAT software tool was able to provide reliable quantitative estimates of the off-target application of inputs that would occur because of limited resolution of the machine-controlled section width and the path orientation in different field shapes.

A Case Study to Evaluate Field Shape Factors for Estimating Overlap Errors with Manual and Automatic Section Control

Understanding how field shape and size may affect overlap errors during spraying operations would provide producers with better information on how to improve field operations and cut costs. The goal of this study was to evaluate field shape factors through single-variable and multivariate regression analyses for predicting overlap from a manual section control (MSC) and two automatic section control (ASC) systems. Actual field coverage data collected from three self-propelled agricultural sprayers with boom widths of 24.8 m were used in the analysis. Results of statistical analyses indicated that significant relationships existed between over-application error and multiple field shape factors. The strongest single-variable relationship existed between field perimeter-to-area ratio (P/A) and the overlap error (% of field area) for the MSC and seven- and nine-section ASC systems, with model standard errors of 4.95%, 1.45%, and 0.81%, respectively. Multivariate regression yielded strong relationships with different combinations of field shape factors and overlap error; however, multivariate models did not result in a vast improvement over the single-variable model using P/A. Errors increased at a greater rate with MSC, which suggested that as field inclusions (e.g., grassed waterways) increase, or the field boundary becomes more complex, overlap error reduction may be reduced with ASC. As expected, nine-section ASC resulted in reduced overlap errors compared to the seven-section system as P/A increased. Comparing models for the ASC systems indicated that the reduction in overlap application may not significantly improve when adding two additional control sections for fields with low P/A values (<0.0175).

Estimating off-rate pesticide application errors resulting from agricultural sprayer turning movements

Pesticide application is an essential practice on many U.S. crop farms. Off-rate pesticide application errors may result from velocity differential across the spray boom while turning, pressure fluctuations across the spray boom, or changes in boom-to-canopy height due to undulating terrain. The sprayer path co-ordinates and the status (on or off) of each boom control section were recorded using the sprayer control console which provided map-based automatic boom section control. These data were collected for ten fields of varying shapes and sizes located in central Kentucky. In order to estimate potential errors resulting from sprayer turning movements, a method was developed to compare the differences in application areas between spray boom control sections. The area covered by the center boom control section was considered the “target rate area” and the difference in these areas and the areas covered by remaining control sections were compared to estimate application rate errors. The results of this analysis conducted with sprayer application files collected from ten fields, many containing impassable grassed waterways, indicated that a substantial portion of the fields (6.5–23.8%) could have received application in error by more than ±10% of the target rate. Off-rate application errors exceeding ±10% of the target rate for the study fields tended to increase as the average turning angles increased. The implication of this is that producers may be unintentionally applying at off-label rates in fields of varying shapes and sizes where turning movements are required.

Standardized Evaluation of Dynamic GPS Performance

Efforts are currently underway through ISO to develop a new standard for testing and reporting the dynamic performance of Global Navigation Satellite System (GNSS) receivers. This paper describes the current status of that dynamic test standard, describes how GNSS receivers would be tested under the current version of the standard, and offers some example test data. Discussions show that the standard will provide a clearer understanding of receiver performance in dynamic agricultural settings. Example tests have revealed that there are still some shortcomings that will have to be addressed by developers of the standard.

Laboratory Performance of a Low Cost Mass Flow Sensor for Combines

Yield mapping technology is considerably well established for grain combines, but not as readily available other harvesting machinery; therefore, researchers have been developing systems to map crops other than grain. Moreover, cost effective alternatives of mapping systems are desired for lower cost harvesting machines such as the pull type dry edible bean harvester. Previous studies have presented low cost alternative for measuring torque on a drive chain driven shaft. This concept of drive torque measurement was implemented on a clean grain bucket elevator of a dry bean harvester, and evaluated as mass flow sensor. Tests were conducted in the Yield Monitor Test Facility (YMTF) of University of Kentucky following the recommendation of ASABE Standard S578. Device was tested within the flow rate range of 0 to 3.4 kg·s-1. At two standard deviation level, the deviation at 3.3 kg·s-1 was ± 4.2% and the deviation at 1.6 kg·s-1 was ± 4%. The average accumulated mass errors were less than 3.1% and the maximum accumulated error was 4.9% at a flow rate of 1.8 kg·s-1.

Laboratory Performance of a Mass Flow Sensor for Dry Edible Bean Harvesters

Due to the importance of yield monitoring, researchers have been developing systems for crops such as tomatoes, forage, sugar cane, citrus, and coffee. A yield monitoring system for pull type dry edible beans harvester has not yet been developed. The goal of this project was to design and test a drive torque measurement device on a clean grain bucket elevator of a dry bean harvester, and evaluate its potential to be used as a mass flow sensor. Tests were conducted in the Yield Monitor Test Facility (YMTF) of University of Kentucky following the recommendation of ASABE Standard S578 (2007) The device was tested within the flow rate range of 0 to 3.4 kg/s. The largest flow rate errors were ±4.2% at 3.3 kg/s and ±4% at 1.6 kg/s. The average accumulated mass errors of the sensor were less than 3.1% and the maximum accumulated error was 4.9% at a flow rate of 1.8 kg/s.

Dynamic GNSS Testing and Applications

Satellite-based global navigation systems are a ubiquitous component in modern guidance systems. Automated guidance in agricultural vehicles is a prime example of how Global Navigation Satellite System (GNSS) receivers can be applied to operations requiring a level or precision, or consistency, which may otherwise be unobtainable. This paper discusses efforts at the University of Kentucky to adopt as well as promote the integration of the ISO/WD 12188-1 standard on dynamic testing of satellite based positioning devices used in agriculture with a focus on how data are acquired and processed. A procedure for data acquisition and analysis has been documented to show the uses as well as some of the difficulties involved with testing GNSS devices. Initial results are encouraging for the use of a Tracking Total Station (TTS) as a non-satellite reference given proper application and calibration methods.

Development of GIS-Based Chemical Distribution Maps from Sprayer Performance Data

Pesticide application is an essential practice on farms in Kentucky where glyphosate resistant crops and no-till farming strategies are becoming more popular. Off-rate pesticide application errors are the result of incorrect concentrations applied to an area of the field and may result from velocity changes along the spray boom while the sprayer is turning, pressure changes across the width of the spray boom, and changes in effective boom height due to undulating terrain. In an attempt to estimate potential errors resulting from sprayer turning movements, a method was developed to compare the differences in application areas between control sections across the spray boom. The area covered by the two center boom control section positions was considered the “target rate” and the difference in these areas and the remaining control sections were compared to determine errors in coverage areas. The results of the analysis conducted on three irregular shaped fields (containing impassable grassed waterways) indicated that a substantial portion of the fields (14-24%) could have been applied well above or below the target application rate +/- 10%. The implication of this is that producers may be under and over applying chemicals to fields where excessive amounts of turning are required during application.

Software Tool for Estimating Overlapped Areas in Agricultural Field Operations

A computational method for estimating overlapped area based on the implement controlled section width was developed and implemented in software with a graphical user interface written in Matlab. The program was divided in three modules: data import, data preparation, and coverage simulation. Nine field boundaries between 9 and 40 ha were evaluated in order to test the software using controlled section widths from 0.5 m to 27m. The estimated overlapped area varied from 9 to 24 % depending on the field shape boundary. The results indicated that overlapped areas varied linearly according to controlled section width. The developed analytical tool was able to provide quantitative estimate of the double coverage of inputs that would occur because of limited resolution of machine section control width and path orientation on different field shapes.