Christian J. Brodbeck

Real-Time Pressure and Flow Dynamics Due to Boom Section and Individual Nozzle Control on Agricultural Sprayers

Most modern spray controllers when coupled with a differential global positioning system (DGPS) receiver can provide automatic section or swath (boom section or nozzle) control capabilities that minimize overlap and application into undesirable areas. This technology can improve application accuracy of pesticides and fertilizers, thereby reducing the number of inputs while promoting environmental stewardship. However, dynamic system response for sprayer boom operation, which includes cycling or using auto-swath technology, has not been investigated. Therefore, a study was conducted to develop a methodology and subsequently perform experiments to evaluate tip pressure and system flow variations on a typical agricultural sprayer equipped with a controller that provided both boom section and nozzle control. To quantify flow dynamics during boom section or nozzle control, a testing protocol was established that included three simulation patterns under both flow compensation and no-compensation modes achieved via the spray controller. Overall system flow rate and nozzle tip pressure at ten boom locations were recorded and analyzed to quantify pressure and flow variations. Results indicated that the test methodology generated sufficient data to analyze nozzle tip pressure and system flow rate changes. The tip pressure for the compensated section control tests varied between 6.7% and 20.0%, which equated to an increase of 3.7% to 10.6% in tip flow rate. The pressure stabilization time when turning boom sections and nozzles off approached 25.2 s but only approached 15.6 s when turning them back on for the flow compensation tests. Although extended periods were required for the tip pressure to stabilize, the system flow rate typically stabilized in less than 7 s. The tip flow rate was consistently higher (up to 10.6%) than the target flow rate, indicating that system flow did not truly represent tip flow during section control. The no-compensation tests exhibited tip pressure increases up to 35.7% during boom and nozzle control, which equated to an 18.2% increase in tip flow. Therefore, flow compensation over no-compensation had better control of tip flow rate. A consistent difference existed in dynamic pressure response between boom section and nozzle control. Increased tip pressure and delayed pressure stabilization times indicated that application variability can occur when manually turning sections on and off or implementing auto-swath technology, but further testing is needed to better understand the effect on application accuracy of agricultural sprayers.

Spatially Monitoring Tractor Performance to Evaluate Energy Requirements of Variable Depth Tillage and Implement Selection

Recent rises in fuel costs have started to impact the bottom line for farm managers, making them consider possible methods to achieve energy savings. Conventional subsoiling can be performed deeper than necessary to alleviate compaction layers. However, site-specific subsoiling permits a subsoiler to be operated at the depth necessary to impale the compaction layer thus, reducing draft forces while also saving fuel. The overall goal of this study was to develop a mobile data acquisition system to monitor equipment performance parameters in real-time to assess and quantify energy requirements for site-specific tillage. A data acquisition system was developed to collect and monitor slip, fuel consumption, axle torque, and draft load data on two site-specific tillage experiments. Results indicated a 54% reduction in draft forces and a 17% reduction in fuel consumption occurred with a shallow depth (9 in.) compared to a deep depth (14 in.). The three

Evaluation of GPS Autoguidance Systems over Varying Time Periods

Autoguidance systems are becoming more popular to Alabama farmers for use in their cropping systems. Reported accuracies of available systems can be different from what the equipment operator experiences in the field. Absolute accuracy of any autoguidance system over a long period of time, such as from season to season, is desirable especially when implementing management strategies such as controlled traffic. The objective of this study was to assess different auto-guidance systems, using from WAAS to RTK differential correction, over various time periods. A non-GPS-based surveying practice was used to establish the absolute equipment traverse during testing. This information was then used to compute path deviations from the desired traverse. Average cross-track error and pass-to-pass error were consistent with manufacturers’ recommendations for the overall study; however, the drive paths deviated from the initial AB line established throughout the study, as represented by the range of cross-track error or pass-to-pass error values. Average RTK cross-track error illustrated a deviation of ±10 cm from the initial AB line over the 15 week testing period. Average SF2 cross-track error was 34 cm with a maximum path deviation of 0.6 m. SF1 average cross-track error was 40 cm with a maximum deviation of 1.4 m, and WAAS cross-track error averaged 24 cm with a maximum deviation of 0.6 m.

Modeling sediment transport from an off-road vehicle trail stream crossing using WEPP model

There is a limited information available pertaining to the adverse effects of Off-Road- Vehicle (ORV) use and trail impacts. As a result, this study was initiated in 2003 to (a) quantify water quality impacts of an ORV trail stream crossing through monitoring of total suspended solids, and (b) conduct WEPP (Water Erosion Prediction Project) simulations to determine longterm sediment loads contributed by the ORV trail stream crossing. To collect suspended sediment samples from the ORV trail stream crossing, ISCO6 6700 water samplers were installed. Data was collected from November 2003 through July 2004. During this time suspended sediment samples were collected for three different operational conditions (open, closed, maintenance). When the study began the trail was open to traffic. The trail was then closed to traffic on January 1, 2004 and went through a two-week maintenance regime in early March. The trail was then opened to ORV traffic on April 1, 2004. The largest suspended sediment load contributed by the stream crossing during this study occurred during the trail closed condition. This storm event had a recorded rainfall of 49 mm, and contributed a suspended sediment load of 109 kg. Since there were no storm events sampled with return intervals of more than one year, the WEPP model was used to estimate the potential long term effects of ORV trail stream crossing. A thirty-year synthetic weather data (generated by CLIGEN) was used to predict sediment yield from the ORV trail stream crossing. The WEPP model suggested that average annual sediment load from the stream crossing is about 126.8 tons/ha, which is much higher than what is allowed by the USDA Forest Service-National Forests in Alabama for temporary roads. The model also suggested that most of the sediment load to the stream is contributed by a steep hillslope section that flows directly to the stream. Hence the modeling study suggests that a BMP needs to be implemented to control sediment loss from ORV trail section that contributes sediment directly to the stream. In addition, the ORV trail stream crossing should be located on as flat a slope as possible.

Gasification of Wood Chips, Agricultural Residues, and Waste in a Commercial Downdraft Gasifier

In this study, gasification of different biomass feedstocks, including pine wood chips, sawdust, peanut hulls, and poultry litter (the latter three in pelletized form), was conducted in a 25 kWe commercially available, mobile downdraft gasifier. Ultimate and proximate analyses were carried out to characterize the biomass feedstocks used for gasification. The synthesis gas obtained from different feedstocks and different operating conditions (biomass flow rate and moisture content) was analyzed using an on-site gas analyzer. Gasification of peanut hull pellets showed the highest heating value (6.1 MJ per normal cubic meter, Nm-3) of synthesis gas, whereas poultry litter gasification gave the lowest heating value (4.8 MJ Nm-3).

Real-Time Pressure and Flow Response for Swath Control Technology

Auto-swath technology is being readily adopted by producers across the US because it can improve in-field equipment efficiency and reduce input usage leading to economic savings. Spray controllers with swath control use GPS to track of areas where inputs have already been applied and areas identified to receive no inputs. However, concerns exist for liquid applicators equipped with auto-swath technology about the system response when shutting ON/OFF of boom-sections or nozzles possibly impacting the desired spray pattern and rate. Therefore, an investigation was conducted to evaluate real-time boom dynamics, pressure and flow, for a typical agricultural sprayer using auto-swath technology. An 18.3-m sprayer was outfitted with commercially available individual nozzle and boom-section control was used to determine if difference existed between these different methods of ON/OFF control. Ten high frequency response pressure sensors were randomly mounted across the boom to measure nozzle tip pressure with another sensor located at the boom manifold to record overall system pressure. A flow meter just before the boom manifold provided system flow response. Two point row scenarios having 20° and 70° angles were conducted at 43.2 l/min application rate and 9.7 km/h ground speed. Auto-boom scenarios were conducted with and with-out flow compensation while auto-nozzle scenarios were conducted without flow compensation. Results indicated that 1) pressure deviation between -28% and 29% during 20° and 70° point row auto-boom scenarios resulted in the spray tip flow rate varying from -19.2% to 12.4 % during auto-boom scenarios; 2) nozzle pressure stabilization time (PST) was up to 19.3 sec. while moving OUT and INTO point rows,; 3) 20° point row presented an example of a scenario where the controller was unable to control the application rate during auto-swath initiation; and 4) the sprayer system dynamics were different for moving INTO versus OUT of point rows for all tests. These results suggest different control algorithms and possible hardware improvements are needed for these operating conditions to minimize application errors.

Exploration of Renewable Energy Usage in a Cement Kiln Using Downdraft Gasification of Poultry Litter

Waste biomass, most notably poultry litter, is a potential source of energy that is widely available and cheap, especially in the southeast. Using poultry litter as an energy source provides a year-round outlet for this waste product. One major energy user that currently utilizes alternative solid fuels is the cement industry. Poultry litter in its raw state, however, is limited in use because of its high chlorine content and relatively large concentration of other unwanted constituents. Downdraft biomass gasification of pelletized poultry litter is a proposed solution to this problem as a means to produce a clean, consistent product gas for injection into the kiln. In this study, this process has been analyzed through experimentation on a pilot-scale 65 Nm3 /hr syngas production downdraft gasifier to determine its effectiveness and consistency in this application. The low ash fusion temperature and high alkali content of poultry litter prove to be difficult obstacles to overcome as ash clinker formation is an issue. Experiments with temperature depression via flue gas recirculation as well as experiments employing an additive (lime) to prevent fusion and aid in chlorine retention in the ash have been carried out. Flue gas recirculation allowed the reduction of the gasifier secondary air oxygen concentration by 40–45%, yielding an approximately 100°C depression in average temperature. Results have shown that the clinkering is temperature independent, at least within the controllable temperature range. Lime also has only a slight effect on the fusion when used to coat the pellets. However, lime addition does display some promise in regards to chlorine capture, as ash analyses show chlorine concentrations of more than four times greater in the lime infused ash as compared to raw poultry litter. Experiments were also conducted to explore the effectiveness of mixing lime with raw poultry litter, the object being to coat more surface area and have a more even mixture. These resulted in more consistent experiments with no ash clinkering.Copyright

Real-time Boom Dynamics on Sprayer Efficacy due to Boom-Section or Nozzle Control

Many current spray controllers when coupled with GPS receivers provide automatic swath (boom-section or nozzle) control capabilities to minimize overlap and application in unwanted areas. This technology can improve application accuracy thereby reducing chemical usage and enhance environmental stewardship. However, sprayer system response from using this technology has not been investigated. Therefore, a study was conducted to develop a methodology to evaluate pressure variations on a typical agricultural sprayer equipped with a controller providing boom-section or nozzle control. To quantify boom dynamics during section/ nozzle control, a testing protocol was established that included 12 simulation patterns under both compensation and non-compensation mode. Real-time pressures were recorded at 4 locations along the boom with data analyzed to quantify pressure variations and compute transition and lag times for observed pressure changes. Results indicated that pressure dynamic response was different for the boom-section and nozzle control scenarios. The boom scenario with compensation and non-compensation experienced an average pressure increase from 8.2% to 15.8% and 6.4% to15%, respectively depending on whether 1 or 2 boom sections were turned OFF. For nozzle control scenarios, the pressure increased during a simulated scenario was proportional to the number of nozzles turned OFF, a trend similar in the boom scenario. A pressure increase occurred for all tests with a maximum of 18% measured. Results indicated an increase in spray tip flow rate from 3.7% to 8.9 % during the boom scenarios and 3.1% to 10.7% during nozzle scenario. Computed transition times for the boom-section scenarios were larger whereas the lag times were higher for the nozzle-control scenarios. A majority of the transition times were under 1 second. In conclusion, additional testing is needed to better understand the effect of automatic swath control on liquid applicators

Linking Within Stand Variability to Timber Growth Characteristics for Site-Specific Forest Management

The adoption of precision agriculture technologies and site-specific management has been limited in the forest industry. Geographic information systems (GIS) and remote sensed imagery have been used in forest management, but at a landscape scale, typically to prescribe and schedule treatments for a diverse collection of relatively large tracts. Individual stands have traditionally been treated uniformly based on their most prevalent characteristics. Sub-stand variability has most often been studied as something for which an efficient inventory sampling strategy can compensate, not as being suggestive of a treatment regime to maximize revenue or ecological benefits. This paper develops a method to generate a site-specific database using ground-based and LiDAR data to estimate individual tree volume to create a timber yield map. Tree diameter at breast height (DBH) was hand measured for each tree across a 3.6 ha site and then LiDAR data was used to estimate individual tree height. Tree location and elevation across the site were determined using a total station. Random tree height measurements were collected and correlated to the LiDAR data (R2=0.57) while the DBH and height for each tree were then used to compute individual tree volume. Finally, management zones were developed based upon the timber yield map to illustrate how database could be used for site-specific management.