Timothy S. Stombaugh

SUITABILITY OF A GPS COLLAR FOR GRAZING STUDIES

The traditional means of tracking animal location in a field is by visual observation. Not only is this method labor intensive, it is also prone to error as the observer can alter cattle movement, observation periods are often too short to obtain confidence in general daily behavior patterns, and observer fatigue becomes an issue. In the 1990s, the University of Kentucky began using GPS collars on cattle to track their position with the goal of incorporating this information into cattle management practices. One of the key unanswered questions regarding the GPS collars is the accuracy of the position data recorded by the collar. The objective of this work was to assess the capabilities and limitations of using GPS collars to track animal movement in grazed watersheds. Static tests were conducted in an open field, under trees, and near fence lines to ascertain the impacts of various field features on collar performance. Dynamic tests were carried out to examine the errors associated with the collars while operated under real-world conditions. Results from these tests indicate that the collars generally provide data with horizontal accuracies of 4 to 5 m. This information will assist researchers in the development of experiments based on collar capabilities and limitations.

A Whole Farm Analysis of the Influence of Auto-Steer Navigation on Net Returns, Risk, and Production Practices

A whole farm economic analysis was conducted to provide a detailed assessment into the economic, risk, and production implications due to the adoption of auto-steer navigation. It was determined that auto-steer navigation was profitable for a grain farmer in Kentucky with net returns increasing up to 0.90% (

Distribution pattern variability of granular VRT applicators

3.35/acre). Additionally, the technology could be used in reducing production risk. Adoption of the technology also alters production practices for optimal use.

Evaluating the Dynamic Accuracy of Low-Cost GPS Receivers

Granular applicators equipped with variable-rate technology (VRT) have gained popularity in recent years as a result of increased interest in variable-rate application. The purpose of this investigation was to characterize distribution patterns at varying rates for different granular applicators. Uniform-rate (UR) tests were conducted to assess the accuracy of variable-rate application from four granular applicators: two spinner-disc spreaders (A and B), and two pneumatic applicators (C and D). Pattern results indicated a consistent triangular pattern for spinner spreader B and consistent patterns for the pneumatic applicators (C and D). However, applicator D produced pattern variations at the center and right side. Simulated overlap analysis generated CVs <20% for applicators B and C. Applicator A performed well at the two lower rates (CVs <19%) but not at the highest rate (CV = 27%). Pattern unevenness for applicator D produced CVs between 25% and 34%. The spinner-disc spreaders over-applied, while the pneumatic applicators under-applied at the margins, suggesting an adjustment to the effective swath spacing or spinner-disc speed is needed to improve application accuracy. Further, overlap plots indicated pattern variability even when acceptable CVs were attained for applicators B and C. Therefore, it is recommended that CVs accompany simulated overlap pattern plots to ensure proper calibration of VRT equipment. Swath spacing analysis indicated that three of the four applicator spacings could be changed from the recommended value to improve application uniformity. Pattern comparisons showed that pattern shifts occurred for applicator A (P = 0.0092) with increasing application rate but not for applicators B, C, and D. These results demonstrate potential application errors with VRT and the need for proper calibration to maintain acceptable performance. Further, this investigation demonstrates the need for a VRT equipment testing standard.

Rate Response Assessment from Various Granular VRT Applicators

This study introduces a method of dynamic accuracy testing for DGPS receivers and compares the dynamic accuracy of five commonly used low-cost DGPS receivers. The dynamic accuracy of five low-cost DGPS receivers (Garmin 16S, Garmin 76, Haicom HI-302, Navman 3420, Holux GM-210) were evaluated and compared while driving on a straight path under field conditions. All systems used WAAS as a source of differential signal. Cross-track error was calculated from the differences in actual position measured by a RTK GPS and position data from each DGPS receiver. Tests were conducted in N-S and E-W directions. The results indicated that the proposed method was successful in comparing the dynamic accuracy of different DGPS receivers under field conditions. The overall cross-track error was higher in the N-S direction than E-W direction for all DGPS receivers in all tests. Overall the Holux GM-210 performed the best in this study. This result is also in agreement with the static accuracy reported by each manufacturer.

Corn Stover Availability and Collection Efficiency Using Typical Hay Equipment

Variable-rate technology (VRT) adds complexity to application equipment, thereby confounding the assessment of applicator performance. The intent of this investigation was to assess the rate response of various VRT granular applicators: two spinner spreaders (A and B), and two pneumatic applicators (C and D). Variable-rate (VR) tests were conducted to quantify the rate response characteristics (delay and transition times) for the applicators. A sigmoidal function was used to model the rate response for five of the six tests. Applicator A exhibited a linear response during decreasing rate changes. Results indicated that only applicator B demonstrated consistent delay and transition times, enabling the use of a single “look-ahead” time for rate response time correction. Contouring of prescription maps increased the transition times for applicator D by enlarging the adjustment area between management zones. Rate changes were quicker for the two newer VR control systems, signifying advancement in hydraulic control valve technology. This research illustrates the need for standard testing protocols for VRT systems to help guide VRT software developers, equipment manufacturers, and end users.

Simulation of fixed- and variable-rate application of granular materials

Corn stover has been identified as a potential feedstock for the production of fermentable sugars and thermochemical processes. The availability and efficiency of typical hay equipment for collecting corn stover has not been well quantified. Corn stover was collected for two years on a central Kentucky farm near Louisville. Six different harvesting treatments, using traditional hay equipment, were used to harvest corn stover. A rotary mower, rotary scythe (flail-type mower with windrow-forming shields), parallel bar rake, and a round baler were utilized. The average stover moisture content prior to grain harvest was above 40%, and field drying was required before baling. All treatments were analyzed for collection efficiency and corn stover yield. The stover collection yields varied from 1.93 to 5.34 dry t/ha, with collection efficiencies (ratio of stover collected to the total above-ground stover excluding grain) between 32.1% and 94.5%. The most promising collection strategy was disengaging the straw chopper and spreader to produce a windrow behind the combine. This windrow could then be baled in a separate operation that resulted in a collection efficiency of 74.1%.

Crop yield response to precision deep tillage

Research has shown that application errors exist with variable–rate technology (VRT) systems. Consequently, using prescription maps for economic and agronomic analyses can generate misleading results. The intent of this article was to develop and validate a spatial data model for generating “as–applied” maps to support the advancement of precision agriculture practices. Previous research modified ASAE Standard S341.2 to include a 2–D matrix of collection pans to assess fixed–rate and variable–rate (VR) deposition of granular fertilizers and agricultural lime from a spinner disc spreader. The “as–applied” spatial data model uses GIS functionality to generate “as–applied” surfaces by merging distribution patterns and a spatial field application file (FAF) into an “as–applied” surface representing the actual distribution of granular fertilizer or agricultural lime across a field. To validate the “as–applied” spatial data model, field studies were conducted by randomly placing collection pans across two fields. Murate of potash was then applied using a VR spinner spreader. The “as–applied” spatial data model was used to predict the amount of material each pan should have received. Comparisons were made between the actual and predicted application rates for two fields, with R2 values of 0.45 (field A) and 0.58 (field B) computed. However, R2 values of 0.16 (field A) and 0.21 (field B) were observed when comparing the actual application rates and prescription maps. These low R2 values indicated poor application by the spinner spreader but demonstrated that the “as–applied” model did a better job of representing the distribution of murate of potash when contrasted with the prescription maps. “As–applied” surfaces provide a means for evaluating fixed–rate and VR application of granular products while enhancing researchers’ ability to compare VR management approaches.

Moisture Content Prediction in the Switchgrass (Panicum virgatum) Drying Process Using Artificial Neural Networks

Experimental precision deep tillage was applied at three sites in central Kentucky with relatively well-drained silt loam soils in no-till crop production. Fields were divided into 0.4 ha (1 ac) grid cells using DGPS mapping. Assessment of soil compaction by machinery traffic was made using multiple soil cone penetrometer measurements and expressed as cone index (CI). Corn, wheat, and soybean yields were depressed in grid cells with CIavg > 1.5 MPa (218 psi) prior to application of tillage treatments at sites 1 and 3, whereas at site 2, where most of the highest average CI values ranged from 1.44 to 1.49 MPa (209 to 216 psi), the opposite was true. In general, deep tillage resulted in yield improvement in compacted grid cells relative to those receiving no deep tillage; however, differences were significant at the 10% level in only two of six instances. Cells tilled to 40 cm generally had higher yields than cells tilled only to the depth at which CIavg > 1.5 MPa (218 psi) (precision deep tillage) at sites 1 and 3. However, the opposite was true for double-crop soybean subjected to limited rainfall. At site 2, tilled cells had higher yields than non-tilled cells, with precision tillage showing the maximum relative yield.

AIR EXCHANGE RATE IN A HORSE TRAILER DURING ROAD TRANSPORT

This article proposes two artificial neural network (ANN)-based models to characterize the switchgrass drying process: The first one models processes with constant air temperature and relative humidity and the second one models processes with variable air conditions and rainfall. The two ANN-based models proposed estimated the moisture content (MC) as a function of temperature, relative humidity, previous MC, time, and precipitation information. The first ANN-based model describes MC evolution data more accurately than six mathematical empirical equations typically proposed in the literature. The second ANN-based model estimated the MC with a correlation coefficient greater than 98.8%.