William E. Hart

MULTI-SPECTRAL SENSOR FOR DETECTION OF NITROGEN STATUS IN COTTON

Based on the spectral characteristics of cotton canopies, a plant nitrogen sensor was designed and fabricated for detection of nitrogen status in cotton plants. The sensor is an active optical multi-spectral sensing unit. It measures spectral reflectance from a cotton canopy in blue, green, red, and near infrared wavebands with a modulated illumination to the cotton canopy. The sensor was tested in the laboratory and field, and promising results were obtained. This article describes the design, implementation, and testing of the sensor.

Comparison of Tractor Ground Speed Measurement Techniques

ABSTRACT PERFORMANCES of fifth wheel, front wheel, and single-beam radar vehicle ground speed sensors were evaluated on an agricultural tractor at operating speeds of 4, 7 and 10 km/h. Surface conditions included a smooth, non-deformable surface, soils subjected to various levels of tillage, and a range of vegetative covers. Based upon calibration values obtained for each sensor during tractor operation over the smooth, non-deformable surface, radar generally produced more accurate indications of true ground speeds than sensors with ground-contacting wheels. Coefficients of variation in indicated ground speed over time were also generally less for the radar unit than for either fifth wheel or front wheel units. The magnitude of the slip between the ground-contacting wheels and the tractive surface varied inversely with surface firmness. Thus, speed sensors having ground-contacting wheels should be calibrated for the specific surface conditions over which vehicle velocity measurement is to be obtained.

SPRAYER BOOM INSTRUMENTATION FOR FIELD USE

Sprayer on-board instrumentation was developed to measure vibration inputs to the boom, boom acceleration response, boom end height response, and sprayer position along a field track with an aim of relating boom dynamics to field spray deposits. Vibration responses included tires, chassis suspension, boom suspension, and any flexure in components (including boom). Twelve accelerometers measured responses in longitudinal (x), vertical (y), and transverse (z) directions at the chassis center rear, boom center, and at each boom end. Accelerometer rating of ±10 g with a manufacturer-rated accuracy of 1% produced satisfactory system responses. An ultrasonic distance sensor operated satisfactorily as a boom height sensor over mown grass with an accuracy of ±0.03 m. A photoelectric-based position-along-track sensor operated satisfactorily with a 23 cm wide target to block the beam with an accuracy of ±6 cm. This position sensor was developed to assist in locating the sprayer and boom dynamics relative to spray deposit samplers in a follow-on study. A PC-based data acquisition system polled sensors at 2.5 kHz. Signal noise was reduced using bandpass (0.1 to 15 Hz) software filtering. Y-accelerations at the boom center ranged from 1.5 to -0.8 g. Response frequencies of the sprayer vehicle and boom ranged from 4 to 7 Hz in x, y, and z directions on a smooth track. A 20 cm track bump resulted in sprayer and boom response frequencies of 1 to 2 Hz in the y direction and 5 to 6 Hz in x and z directions. The bump increased the peak acceleration power up to a factor of 19 for the y direction at both boom ends compared with a smooth track. A 20 cm dip and an opposing 20 cm bump in the sprayer track had an insignificant effect in shifting primary response frequencies in the y direction. However, the dip/bump reduced the response frequency (<5 Hz) in the x and z directions at the boom center. A one-half sprayer tank load of water (1514 L) dampened vehicle vibration so that the water load changed the main response frequency (<4.5 Hz) and reduced power levels (~55%) in the y direction at the boom center. The developed instrumentation system may be useful in the design of future sprayers and spray booms and assist decisions on sprayer suspensions and operating speeds, boom design length, and use of active boom suspensions.

Effect of Venturi-Type Nozzles and Application Volume on Postemergence Herbicide Efficacy1

Abstract: Field studies were conducted to compare venturi-type nozzles to a fan nozzle with respect to the efficacy of postemergence herbicides applied to common cocklebur and broadleaf signalgrass. Spray solutions of glufosinate, glyphosate, and paraquat were applied through all combinations of three nozzles and two application volumes. Venturi nozzles were a Delavan Raindrop Ultra (RU) and a Spraying Systems AI Teejet (AI). A Spraying Systems XR Teejet (XR) fan nozzle was included as a standard. Previous work indicated droplet size spectra differed among these nozzles. There was a difference in common cocklebur control among nozzles (AI = XR > RU), although control was at least 90% for all nozzles. Herbicide choice had a greater effect on broadleaf signalgrass control than nozzle type. Broadleaf signalgrass control differed among herbicides (glufosinate = paraquat > glyphosate) and among nozzles (AI = XR > RU). Herbicide performance varied between nozzles (AI > RU), but the AI nozzle was as effective as the XR fan nozzle. Nomenclature: Glufosinate; glyphosate; paraquat; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash #3 BRAPP; common cocklebur, Xanthium strumarium (L.) # XANST. Additional index words: Drift. Abbreviations: AI, Spraying Systems AI Teejet; RU, Delavan Raindrop Ultra; VMD, volume median diameter; WAT, weeks after treatment; XR, Spraying Systems XR Teejet.

DESIGN AND EVALUATION OF A COTTON FLOW RATE SENSOR

An optically–based system for measuring cotton flow rate was designed and tested in both field and laboratory environments. Accuracy was documented by comparing actual and predicted load weights. When field–tested on a cotton harvester, results were positive, with an average absolute error of 4.7%. A laboratory test was subsequently designed and conducted to gather data describing relationships between system performance and variables such as cotton flow rate, cotton moisture content, and cotton variety. The accuracy results of the laboratory test confirmed those generated in the field, with an average absolute error of 3.4%. Additionally, laboratory test results indicated a moderate correlation between average flow rate and absolute error. Variety also affected system performance, with an average absolute error of 2.4% for one variety, versus 4.9% for another. Moisture content had no detectable effect on accuracy in the laboratory test. The technology described herein has been patented and licensed to industry for application on mobile equipment.

Implementation and Field Evaluation of a Cotton Yield Monitor

An optically–based cotton flow rate measurement device was developed for use in a site–specific yield mapping system. Variations of the final design were field–tested in Tennessee during three harvest seasons. System performance was evaluated by harvesting loads of cotton, integrating flow rate measurements over time to obtain a predicted total mass for each load, and comparing the predicted mass values with actual mass measurements acquired using scales. Integrated flow rate measurements consistently predicted actual load masses with a mean absolute (unsigned) error of 4.0% for all of the loads harvested during the tests. The mean error (signed) was –0.1% with a sample standard deviation of 5.1%. Sensors were never cleaned during any of the harvest seasons, and performance degradation due to debris accumulation on sensor faces was not observed. A subset of test data was analyzed to determine how changing field conditions affected system performance. Data were evaluated for detectable performance effects due to differences in cotton variety, seed cotton moisture content, average cotton flow rate, total load weight, and/or the amount of time elapsed since last system calibration. Cotton variety and average cotton flow rate were shown to affect load mass prediction errors. These results suggest that the system calibration should be checked when the variety being harvested changes, as additional calibrations may be necessary to provide optimum results, and that further optimization of flow rate prediction algorithms may be possible.

Site-Specific Weed Management in Corn (Zea mays)1

Site-specific weed management can increase crop production efficiency by minimizing herbicide input costs without compromising crop yields. A reduction in herbicide inputs resulting from site-specific weed management may also decrease the probability level of nonpoint pollution compared with conventional herbicide applications. A 4.5-ha field was selected to compare site-specific and conventional weed management techniques in 1997 and 1998 at Knoxville, TN. Variable rate applications (VRAs) of atrazine preemergence (PRE) followed by dicamba postemergence (POST) were investigated for the reduction of herbicide inputs and their resulting impact on weed control and corn yield. VRAs of atrazine were on the basis of weed density data collected in 1996. VRAs of dicamba were according to common cocklebur density evaluations within the field. Compared with conventional applications, atrazine usage was decreased by 43 and 32% in the site-specific application treatments in 1997 and 1998, respectively. VRAs of dicamba reduced herbicide inputs by greater than 45% for 1997 and 1998. Corn yields were similar for the conventional and site-specific treatments in both years. On the basis of these data, site-specific herbicide applications have the greatest potential and least risk for managing weeds when POST or PRE + POST variable rate herbicide applications are used. Nomenclature: Atrazine; dicamba; common cocklebur, Xanthium strumarium L. #3 XANST; corn, Zea mays L. ‘Dekalb 689’. Additional index words: Brachiaria platyphylla (Griseb.) Nash, broadleaf signalgrass, geographical information systems, global positioning systems, variable rate application. Abbreviations: DGPS, differential global positioning system; GIS, geographic information system; OM, organic matter; POST, postemergence; PRE, preemergence; VRA, variable rate application.

DEVELOPMENT OF A SYSTEM TO MANAGE PESTICIDE–CONTAMINATED WASTEWATER

One of the primary problems related to pesticide use is disposal of the low–concentration pesticide–contaminated wastewater resulting from leftover mixes, equipment rinsing, and general clean–up. The costs, safety issues, and potential environmental impacts associated with this pesticide–contaminated waste are major concerns for most applicators. As part of a broad effort by the University of Tennessee Agricultural Experiment Station and the Tennessee Agricultural Extension Service, researchers have been carrying out a series of projects that will result in construction of full–scale wastewater handling facilities on branch research stations. This study reports on the first project phase, whose objectives were: to choose a wastewater disposal technique from alternatives presented in the scientific literature, and to propose an optimal set of operating conditions that could reasonably be followed by typical pesticide applicators. The wastewater disposal technique selected by the study was designated the Soil–Based BioReactor, or SBBR. This method, which has been in use for quite some time, involves application of pesticide–contaminated wastewater to soil beds. The water evaporates from the moist soil surface, and the pesticide is adsorbed to the soil and then broken down by chemical and biological activity. Earlier studies found this to be an effective technique with no long–term accumulation of pesticide, no measurable volatilization of pesticide, and low management requirements. These earlier studies, however, made no attempt to optimize the system, so that became the second study objective. The optimum system resulting from this study used a medium–fine textured soil (a silt loam), operated at a temperature elevated above the ambient much as would be the case in a greenhouse, and used an application method providing five days of near–saturation followed by five days of drying. Under these conditions, and assuming 180 days of wastewater application followed by 120 days of clean water application, over 98% of atrazine and over 90% of fluometuron active ingredients applied with the wastewater had dissipated. The study results indicate that an SBBR system using simple construction and management techniques can effectively dispose of pesticide–contaminated wastewater on a research farm or for a typical small– to medium–size applicator.

Biomass Harvesting of High-Yield Low-Moisture Switchgrass: Equipment Performance and Moisture Relations

Commercial hay and forage equipment was tested for biomass harvesting of high-yield, low-moisture switchgrass for overall suitability, mass throughput rate, and effects on switchgrass drying at a southeast U.S. location. Equipment included disc mower, mower conditioner, tedder, rotary rake, round baler, and forage harvester operated in switchgrass yielding up to 12.4 Mg DM/ha. A one-cut annual switchgrass harvest during winter was investigated for equipment handling of voluminous, light (dry) material. A first of two-cut harvest during summer was investigated for in-field switchgrass drying. Equipment throughput rate was presented for different losses, since machinery performance reporting is not fully standardized on the basis of productivity losses. Results showed that a disc mower equipped with a safety curtain became plugged with switchgrass from a one-cut harvest due to reduced clearance to material flow created by the curtain support. The mower conditioner operated in straight-standing, one-cut switchgrass at speeds up to 16.4 km/h and throughput rate up to 57 Mg DM/h. However, in extremely lodged switchgrass, the mower conditioner had to be operated at reduced speeds to minimize plugging. The pto-powered rotary rake handled the dry voluminous material well. The round baler performed at a maximum throughput rate of 48 Mg DM/h at 14.0 km/h. Throughput rates measured for mower conditioner and round baler were greater than previously reported, even when considering different productivity losses. The round baler equipped with a MegaWide™ Plus pickup did not limit baler performance as previously reported for other pickups. However, baler limitations were noted for switchgrass stems not aligned with the pickup, hitch entanglement with voluminous windrows, and collection of late season broken fines at critical baler locations. Mean round bale density ranged from 136 kg DM/m3 for the first of two-cut harvest in the summer to 168 kg DM/m3 for one-cut harvest in the winter. Maximum bale density was 173 kg DM/m3 for net-wrapped one-cut harvest. Mean bale density of twined bales was significantly less (p=0.05) than bale density for net-wrapped bales for the one-cut harvest. The forage harvester operated without problem at 3.2 km/h and produced particle geometric mean dimensions of 15.3 mm for the first of two-cut harvest in the summer compared to 8.5 mm for the one-cut harvest in the winter for the same theoretical length of cut. The mower-conditioner and tedder harvest treatment promoted rapid switchgrass drying from 67% to 18% moisture content (wet basis) within 48 h after cutting. The mowed and tedded treatment reached 23% moisture content in 188 h. The Rotz drying model predicted moisture contents that fell between the mower and mower-conditioner treatments for elapsed times up to 72 h after cutting, but the model response to tedding and precipitation resulted in increased differences between predicted and actual values. Overall, current hay and forage harvest equipment have improved capacity, but high-yielding voluminous, light switchgrass exposed equipment limitations.

Hybrid Kentucky Bluegrass Tolerance to Preemergence and Postemergence Herbicides

Field studies were conducted near Knoxville, TN, from 2003 to 2005 to evaluate the response of ‘Thermal Blue’, a new interspecific hybrid Kentucky bluegrass to commonly applied PRE and POST herbicides for weed management. Dithiopyr, oryzalin, oxadiazon, pendimethalin, prodiamine, quinclorac, and trifluralin applied at seeding injured hybrid bluegrass greater than 81% and reduced hybrid bluegrass cover greater than 57%. In a second study, established hybrid bluegrass was treated POST with acetolactate synthase–inhibiting herbicides including bispyribac-sodium, chlorosulfuron, foramsulfuron, halosulfuron, imazapic, imazaquin, metsulfuron, rimsulfuron, sulfosulfuron, and trifloxysulfuron at low and high rates (one and two times the suggested use rates in Kentucky bluegrass or other turfgrasses). By 5 wk after treatment (WAT), foramsulfuron at 88 g ai/ha and trifloxysulfuron at 35 g ai/ha injured hybrid bluegrass greater than 26% and reduced visually estimated quality and chlorophyll meter indices. However, hybrid bluegrass injury was no longer evident at 10 WAT. In a third study, established hybrid bluegrass was treated with clethodim, diclofop-methyl, fluazifop-p-butyl, and sethoxydim applied at low, medium, and high rates (0.5, 1, and 2 times the registered Kentucky bluegrass or other turfgrass use rates). Clethodim applied at 280 and 560 g ai/ha, fluazifop at 420 g ai/ha, and sethoxydim at 630 g ai/ha injured hybrid bluegrass 5 WAT. These treatments also reduced quality (to less than 5 on a scale of 1 to 9) and chlorophyll meter indices (24 to 37%) when compared to the untreated control. By 10 WAT, only clethodim at 560 g ai/ha caused injury (14%). By 10 WAT, hybrid bluegrass had recovered and injury was only observed in plots treated with clethodim at 560 g ai/ha. No differences in chlorophyll indices or quality were observed at 10 WAT for any POST graminicides. Nomenclature: Bispyribac-sodium, chlorosulfuron, clethodim, diclofop-methyl, dithiopyr, fluazifop-p-butyl, foramsulfuron, halosulfuron, imazapic, imazaquin, metsulfuron, oryzalin, oxadiazon, pendimethalin, prodiamine, quinclorac, rimsulfuron, sethoxydim, sulfosulfuron, trifloxysulfuron, trifluralin, Kentucky bluegrass, Poa arachnifera Torr. × P. pratensis L. ‘Thermal Blue’