Papers by Michael Boyette
Safety and efficacy of linuron with or without an adjuvant or S-metolachlor for POST control of Palmer amaranth (Amaranthus palmeri) in sweetpotato
Weed Technology, 2021
Field studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpota... more Field studies were conducted to evaluate linuron for POST control of Palmer amaranth in sweetpotato to minimize reliance on protoporphyrinogen oxidase (PPO)-inhibiting herbicides. Treatments were arranged in a two by four factorial in which the first factor consisted of two rates of linuron (420 and 700 g ai ha−1), and the second factor consisted of linuron applied alone or in combinations of linuron plus a nonionic surfactant (NIS; 0.5% vol/vol), linuron plus S-metolachlor (800 g ai ha−1), or linuron plus NIS plus S-metolachlor. In addition, S-metolachlor alone and nontreated weedy and weed-free checks were included for comparison. Treatments were applied to ‘Covington’ sweetpotato 8 d after transplanting (DAP). S-metolachlor alone provided poor Palmer amaranth control because emergence had occurred at applications. All treatments that included linuron resulted in at least 98% and 91% Palmer amaranth control 1 and 2 wk after treatment (WAT), respectively. Including NIS with linuron...
Energies, 2021
Supplementing fossil fuels with solar air tempering for brooding young livestock could reduce ene... more Supplementing fossil fuels with solar air tempering for brooding young livestock could reduce energy use and improve indoor air quality. Metal transpired solar collectors (TSC) are effective but too expensive for heating livestock buildings. An inexpensive 12.7 m2 dark grey landscape-fabric-based transpired solar collector (fTSC) was evaluated in a swine nursery with two herds of pigs. A fraction of the fTSC area was underlain with phase change material (PCM) to store excess heat. The Test room with the fTSC was compared with an adjacent identical Control room, each with 120 piglets. The fTSC provided supplemental heating, e.g., with a suction velocity (Vs) of 0.027 m/s during a 9 h period, air temperature was increased by 11.6 °C (mean irradiance of 592 W/m2). Between 4 pm and 9 pm that same day, the PCM increased air temperature by 3.9 °C. The fTSC did not reduce propane use or improve pig performance. Higher Vs, operational changes and controller modifications could improve syste...
Herbicide systems including linuron for Palmer amaranth (Amaranthus palmeri) control in sweetpotato
Weed Technology, 2020
Field studies were conducted to determine sweetpotato tolerance to and weed control from manageme... more Field studies were conducted to determine sweetpotato tolerance to and weed control from management systems that included linuron. Treatments included flumioxazin preplant (107 g ai ha−1) followed by (fb) S-metolachlor (800 g ai ha−1), oryzalin (840 g ai ha−1), or linuron (280, 420, 560, 700, and 840 g ai ha−1) alone or mixed with S-metolachlor or oryzalin applied 7 d after transplanting. Weeds did not emerge before the treatment applications. Two of the four field studies were maintained weed-free throughout the season to evaluate sweetpotato tolerance without weed interference. The herbicide program with the greatest sweetpotato yield was flumioxazin fb S-metolachlor. Mixing linuron with S-metolachlor did not improve Palmer amaranth management and decreased marketable yield by up to 28% compared with flumioxazin fb S-metolachlor. Thus, linuron should not be applied POST in sweetpotato if Palmer amaranth has not emerged at the time of application.
Renewable Energy, 2018
The objective of this study was to understand the effect of airflow and insulation on syngas and ... more The objective of this study was to understand the effect of airflow and insulation on syngas and biochar generations of rice hulls and woodchips in a top-lit updraft gasifier. Biochar yield decreased with increasing airflow. The highest biochar yields of 39% and 27% were achieved at 8 L/min airflow for rice hulls and woodchips, respectively. The mass fraction of syngas in the products increased with increasing airflow, which ranged from 88 to 89% for rice hulls and 93 to 94% for woodchips. The H 2 composition in syngas also increased at higher airflow rates; it peaked at 4.2-4.4% for rice hulls and 5.7-6.6% (v/v) for woodchips, which was not affected by insulation. The carbon monoxide content in syngas ranged from approximately 12 to 15% (v/v) and was not affected by airflow or insulation.
Renewable Energy, 2018
Solar heating has great potential to displace fossil fuels in agricultural and industrial space h... more Solar heating has great potential to displace fossil fuels in agricultural and industrial space heating. The conventional metal transpired solar collectors (mTSC) is highly-efficient but its high cost has impeded its adoption. While the plastic TSC (pTSC) would be less-expensive than the mTSC, it requires perforation. Since a high absorptance, non-woven landscape fabric is widely available and inexpensive, it could be costeffective solar collector. The landscape fabric collector (fTSC) was compared with mTSC (anodized aluminum) and pTSC for temperature rise (T) and efficiency () at two suction velocities (V s ). The mTSC and pTSC had porosity of 1.2% while the fTSC had a porosity of 80%. At 0.047 m/s, the fTSC produced higher average T (by at least 2 °C) and average (by at least 10%) than the mTSC and pTSC that were similar in performance. At the higher V s of 0.060 m/s, the fTSC slightly outperformed the mTSC while the pTSC had the lowest T and . Superior performance of the fTSC was likely due to lower energy losses than the other two collectors as was indicated by its scanning electron microscope images. Modeling the fTSC as a simplified packed bed may be appropriate and challenges have been identified. Practical scaleup suggestions are provided. The fTSC is the least expensive solar air heater for space heating.
Resources, Conservation and Recycling, 2018
Current estimates of food loss at the farm level are either carried forward from decades-old esti... more Current estimates of food loss at the farm level are either carried forward from decades-old estimates that rely on data from small farms using alternative agricultural practices, or they are based on grower estimates reported during interviews. A straightforward protocol adaptable to many crops is necessary to provide comparable data that can begin to fill gaps in knowledge on food loss in the US. Accurate estimation of on-farm losses for fruits and vegetables can inform ongoing national food loss and waste discussions and farm-level business decisions that hold potentially positive impacts for farm viability and resource-use efficiency. This paper describes a straightforward methodology for field-level measurement and demonstrates its utility on six vegetable crops harvested in 13 fields of a 121-hectare North Carolina vegetable farm. In this case, results showed that on average, approximately 65% of the unharvested crop that remained in the field was of wholesome, edible quality, although the appearance may not meet buyers' specifications for certain markets. The overall estimated average of vegetable crops that remained unharvested, yet were wholesome and available for recovery, was 8840 kg per hectare on the case study farm. The portion of the grower's reported total marketed yield that remained unutilized in the field averaged 57%, a figure greatly exceeding current estimates of farm level loss. Developing strategies to utilize these losses could enable growers to increase the amount of fresh produce moving into the supply chain, and represent a path towards sustainable intensification of vegetable crop production.
HortScience, 2000
The `Beauregard' sweetpotato variety is very prone to damage to its skin. We evaluated severa... more The `Beauregard' sweetpotato variety is very prone to damage to its skin. We evaluated several preharvest treatments to reduce skinning so that less damage was done at harvest, during transport, and packing. Three field tests were conducted in 1998 (two tests) and 1999 (one test) in North Carolina. Treatments were implemented 1 and 2 weeks prior to harvest and were either chemical or mechanical. The three mechanical treatments were flail mowing, flail mowing and barring off, and vine snatching. The following chemical treatments were made: PREP, Diquat, Dessicate II, and 2,4-D at various rates. Sweetpotatoes were harvested and roots were graded. Subsequently, U.S. No. 1 root subsamples were obtained from each plot in order to evaluate the effects of treatment on skin tightening of roots. Roots were evaluated from each plot for skin toughness using a “skin-o-meter” where a pressurized stream of water was directed at a sweetpotato. The roots were then evaluated for skinning by chec...
HortScience, 2004
Sweetpotato roots, especially the cultivar Beauregard, tend to experience epidermal loss during h... more Sweetpotato roots, especially the cultivar Beauregard, tend to experience epidermal loss during harvest and postharvest handling which results in a less attractive product in the market. A survey study was conducted among North Carolina (N.C.) sweetpotato growers in Fall 2001 and 2002. The purpose of the survey was to gather information and try to correlate cultural practices, growing conditions and site characteristics with the occurrence of attractive roots and to define new scientific approaches to reducing epidermal loss. Samples were obtained from 42 N.C. farms. Survey field information and laboratory results were correlated to identify possible factors affecting the appearance of the roots. 1300 roots were used to measure skin adhesion, peeling susceptibility, skin moisture, skin anthocyanin and lignin content. From survey questions, 50 characteristics were defined for each sample, according to field characteristics, cultivar information, cultural practices and harvest and pos...
Competency Based Training Program in Horticulture for County Extension Agents in North Carolina
Acta Horticulturae, 2004
Energies, 2016
The performance of a top-lit updraft gasifier affected by biomass (pine wood) particle size, mois... more The performance of a top-lit updraft gasifier affected by biomass (pine wood) particle size, moisture content and compactness was studied in terms of the biochar yield, biomass burning rate, syngas composition and tar content. The highest biochar yield increase (from 12.2% to 21.8%) was achieved by varying the particle size from 7 to 30 mm, however, larger particles triggered tar generation that reached its maximum of 93.5 g/m 3 syngas at 30-mm biomass particles; in contrast, the hydrogen content in syngas was at its minimum of 2.89% at this condition. The increase in moisture content from 10% to 22% reduced biochar yield from 12% to 9.9%. It also reduced the tar content from 12.9 to 6.2 g/m 3 which was found to be the lowest range of tar content in this work. Similarly, the carbon monoxide composition in syngas decreased to its minimum of 11.16% at moisture content of 22%. Finally, the biomass compactness increased biochar yield up to 17% when the packing mass was 3 kg. However, the addition of compactness also increased the tar content in syngas, but little effect was noticed in syngas composition.
Agricultural Engineering International Cigr Journal, Nov 27, 2013
Pretreatment of lignocellulosic biomass for enhancing sugar yields has been studied extensively o... more Pretreatment of lignocellulosic biomass for enhancing sugar yields has been studied extensively over the years. Conventional methods employed to preprocess biomass to make it conducive for enzymatic hydrolysis have been hampered by issues like poor energy efficiency and production of undesirable by-products. Ultrasonication, which involves the treatment of biomass through ultrasonic sound waves in a liquid medium without additional chemicals, is believed to have potential for biomass pretreatment. In this study the effects of ultrasonication on switchgrass, a potential feedstock for bioethanol production due to its high cellulosic content, were investigated. Results of compositional analysis and scanning electron microscopy conducted to visualize structural disintegration in sonicated samples were used to select pretreated samples for enzymatic hydrolysis at different enzyme loadings. Temperature controlled ultrasonication for 60 min at 100% amplitude in a stainless steel vessel, resulted in the highest carbohydrate conversions of 84.6% and 84.7% with Cellic® CTec2 and Alternafuel 200 L at 0.3 g enzyme protein g -1 dry biomass, respectively. However ultrasonication did not significantly impact composition of switchgrass and subsequent hydrolysis of untreated and treated samples was not significantly different. Based on the overall results, it is inferred that although ultrasonication alone did not provide enhanced sugar generation from switchgrass, its tendency to disrupt biomass structure could be utilized for preliminary size reduction steps and performance could be improved by further investigation of frequencies, amplitudes, enzyme loadings and process operation parameters.
BioResources, 2015
Airflow and the type of biomass are the two most important factors influencing the performance of... more Airflow and the type of biomass are the two most important factors influencing the performance of a biomass gasifier. In this research, the effects of air flow rate (air-fuel equivalence ratios of 0.21, 0.25, and 0.29) and biomass type (woody biomass, agricultural residue, and perennial grass) on the performance of an updraft biomass gasifier were evaluated based on its tar and producer gas generation. It was found that increasing airflow increased the formation of tar species for all biomass types studied, but no significant differences in producer gas composition were found when the air-fuel equivalence ratio was changed. Thus, air-fuel equivalence ratios ranging from 0.21 to 0.25 were deemed appropriate for minimal tar generation. The results also showed that different biomass types generated producer gas with significantly different tar contents: woodchips yielded the most tar, followed by sorghum stover and prairie hay. The higher heating value of producer gas from various biomass types was also significantly different. Wood chip-derived producer gas had the greatest higher heating value, followed by prairie hay and sorghum stover. The carbon monoxide content in the produce gas of the three biomass types also exhibited significant differences with varying biomass type, similar to the higher heating value, but there were no significant differences in the H2 content with varying biomass type or airflow.
Influence of Cultivar and Plant Morphology on Mechanical Harvesting Efficiency of Flue-Cured Tobacco
Tobacco Science, 2008
Abstract Experiments were conducted at 4 locations in 2003-2004 to investigate the influence of 1... more Abstract Experiments were conducted at 4 locations in 2003-2004 to investigate the influence of 10 cultivars and their morphological characteristics on mechanical harvesting efficiency and to develop a ranking system for use in variety testing. Treatments (cultivars) were replicated four times and arranged in a randomized complete block design. Leaf angle, leaf curvature, and internode spacing were measured immediately prior to each of the final three harvests. Harvesting efficiency was determined by the number of lost leaves for harvests 2, 3, and 4 and by measuring non-harvested stem material (stem loss) after harvest 4. Highly significant differences among cultivars in leaf angle, leaf curvature, and internode spacing were found before each harvest. However, these differences did not impact mechanical harvesting efficiency, except at final harvest, where significant differences in leaf and stem loss were found among cultivars. Leaf angle and internode spacing were significantly correlated with stem los...
Design of a Post-Frame Burley Tobacco Curing Structure for Wire-Frame Racks
Tobacco Science, 2012
Abstract The purpose of this research was to develop a post-frame structure to utilize wire-frame... more Abstract The purpose of this research was to develop a post-frame structure to utilize wire-frame racks in the curing of burley tobacco in nontraditional growing areas. Since the 2004 federal tobacco quota buyout legislation, burley tobacco production has moved into the piedmont and coastal plain regions of North Carolina, where there was no existing burley curing infrastructure. This presented a unique opportunity to build curing infrastructure based on the most efficient and least costly alternatives. The current trend for mechanically harvested burley tobacco utilizes the cut-notch method. Wire-frame racks are used by many growers as part of an infield curing structure for cut-notch harvested plants. Incorporating wire-frame racks into a post-frame structure provides greater protection from adverse weather than a typical in-field wire-frame curing structure. All of the in-field advantages and mechanisms of wire-frame racks are retained with this design. A 2-tier test building was designed and construct...
On Farm Drying of Sweetpotato Chips
2012 Dallas, Texas, July 29 - August 1, 2012, 2012
Drying sweetpotatoes cut into pieces to preserve them for later use has been practiced since anti... more Drying sweetpotatoes cut into pieces to preserve them for later use has been practiced since antiquity in Central and South America, the geographical center of the sweetpotato’s origin. The US presently produces less than 455,000 kg (one million pounds) of dried sweetpotatoes per year and imports approximately 2.27million kg (5 million pounds) principally from China and Peru. Much of the dried sweetpotato products imported into the US are used by the pet food industry as a gluten free carbohydrate source. In June 2011, a project was undertaken to demonstrate the feasibility of slicing sweetpotatoes and drying them in bulk tobacco barns. Since the majority of both flue-cured tobacco and sweetpotatoes are grown in the same general area of North Carolina and often by the same growers, it seemed only natural to utilize existing barns that remain idle for most of the year except in the late summer and early fall tobacco curing season. The purpose of this project was to produce various dried sweetpotato products to distribute for evaluation by potential users and customers. It should be noted that the tobacco barn utilized in this study was thoroughly cleaned prior to the test to remove all tobacco. The sweetpotatoes were cut lengthways into approximately 6.3 mm (1/4 inch) thick slices placed into metal mesh drying boxes and force-air dried at approximately 66 C (150 F) dry bulb and 40 C (104 F) wet bulb for 60 hours. Approximately 1370 kg (3015 lbs.) of dried material was recovered from the slightly over 7328 kg (16123 lbs.) of fresh sweetpotatoes giving a yield of about 18.7 %.
A comparison of chemical pretreatment methods for improving saccharification of cotton stalks
Bioresource Technology, 2007
The effectiveness of sulfuric acid (H(2)SO(4)), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O... more The effectiveness of sulfuric acid (H(2)SO(4)), sodium hydroxide (NaOH), hydrogen peroxide (H(2)O(2)), and ozone pretreatments for conversion of cotton stalks to ethanol was investigated. Ground cotton stalks at a solid loading of 10% (w/v) were pretreated with H(2)SO(4), NaOH, and H(2)O(2) at concentrations of 0.5%, 1%, and 2% (w/v). Treatment temperatures of 90 degrees C and 121 degrees C at 15 psi were investigated for residence times of 30, 60, and 90 min. Ozone pretreatment was performed at 4 degrees C with constant sparging of stalks in water. Solids from H(2)SO(4), NaOH, and H(2)O(2) pretreatments (at 2%, 60 min, 121 degrees C/15 psi) showed significant lignin degradation and/or high sugar availability and hence were hydrolyzed by Celluclast 1.5L and Novozym 188 at 50 degrees C. Sulfuric acid pretreatment resulted in the highest xylan reduction (95.23% for 2% acid, 90 min, 121 degrees C/15 psi) but the lowest cellulose to glucose conversion during hydrolysis (23.85%). Sodium hydroxide pretreatment resulted in the highest level of delignification (65.63% for 2% NaOH, 90 min, 121 degrees C/15 psi) and cellulose conversion (60.8%). Hydrogen peroxide pretreatment resulted in significantly lower (p<or=0.05) delignification (maximum of 29.51% for 2%, 30 min, 121 degrees C/15 psi) and cellulose conversion (49.8%) than sodium hydroxide pretreatment, but had a higher (p<or=0.05) cellulose conversion than sulfuric acid pretreatment. Ozone did not cause any significant changes in lignin, xylan, or glucan contents over time. Quadratic models using time, temperature, and concentration as continuous variables were developed to predict xylan and lignin reduction, respectively for sulfuric acid and sodium hydroxide pretreatments. In addition, a modified severity parameter (log M(0)) was constructed and explained most of the variation in xylan or lignin reduction through simple linear regressions.
Energies, 2016
Yellow poplar (Liriodendron tulipifera) was chosen as the woody biomass for the production of cha... more Yellow poplar (Liriodendron tulipifera) was chosen as the woody biomass for the production of charcoal for use in a liquid fuel slurry. Charcoal produced from this biomass resulted in a highly porous structure similar to the parent material. Micronized particles were produced from this charcoal using a multi-step milling process and verified using a scanning electron microscope and laser diffraction system. Charcoal particles greater than 50 µm exhibited long needle shapes much like the parent biomass while particles less than 50 µm were produced with aspect ratios closer to unity. Laser diffraction measurements indicated D10, D50, and D90 values of 4.446 µm, 15.83 µm, and 39.69 µm, respectively. Moisture content, ash content, absolute density, and energy content values were also measured for the charcoal particles produced. Calculated volumetric energy density values for the charcoal particles exceeded the No. 2 diesel fuel that would be displaced in a liquid fuel slurry.
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Papers by Michael Boyette