Horticultural Sciences Department

You are here

Issue No. 593

The Vegetarian Newsletter 

A Horticultural Sciences Department Extension Publication on 
Vegetable and Fruit Crops 

Eat your Veggies and Fruits!!!!!

Publish Date: 
July 2014

Transporting farm workers:  Carpools

Thissen, C.; M. Bayer; and F. Roka.

Over the next four months, beginning with this issue, we will cover topics related to transportation of farm workers.   In addition to the Florida Department of Transportation (DOT), two other agencies focus on transportation of farm workers:  the U.S. Department of Labor (DOL) and the Florida Department of Business and Professional Regulations (DBPR).   DOL and DBPR investigators enforce transportation rules set out in the Migrant and Seasonal Agricultural Worker Protection Act (MSPA) as well as many DOT standards officially adopted by MSPA. 

In this article we discuss carpools and the relevant MSPA and the Florida State regulations regarding the transportation of farm workers.

First we must acknowledge that there are no regulations forcing any employer, including farm employers, to transport workers to a worksite. If workers need to find their own transportation, they may choose to form carpools. A carpool occurs when two or more people agree to ride together to work in the same vehicle.  While this definition may seem obvious, it is important to emphasize that a carpool is a voluntary arrangement among the workers for which the driver, or owner of the vehicle, is compensated only for the cost of the gas.  Equally important is to recognize when a carpool is NOT a carpool. If any one or more of the following conditions exists, the carpool is NOT a carpool:

1.       The Farmer, Supervisor, or farm labor contractor (FLC) are involved in any way

2.       The Farmer, Supervisor, or FLC tell workers who to ride with

3.       The driver’s job is conditional on driving the workers

4.       The Supervisor, Farmer or the FLC pays for gas

5.       The driver is directed or requested by a Supervisor, Farmer, or FLC

6.       Vehicle owner earns more than the others who ride with him/her

7.       The vehicle driver is paid more than others who ride with him/her

8.       A Supervisor, FLC or the Farmer owns the Vehicle

9.       Big vans, recreational vehicles or buses are used

10.   Owner of the vehicle is not part of the carpool

11.   The driver or owner of the vehicles receives more than the actual operating cost from the workers

Why do we care if a carpool is NOT a carpool?  We care because if a driver or vehicle owner makes a profit from transporting workers, or if a driver is directed by the farm owner or supervisor to transport workers, then the vehicle and driver must adhere to all of the federal and state requirements of farm labor buses and vans. Farm labor vehicles must be inspected and insured as required by MSPA and Florida regulations. “Transporting farm workers” is one of the functions performed by farm labor contractors (FLCs) and any person driving farm workers as part of a non-bona fide carpool, may be considered a de facto labor contractor and subject to hold both federal (DOL) and state (DBPR) FLC licenses. If the vehicle is owned by someone other than a farmer, it must be “authorized” (Transportation Authorized - TA) on both federal and state Farm Labor Contractor Certificates of Registration.  In addition, the driver must have a federal and state Farm Labory Contractor Certificate of Registration that is Driving Authorized – DA, plus have the proper Department of Transportation operator’s license for the vehicle.  A valid Class E driver’s license is usually all that is required for small vans and cars, while a Commercial Driver’s License (CDL) is needed for larger, Commercial Motor Vehicles (CMVs) like labor buses.  

If the vehicle is used, or caused to be used, by an Agricultural Employer or Association, TA is not required, but the vehicle must still be properly insured and safety inspections must be done as required by the regulations.  If the driver is an employee of the farmer, the employee must have the correct operators’ license, but does not need a federal or state FLC- DA certificate. 

Regardless of whether the driver is an employee of a FLC, farm, or agricultural association, the vehicle itself must be licensed and meet all the safety requirements. Further, the vehicle must carry adequate liability insurance and Workers’ Compensation.

Who is responsible?   Anyone who “causes” the workers to be transported is responsible.  Generally this includes the driver AND the farm labor contractor AND the grower/farmer.  If an Agricultural Employer allows a driver of a car, van, or small truck to bring workers into the field or grove, that employer should have the knowledge to determine if it really is a car pool.  According to several DOL investigators, “Most of the time it’s not a car pool.”  A farm supervisor should ask questions to determine the true arrangement between the workers and driver.  If the driver is extracting a profit for transporting workers, the farm can make a decision whether or not to tolerate the practice. MSPA regulations do not allow workers to be charged for transportation. Therefore, if the driver continues to provide transportation, the farming operation must pay for all costs and ensure that the driver is properly licensed and that the vehicle meets all safety standards.

 Authors:   Thissen, C.; M. Bayer; and F. Roka.  

Carlene Thissen and Fritz Roka work for the University of Florida at the Southwest Research and Education Center, Immokalee, FL, 239-658-3400.  carlene@ufl.edu, fmroka@ufl.edu

Mike Bayer is a former DOL-WHD Investigator, now with Curran, Bayer & Associates, West Palm Beach, 561-371-0126 mtbayer@curranbayer.com  

ABOUT THE FARM LABOR SUPERVISOR TRAINING PROGRAM

The Farm Labor Supervisor (FLS) Training Program is a University of Florida/IFAS Extension program. Begun in 2010, the program is coordinated by Fritz Roka and Carlene Thissen at the Southwest Florida Research & Education Center. Each year from late September through early November a core group of topics are taught at several locations across Florida and in partnership with county extension faculty.  These topics cover laws that keep farm workers safe, fairly paid, and in a working environment free from discrimination and harassment.  The program is offered in both English and Spanish. If there is sufficient interest, individual classes of combinations of classes can be arranged at times and locations convenient for the participants. We also provide training at grower locations that incorporates grower-specific policies and procedures.  For more information, contact Carlene Thissen, 239-658-3449, carlene@ufl.edu.


Using Cover Crops for Integrated Pest Management Benefits

Robert Hochmuth, Multi-county Extension Agent

Suwannee Valley Agricultural Extension Center, Live Oak, FL

Adopting integrated pest management practices in the South is increasingly being practiced on various sized family farms by farmers who live on the farms and are committed to enhancing environmental quality and conserving natural resources.  Both large and small farms play an important role in supporting the competitiveness and sustainability of U.S. rural economies.  Southern farmers continue to face many challenges, including marginal profitability and uncertain economic security.  One key production challenge for farmers in the South is the cost of effectively managing the myriad of pests that infest their crops.  Southern farmers must combat many insect pests, diseases, and weeds almost year-round. 

To support southern farmers’ efforts to manage pests sustainably, a unique, hands-on, whole farm “Living Extension IPM Field Laboratory” has been created at the University of Florida, Institute of Food and Agricultural Sciences (UF-IFAS), Suwannee Valley Agricultural Extension Center (SVAEC) with support from the USDA, NIFA EIPM-CS Program, UF-IFAS Extension, Southern IPM Center and Southern SARE.  This specialized IPM learning environment is used continuously to demonstrate how to enhance agro-ecological systems for specialty crop farmers and other clientele groups by adopting a diversity of beneficial cultural and ecological practices prior to use of chemical pesticides.  Thus, the IPM training program provides an infrastructure for delivering whole farm pest management practices. The field laboratory includes, but is not limited to: maintaining annual and permanent plantings that attract beneficial organisms and provide year round habitats, demonstrating strategic trap cropping systems, providing beneficial vertebrate habitats (e.g., bat houses, bluebird houses, chickadee houses, and brush piles), utilizing banker plant systems (especially in greenhouse programs), demonstrating how to increase natural pollinators, and enhancing the ecological contribution of the lake, surrounding forest and other natural resources on the farm (Figures 1 and 2). Small farm specialty crop producers in the region have participated in training workshops at the SVAEC and now want to implement some of the sustainable IPM practices on their farms but require assistance in selecting appropriate cover crops and monitoring their impact on pest abundance and crop yields.  The 300-acre SVAEC is a showcase of best practices for ecological farm management  that includes: an eight acre pond, hardwood and pine forests, softened fence line vegetation, conservation tillage agronomic and horticultural crops, cover crops, invasive plant management, a transitional organic area, protected agriculture, fruit and nut orchards, and native plant habitats for beneficial arthropods.  Trials at the SVAEC incorporate both annual and perennial crop habitat areas. One area of emphasis is on annual cover crops, including buckwheat, sunflowers, triticale, rye, sesame, and sunn hemp.  At SVAEC the best results were obtained by planting cover crops such as rye, triticale and sunn hemp in large blocks as a rotational crop on land after the cash crop was grown. Buckwheat and sunflower, on the other hand, were grown in strips within the cash crops.  Sunflower (cultivar Giganteus) has been very effective as a trap crop for leaf-footed bugs.  Buckwheat planted in strips at SVAEC has been very effective in increasing beneficial arthropods.  The research conducted at SVAEC showed the importance of making successive plantings of buckwheat throughout the year, every 30-60 days from March to November. This planting strategy follows a schedule so that cover crop habitat is maintained year-round.  This strategy is essential to maintain beneficial arthropod populations at high levels because they need pollen and nectar sources as well as physical habitat.  The cover crop plantings on these farms provide habitat for several beneficial arthropods that parasitize or prey on pests.  Based on three prior years of observations and monitoring beneficial arthropods in such plantings, the populations increase very quickly, within one year from establishing the habitat areas.  Beneficial arthropods commonly found included lady beetles, a diversity of parasitic wasps, big eyed bugs, spiders, assassin bugs, minute pirate bugs, lacewing larvae, syrphid fly larvae, and many species of native pollinators.  Much is known about various crops that attract beneficial arthropods but it was unexpected to determine that sesame is incredibly attractive to many large native pollinator species, more attractive than most historically preferred plants.  Sesame has a very large funnel shaped flower and abundant extrafloral nectaries making it a high value habitat crop. Sesame is being evaluated in a mixed species cover crop during the warm season months to determine its attractiveness to natural enemies and pollinators.

The ongoing use of cover crops at SVAEC has transformed past pest management practices which were based on weekly broad spectrum pesticide applications to much less frequent targeted treatments based on scouting and pest thresholds.  This conversion has resulted in more than a 50% reduction in insecticide applications on the 300-acre farm over a three-year period.  Not only was there a reduction in overall number of insecticide applications, but selection of low-risk pesticides protected the beneficial arthropods.  Thus, the benefits of using sustainable cover crops for multiple purposes, including IPM, on small farms in the Suwannee Valley of Florida have been proven. 


Water Savings of Center-Pivot Irrigation for Commercial Snap Bean Production in Southwest Florida

Xiaolin Liao1, Guodong Liu1, Lincoln Zotarelli1, Crystal Snodgrass2, Alan Jones3

1Horticultural Sciences Department, University of Florida-IFAS, Gainesville, Florida, USA, 32611

2Manatee County Extension, University of Florida-IFAS, Palmetto, Florida, USA, 34221

3Jones Potato Farm, Parrish, FL 34219

Florida has to face many challenges to meet future demands for water. Agriculture is one of the two largest water consumers (the other is public supply) and accounts for approximately 80% of all water use. Thus, saving water in agriculture is imperative. Currently, seepage irrigation is one of the most commonly used irrigation methods for commercial crop production in Florida but has the disadvantage of low water use efficiency. There are alternative irrigation systems with much greater water use efficiency such as center pivot irrigation. For example, our data generated from a potato study show that seepage irrigation and center pivot irrigation used 524,106 and 201,479 gallons of irrigation water per acre in the growing season of 2014. Center pivot irrigation saved 322,627 gallons of irrigation water per acre as compared with seepage irrigation. The objective of this study was to estimate the water use of seepage irrigation compared to center pivot irrigation for commercial snap bean production in Florida.

Materials and Methods

This snap bean (var. Caprice) study was conducted on two commercial farms located in Southwest Florida from February to April, 2014. Two irrigation treatments including seepage and center pivot were replicated four times for a total of eight plots on each of two farms. Each plot was 50 feet in length and consisted of 12 rows with 40 inch between-row spacing. Five soil moisture sensors were installed for each irrigation system on each farm at five depths: 4, 8, 12, 20, and 28 inches (10, 20, 30, 50, and 80 cm) to monitor soil moisture contents. All other field practices were the same except for the irrigation systems. The previous crop was potato. The acreage of this study was 256 for center pivot irrigation and 35 acres seepage irrigation. Rain gauges and water flowmeters were used to record rainfall and irrigation water usage of the two irrigation systems on the two farms, respectively.

Results and Discussion

The water application was 5.4 and 2.1 inches for seepage and center pivot on Farm 1, and 5.4 and 2.7 inches for seepage and center pivot on Farm 2 (Figure 1). The difference in water usage was approximately 3 inches during the 55-day growing season. This difference means that using center pivot irrigation saved 81,900 gallons of irrigation water per acre. The acreage of this study had 256 acres using center pivot irrigation. Thus, this experimental area saved a total of 20,966,400 gallons of water during the 55 days. Center pivot irrigation saved 49% to 60% of irrigation water as compared with seepage irrigation on the two farms. The cumulative rainfall was approximately 5.7-5.9 inches contributing more than 50% of the total water usage during the growing season (Figure 1). However, root-zone (top 12 inches, 30 cm) moisture contents with center pivot irrigation were greater than those with seepage irrigation (Figure 2). This result showed that center pivot irrigation kept the root-zone soil better moistened than seepage irrigation even though the center pivot irrigation system used 49% to 60% less irrigation water than the seepage irrigation system. These percentages may be overestimated. In a dry year, rainfall is usually much less than irrigation water. The total amount of irrigation water is much greater than that in a wet year. This project also covers a potato study. We have already conducted a two-year study of potato on the same farms. The cumulative rainfall in the potato study was, for example, 2.2 inches but evaporespiration (ET) was 10.2 inches during the potato growing season in 2013. This year was relatively wet. The average rainfall was 5.8 inches but evaporespiration (ET) was only 6.1 inches. The respective average of irrigation water was 24.3 and 13.4 inches for 2013 and 2014. The percentage of water savings of center pivot irrigation was 41% in 2013 and 57% in 2014. The percentage of water savings was overestimated in 2014. However, the absolutely irrigation water savings was only slightly (<5%) different: 338,340 and 322,627 gallons/ acre for 2013 and 2014, respectively.

More research is needed to better understand the impacts of center pivot irrigation on commercial snap bean production. Water and nutrients go hand in hand. Every change in irrigation impacts crop nutrition.  The current fertilization program is used for seepage irrigation for decades. Seepage irrigation provides water from below the crop’s root zone through the soil profile whereas center pivot irrigation supplies water from above the crop and the force of falling water may wash nutrients, particularly nitrate, away from the root zone. For center pivot irrigation, a more proper fertilization program such as fertigation needs to be adopted to better manage the nutrients such as nitrogen and potassium for commercial snap bean production.

Acknowledgements

This study is supported by Southwest Florida Water Management District (SWFWMD) (Contract #: 13C00000017). We thank Mr. David Fleming at Jones Potato Farm for helping with this research.

593.3.1.PNG

Figure 1. Water usage (inches) for snap bean using seepage irrigation and center pivot irrigation.

593.3.2.PNG

Figure 2. Soil moisture contents at different depths (4, 8, 12, 20, and 28 inches, i.e., 10, 20, 30, 50, 80 cm) with seepage irrigation and center pivot irrigation on the two farms.


New Technologies Guiding  Improved Nematode Management Strategies Using Soil Fumigants.

J.W. Noling

University of Florida, IFAS, Citrus Research & Education Center,

Lake Alfred, FL 33850

Fumigants are extensively used  as a foundation treatment for pest management for a wide range of soil infesting weeds, nematode, and disease organisms in Florida agriculture.  Methyl bromide, which we can’t use anymore, was revered for its broad-spectrum activity against this broad and  diverse mix of pests.  The very high vapor pressure of methyl bromide ensured that it flash volatilized almost immediately upon release into soil, traveled  as an extremely fast moving front through soil and dissipated to sub lethal levels quickly after application (4-7 days). We have discovered that the fumigant alternatives to methyl bromide that we rely upon for nematode, disease, and weed  control ( such as 1,3-dichloropropene) have  vapor pressures considerably less than that of methyl bromide.  As a result, they require considerably more time to volatilize from the injected liquid state to a gas and to radially expand outwards.  In general, these fumigants can  require up to 3-4 times longer  than that of methyl bromide to volatilize and dissipate from soil  to sub-phytotoxic levels  when conditions are cool and wet. This is particularly problematic in the fall in fields with high water tables and repeated rainfall.  Under these conditions, treated soil volumes are not achieved and hydrolytic degradation of the fumigant can further compromise fumigant spreading and efficacy. Under saturated conditions, many of these fumigants can remain in soil indefinitely.  The slower volatilization and diffusion renders most of the methyl bromide alternatives  vulnerable to influence from suboptimal environmental conditions (soil moisture, temperature). The challenge with alternatives is thus to ensure that the dose and placement of the fumigant are adequate to achieve a lethal concentration x time  product within an acceptable treated volume of soil to manage pests and produce profitable crop yields.   

Potato Research: To address dose and placement issues associated with the alternative fumigants, we initiated a two year project in the fall of 2011, funded by a USDA Specialty Crops Grant, to study the impact of prefumigation soil moisture conditions on soil movement and dissipation of fumigant gases. For these studies, a MiniRae 2000 PID-VOC meter was used to measure fumigant volatiles in soil atmospheres.     For purposes of this newsletter article, I would like to describe  only some of  the results of those  studies, particularly as a starting point for discussion of our current research efforts. These USDA studies repeatedly showed that  fumigant escape from soil was delayed, fumigant movement retarded, and effectiveness of the treatment reduced, under wet soil conditions.  Under dry conditions, fumigant gas movement was shown  to be rapidly upward without much lateral movement toward the shoulders of the packed bed.

In general and with summary of both years of this study it should come as no surprise to anybody that  highest concentration and overall dosage of 1,3-D in soil air were observed in the bed middle at the depth of fumigant injection into the soil.  Irrespective of soil moisture status at the time of injection, fumigant gases moved principally upwards and outwards of the bed. This was not exclusively the result of a chimney effect of gas moving upwards along the chisel trace because the soil was disk hilled over the chisel trace and then pressed to form a 10-inch tall bed immediately after soil injection. Clearly from a distance standpoint, this is the shortest pathway of least resistance for gases to move up and out of the bed. This was observed for both dry and wet soil.  It simply did not matter what the soil moisture condition was , wet or dry, gases moved up and out of the bed.  These results strongly suggested that if radial and lateral movement from the point of injection is inadequate, then some change in application methodology must be considered to expand the width and depth of the cross sectional area of the treated zone to insure a more uniform distribution of fumigant concentration across and beneath the bed.  

In other vegetable crops grown in Florida, strawberries being good example, fumigants are currently delivered via two shanks rather than one to the raised strawberry bed which is roughly equivalent to the size of the raised potato bed.  This is not done to utilize a higher application rate of the fumigant but to ensure application and dose uniformity across the bed. We are now of the belief that improving uniformity will require provisions for at least two release or injection points of the fumigant within the bed as it travels down the row.    Based on the results that we obtained, our interest in potato was guided towards increasing the number of release points of the fumigant per bed using a winged device like a Nobel plow (Figure 1), retrofitted with injection ports on each wing of the plow.  Wings like these are self-cleaning and require less horsepower to pull through the soil when compared with a second chisel per bed.  I am happy to say that a prototype has been developed and is now in its first year of testing.  Illustrated in Figure 1, is the new potato soil fumigation rig designed by TriEst Ag Group, Tifton GA, (Perry Fuller, William Upchurch) to precision-place soil fumigants deeper into the soil profile using ripper shanks with Challenger wings situated at the bottom of the shank. The purpose of the bottom wings is to split the liquid fumigant stream from one into three separate streams within an 8-inch band to physically assist lateral spreading and expand the volume of the fumigant treated zone.

For these studies the MiniRae VOC meter proved to be a very useful tool and sensitive instrument within grower’s fields to detect phytotoxic concentrations of fumigant gases prior to planting as well as to define movement and diffusion of fumigant gases from the point of injection over time and soil depth. We believe that we have identified limitations of the current fumigant delivery systems used, which in turn has guided us in new directions for application system improvement.  We believe splitting the dose into two and three fumigant streams has the potential to improve distribution uniformity of fumigant concentration across the bed which is expected to enhance efficacy and potato yield. Improved uniformity may actually also result in lower atmospheric emissions due to reduced fumigant density gradients which help drive movement up and out of the bed. 

Strawberry Research:   A  MiniRae PID-VOC meter is also being used to characterize concentration of fumigant gases in soil air in 4-inch diameter x 40-inch deep columns of soil (Figure 2) above and below traffic pans (equipment compacted zones) occurring between a soil depth of 8 to 10 inches of the flat, leveled field surface. In practical terms, the compaction zone occurs just below the depth of the deepest tillage operation or implement used in the field and is a layer known to restrict fumigant movement into deeper soil profiles. To collect these data, a new soil probing  system is being used to incrementally measure nematode population density and soil fumigant gas concentration with soil depth. Contiguous soil cores are  acquired using a specialty built stainless steel probe mounted onto a hydraulic ram and a steel frame attached at three points at the rear of a tractor. The new system is something we call the Probinator (Figure 2A).  The probe and hydraulic ram, first used here in Florida by David Wright (UF / NFREC), is first situated over a specific location over the plant bed and then raised and lowered using tractor supplied hydraulics. In the scenario depicted, distribution of 1, 3-dichloropropene (Telone II; 18 gpa) gas was measured after drip fumigation treatment. Measurements were acquired at 10 soil depths, each representing a 4-inch increment of soil (2, 6, 10, 14, 18, 22, 24, 28, 32 and 36 inch mean soil depths) measured from the bed top within the steel ring inserts of the probe (Figure 2 B,C). For the studies being reported here, average fumigant gas concentrations for each bed and depth location were averaged from at least four random locations within bedded rows receiving the fumigant treatment.  Peak soil air concentrations from the MiniRAE 2000 over a 30-second sampling period were used to characterize soil atmosphere concentrations, retention characteristics of fumigants over time, as well as relative differences in vertical, gas phase movement of the fumigant with time and depth. For most field locations, fumigant concentrations were monitored until soil disappearance (typically 5-7 days). 

What is the strawberry crop research telling us?   Figure 3 depicts an illustrated example of typical fumigant concentrations in soil air observed above and below a compacted strawberry traffic  pan shortly after either drip or shank injection of the fumigant to a soil depth of 8-12 inches.  As illustrated, the compacted traffic pan acts as a very effective  impermeable layer to fumigant gas diffusion into deep soil profile. The strawberry traffic pan does not however appear to inhibit the upward or downward movement of plant pathogenic nematodes such as the sting nematode, Belonolaimus longicaudatus.  Concurrent sampling for nematodes before and after shallow fumigant treatment clearly shows that prior to treatment, nematodes can be detected and recovered from soil at depths of 3 feet or more (Figure 4), and can survive fumigant treatments which do not appreciably diffuse through the traffic pan. The nematode sampling data and absence of the fumigant below the traffic pan help to explain the cause of such poor crop performance after some soil fumigations and why new problems with sting nematode continued to emerge.  The challenge now is how to destroy the traffic pan and to determine how to best place the location and timing of fumigant treatment to target the application to nematodes inhabiting deep soil horizons. In-row subsoiling prior to or at the time of fumigant treatment has become a valuable production tool and conservation tillage practice for many different crop producers to alleviate soil compaction and improve fumigant performance.  As hopefully you would expect, we fully intend on developing and evaluating new subsoiling, deep shank tillage (subsoiling) and fumigant application systems to improve nematode management throughout a much deeper soil profile and enhance overall strawberry crop response.  We also believe that these new systems not only have the potential to provide season long nematode control but also help reduce potential fumigant emissions from treated fields.

Overall, I think it is easy to understand how being able to quickly and easily monitor nematode populations and soil gases from their different emission points within the plant row have played a significant role in the development and potential improvement to fumigant application technologies to enhance nematode control and yields of two different crops. We clearly could not have done this without the new technologies consisting of the MiniRae PID -VOC meter  and Probinator deep soil probing systems. Being able to do this quickly and efficiently has helped us to identify the shortcomings of the currently used systems which in turn have helped guide us in new directions for application system improvement.

Figure 1.  Illustration of new potato fumigation rig designed by TriEst Ag Group, Tifton GA, to precision-place soil fumigants deeper into the soil profile using Ripper Shanks with bottom wings. The purpose of the bottom wings are to split the liquid fumigant stream from one into three separate streams within an 8-inch band to physically assist lateral spreading and expand the volume of the fumigant treated zone.

593.4.1_0.PNG

Figure 2.  The Probinator, a specially designed probe and hydraulic ram used to collect 4-inch diameter x 40-inch deep soil cores for nematode population density and fumigant gas concentration (A, B) determinations.  The steel probe  is first situated over a specific site on the top of the plant bed (A)  and then raised and lowered using tractor supplied hydraulics. After drip fumigation treatment, distribution of 1, 3-dichloropropene (Telone II; 12- 18 gpa) gases were  measured using a MiniRae PID-VOC meter at 10 soil depths and 4-inch increments (2, 6, 10, 14, 18, 22, 24, 28, 32 and 36 inch mean soil depths) measured from the bed top within the steel ring (B,C) inserts of the probe (C).

593.4.2.PNG

593.4.3.PNG

593.4.4.PNG