Soil penetrometerSpring 2014
Available at: https://works.bepress.com/david_a_bainbridge/37/
Soil penetrometer
A soil penetrometer measures the many complex factors that affect soil strength. It chronicles the challenge a root tip will face in extending into the soil. Soil moisture is an important aspect of this, so measurements between sites are best used as comparisons on a given date. Measurements across time are also useful, but will reflect seasonal changes in moisture. A gravimetric soil moisture measurement can be helpful to compare different sites at different times. Bulk density measurements or organic matter measurements can also add more detail to your understanding of the site soil. Mid- Spring is often a good time to sample as it is likely to be the most important time for plant establishment and exhibit the greatest differences in moisture content.
Procedure Clip a new strip of 2” wide tape on the stick after slipping it
under the slide frame. Remove the slide hammer snubber cord. Label the tape at the top with the date, site name and specific
location and your initials or name. Hold the penetrometer vertically where you wish to measure
soil strength by holding the wooden stick at a comfortable height.
First hold the tip of the penetrometer at the soil surface and make a mark on the tape using the top of the sliding frame to guide your pen. Label this S for soil surface. Hold the pencil or waterproof pen at the same angle for every mark.
With the weight at the bottom of the slide let the tip penetrate into the soil by its own weight, mark a line on the tape at this point and label this F for free fall.
Then lift the slide hammer to the top of the shaft and let it drop, marking the tape after each drop. I usually make the 5, 10, 15, 20 lines longer to help in later data writeup.
Don’t throw or force the hammer to drop, just lift it and let it drop in freefall. If you hold the pen in your hammer hand this can go quite quickly. Keep the penetrometer vertical for each drop by keeping your holding arm in the same position (you can also put a two way level on the stick but it is not necessary once you get used to it. A second person holding the stick makes it faster and easier.
If you hit a rock and penetration stops, start over again nearby. The pin can penetrate a considerable distance in soft soils, but the most important soil characteristics are usually within the top 0-30 cm where a seedling would start to grow.
For a rapid survey you might just mark hits at 5, 10, and 15 drops. In dry hard soils you may only get in 5 cm after thirty drops. No sense spending more time if the pin is not moving. If you drive the pin in too deep in hard ground it can be hard to pull out. Pull up on the lower part of the pin.
After you reach the end of the sampling remove the tape and fold it neatly. I prefer to keep the paper tapes in a ziplock plastic bag. This keeps them dry and clean and easier to sort out when you get back to the lab.
David A. Bainbridge sustainabilityleader@gmail.com
Simple impact penetrometer, Ant Hill Restoration Project Anza Borrego Desert State Park
Restoration Notes v2n3 2014
Equipment and vehicle operation, agricultural operations, horses, mountain bikes, and pedestrians can leave a lasting legacy of compacted soil. This can reduce infiltration, slow or prevent root growth, and prevent or inhibit vegetation recovery.
Serving Sizes
Plotting Trim the tapes and lay them out on lined white paper,
matching soil surface lines to a bold line running across the top of the paper. Transfer all needed information on site location. Tape them down with clear tape, leaving room between tapes to note distances. Then lay your mm ruler on the center of the marks and note the distance to each line from zero at the soil surface line. Transfer the numbers to the excel spreadsheet. I use negative numbers because I think it makes more intuitive sense to see the plot this way.
Compacted soils on project sites can be improved by breaking up the soil as deeply as possible. This should be done without inverting the soil layers to maintain a natural fertility gradient.
A ripping tooth, backhoe bucket with teeth, spader or auger can be used to de-compact soil. A spader instead of a tiller should be used to prevent soil inversion. A garden fork, square tine, can be used to decompact soils that are not in extremis, but for severely disturbed sites powered equipment will be needed.
CLIP LOCK THE FRAME for TRAVEL If you will be walking to the site or between sample locations with
the penetrometer use the big clips to lock the sliding frame in place with the clips on the yellow marks. Use the small elastic cord to secure the slide hammer to avoid pinches. Carry the penetrometer by holding the wood stick about mid-frame for balance.
Not full scale
Build your own penetromer for about $50 It is not difficult to make your own soil penetrometer. The parts
can be found at hardware, auto supply (slide hammer for dent removal), and office supply stores. I experimented quite a bit before settling on this design and it has worked faithfully for more than 20 years. It was also loaned and used by others.
For several years I had a self-marking version that marked the tape when the hammer was lifted--but it eventually succumbed to rough treatment in the back of field trucks. You may find it a help if you will be working alone. I used a double linkage lever to swing the pencil stub.
The 1 kg hammer with 6 mm blunt bullet shaped tip was best and resisted damage when hitting rocks. A drop height of 60 cm gave good penetration on commonly encountered soil conditions.
Weld on the sleeve to act as the anvil for the dropped hammer. The drill extension can be welded to the rod but will be stronger if it is placed in a drilled hole in the end of the slide bar first. Weld cross bar at the top.
The drill bit extension has a hex set screw so that you can change tips. To maintain this function over time the hole must be tapered slightly so the mashing doesn’t lock the tip in.
Round off the edges of the wood stick, all brackets and metal edges. Nylock nuts improve durability.
Metal handle used as slide guide, hinge used as cross bar
UHMW plastic strips used to build guide channel
For more information on soil strength and treatment of compacted soils see:
Bainbridge, D. A. 2007. A Guide to Desert and Dryland Restoration. Island Press, Washington, DC.
Bainbridge, D. A. 1993. Soil compaction. Land and Water. 37(1):42-43. http://works.bepress.com/david_a_bainbridge/subject_areas.html http://alliant.academia.edu/DavidBainbridge www.sustainabilityleader.org
Sostenga el penetrómetro verticalmente donde se desea medir la resistencia del suelo sosteniendo el palo de madera a una altura cómoda.
Primero sostenga la punta del penetrómetro en la superficie del suelo y hacer una marca en la cinta con la parte superior del marco de deslizamiento para guiar su pluma. Etiqueta de este S para la superficie del suelo. Sostenga el lápiz o la pluma a prueba de agua en el mismo ángulo para cada marca.
Con el peso en la parte inferior de la diapositiva que la punta penetre en el suelo por su propio peso, marque una línea en la cinta en este punto y la etiqueta de esta F para caída libre.
A continuación, levante el martillo deslizante hacia la parte superior del eje y la dejó caer , marcando la cinta después de cada caída. Normalmente suelo hacer los 5 , 10 , 15, 20 líneas más para ayudarle en writeup datos más tarde.
No arroje ni forzar el martillo para caer, tan sólo levante y la dejó caer en caída libre. Si mantiene la pluma en la mano un martillo que esto puede ir bastante rápido . Mantenga el penetrómetro vertical para cada gota, manteniendo su brazo de sujeción en la misma posición (también se puede poner un nivel de dos vías en el palo, pero que no es necesario una vez que te acostumbras a él. Una segunda persona que sostiene el bastón hace que sea más rápido y más fácil.
Si usted golpea una roca y paradas de penetración , empezar de nuevo cerca. El pasador puede penetrar una distancia considerable en suelos blandos , pero las más importantes características del suelo son por lo general dentro de los 0-30 cm superiores , donde una planta de semillero comenzaría a crecer.
Para una encuesta rápida que sólo podría marcar imparables en 5 , 10 , y 15 gotas. En suelos duros y secos que sólo puede estar en 5 cm al cabo de treinta gotas. No tiene sentido gastar más tiempo si la clavija no está en movimiento. Si usted conduce el pasador en lo profundo de la tierra dura que puede ser difícil de sacar. Tire hacia arriba de la parte inferior del pasador.
Después de llegar a la final de la toma de muestras retire la cinta y doblar prolijamente. Prefiero mantener las cintas de papel en una bolsa de plástico ziplock. Esto los mantiene seco y limpio y más fácil de resolver cuando vuelvas al laboratorio.
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Marking sites for remeasuring soil properties is challenging. These stakes were too short and the paint and tape faded. Metal fenceposts 1 m tall are better. Blue paint is often easier to see. Reflective tape helps as well.
Disturbance impacts on soil strength, Anza Borrego Desert State Park
uncorrected Google translations
Spring 2014
Soil penetrometer