Soil Resource Guide PDF

Soil Resource Guide PDF

Soil Resource Guide

Soil Resource Guide

Everything you need to know about:

1 Soil Soil monitoring Soil sensors

CONTENTS Why is Soil Monitoring So Important? .

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How Do Soil Sensors Work? .

SOIL Soil Geomorphology.

6 Soil Horizons . 6 Soil Orders and Taxonomy. 7 The 12 Orders of Soil Geomorphology. 7 Soil Textures . 9 Soil Properties . 9 Dielectric Permittivity . 10 Dielectric Theory. 11 How Temperature Affects Dielectric Permittivity. 13 Measuring Apparent vs. Imaginary Dielectric Permittivity . 13 Salinity / Electrical Conductivity (EC) . 14 Bulk EC Versus Pore Water EC. 14 Bulk EC and EC Pathways in Soil. 14 Application of Bulk EC Measurements . 15 Total Dissolved Solids (TDS) . 15 Soil Matric Potential. 16 Soil pH. 16 Soil Texture. 17 Soil Bulk Density. 17 Shrink/Swell Clays. 17 Ped Wetting . 17 Rock and Pebbles. 18 Bioturbation. 18 Soil Monitoring Applications. 19 Archeology . 19 Erosion Studies . 19 Agriculture . 19 Biofuel Studies. 19 Drought Forecasting Models. 20 Landslide Studies. 20 Mesonets and Weather Station Networks. 20 Dust Control. 20 Phytoremediation . 20 Soil Carbon Sequestration Studies. 21 Watershed Hydrology Studies. 21 Wetland Delineation Indicators . 21 Satellite Ground Truth Studies. 21 Reservoir Recharge from Snowpack. 21 Sports Turf. 21 Soil Moisture and Irrigation. 22 Soil Moisture Measurement Considerations for Irrigation. 22 Fill Point Irrigation Scheduling. 23 Mass Balance Irrigation Scheduling. 23

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Soil Resource Guide

SOIL SENSORS Volumetric Water Content Sensors. 26 Tensiometers (Soil Matric Potential Sensors). 26 Single-Point Measurement. 27 Soil Profiling Probes. 28 Permanent and Semi-Permanent Installations . 29 Portable Soil Sensors. 29 Soil Sensor Technologies. 30 Capacitance (Charge). 31 Frequency Domain Reflectometry (FDR) / Capacitance (Frequency). 32 Coaxial Impedance Dielectric Reflectometry. 32 Time Domain Reflectometry (TDR). 33 Determining Soil Moisture Content Without Sensors. 34 Time Domain Transmissometry (TDT) . 34 Other Technologies. 34 Determining Soil Moisture Content Without Sensors. 34 Soil Sensor Calibration. 36 Sensor Accuracy. 36 Glossary . 39 References. 49

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Why is Soil Monitoring So Important? Soil is an important natural resource, just as the air and water that surround us are. Unfortunately it has been over- looked in the past and taken for granted with disastrous results, such as the North American dust bowl of the 1930s. Today, the role of soil health on our climate as a whole is taken more seriously, with researchers at organizations such as the USDA-ARS (US Department of Agriculture, Ag- ricultural Research Service) looking into how exactly soil interacts with the rest of our environment.

it possible to remotely monitor soil and track parameters that simply can’t be easily or quickly measured by hand. Soil probes are now extremely accurate and offer an un- paralleled look at what is going on below the surface. They give instantaneous information on soil moisture content, salinity, temperature, and more. Soil sensors are an im- portant tool for anyone involved with soil, from a small- town farmer trying to increase his crop yield to research- ers looking at how soil retains and releases CO2. More importantly, just as computers have increased in power and dropped in price due to economies of scale, advanced soil measurement systems can be found at prices that are affordable for everyone.

Because of ongoing research and general interest in soil health and sustainability growing every year, monitoring soil in a more substantial and quantifiable way is becoming more important. Monitoring soil in the past meant going out and physically handling the soil, taking samples, and comparing what was found to existing knowledge banks of soil information. While nothing will replace actually going out and handling the soil for basic information, today’s technology makes How Do Soil Sensors Work? Soil moisture sensors (or “volumetric water content sen- sors”) measure the water content in soil, and can be used to estimate the amount of stored water in a profile, or how much irrigation is required to reach a desired amount of saturation. These sensors can be portable and used for in- stant measurements or installed for long-termmonitoring. No commercially available soil moisture sensor measures water directly . Instead, they measure changes in some other soil property that is related to water content in a predictable way. The other soil property becomes a proxy for water content. Common soil properties that change in relation to water content and are easy to measure include dielectric permittivity and matric potential. Sensors that measure dielectric permittivity are the most common type of soil moisture sensor. These sensors use different technologies to measure the permittivity of the surrounding soil. Regardless of the technology used in a sensor, the same principle applies: the bulk dielectric permittivity of soil

changes with volumetric water content. A simple way to think of permittivity is as stored electrical energy. The sensor generates an electric field in the soil. Because water molecules are polar, unbound water mol- ecules in the soil rotate to line up with the electric field lines. The rotation of unbound water molecules requires ener- gy—stored as potential energy in the aligned water mole- cules. More water in the soil stores more energy, and the higher the bulk permittivity of the soil will be. In order for any soil probe to work, no matter the type, it must make contact with the soil. The greatest accuracy will be obtained when the soil probe is fully surrounded by the soil, with no gaps or air holes between the probe and the soil. The probe then sends electrical signals into the soil, measures the responses, and relays this information to a >Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 42 Page 43 Page 44 Page 45 Page 46 Page 47 Page 48 Page 49 Page 50

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