Glossary

6" sensors

Sensors located six inches below ground, evaluating the soil for deep to shallow-rooting plants.

There is a large amount of growth at the 6-inch depth, where Teralytic probe sensors measure soil moisture, salinity, soil, temperature, pH, nitrate, potassium, phosphorus, aeration, and respiration.

18" sensors

Sensors located 18 inches below ground, evaluating the soil for moderate to deeper-rooting plants.

Teralytic probe sensors at the 18-inch depth measure soil moisture, salinity, soil, temperature, pH, potassium, nitrate, phosphorus, aeration, and respiration.

36" sensors

Sensors located 36 inches below ground, evaluating the soil for deep-rooting plants like trees and large shrubs.

Teralytic probe sensors at the 36-inch depth measure soil moisture, salinity, soil, temperature, pH, potassium, nitrate, phosphorus, aeration, and respiration.

Aeration

The available oxygen content in the soil.

A soil's aeration relates to the microbes' and plant roots' ability to respire (create energy) as well as the moisture content of the soil. A low rate of oxygen diffusion in soils typically relates to poor soil structure and compaction from low porosity (i.e. less pore space in the soil). When soil has a low rate of oxygen diffusion, or low aeration, flooding may have occurred. If soil is flooded for more than two days, root growth for most plants will be inhibited.

Air temperature

The degree of heat in the air.

Each crop has its own optimal maximum and minimum temperature conditions for their growth and development. Too high or too low of air temperatures can be detrimental for plants.

Humidity

The amount of water vapor in the atmosphere.

Relative humidity impacts growth as plants transpire. When humidity and temperatures rise, plants close there stomata to reduce water losses within plants. This prevents plants from performing photosynthesis.

Illuminance

Describes the measurement of the amount of light spreading over, or illuminating, a given surface area such as a field.

Illuminance, or light, is measured in lux (lx). Lx is a measure of the intensity of light that hits or passes through a surface, as perceived by the human eye. For plants, about 1,100 lx for at least 12 hours per day is typically the minimum light requirement to gain any benefit from fertilization. Above 10,000 lx is preferred, however, too much direct light or change in light intensity can result in leaves bleach and scald, and often plants will die.

Nitrate (NO
3
)

One of the inorganic forms of the macronutrient, nitrogen, a chemical element naturally occurring in soil that plants utilize for growth.

For growth, plants require a substantial amount of nitrogen, a macronutrient. It is used in plants for chlorophyll, amino acids, and nucleic acids through its inorganic form of nitrate.

Nitrate leaching

The loss of nitrate due to rainfall and/or irrigation moving it further down in the soil, past the root zone.

Nitrate leaching takes place as nitrate in the soil profile moves along with water downward past the root zone. Leaching can be reduced as nitrogen is applied at the right rate, time, place, and type of fertilizer.

pH

The measure of the acidity or alkalinity of a soil, also known as the soil reaction.

In scientific terms, pH is the negative logarithm of the hydrogen ion concentration, or -log [H+]. This measure of the acidity and alkalinity in soils will range from pH 0 to pH 14. A pH of 7 is neutral, below 7 is acidic, and above 7 is alkaline. The optimal pH range for most plants range from pH 5.5 to pH 7.0. However, many varieties of plants are able to thrive outside of this range.

Phosphorus

A chemical element naturally occurring in soil and required for various plant functions.

Typically taken up by plants as H2PO4- and HPO42-, phosphorus (P) is required for plant functions such as energy transfer reactions, development of new tissues, root development, and protein synthesis. In reference to fertilizer, phosphorus is usually reported as P or P2O5 in reference to fertilizer.

Porosity

The amount of space between soil particles.

Soils porosity is the volume that is not occupied by solid material. Ideal soil for plant growth contains 50% pore space and 50% solids. This allow for adequate water and air flow storage and movement in soils. Compaction can reduce soil porosity resulting in causing less water and air storage in soil.

Potassium

A chemical element naturally occurring in soil and providing plants with better root growth and drought tolerance.

Typically taken up by plants as K+, potassium provides plants with better root growth and improves drought tolerance. It also activates enzymes involved in plant growth and helps build cellulose. In reference to fertilizer, potassium is reported as K2O.

Respiration

The release of carbon dioxide due to soil organisms respiring.

Carbon dioxide (CO2) is a bi-product of plant root and microbial metabolism, or energy production, in the soil. The soil respiration is reflective of the productivity of the soil. A higher concentration of CO2 (more than 3%) relates to the organic material (carbon in the form of dead plant material), roots exudates, dead microbes, nutrient availability, oxygen present, moisture, temperature, and microbial population. When CO2 concentration is too high (>10%), plants and microbes are impacted negatively. A sustained accumulation of high CO2 suggests compacted soils with poor air flow back to the surface.

Root penetration

The process of roots growing through the soil.

Root penetration is highly impacted by characteristics such as soil structure, texture, moisture, and compaction. Adequate root penetration take place in soils allowing for ample pore space, aeration, and drainage. Poor root penetration occurs in compacted and/or shallow soils with smaller pores.

Salinity

The total salt content in the soil, reported as electrical conductivity (EC).

The salt content of soil includes chlorides, sulfates, perboric acid, bicarbonates, calcium, magnesium, sodium, and potassium. This can be added to soil from irrigation water, fertilizer, or naturally due to soil/rock weathering. When salinity is too high, production/yield decreases as plants have to invest more energy in keeping the salts out of their tissue (i.e. osmotic regulation). Salinity is reported as electrical conductivity (EC) in dS/m or mmhos/cm. Different crops will have varying tolerances. Plants further along on in growth and development tend to have a higher tolerance to salinity than less developed plants.

Soil erosion

The detachment and transportation of soil particles by wind, water, ice, or gravity.

Soil erosion can occur in many forms, from a slow and unnoticed process to sometimes occurring an alarming rate. Erosion causes a loss of topsoil, or a loss of fertile land for farming.

Soil moisture

The available water content (AWC) of the soil, or the amount of water available to the plant for uptake.

Teralytic is reporting soil moisture as the soil's available water content (AWC), or the amount of water in the soil that is available for growing crops. This is typically water that remains in the pores of the soil between field capacity (FC) and permanent wilting point (PWP). Water in larger pores of the soil drains via gravity, and any water that remains is being held by capillary forces. FC is the water held in soil 24 to 48 hours after a precipitation or irrigation event, and PWP is the point at which the water is held too tightly by the soil for plants to extract it for use.

Soil temperature

The warmth in the soil, measured by the heat exchanged between the soil and soil surface.

A soil's temperature impacts many factors. These include seed germination, nutrient uptake and availability, plant growth, microbial processes, soil movement (freezing and thawing), carbon and nutrient loss (fires), water flow and evaporation. Changes in soil temperature typically lag behind air temperature changes.

Terascore

An overall ranking of soil quality influenced by static and dynamic soil properties as well as management.

Teralytic developed the Terascore to determine soil quality by ranking static and dynamic properties. These include soil texture, moisture, infiltration and drainage, slope, organic carbon content, O2, salinity, fertility, pH, and NPK, as well as climate factors. The soil profile of each individual farm is incredibly unqiue, and the overall ranking of soil quality is influenced by factors far beyond a simple soil texture designation of sand, silt, or clay. Iowa and California, for example, experience very different rainfall, light, temperature, humidity, air, and wind. And while many crops will grow on level terrain, some crops like avocado and grapes are grown on hillsides—lending to lower infiltration in the ground and increased erosion. The Terascore weighs these factors by importance based on scientific and historical data, providing farmers with a soil health score and recommendations for improvement.

Waterlogging

When a soil is saturated and the water remains in the soil for an extended period of time.

Waterlogging leads to a lack of oxygen in the soil profile, meaning plant roots cannot respire. Implementing a drainage system can help remove excess water.

°C

Degrees Celsius, the metric unit of temperature.

The unit of temperature used in the majority of the world besides the United States. Temperature (°C) = (Temperature(°F) - 32) × 5/9

°F

Degrees Fahrenheit, the unit of temperature.

The unit of temperature primarily used in the United States, and is also used in the Cayman Islands, Palau, Bahamas, and Belize. Temperature (°C) = (Temperature(°F) - 32) × 5/9

dS/m

DeciSiemen per meter, a unit of electrical conductivity.

Electrical conductivity (EC) is often used as a measurement of soil salinity. DeciSiemen per metre (dS/m) and millimho per centimetre (mmho/cm) are the most commonly used EC units.

Footcandle (FC)

The non-SI unit of illuminance, equal to the illuminance cast on a surface by a lighted standardized wax candle located one foot away.

One footcandle refers to the degree of illumination cast on a surface by a lighted standardized wax candle located 1 foot away; 100 footcandles is 1 foot away from 100 candles that are lighted simultaneously. One footcandle is equal to 10.76391 luces and 1 lux is approximately equal to 0.093 footcandle.

kg/ha

Kilograms per hectare.

A measurement typically used for fertilizer application rates. 1 kilogram/hectare (kg/ha) = 0.89 pounds/acre (lbs/a).

lbs/acre

Pounds per acre.

A measurement typically used for fertilizer application rates. 1 pound/acre (lbs/a) = 1.12 kilograms/hectare (kg/ha).

lux (lx)

The SI unit of illuminance, equal to one lumen per square meter.

Lux (pl. luces) is the unit of illumination that a surface receives one meter away from a light source. It is equal to one lumen per square meter.

ppm

Parts per million.

Parts per million can refer to any unit where there is one part per million. For example,1 milligram/kilogram is equal to 1 ppm. 1 ppm = 0.0001%, and 1000 ppm is equal to 0.1%.