Soil Water, Irrigation, and the Hydrologic Cycle

Comprehensive vocabulary flashcards covering soil moisture potential, hydrologic movements, irrigation efficiencies, soil physical properties, and plant nutrient management.

Ideal Soil Composition

The optimal physical proportion of components in soil consisting of $25\%$ air, $25\%$ water, and $50\%$ solids.

Matric Potential

The component of soil water potential resulting from the attraction of water to soil solids (adhesion and capillarity); it is not appreciably influenced by the force of gravity and is more negative than pure water.

Percolation

The movement of water downward through the soil profile.

Infiltration

The process by which water enters the soil pore space and becomes soil water.

Field Capacity (FC)

The soil moisture content after full saturation once excess water has drained away due to gravity and matric forces begin to dominate subsequent water movement.

Cohesion

The attractive force between water molecules that causes them to stick to one another.

Adhesion

The attractive force binding water molecules to solid soil surfaces (the soil matrix).

Water Use Efficiency (WUE)

The amount of evaporative water required to produce $1\,\text{kg}$ of plant dry matter.

Transpiration Pull

The primary driving force that lifts water from roots to leaves against gravity due to water potential gradients extending from the soil, roots, stem, and leaves into the atmosphere.

Water Table

The upper boundary of the zone of saturation; the level to which water will rise when an excavation or deep hole is dug into the ground.

Evapotranspiration (ET)

The combined total water loss occurring directly from soil surface evaporation and plant transpiration.

Perc Test

A percolation test conducted on-site to assess soil drainage suitability for a septic tank system.

Water Molecule Polarity

The asymmetrical electrical charge distribution of a water molecule resulting from an $\text{H}-\text{O}-\text{H}$ bond angle of $105^\circ$.

Components of Total Soil Water Potential

The energetic components determining total soil water potential, comprising gravitational, matric, submergence, and osmotic potentials.

Water Content vs. Soil Water Potential

A distinction where water content describes the physical amount of water present, whereas soil water potential refers to the energy status of that water.

Volumetric Water Content

The volume of liquid water associated with a specified volume of dry soil (typically measured per $1\,\text{m}^3$).

Preferential Flow

The rapid downward movement of water through specific pathways or channels in the soil profile in preference to slower, uniform movement through the bulk soil matrix.

Available Water Content (AWC) / Plant-Available Water (PAW)

The quantity of water retained in a soil between its permanent wilting point (PWP) and its field capacity (FC).

Soil Moisture Release Curve

A graphical curve showing the relationship between soil water content and soil matric potential across different soil textures, used to assess available water content and irrigation timing.

Clear Plastic Mulch

A surface soil covering that results in the highest summer soil temperatures by transmitting solar radiation directly while trapping heat.

Secondary Macronutrients

The trio of essential plant macro-elements consisting of calcium ($\text{Ca}$), sulfur ($\text{S}$), and magnesium ($\text{Mg}$).

N-P-K

The three numbers commonly printed on a fertilizer container indicating the guaranteed analysis of nitrogen, phosphorus, and potassium.

Haber-Bosch Process

An industrial manufacturing process operating under high pressure and heat to synthesize ammonia by fixing atmospheric nitrogen gas.

Field Water Efficiency

The percentage of applied water consumed by crop transpiration, defined by the formula: $\frac{\text{water transpired by the crop}}{\text{water applied to the field}} \times 100$.

Water Application Efficiency

The efficiency percentage comparing the amount of water available or allocated for field irrigation against the amount of water actually used in plant transpiration.