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Explore how soil properties affect runoff, infiltration, and plant growth. Learn common terms describing soil profiles and properties. Understand the main processes of wetting and drying soil. Discover methods to quantify soil water storage and changes over time.
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Soil Water Processes • Learn how soil properties influence runoff, infiltration and plant growth. • Learn some of the common terms that are used to describe soils profiles and soil properties. • Learn about the main processes that occur when a soil wets and drys. • Learn how to quantify the amount of water that is stored in the soil and how this amount changes with time.
Terms • Voids/Pores • Saturated
Volumetric Soil Water Content Volumetric Soil Water Content=Vw/Vt
Gravimetric Soil Water Content Gravimetric Soil Water Content=mw/ms
TermsBulk Density • Mass of soil per unit volume • Density of soil particles usually near 165 lb/ft3 or 2.65 g/cm3 • Compare different soils
Terms • Tension-infiltration • Adhesion, Cohesion, Capillary, Suction Forces • Gravity-infiltration • Small pores vs. Large pores • Field capacity & Wilting point
Water Retention Figure 3.4
Hysteresis Figure 3.5
Plant Response to Soil-Water Content Figure 3.10
Estimating Infiltration Rates • Empirical Methods • Horton and Green-Ampt Equations • Physical Based Methods • Darcy’s Law • Flow related to hydraulic gradient and soil type
Seasonal Soil Water Balance SM P IR Q G ET SM is the change in soil water storage in the soil profile P is precipitation IR is irrigation G is percolation water ET is evapotranspiration Q is surface runoff
Seasonal Soil Water Balance in Ohio Fig. 3.23