Soil Water Processes:Chapter 3 Learn how soil properties influence runoff, infiltration and plant growth. 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 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 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. Learn how to quantify the amount of water that is stored in the soil and how this amount changes with time.

Soil Texture Figure 3.1

Figure 3.2 Textural Triangle

Terms Voids/Pores Voids/Pores Saturated Saturated

Figure 3.3 Soil Matrix

Porosity Equation 3.3

Volumetric Soil Water Content Equation 3.4 Volumetric Soil Water Content=Vw/Vt

Degree of Saturation Equation 3.5

Gravimetric Soil Water Content Equation 3.6 Gravimetric Soil Water Content=m w /m s

Terms Bulk Density Mass of soil per unit volume Mass of soil per unit volume Density of soil particles usually near 165 lb/ft 3 or 2.65 g/cm 3 Density of soil particles usually near 165 lb/ft 3 or 2.65 g/cm 3 Compare different soils Compare different soils

Bulk Density Equation 3.8

Dry Bulk Density Equation 3.10

Terms Tension-infiltration Tension-infiltration Adhesion, Cohesion, Capillary, Suction Forces Adhesion, Cohesion, Capillary, Suction Forces Gravity-infiltration Gravity-infiltration Small pores vs. Large pores Small pores vs. Large pores Field capacity & Wilting point Field capacity & Wilting point

Water Retention Figure 3.4

Hysteresis Figure 3.5

Plant Response to Soil-Water Content Figure 3.10

Plant Available Water versus Texture Figure 3.5

Soil-Water Relationships Figure 3.6

Fig Factors Affecting Water Movement in Soils

Estimating Infiltration Rates Empirical Methods Empirical Methods Horton and Green-Ampt Equations Horton and Green-Ampt Equations Physical Based Methods Physical Based Methods Darcy’s Law Darcy’s Law Flow related to hydraulic gradient and soil type 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

Fig Seasonal Soil Water Balance in Ohio

Fig. 4.1

Fig. 4.4

Fig. 4.5

Fig. 4.6

Annual Pan Evaporation in the USA