Soil Water Processes:Chapter 3

1. Soil Water Processes:Chapter 3 • 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.

2. Soil Texture Figure 3.1

3. Textural Triangle Figure 3.2

4. Terms • Voids/Pores • Saturated

5. Soil Matrix Figure 3.3

6. Porosity Equation 3.3

7. Volumetric Soil Water ContentEquation 3.4 Volumetric Soil Water Content=Vw/Vt

8. Degree of SaturationEquation 3.5

9. Gravimetric Soil Water ContentEquation 3.6 Gravimetric Soil Water Content=mw/ms

10. 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

11. Bulk DensityEquation 3.8

12. Dry Bulk DensityEquation 3.10

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

14. Water Retention Figure 3.4

15. Hysteresis Figure 3.5

16. Plant Response to Soil-Water Content Figure 3.10

17. Plant Available Water versus Texture Figure 3.5

18. Soil-Water Relationships Figure 3.6

19. Factors Affecting Water Movement in Soils Fig. 3.16

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

21. 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

22. Seasonal Soil Water Balance in Ohio Fig. 3.23

23. Fig. 4.1

24. Fig. 4.4

25. Fig. 4.5

26. Fig. 4.6

27. Annual Pan Evaporation in the USA