Oak Hill Case

1. Oak Hill Case Soil Physical Problems

4. Surface Drainage Reflects the ease with which water can move downslope. Reflects access to catch basins through which surface water can be removed from a site. Internal Drainage Reflects the ease with which water can move through the soil matrix. Reflects the presence or absence of obstacles (e.g., pans, layers) to internal soil water movement. Poor Drainage

5. Surface Drainage To the extent that water falls at a rate in excess of a turf’s infiltration capacity, the excess will flow downslope and accumulate in depressions. Catch basins situated in depressions can remove surface water and conduct it to drain lines or elsewhere.

6. Internal Drainage Water moves through the pores permeating the soil matrix. The larger the pores, the faster the movement of water through the soil.

7. Soil Aeration As water drains from the macropores, O2 is drawn in and CO2 and other gases are liberated from the soil. A favorable relationship between O2 and CO2 in the turf rootzone is thus maintained.

8. Capillary (available & unavailable water) Saturated soil Dry soil Unavailable water Gravitational Water Decreasing Soil Moisture

9. Soil Water Movement Therefore, the rate at which water moves through the soil reflects its porosity and pore-size distribution. Soils with a high proportion of macropores (i.e., coarse textured soils) conduct water more rapidly than finer textured soils. As the surface dries from ET, water moves up from lower regions of the soil.

10. Water Potential (Yw) YW is a measure of the energy status of water; as free standing water has no energy, its YW = 0. Soil water potential is symbolized by YSW The components of soil water potential are: • matric potential (YM) • osmotic potential (YO) • pressure potential (YP) YSW = YM +YO +YP YSW is measured in units of pressure, including bars and Pascals; 1 bar = 100 kP or 1 cb = 1 kP.

11. W = < 0 (due to M) W = 0 W = > 0 (due to P) pure water

12. Water potential gradient Low SW High SW

13. Matric Potential M higher lower

14. Lower W Higher W higher lower

15. Matric Potential (YM) This reflects the amount of water retained by the soil matrix. As this amount declines, the water films surrounding soil particles become thinner and are held more tightly, and YW decreases correspondingly. • At saturation, YM is near 0. • At field capacity, YM = -0.1 to -0.33 bar (-10 to -33 kPa). • At the permanent wilting point, YM = -15 bar (-1500 kPa).

16. higher lower Osmotic Potential O pure water salty water

17. Osmotic Potential (YO) This reflects the concentration of solutes in the soil water. As this concentration increases, YO decreases. In pure water (containing no solutes), YO = 0. In saline soils, the combination of YO and YM can reduce YSW dramatically, especially as the soil dries (e.g., where YO = -216 kP and YM = -200 kP, YSW = -416 kP, which indicates a major reduction in soil water availability).

18. 105° +√ +√ -√ H H O

20. Ca2+

21. Pressure Potential (YP) This reflects the positive pressure to which water may be subjected in some environments. In a glass of water, the water at the top of the glass would have a YP of 0; however, the YP of the water at the bottom would have a positive number. Where a perched water table exists above the base of a soil or sand layer, the YO may be positive as well; however, YO = 0 in most soils.

22. Components of SW

23. SWUnits of Measurement

24. M + O = SW

27. Textural Layers Textural layers within the soil profile can seriously disrupt water movement. Where a fine textured layer occurs above a coarse textured layer, a perched water table can form. Conversely, where a coarse textured layer occurs above a fine textured layer, a temporary water table can form.

28. Black Layer

29. ET THATCH SOIL

33. Soil Structure As a soil becomes more compacted: • bulk density increases • porosity (especially macroporosity) decreases • water movement through the soil is restricted