AGEN 2363 Chpt. 14 notes: Soil Drainage.

I. Introduction.

A. Problems with wet soils:

B. Types of soil wetness problems:

1. surface ponding –

2. internal soil drainage problems –

a. How recognized:

b. classification:

- well-drained soil =

- poorly drained =

- very poorly drained =

c. What is a ‘gleyed’ soil horizon?

3. flooding: classifications:

- occaisional, frequent

Can a soil have a wetness problem yet show profile characteristics that indicate a

well-drained soil? Explain.

II. Renovation of wet soils.

A. Methods

1. tile drainage: random, regular, or interceptor design

2. ditch work: main ditch, field ditches: random, regular, or interceptor design

3. ‘mole’ drains

4. dikes, levees, pumps

5. precision land leveling

6. bedding systems and mounds

7. vertical wells

8. French drains

B. Maintenance.

outlet debris cleaning, sedimentation of ditches, re-leveling

III. Wetlands.

A. Definition of a ‘wetland’:

B. Three characteristics of a ‘wetland’:

1. A wetland hydrology or water regime.

2. Hydric soils = very poorly drained soils, gleyed horizons, ponded during wet

seasons.

3. Hydrophytic plants: EX. cattails, horsetail, swamp smartweed, etc.

C. Wetlands occupy approximately 14% of the world’s ice-free soils!

D. Value of wetlands to the environment and society:

1. wildlife and recreation

2. filters for sediment and pollutants

3. ground water recharge

E. Areas where wetlands are found:

1. flood plains

2. depressions

3. artesian seep spots

4. artificial

F. Chemical aspects of some wetlands.

1. alkaline seeps

2. microbial reduction of sulfur (Thiobaccillus sp. bacteria) and iron (Ferrodoxin sp.)

3. organic matter buildup

4. nitrate-nitrogen reduction and conversion to N₂, N₂O, and NO by denitrifying bacteria.