1. Soils

2. Man—despite his artistic pretensions, his sophistication, and his many accomplishments—owes his existence to a six-inch layer of topsoil and the fact that it rains. - Author Unknown

3. Soil: Definition Solid earth material that has been altered by physical, chemical and organic processes so that it can support rooted plant life. Engineering definition: Anything that can be removed without blasting

4. Soil Production

5. Soil Production: Inputs Conversion of rock to soil

6. Soil Production: Outputs Downslope movement of soil

7. Soil Thickness: Storage Soil thickness reflects the balance between rates of soil production and rates of downslope soil movement. Slope Weathering Rate

8. Factors of Soil Formation Climate Organisms Parental Material Topography Time

9. Factors of Soil Formation Climate Temperature and precipitation Indirect controls (e.g., types of plants) Weathering rates The greater the rainfall amount, the more rapid the rate of both weathering and erosion.

10. Factors of Soil Formation Organisms Types of native vegetation Weathering is dependent of plant growth Plant and animal activity produces humic acids that are powerful weathering agents. Plants can physically as well as chemically break down rocks. Plants stabilize soil profiles, Animals (including humans) tend to increase erosion.

11. Soils on hillslopes reach an equilibrium thickness, often about 1 m. Soils on flat surfaces, such as floodplains or plateaus, tend to thicken through time due to weathering rates being greater than sediment transport rates. Factors of Soil Formation

12. Inputs from outside ecosystem –Atmospheric inputs Precipitation, dust, deposition –Horizontal inputs Floods, tidal exchange, erosion, land-water movement Inputs from within ecosystem –Litterfall and root turnover Additions to Soils

13. Decomposition of organic matter Humification to form complex organic matter Weathering of rocks –Physical weathering Fragmentation of rock –Freeze-thaw; drying-wetting; fire Physical abrasion –Abrasion by glaciers –Chemical weathering Dissolves primary minerals Forms secondary minerals Transformations

14. Breakdown of soil organic matter to form soluble compounds that can be absorbed or leached Depends on –Quantity of input –Location of input (roots vs. leaves) –Environment Temperature Moisture Decomposition

15. Physical weathering breaks rocks into small mineral particles.

16. Chemical weathering dissolves and changes minerals at the Earth’s surface.

17. Decomposing organic material from plants and animals mixes with accumulated soil minerals.

18. Parent material (bedrock) undergoes weathering to become regolith (soil + saprolite).

19. Rates of Soil Development U.S. Department of Agriculture estimates that it takes 500 years to form an inch of topsoil. That’s less than 0.01 mm yr -1

20. Erosion of Natural Capital Modern rates of soil loss are 100 to 1000 times rates of soil formation (typically mm yr -1 to cm yr -1 in agricultural settings). Sets up a fundamental problem due to the erosion of natural capital!

21. Soil and the Life-Cycle of Civilizations How long would it take to erode 1 m thick soil? Thickness of soil divided by the difference between Rate of soil production and erosion. 1 m ≈ 1000 years 1mm -.01 mm This is about the life-span of most major civilizations...

22. National Archives: 114 SC 5089 A nation that destroys its soils, destroys itself. – President Franklin D. Roosevelt, Feb. 26, 1937.

23. Topics How soils affect agriculture –Nutrients –Water –Ph and other chemistry –texture How agriculture effects soil –Erosion –Nutrients –Compaction –Burning –Chemicals

24. Soils effect food production Food production effects soils

25. Soil properties that promote or inhibit plant growth nutrient reserves, water holding capacity, and favorable structure for root growth the size and continuity of pores, aggregate stability, impedance, and texture, which together determine soil structure chemical properties such as organic matter content and composition, nutrient stocks and availability, mineralogy amount of elements and compounds that are deleterious to plant growth biological attributes such as the quantity, activity, and diversity of microbial biomass and soil fauna

26. Soil respiration rate

27. CGT = composted cotton gin trash (organic compost)

28. Physical properties of soil The physical properties of soils — texture, structure, density, porosity, water content, strength, temperature, and color — determine the availability of oxygen in soils, the mobility of water into or through soils, and the ease of root penetration.

29. Soil bulk density Soil bulk density is the mass of soil per unit volume in its natural field state and includes air space and mineral plus organic materials. Bulk density gives useful information in assessing the potential for leaching of nutrients, erosion, and crop productivity. Runoff and erosion losses of soil and nutrients can be caused by excessive bulk density when surface water is restricted from moving through the soil. Bulk density provides an estimate of total water storage capacity when the soil moisture content is known.

31. Soil infiltration rate Infiltration is the process of water entering the soil. Infiltration rate is dependent on the soil type; soil structure, or amount of aggregation; and the soil water content Soil crusting, compaction, vegetative cover, and root and earthworm channels also influence the ability of water to move through (infiltrate) soil layers. Infiltration is important for storing water in the soil profile for plant growth and for reducing runoff and erosion.

34. Water holding capacity

35. Soil degradation Water erosion, wind erosion, chemical degradation (including nutrient depletion and loss of organic matter) salinization, acidification chemical pollution deterioration of physical properties especially compaction

36. Actions in food production that affect soils negatively Initial land clearance Tillage –Erosion –compaction Harvest of crops –Removal of organic matter and nutrients Irrigation –Salts –Chemicals –Leaching –Erosion Burning crop residues

37. Conservation tillage which leave a minimum of 30% of crop residue on the soil surface or at least 1,000 lb/ac (1,100 kg/ha) of small grain residue on the surface during the critical soil erosion period. This slows water movement, which reduces the amount of soil erosion. Conservation tillage systems also benefit farmers by reducing fuel consumption and soil compaction. By reducing the number of times the farmer travels over the field, farmers realize significant savings in fuel and labor. Conservation tillage was used on about 38%, 109,000,000 acres (440,000 km 2 ), of all US cropland, 293,000,000 acres (1,190,000 km 2 ) planted as of 2004 according to the USDA.

39. Benefits of tillage Plowing loosens and aerates the top layer of soil which can facilitate the planting of the crop. It helps in the mixing of residue from the harvest, organic matter (humus) and nutrients evenly throughout the soil. It is used for destroying weeds. Drys the soil before seeding

40. Negative effects of tillage Dries the soil before seeding. The soil loses nutrients and ability to store water Erosion of soil. Higher rate of fertilizer and chemical runoff. Decreases the water infiltration rate of soil. Reduces organic matter in the soil Destroys soil aggregates Compaction of the soil

41. Burning crop residues

42. Burning crop residues: pro and con Kills insects pests and weeds For specific crops like grass seeds it increases productivity Exposes soil to spring warming faster Smoke is a health hazard Burns organic matter in soil Loss of nutrients

43. Irrigation methods Surface or flood Sprinkler Drip Subsurface

44. Surface or flood irrigation

45. Sprinkler irrigation: center pivot

46. Sprinkler irrigation: hand line

47. Sprinkler irrigation: traveling irrigation guns

48. Drip irrigation

49. Subsurface irrigation

50. Actions in food production that benefit soils Cover crops Green manure Strip Cropping Contour plowing Wind breaks Addition of compost Addition of chemicals such as lime to balance ph Irrigation –Increase moisture content

51. Shelter Belts

56. Inca technology

57. China

58. Soil loss rates Location Mm/yr soil lost pre ag Mm/yr soil lost after ag Bethany, MO0.04558911.1 Tyler, TX0.0160183.6 Guthrie, OK0.0046543.5 Clarinda, Iowa0.0116973.7 Statesville, NC0.0018563.4

63. Summary There is a close linkage between soils and agriculture, with each greatly affected by the other You must understand the nature and structure of soil to understand how they interact. Remember soil is the basis for human life and civilization

64. Study Guide List 4 ecosystem functions of soils Sustaining biological activity including growing crops Regulating water flow Filtering and buffering chemicals, especially toxics Storing nutrients and elements such as carbon and nitrogen List some soil properties that promote plant growth Amount of nutrient reserve, water holding capacity, structure of the soil allowing root penetration, lack of toxic substances, micronutrients, List 2 aspects of agriculture that increase and 2 that decrease soil respiration Increase: adding organics and amendments, irrigating to proper moisture content Decrease: burning residues, tillage, many chemicals that kill biota It is the metabolic activity of the soil ecosystem and is normally measured by CO2 production. What level of soil respiration would you expect from pure sand or clay? No respiration as there are no living components of pure sand or clay. What factors important to plant growth are affected by the physical properties of the soil? The water content, root penetration ability and oxygen content are all affected by the physical properties of the soil. What is bulk density of soil? It is the mass of soil per unit volume. What would be the impact of a soil that allowed little soil infiltration? Water, either from rain or irrigation would run off the surface rather than penetrating to the topsoil and subsoil. List factors caused by agriculture that degrade soil Water erosion, chemical degradation, salinization, acidification, chemical pollution, deterioration of physical properties What is the impact of soil degradation on yield per hectare? Yield declines as soil degrades. What is conservation tillage? It is leaving residues of the previous crop on the surface when the ground is tilled. Why is conservation tillage cheaper for the farmers? Primarily because the tilling device does not go as deep into the ground, so it takes less gas to pull the device through the field. Tillage exposes soil to the air and in the spring causes it to dry. Is this good or bad for farming? Both, if the soil is too wet it is good, but if soil moisture is limiting it will be bad. How does farming lead to soil compaction and what are some of the consequences? Driving machinery across a field compresses the soil, removing air spaces and making the water holding capacity and the infiltration rates lower. Why does deep plowing lead to more CO2 flux that conservation tillage? More soil and organic matter is exposed to the air and thus respires. What are some benefits to farmers of burning crop residues? Killing insects and weed seeds, exposing the soil to the sun, may increase productivity List actions that farmers can take to improve soil productivity. Cover crops, green manure, wind breaks, compost, strip cropping, contour plowing, terracing, some chemicals such as lime, irrigation when soil moisture is limited. How does a shelter belt of trees protect soil productivity? They reduce the wind and thus both drying and wind caused erosion