The Edaphic Factor I. Thomas G Chastain CROP 200 Crop Ecology and Morphology

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1 The Edaphic Factor I Thomas G Chastain CROP 200 Crop Ecology and Morphology

2 Edaphology is the study of influence of soils on plants and other living things. The Edaphic or Soil Factor is important because of the intimacy of contact between the plant and soil through the root system, and that both the plant and soil are strongly influenced by each other. The nature and properties of the soil determines its productivity as a substrate for crop production. White Mountains of New Hampshire vegetation is influence by the depth of soil (TG Chastain photo)

3 The soil is a major factor in determining the relative distribution and abundance of plant species within plant communities, and is a major defining characteristic of the plant communities themselves. The ecotone is the transitional boundary between two plant communities. Ecotone between plant communities dominated by serpentine and non-serpentine soils in California coastal mountains (top), California juniper on serpentine soil (right) TG Chastain photos

4 Serpentine Soil Non-Serpentine Soil Relative Species Density (%) Digger Pine Leather Oak White Leaf Manzanita Chamise Jepson Ceanothus Yerba Santa Buckbrush California Juniper Relative Species Density (%) Knobcone Pine Black Oak Scub Interior Live Oak Chamise Common Manzanita Western Redbud Birch-leaf Mountain Mahogany 0 Overstory Understory 0 Overstory Understory Effect of serpentine and non-serpentine soils on vegetation in California coastal mountains (Chastain, 1980)

5 Plant species that grow on serpentine soils must be tolerant of very high levels of chromium, nickel, and magnesium. Some species are found in both soils while others only in one or the other soils. Graphic source: University of Florida

6 The soil factor in the crop community (cropping system) is an important determinant of productivity, and can be a defining characteristic of the farming systems that can be employed within a region. The relative distribution and abundance of the crops and weeds within the cropping system is a function of the soil factor. Soil tillage in Willamette Valley field (TG Chastain photo)

7 The soil is a 3-phase system: 1. Solid phase minerals and organic solids in the soil. 2. Solution phase includes water and materials dissolved in soil water. 3. Gaseous phase the soil atmosphere. (TG Chastain photo)

8 The soil provides anchorage for the plant and a ready source of water and nutrients to be accessed by the root system for growth and development, and for yield of the crop. But the soil is full of life itself, and is the habitat for many organisms, some beneficial, and some harmful for crop production. European crane fly larvae (Ken Gray photo), tall fescue plant shoot and roots (TG Chastain photo)

9 Soil Particles 1. Sand Large size particle, 0.05 to 2.0 mm. 2. Silt Medium size particle, to 0.05 mm. 3. Clay Very small particle, less than mm. Soil classes and particle size distribution

10 Soil survey - mapping the geographic distribution of soils on the landscape. Soil drainage, steep terrain, erosion potential, etc. limit the cropping choices for fields. Heavily eroded wheat field (TG Chastain photo) 12 Dayton Silt Loam 14 Bashaw Clay 36 Amity Silt Loam 155 Waldo Silty Clay Loam 170 Willamette Silt Loam 177 Woodburn Silt Loam

11 The vertical distribution of soil is known as the soil profile. The soil profile is composed of horizontal layers known as horizons. The uppermost horizon or surface soil typically has more organic matter than horizons resident at greater depth in the soil profile. The subsoil has less organic matter and typically less biological activity than the surface soil. Surface Soil Subsoil Parent Material Bedrock

12 Soil Tillage - the primary purpose of tillage is to prepare a seedbed. Secondary purposes of tillage include: 1. Control weeds 2. Improve infiltration of air and water into soil 3. Incorporate fertilizers and pesticides into soil 4. Enhance root penetration into soils Moldboard plow in wheat stubble (John McManigal photo)

13 Primary Tillage Equipment 1. Moldboard Plow Lifts and inverts soil and buries crop residues 2. Disk Stirs, mixes, partially inverts soil 3. Sweep Lifts and stirs soil without burying crop residues 4. Chisel Plow Narrow points used for deep tillage 5. Rotary Tillage Mixes, stirs, pulverizes soil. Moldboard Chisel Disk (top TG Chastain photo), chisel plow (bottom - John McManigal photo)

14 Secondary Tillage Equipment 1. Harrow Spring tooth, disk and roller harrows are used to provide the finishing touches on seed beds. 2. Field Cultivator Seed bed preparation, weed control, and incorporation of fertilizers. 3. Rod Weeder Specialized implement used for weed control and soil moisture conservation in fallow seed beds. Spring tooth harrow (top), rod weeder (bottom), John McManigal photos

15 Soil Tillage and Erosion Erosion caused by tillage results in: 1. Reduced productivity of the soil. 2. Reduced soil water storage. 3. Tillage reduces residue on the soil surface contributing to further erosion losses. Chisel plow on hill slope (top John McManigal photo), erosion damage in steep Palouse wheat field (bottom TG Chastain photo)

16 Erosion can remove valuable soil from fields, especially by the action of water and wind. The soil may be deposited in water supplies, thereby causing pollution of water resources. (USDA photos) Wind erosion Water erosion Erosion polluted water

17 Strategies for erosion control: 1. Minimum tillage tillage implements that maintain crop residue and clods on the soil surface. 2. Direct-seeding (no-till) drill crops into field without tillage. 3. Farming system practices terraces, strip cropping, divided slope or contour farming, grass waterways. Direct seeding (top John McManigal photo), terraced field (bottom USDA photo), and divided slope (left - TG Chastain photo).