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Describe the tilth of the A Horizon of your My Favorite Soil
Jim Miller 01438255 LRES 201 Worksheet 10/6/05 My Favorite Soil Due: 10/11/05
1. Describe the tilth of the A Horizon of your My Favorite Soil . Give specific educated guesses for texture, structure, aggregation, consistence. Db and % pore.
ANS: Tilth: The A horizon has medium high tilth due to the generations of plants adding organic matter to the A horizon. The color was dark gray. The soil easily crumbles while in a low moisture state.
Texture: The soil is generally uniform in color and texture, with with evidence of root canals and worm tubes, The feel test indicated that it had a higher content of loam than clay because it is closely related to organic matter. Some grit was noticed. The probable percentages of materials (Fig. 4.6) is that of a silty clay loam, which puts it in the range of 30-60% sand, 25-40 % clay, and 60-75% loam.
Structure: The predominate material is loam and appears to have a spheroidal structure (p. 103). The Mollisol A horizon shown on Plate 8, p 114, approximates the A horizon of my favorite soil.,
Aggregation: Due to the presence of massive vegetation and the 14” annual precipitation, the soil was aggregated as shown on Plate 8.
Consistence: The low moisture larger clods taken near the surface were broken by hand pressure, but not the pea sized clods. Both sizes of clods taken at 8” with more moisture content were easily crushed by hand. When hydrated, the soil became somewhat more cohesive, but not stickily, although some clay content could be felt. In the soil's low moisture state, it was easily penetrated with a shovel by standing on the rim of the shovel.
Bulk density, pore space: The bulk density, taken at 8” of depth, is probably in the range of 1.3Mg/m3. The pore space is probably 50%.
ANS: The Guidelines for Soil Tilth (p. 126) state:
Minimum tillage: Because of the slope and the use of the land for agroforestry, the landscape will be changed on the slopes to a series of terraces. Please refer to the attached drawing and the description in the Home Grown Organics Farmstead Business Plan submitted as part of My Favorite Soil report. This work involves a one time removal of the A horizon, some relocation of the B horizon, mixing of the topsoil with composted organic matter and placement along the outer (down slope) side of the bench.
Traffic: As much as possible, machinery and equipment will stay on the farm road which zig-zags along the face of the hill. Small equipment and vehicles, such as an ATV will use the inside (up hill) side of the bench which is composed of the soil from the B horizon.
Mulching: The top soil, prior to being replaced, will be amended with about 25% well composted organic matter, following good biodynamic agricultural practices. After inserting Aquapore foam drip irrigation tubing about 2” underground, a geofabric “weed stop” will cover the replaced top soil. This fabric will allow water and air to pass through its pores, is black and prevents weed seeds from germinating, of if they do germinate, will not grow through the fabric. The black weed stop will use solar radiation to heat the soil in the early spring to promote growth. During the summer, straw and other carbon residue will be placed on top of the weed stop to reduce the soil temperature.
Crop residue: The initial supply of organic matter from the compost will be supplemented during the growing season with compost tea applied as a defoliant and a drench. As a liquid, it will penetrate the weed stop, enter the soil and feed the soil food web.
Green manure: Initially, the present weeds will act as green manure and will be incorporated into the top soil as part of the removal, mixing and replacement process. This process will add considerable air pockets. By using compost containing large pieces of plant stock and lumps of cellulose, the soil tilth will remain higher than if the compost were all fine particles.
Gypsum: The pH of the soil is about 7.5 which is the correct balance for hazelnuts and asparagus. No soil amendment is needed. Because of the weed stop, surface aggregation is neither necessary nor wanted.
ANS:
Consistency of cohesive material: For buildings, the A horizon would be removed and used in conjunction with building the terraces. The B horizon is a light tan, calcareous soil similar to the B horizon of Plate 12, p.114. Using Table 4.6, pg. 126 guidelines: The B horizon is hard, firm when moist, moderately cemented, crushes with difficulty by hand , but can be crushed under foot. In situ, the soil is very firm and the blunt end of a pencil makes a .5 cm impression (in situ). The thumb nail easily penetrates.
Plasticity index: In a wet condition, the B horizon soil exhibits low plasticity, in that it cannot easily be molded into various shapes and stay in that shape when handled.
COLE: The coefficient of linear extensibility of the B horizon is low. It does not change much in linear shape and size when water is added, nor will it shrink much when dried from its wet state. (p. 131)
Slope failure: The retaining walls are so designed as to overcome any likely force exerted by the soil uphill of the wall. Another purpose of the retaining wall is to reflect the sun onto the north side of the plants, thus imparting solar energy and enhancing photosynthesis. After walking the property, no evidence of landslide or erosion was observed of the soil in its native state.
The bearing strength: The B horizon appears to be a good candidate for placement of foundations for buildings. At the top of the hill, two residential complexes are planned. The A horizon is thin and there are more noticeable outcroppings of slate. Near the bottom of the hill, a three story warehouse will be built with the back of the first story against the 9' deep side-cut excavation into the B horizon. Generally, the deeper one goes, the greater the compaction and the better the bearing value.
As to buildings, each complex area will use a common septic tank and drain field which will be in the B horizon. Because the probable pore space in the B Horizon is about 50%, we should get good percolation rates. See the business plan for further details.
1. Describe the tilth of the A Horizon of your My Favorite Soil . Give specific educated guesses for texture, structure, aggregation, consistence. Db and % pore.
ANS: Tilth: The A horizon has medium high tilth due to the generations of plants adding organic matter to the A horizon. The color was dark gray. The soil easily crumbles while in a low moisture state.
Texture: The soil is generally uniform in color and texture, with with evidence of root canals and worm tubes, The feel test indicated that it had a higher content of loam than clay because it is closely related to organic matter. Some grit was noticed. The probable percentages of materials (Fig. 4.6) is that of a silty clay loam, which puts it in the range of 30-60% sand, 25-40 % clay, and 60-75% loam.
Structure: The predominate material is loam and appears to have a spheroidal structure (p. 103). The Mollisol A horizon shown on Plate 8, p 114, approximates the A horizon of my favorite soil.,
Aggregation: Due to the presence of massive vegetation and the 14” annual precipitation, the soil was aggregated as shown on Plate 8.
Consistence: The low moisture larger clods taken near the surface were broken by hand pressure, but not the pea sized clods. Both sizes of clods taken at 8” with more moisture content were easily crushed by hand. When hydrated, the soil became somewhat more cohesive, but not stickily, although some clay content could be felt. In the soil's low moisture state, it was easily penetrated with a shovel by standing on the rim of the shovel.
Bulk density, pore space: The bulk density, taken at 8” of depth, is probably in the range of 1.3Mg/m3. The pore space is probably 50%.
- Give specific management action for each of the seven Guidelines for Soil Tilth as appropriate.
ANS: The Guidelines for Soil Tilth (p. 126) state:
Minimum tillage: Because of the slope and the use of the land for agroforestry, the landscape will be changed on the slopes to a series of terraces. Please refer to the attached drawing and the description in the Home Grown Organics Farmstead Business Plan submitted as part of My Favorite Soil report. This work involves a one time removal of the A horizon, some relocation of the B horizon, mixing of the topsoil with composted organic matter and placement along the outer (down slope) side of the bench.
Traffic: As much as possible, machinery and equipment will stay on the farm road which zig-zags along the face of the hill. Small equipment and vehicles, such as an ATV will use the inside (up hill) side of the bench which is composed of the soil from the B horizon.
Mulching: The top soil, prior to being replaced, will be amended with about 25% well composted organic matter, following good biodynamic agricultural practices. After inserting Aquapore foam drip irrigation tubing about 2” underground, a geofabric “weed stop” will cover the replaced top soil. This fabric will allow water and air to pass through its pores, is black and prevents weed seeds from germinating, of if they do germinate, will not grow through the fabric. The black weed stop will use solar radiation to heat the soil in the early spring to promote growth. During the summer, straw and other carbon residue will be placed on top of the weed stop to reduce the soil temperature.
Crop residue: The initial supply of organic matter from the compost will be supplemented during the growing season with compost tea applied as a defoliant and a drench. As a liquid, it will penetrate the weed stop, enter the soil and feed the soil food web.
Green manure: Initially, the present weeds will act as green manure and will be incorporated into the top soil as part of the removal, mixing and replacement process. This process will add considerable air pockets. By using compost containing large pieces of plant stock and lumps of cellulose, the soil tilth will remain higher than if the compost were all fine particles.
Gypsum: The pH of the soil is about 7.5 which is the correct balance for hazelnuts and asparagus. No soil amendment is needed. Because of the weed stop, surface aggregation is neither necessary nor wanted.
3. Describe the real or expected engineering properties of your soil (plasticity index, high or low. COLE properties which would contribute to slope failure, bearing strength dry and wet.
ANS:
Consistency of cohesive material: For buildings, the A horizon would be removed and used in conjunction with building the terraces. The B horizon is a light tan, calcareous soil similar to the B horizon of Plate 12, p.114. Using Table 4.6, pg. 126 guidelines: The B horizon is hard, firm when moist, moderately cemented, crushes with difficulty by hand , but can be crushed under foot. In situ, the soil is very firm and the blunt end of a pencil makes a .5 cm impression (in situ). The thumb nail easily penetrates.
Plasticity index: In a wet condition, the B horizon soil exhibits low plasticity, in that it cannot easily be molded into various shapes and stay in that shape when handled.
COLE: The coefficient of linear extensibility of the B horizon is low. It does not change much in linear shape and size when water is added, nor will it shrink much when dried from its wet state. (p. 131)
Slope failure: The retaining walls are so designed as to overcome any likely force exerted by the soil uphill of the wall. Another purpose of the retaining wall is to reflect the sun onto the north side of the plants, thus imparting solar energy and enhancing photosynthesis. After walking the property, no evidence of landslide or erosion was observed of the soil in its native state.
The bearing strength: The B horizon appears to be a good candidate for placement of foundations for buildings. At the top of the hill, two residential complexes are planned. The A horizon is thin and there are more noticeable outcroppings of slate. Near the bottom of the hill, a three story warehouse will be built with the back of the first story against the 9' deep side-cut excavation into the B horizon. Generally, the deeper one goes, the greater the compaction and the better the bearing value.
4. Give management recommendations:Cropping will be on terraces as stated above, with hazelnut bushes in rows, below which and to the side, are asparagus plants. This two level system takes advantage of the fact that the hazelnuts will lose their leaves during the fall, thus allowing the asparagus in the fern stage to gather more light. Conversely, during the hot summer, the fully leafed hazelnuts will provide needed shade to the asparagus plants. The planting arrangement also reduces land use and irrigation costs.
As to buildings, each complex area will use a common septic tank and drain field which will be in the B horizon. Because the probable pore space in the B Horizon is about 50%, we should get good percolation rates. See the business plan for further details.
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