Agriculture Reference
In-Depth Information
are also used on crops ranging from wheat and barley to tomatoes and berries. A
large number of farms also use surface irrigation on pasture acreage. The efficiency
of surface irrigation on all of these crops could be improved with precision land
grading.
Since precision grading constitutes a long-term investment in the land, it will
require several years of production to recover the costs invested. Therefore, land
chosen for precision grading should be land that has a high probability of remaining
in production for several years into the future.
6.4.3 Factors Affecting Land Grading and Development
Successful land planning and grading requires knowledge of engineering, agricul-
tural, and architectural branches. The following factors should be considered for
selecting and designing land grading:
6.4.3.1 Topography
The primary design determinant is the form of the land, its slope characteristics,
storm-water runoff, and surface drainage patterns. Topographic analysis reveals
where favorable views exist.
Excavation and fill materials to be required for or obtained from such structures
as ditches, pads, and roadways should be planned for as a part of the overall grading
job. The cut-to-fill ratio will normally be between 1.30 and 1.50 to allow for losses
due to compaction, hauling, and undercutting.
6.4.3.2 Soil, Hydrologic, and Geologic Conditions
Soil and subsoil condition affect grading and planting options. Subsoil bore test,
analysis, and geologic mapping provide important information regarding soil com-
paction, rock strata, drainability, erosivity (erosion susceptibility), water table
(aquifer) position, etc. All these factors should be considered with respect to
intended objective, since soil and hydrology must be compatible with the target
vegetation.
Soils should be deep enough so that, after the needed grading work is done, an
adequate, usable root zone remains over most of the field that will permit satisfactory
crop production with proper conservation measures. Limited areas with shallower
soils may be graded to provide adequate drainage, irrigation grades or a better field
arrangement.
6.4.3.3 Climate and Microclimate
Competent design should always take into account the sunshine, temperature, shade,
precipitation, wind, etc.
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