Ohio State University Extension Bulletin

Biosolids Application to Agriculture
Utilizing Biosolids Analysis to Meet Crop Nutrient Needs

Bulletin 879-99

7. Consider site.

Table 5. Slope criteria for land application of sludge
Slope Requirements for Use
Greater than 12% Not to be used for land
6% to 12% (1) To be used only when a minimum of 80% of the soil is covered with vegetation;
(2) Immediate incorporation or injection is the method to be used.
Less than 6% Most desirable for land application.
Source: 1996, Ohio EPA, Land Application of Sludge Manual.

Limitations of soil types

  1. Sandy Loam: The coarse-texture high permeability of this soil has the potential to leach nitrates. This type of soil is also subject to a change in pH, which could affect the availability of metals.
  2. Loams: Best suited to sludge application, few restrictions.
  3. Silt Loams: Soil crusting, erosion, and compaction.
  4. Clay, Silty Clays, Clay Loams, Silty Clay Loams: These soils are finely textured and have slow permeability and they are erodible. Ponding can occur causing odor problems and compaction.


Available Moisture
in Soil 		Sandy
Loamy Sands
 Sandy Loam
Fine Sandy Loam
 Very fine Sandy Loam,
Loam, Silt Loam, Silt
Clay Loam, Sandy Clay
Loam Silty Clay Loam		 Sandy Clay
Silty Clay, Clay
Fine and Very Fine
Textured Soils
0 percent
Soil Depth
Amount to Reach

AWCa
Dry, loose and single- grained; flows through fingers.
0-8"
1" 		0-24"
2.6"
Dry and loose; flows through fingers.
0-8"
1" 		0-24"
2.6"
Powdery dry; in some places lightly crusted but breaks down easily into powder.
0-8"
1.5" 		0-24"
3.5"
Hard, baked and cracked; has loose crumbs on surface in some places.
0-8"
1" 		0-24"
2.6"
50 percent
or less
Soil Depth
Amount to Reach

AWCa
Appears to be dry; does not form a ball under pressure.b
0-8"
0.75" 		0-24"
2.0"
Appears to be dry; does not form a ball under pressure.b
0-8"
0.75" 		0-24"
2.0"
Somewhat crumbly but holds ogether under pressure.

0-8"
1.1" 		0-24"
2.6"
Somewhat pliable; balls under pressure.

0-8"
0.75" 		0-24"
2.0"
50 to 75 percent
Soil Depth
Amount to Reach

AWCa
Appears to be dry; does not form a ball
under pressure.b
0-24"
0.5" 		0-8"
1.3"
Balls under pressure but seldom holds together.
0-24"
0.5" 		0-8"
1.3"
Forms a ball under pressure; somewhat plastic; slicks slightly under pressure.
0-24"
0.75" 		0-8"
1.8"
Forms a ball; ribbons out between thumb and forefinger.
0-24"
0.5"
1.3"
75 percent to
field capacity
Soil Depth
Amount to Reach
0-8"
AWCa
Sticks together slightly; may form a very weak
ball under pressure.
0-24"
0.25" 		0-8"
0.6 "
Forms weak ball that breaks easily; does not slick.
0-24"
0.25" 		0-8"
0.6 "
Forms ball; very pliable; slicks readily if relatively high in clay.
0-24"
0.4" 		0-8"
0.9 "
Ribbons out between fingers easily; has a slick feeling.
0-24"
0.25"
0.6 "
At field capacity
(100 percent)
 On squeezing, no free water appears on soil but wet outline of ball is left on hand. Same as for coarse-textured oils at field capacity. Same as for coarse-textured oils at field capacity. Same as for coarse-textured oils at field capacity.
Above field capacity
 Free water appears on soil is bounced in hand. Free water is released with kneading out.. Free water can be squeezed forms on surface. Puddles; free water.
a available water capacity
b Ball is formed by squeezing a handful of soil very firmly
Source: USDA, Soil Conservation Service, National Engineering Handbook (Section 15, Irrigation).

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