Each soil layer has a permeability rating, but the soil's permeability is determined by the relative rate moisture and air move through the most restricting layer within the upper 40 inches of the effective root zone. For contests, the subsoil texture sample in the box will be used to determine the permeability. Subsoil texture and structure are of primary importance in determining permeability. Four levels of permeability are recognized in Oklahoma land judging.

Rapidly permeable --- Soils with coarse-textured subsoils that are granular or single-grained are rapidly permeable. Subsoils tend to be very friable or loose when moist, and exhibit little restriction of water or air.

Moderately permeable --- Moderately coarse- and medium-textured subsoils are moderately permeable regardless of structure. They are friable to very friable with large pores. Roots are abundant. A few soils with moderately fine texture and granular subsoils, are also moderately permeable.

For contest, the subsoil texture sample in the box will be used to determine the permeability.

Slowly permeable --- Soils that have moderately fine-textured subsoils with angular and subangular blocky structure are slowly permeable. The subsoils are firm when moist and hard when dry. Roots are common. Length differences of vertical and horizontal cracks are negligible. Soil peds often have thin, discontinuous, clay films on surfaces and tend to break more easily along the vertical axis than in the very slowly permeable soils. Soils frequently have thick surface and transitional horizons from the surface to the most clayey horizon in the profile.

Very slowly permeable --- Soils that have dense, fine-textured subsoils and claypan soils are very slowly permeable. Their structure is coarse, angular blocky or massive with very few visible pores. Roots are few and generally follow ped faces and cracks. These subsoils are very firm when moist and very hard when dry. Soil peds have thick, continuous, clay films on surfaces. Horizontal cracks are longer than vertical ones. (Moddling and grayish subsoil colors are not required for a soil to have a very slow permeability in Oklahoma.)

Surface Runoff
Surface runoff is the relative rate water is removed by flowing over the soil surface. This includes rainfall, as well as water from adjacent slopes. It is the combined effect of soil slope, position in the landscape, permeability, and infiltration rate on runoff. Four classes of runoff are recognized in Oklahoma land judging.

Rapid --- Water is removed from the surface at a rapid rate. A large amount of rainfall is lost and only a small portion moves into the soil increasing the erosion hazard. This is a result of compaction, clayey textures and/or slopes greater than 3% (except when the soils are rapidly permeable).

Moderate --- Water drains away readily but yet slow enough that a large amount of the water enters the soil. This condition causes little erosion hazard and is considered a normal amount of runoff. This condition occurs on slopes of 1% to 3% (except when the soils are rapidly permeable).

Slow --- Water flows away so slowly that free water covers the soil for moderate periods. This increases the moisture supply but may interfere with farming operation. This condition occurs on slopes of 0 to 1% and includes soils with moderate, slow, or very slowly permeable subsoils.

Very Slow --- Water is removed so slowly or stands so long that the soil remains wet for long periods. Most of the water either passes through the soil or evaporates. Generally this condition occurs on level to slightly concave slopes. However, deep sandy soils with rapidly permeable subsoils on slopes also have very slow runoff because the infiltration is so high that rainfall produces little or no runoff.

Major Factors
These factors are conditions that keep land from being Class I. If only one factor keeps a site from being Class I, that factor determines land class. When two or more factors are involved, the situation may be more complex. The number to identify is not given and is the contestants decision. If other factors are listed on the site card, check the appropriate practice. Major factors include:

Surface Texture --- Surface soil texture is not a major factor except for sandy soils. Sandy soils can be no better than Class III because of erosion hazards of both wind and water that are very difficult to control.

Soil Depth --- Only shallow or very shallow soils will be major factors.

Slope --- Slope over 1% will be considered a major factor.

Erosion --- All conditions except none to slight will be considered a major factor.

Permeability --- Rapid or very slow permeability will be a major factor.

Surface Runoff --- Only very slow (rapidly permeable sandy soil excepted) and rapid runoff conditions will be considered as major factors.

General Guide for Selecting Land Capability Classes
Land Capability Classes
Land is classified by USDA on the basis of permanent limitations or hazards in its use from the standpoint of keeping the soil permanently productive. The soil features of a particular area are all considered when determining the land capability class. There are eight recognized classes of land. They are divided into cultivated and non-cultivated.

Cultivated
Class I --- Soils in Class I are suited for cultivation over a long period of time and have no limitations that restrict their use. They are deep, nearly level, well to moderately-well drained, and subject to no more than slight erosion.

Class II --- Soils in Class II are suited for cultivation over a long period of time, but they have some hazards and limitations such as gentle slope, slight erosion, or moderate wetness that reduce the choice of plants or require moderate conservation practices that are easy to apply.

Soil Factor		Best Land Class
Texture (1):	Coarse textured Moderately coarse, medium Moderately line and fine	III I I
Depth (2):	Deep or moderately deep Shallow Very shallow	I III VII
Slope (3):	Nearly level (0 to 1%) Gently sloping (1% to 3%) Moderately sloping (3% to 5%) Strongly sloping (5% to 8%) Steep and very steep (8% to 15%+)	I II III IV VI
Erosion (4):	None to slight erosion Moderate Severe or very severe	I II VI
Permeability (5):	Rapid Moderate and slow Very slow	III I II
Runoff (6):	Rapid Moderate and slow Very slow	III I II

Class III --- Soils in Class III are good for cultivated crops, but have severe limitations that reduce the choice of plants and/or require special conservation practices that are more difficult to apply. Terracing and other water control measures will be needed.

Class IV --- Soils in Class IV can be cultivated, but they have very severe limitations that restrict the choice of plants, require very careful management, special conservation, or both. They are sloping, moderately eroded soils with poor characteristics. Cultivated areas should be strip tilled, terraced, and farmed on the contour. They are best suited for pasture and hay meadows.

Non-Cultivated
Class V --- Soils in Class V have little or no erosion hazards, but have other limitations that make them unsuitable for cultivation. Limitations are impractical and very expensive to remove and limits their use to pasture, range, woodland, or wildlife food and cover. Limitations include very poor surface and internal drainage or frequent flooding. (Frequent flooding will be shown with "other factors" when it occurs.)

Class VI --- Soils in Class VI have severe limitations such as steep slopes, severe erosion, shallowness, and rockiness that make them generally unsuited for cultivation and limits their use to pasture or range, woodland, or wildlife food and cover.

Class VII --- Soils in Class VII have many very severe limitations similar to Class VI that make them unsuited for cultivation and that restrict their use to grazing, woodland, or wildlife.

Class VIII --- Soils and land forms in Class VIII have limitations that preclude their use for crop, pasture, or timber production and restrict their use to wildlife, recreation, or aesthetics. This land has little or no economic value.

Interpretations of Land Treatments
Part 2 of Land Judging deals with vegetative and mechanical conservation practices used to protect the soil and provide permanent protection. State and local conditions may require some modification of the following recommendations.

Vegetative
For cropland use on Class I through IV
1. Row crop with occasional close seeded soil-conserving crop -- applicable to Class I land.

2. Row crop with close seeded soil conserving crop every other year -- applicable to Class II land.

3. Row crops not more than 2 of 4 years -- applicable to Class III land.

4. Row crops not more than 1 of 4 years -- applicable to Class IV land.

5. Return crop residue to the soil.

6. Practice Conservation Tillage Ñ provides for a protective cover by leaving crop residue of any previous crop as a mulch on or mixed in the surface (first few inches) of the soil. At least 30% residue should remain on the soil surface after planting.

For Pasture, Range, Wildlife, or Commercial Woodland
7. Establish recommended grasses and legumes. This practice is used when permanent vegetation is needed. Because of differences in interpretation this practice will be used on all Class V, VI, and VII except where tree plantings are made.

8. Proper pasture or range management. The application of practices to keep plants actively growing; to encourage the growth of desirable grasses and legumes while crowding out weeds and brush, and minimize soil erosion.

9. Protect from burning.

10. Control grazing. Carry out a system of deferred or rotational grazing and proper stocking that will maintain or improve desirable vegetation on pasture or range. The practice should not be used where tree plantings are made.

11. Plant recommended trees for farmstead and field windbreaks, and commercial woodland plantings.

12. Harvest trees selectively. A system of cutting in which single trees, usually the largest, or small groups of such trees are removed and reproduction secured under the remaining stand.

13. Use only for wildlife or recreation area. This means protection or the development of areas that cannot be used for grazing, forestry, cultivation, or urban.

Mechanical
14. Control brush or trees. This may be accomplished by spraying with chemicals and/or use of machinery. The purpose is to improve the desirable vegetative cover by removing or killing undesirable brush and trees (Class I to VI). This practice should not be used when bushy plants and trees are less than two inches (2") in diameter at 5 feet above ground (Class I to IV). These can be controlled by normal farm plowing.

15. Terrace and farm on contour. Terrace is an embankment or ridge of earth constructed across the slope to control runoff and minimize erosion. Conduct farming operations on the contour or at right angles to slope direction. For contest purposes all cultivated soils with slopes over 1%, will be considered as needing terraces, except soils with coarse texture.

16. Maintain terraces. Practices that keep field terraces working effectively. Use only with practice 15.

17. Construct diversion terrace. A diversion terrace is a channel with a supporting ridge on the lower side. Usually it has greater horizontal and vertical spacing and is constructed to handle a larger flow of water than normal field terraces used when overhead water is a factor. This is always given information.

18. Install drainage system. The drainage system is used to remove excess surface or ground water from land by means of surface or subsurface drains. Used only when moderate wetness is given as a factor.

19. Control gullies. One or more conservation practices that will adequately control runoff and erosion. Used any time active gullies are within the field area. Gullies should be at least 6 inches deep and 12 inches wide. Irregularities, rills, and channels in a field that are grassed over with no signs of erosion are not considered as needing control, unless specifically given as a condition.

20. No mechanical treatment needed. Use when brush and trees, erosion, gullies, drainage, or overhead water are not problems.

Fertilizer and Soil Amendments
Fertilizers and soil amendments are essential to the production of crops. No set of limits with regard to lime or fertilizer requirements will fit all areas of the country and all crops. The intent of this section is to familiarize contestants with soil fertility requirements and terminology and identify deficiencies from given soil test values.

pH
Soils with a pH of 5 or less are usually the soils requiring lime. However, lime is recommended on soils with a pH up to and including 6.3. Above this pH, no lime is recommended. Soils with a pH above 8.0 are alkaline and may indicate a salinity problem. The use of sulfur or similar amendment should be applied to reduce the pH to a more favorable level. Therefore, when any pH value given for a field is 6.3 or less or above 8.0, practice No. 21 is checked.

Phosphorus (P)
Low levels of phosphorus in Oklahoma soils are 25 lbs./acre or less. However, soils with phosphorus levels up to 60 lbs./acre do require the addition of phosphorus for maximum production. When any value is given less than 60 lbs./acre, check No. 22 on the scorecard.

Potassium (K)
Soils with potassium levels of 125 lbs./acre or less are considered deficient and require the addition of potassium. Potassium is recommended to some extent on soils with as much as 300 lbs./acre for certain crops, but above that level no potassium is added. When any value is given that is less than 300 lbs./acre, check No. 23 potassium on the scorecard.

Nitrogen (N) No established level of nitrogen in the soil adequately indicates sufficiency or deficiency for all crops. Any value that would be deficient for corn, cotton, or small grains may be adequate for clovers or alfalfa. On the other hand, an adequate level of nitrogen for small grains or corn may be a deficient amount for maximum production of Bermuda grass. The adequate level of nitrogen in the soil is dependent on the yield goals.

For contest purposes, nitrogen will be given as adequate or deficient without a numerical value. Check nitrogen, No. 24 on the scorecard, when the deficiency is indicated.

Example: Soil test information shows:
pH --- 5.5
Phosphorus --- 30 lbs./acre
Potassium --- 325 lbs./acre
Nitrogen --- Deficient
On the scorecard Nos. 21, 22, and 24 will be checked.

General Instructions and Interpretations
Contestants from distant areas will tend to interpret what they see in light of their own conditions. For this reason it is necessary to explain in detail those items that may have local variations.

Present Practices or Cover on the Land
Disregard practices and/or cover on the land at the time of the contest, except for brush and trees that might occur on Class I and VI. Should this condition occur, it would be necessary to remove brush, trees, and timber to reach the most intensive use. In other words, use practice 14. If terraces are needed and terraces are already on the area use practice 15, terrace and farm on the contour. Should a cover of grass be on an area of Class V, VI, or VII land, use practice 7, establish recommended grasses or legumes.

Other Factors
When factors exist that are not observable by the contestant from a single observation, but affect the treatment and land capability, they will be given for each field under "other factors." Contestants will then prescribe the correct treatment based on these factors. Factors that will be given that influence treatment are:

Wetness --- Wetness would be a factor to keep land out of Class I. Only moderately-wet land can effectively benefit from installation of a drainage system. Use practice 18 under treatments. Installing drainage system on wet, Class V soil is not recommended.

Flooding --- Flooding is not considered on slopes over 3 percent. Flooding would place an area in Class V. Practices 14 and 20 would be possible treatments.

Overhead Water --- This condition does not change the land class out of Class I, but would require a diversion terrace (practice 17). Practice 16 is not checked when using diversion terraces. They are constructed much larger than conventional terraces and are usually not farmed. These could be constructed on adjoining property where maintenance was not possible.

Needs Wind Break --- Where this is indicated, practices 9 and 11 would be needed.

Desires Post or Wood Lot --- This factor shown would call for practices 9, 11, and 12.

Timber production --- Operator desires to go into timber production in adapted areas. Would also require practices 9, 11, and 12.

Next Page