Limitations of soils in Class III restrict the amount of clean cultivation; 

 timing of planting, tillage, and harvestingj choice of crops or a combina- 

 tion of these items= The limitations may result from the effects of one or | 

 more of the followings (1) moderately steep slopes; (2) high susceptibility " 

 to water or wind erosion or severe adverse effects of past erosion; (3) fre- 

 quent overflow accompanied by some crop damage; (4) very slow permeability 

 of the subsoil; (5) wetness or some continuing waterlogging after drainage; 

 (6) shallow depths to bedrock, hardpan, fragipan, or claypan that limits the 

 rooting zone and the water storage; (7) low moisture-holding capacity; (8) 

 low fertility not easily corrected; (9) moderate salinity or alkalinity, or 

 (10) moderate climatic limitations. 



When cultivated, many of the wet, slowly permeable but nearly level soils in 

 Class III require a drainage system and a cropping system that maintains or 

 improves the structure and tilth of the soil. To prevent puddling and to 

 improve permeability it is commonly necessary to supply organic material to 

 such soils and to avoid working them when they are wet. In some irrigated 

 areas, part of the soils in Class III have limited use because of high water 

 table, slow permeability, and the hazard of salt or alkali accumulation. 

 Each distinctive kind of soil in Class III has one or more alternative com- 

 binations of use and practices required for safe use, but the nvuaber of 

 practical alternatives for average farmers is less than for soils in Class II. 



Class IV . — Soils in Class IV have very severe limitations that restrict the 

 choice of plants, require very careful management, or both. 



The restrictions in use for these soils are greater than those in Class III, 

 and the choice of plants is more limited. When these soils are cultivated, 

 more careful management is required and conservation practices are more dif- 

 ficult to apply and maintain. Soils in Class IV may be used for crops, 

 pasture, woodland, range, or for wildlife food and cover. 



Soils in Class IV may be well suited to only two or three of the common crops 

 or the amount of harvest produced may be low in relation to inputs over a 

 long period. Use for cultivated crops is limited as a result of the effects 

 of one or more permanent features such as (1) steep slopes, (2) severe sus- 

 ceptibility to water or wind erosion, (3) severe effects of past erosion, 

 (4) shallow soils, (5) low moisture -holding capacity, (6) frequent overflows 

 accompanied by severe crop damage, (7) excessive wetness with continuing 

 hazard of waterlogging after drainage, (8) severe salinity or alkalinity, 

 or (9) moderately adverse climate. 



Many sloping soils in Class IV in humid regions are suited for occasional 

 but not regular cultivation. Some of the poorly drained, nearly level soils 

 placed in Class IV are not subject to erosion but are poorly suited to in- 

 tertilled crops because of the time required for the soil to dry out in the 

 spring and because of low productivity for cultivated crops. Some soils in 



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