APPENDIX D 



after drainage; (4) shallow depths to bedrock, gravel, hardpan, fragipan 

 or claypan that limits the rooting zone and the water storage capacity 

 of the soil, and (5) low annual rainfall (10 to 14 inches) if not 

 irrigated. 



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 wet. Each 

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

 binations of use and practices required to protect the soil resources. 

 The number of practical alternatives for safe use under cropping systems 

 is less than for soils in class II. 



Class IV 



Lands in class IV have very severe limitations that restrict the 

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



The restrictions are more severe than for class III land, and the 

 choice of crops more limited. Where land in this class is cultivated, 

 careful management is required and conservation practices are difficult 

 to apply and maintain. Land in class IV may be used for crops, pasture, 

 woodland or for wildlife food and cover. 



Soils in class IV may be well suited to only two or three of the 

 more common crops and production is generally low in relation to inputs 

 over a long period. The choice of crops is limited as a result of the 

 effects of one or more permanent features such as (1) steep slopes, (2) 

 severe susceptibility to erosion, (3) severe effects of past erosion, 

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

 flows accompanied by severe crop damage from ponding, (7) excessive 

 wetness with continuing hazard of waterlogging after drainage, and (8) 

 cold climate, growing season 60 to 90 days. 



Many sloping lands in class IV are not suited for regular cultiva- 

 tion. Some of the poorly drained soils on nearly level land placed in 

 class IV are not subject to erosion but are poorly suited to intertilled 

 crops because of wetness. Many soils in class IV are well suited for 

 hay and pasture use. 



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