APPENDIX I 



Soil-Drainage Classes 



0. Very poorly drained. Water is removed from the soil so slow- 

 ly that the water tal)le remains at or on the surface the greater part 

 of the time. Soils of this drainage class usually occupy level or de- 

 pressed sites and are frequently ponded. Very poorly drained soils 

 in the podzolic soil regions commonly have dark-gray or black surface 

 layers and are light gray, with or without mottlings, in the deeper parts 

 of the profile. In the grassland regions, very poorly drained soils com- 

 monly have mucky surfaces with distinct evidences of gleying. These 

 soils are wet enough to prevent the growth of important crops (except 

 rice) without artificial drainage. 



1. Poorly drained. Water is removed so slowly that the soil re- 

 mains wet for a large part of the time. The water table is commonly 

 at or near the surface during a considerable part of the year. Poorly 

 drained conditions are due to a high water table, to a slowly permeable 

 layer within the profile, to seepage, or to some combination of these 

 conditions. In the podzolic soil region, poorly drained soils may be 

 light gray from the surface downward, with or without mottlings. 

 Among the dark-colored soils of the grasslands, poorly drained soils 

 commonly have slightly thickened dark-colored surface layers. The 

 large quantities of water that remain in and on the poorly drained soils 

 prohibit the growing of field crops under natural conditions in most 

 years. Artificial drainage is generally necessary for crop production, 

 provided other soil characteristics are favorable. 



2. Imperfectly or somewhat poorly drained. Water is removed 

 from the soil slowly enough to keep it wet for significant periods but 

 not all of the time. Imperfectly drained soils commonly have a slowly 

 permeable layer within the profile, a high water table, additions through 

 seepage, or a combination of these conditions. Among the podzolic 

 soils, somewhat poorly drained soils are uniformly grayish, brownish, 

 or yellowish in the upper A horizon and commonly have mottlings 

 below 6 to 16 inches in the lower A and in the B and C horizons. Among 

 the dark-colored soils of the grasslands, somewhat poorly drained soils 

 have thick, dark A horizons, high in organic matter, and faint evi- 

 dences of gleying immediately beneath the A horizon. The growth of 

 crops is restricted to a marked degree, unless artificial drainage is pro- 

 vided. This is the lowest drainage class in which a zonal soil retains 

 enough of its characteristics to be classed in that order. Many soils 

 with this drainage class cannot be placed in the zonal order. 



3. Moderately well drained. Water is removed from the soil some- 

 what slowly, so that the profile is wet for a small but significant part 

 of the time. Moderately well drained soils commonly have a slowly 

 permeable layer within or immediately beneath the solum, a relatively 

 high water table, additions of water through seepage, or some com- 

 bination of these conditions. Among podzolic soils, moderately well 

 drained soils have uniform colors in the A and upper B horizons, with 

 mottling in the lower B and in the C horizons. Among the dark-colored 



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