Nitrate Leaching Class Ranges

This is a statewide Arc/Info data set of nitrate leaching class ranges for
soils in Illinois. It was generated to aid in determining aquifer sensitivity
to nitrate leaching in Illinois. The source map was digitized at 1:250,000, but
was developed from source data mapped at 1:15,000. The publication of this map
was at 1:500,000. Nominal scale is 1:250,000.

This data set contains the four trimmed range values presented on the ISGS map
Nitrate Leaching Classes of Illinois. Range values were determined for the
nitrate leaching classes in each soil association to give an indication of the
variability within a specific leaching class. This data set is necessary
because each soil association (in data set *path_name_suppressed*/no3leach)
could have only a single leaching class value assigned to it. In this data set
the item NO3INDEX_RANGE contains a 10% trimmed range for the leaching class
characteristics of each association. This item was calculated by sorting the
component soil series in order of their leaching characteristic within the
association. The trimmed range is the domain of leaching characteristic values
between the 90th and 10th quantiles in the sorted list. The range was trimmed
(by 10% at either end) to reduce the significance of extreme values. These data
were used as an overprint on the published map. (see cross references).