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The goal of {hydricsoils} is to provide easy access to definitions,criteria, and area of applicability for ‘Field Indicators of HydricSoils in the UnitedStates’ and also toprovide tools which assist in evaluating associated soil morphology.

You can install the development version of {hydricsoils} like so:

if(!require("remotes")) install.packages("remotes")remotes::install_github("brownag/hydricsoils")

This basic example shows how to determine the area of applicability ofindicator “A9” (also known as “1 cm Muck”).

library(hydricsoils)#> hydricsoils v0.1.2 -- using:#>  - 'Field Indicators of Hydric Soils in the United States' v9.0 (2024)#>  - 'Land Resource Regions and Major Land Resource Areas of the United States, the Caribbean, and the Pacific Basin' v5.2 (2022)data(fihs,package="hydricsoils")subset(fihs,fihs$indicator=="A9",select= c("usage","usage_symbols","except_mlra"))#>                                                                                            usage#> 9 For use in LRRs D, F, G, H, P (except for MLRA 136), and T; for testing in LRRs C, I, J, and O#>      usage_symbols except_mlra#> 9 D, F, G, H, P, T         136

If we load the MLRA v5.2 database usinglrrmlra_geometry() (requires{terra}) we can visualize theextent of where the “A9” indicator is used.

There is a function in the package calledplot_indicator_usage() whichsimplifies the process of loading and subsetting the geometry. Itprovides some simple defaults for visualizing areas where usage is“Approved”, “Excluded” or in “Testing”.

plot_indicator_usage("A9",test_areas=TRUE,ext= c("Approved","Excluded"),crs="EPSG:5070",plg=list(x="bottomleft"))#> Loading required namespace: terra

Next let’s find all of the indicators that can be used in LRR “C” (alsoknown as the “California Subtropical Fruit, Truck, and Specialty CropRegion”)

subset(fihs,fihs$indicator%in% usesym_to_indicator("C"),select= c("indicator","indicator_name"))#>    indicator              indicator_name#> 1         A1          Histosol or Histel#> 2         A2             Histic Epipedon#> 3         A3                Black Histic#> 4         A4            Hydrogen Sulfide#> 5         A5           Stratified Layers#> 11       A11 Depleted Below Dark Surface#> 12       A12          Thick Dark Surface#> 18       A18            Iron Monosulfide#> 19        S1         Sandy Mucky Mineral#> 22        S4         Sandy Gleyed Matrix#> 23        S5                 Sandy Redox#> 24        S6             Stripped Matrix#> 30        F1         Loamy Mucky Mineral#> 31        F2         Loamy Gleyed Matrix#> 32        F3             Depleted Matrix#> 33        F6          Redox Dark Surface#> 34        F7       Depleted Dark Surface#> 35        F8           Redox Depressions

Compare to LRR “D” (also known as the “Western Range and IrrigatedRegion”)

subset(fihs,fihs$indicator%in% usesym_to_indicator("D"),select= c("indicator","indicator_name"))#>    indicator              indicator_name#> 1         A1          Histosol or Histel#> 2         A2             Histic Epipedon#> 3         A3                Black Histic#> 4         A4            Hydrogen Sulfide#> 9         A9                   1 cm Muck#> 11       A11 Depleted Below Dark Surface#> 12       A12          Thick Dark Surface#> 18       A18            Iron Monosulfide#> 19        S1         Sandy Mucky Mineral#> 22        S4         Sandy Gleyed Matrix#> 23        S5                 Sandy Redox#> 24        S6             Stripped Matrix#> 30        F1         Loamy Mucky Mineral#> 31        F2         Loamy Gleyed Matrix#> 32        F3             Depleted Matrix#> 33        F6          Redox Dark Surface#> 34        F7       Depleted Dark Surface#> 35        F8           Redox Depressions

These outputs match the information we can find in the guide in Appendix1.

It is important to remember that the area of applicability across LandResource Regions and Major Land Resource Areas can subtly differ.

The main difference between LRRs “C” and “D” is that indicator “A5” isapproved for use in LRR “C” whereas “A9” is approved for use in LRR “D”.Note that while “A9” is available for testing in “C”, “A5” is not beingconsidered for use in LRR “D”.

We can visualize this by expanding the first example to include “A5” ina separate pane. We limit the extent to just LRRs “C” and “D”.

x<- lrrmlra_geometry()xext<- subset(x,x$LRRSYM%in% c("C","D"))par(mfrow= c(2,1))plot_indicator_usage("A5",test_areas=TRUE,ext=xext,plg=list(x="bottomleft"))plot_indicator_usage("A9",test_areas=TRUE,ext=xext,plg=list(x="bottomleft"))

In future updates I hope to include:

• _ A defineddata.frame format with standard column names, datatypes, and relationships that are needed to evaluate criteria for allestablished and provisional indicators

• _ A glossary with definitions of key criteria and terms

• _ An index to figures and pictures from the guide, and mapping offigures to specific indicators

• _ Parsing of LRRs and MLRAs where provisional indicators are beingtested

• _ Routines for automatic evaluation of input data to determine whichindicators may be met

• _ Spatial methods for determining appropriate indicators to consider

• ✔️ Helpers for creating graphics depicting whereindicators are used or not (DONE: seeplot_indicator_usage())

The data and routines in thisR package (hereafter the “Work”) arenot intended as a replacement for a thorough understanding of the latestedition Field Indicators of Hydric Soils as distributed by officialsources.

This Work is released under the Creative Commons 1.0 Universal license.In particular the Work is provided “as-is” and makes no representationsor warranties of any kind, express, implied, statutory or otherwise,including without limitation warranties of title, merchantability,fitness for a particular purpose, non infringement, or the absence oflatent or other defects, accuracy, or the present or absence of errors,whether or not discoverable, all to the greatest extent permissibleunder applicable law.

United States Department of Agriculture, Natural Resources ConservationService. 2024. Field Indicators of Hydric Soils in the United States,Version 9.0. Available online:https://www.nrcs.usda.gov/resources/guides-and-instructions/field-indicators-of-hydric-soils

United States Department of Agriculture, Natural Resources ConservationService. 2022. Land resource regions and major land resource areas ofthe United States, the Caribbean, and the Pacific Basin. U.S. Departmentof Agriculture, Agriculture Handbook 296. Available online:https://www.nrcs.usda.gov/resources/data-and-reports/major-land-resource-area-mlra