2017 NACTA Contest FAQs for 4-Year Universities
1. Do you recognize Cd horizons in the contest area?
a. We have Permian mudstones and shales in the contest area that have
traditionally been described with a Cr designation, sometimes with the addition
of suffix k and/or t (Yes, we can have Crkt). Some people have suggested that our
Cr horizons should be designated Cd horizons because material from the
material will mostly slake in water, although it could take several days of soaking.
Our experience is that these mudstones and shales are at least partly cemented
with carbonates. When you see these materials in the field, we are curious about
your opinion and whether you would designate them as Cr or Cd. It is not a big
deal anyway because paralithic and densic contacts are both root limiting layers.
For this contest, we decided to make this an easy decision. We will not use the
suffix d on the contest, and densic contact is not on the scorecard.
2. For hydraulic conductivity (Table 10), I see that you have combined the six hydraulic
conductivity classes into three: High, Moderate, and Low. This is great, as it is how the
NACTA rules have always been. But for the surface runoff classes (Table 18), the six
hydraulic classes have not been combined into three, making it hard to choose an
answer. Could you look at Table 19 and let me know what answer a student should
choose for a slope of 9% and moderate surface hydraulic conductivity?
a. Sometimes trying to simplify actually makes things harder. Our intent was to
recognize six hydraulic conductivity classes as indicated in the Soil Survey
Manual but to lump them into three as has been done in the past to make it
easier for the judgers. However, for runoff classes, the judgers need to use the
six hydraulic conductivity classes to get the correct runoff classes. Using only the
three hydraulic conductivity classes can result in an illogical runoff class for some
soils in the contest region. Hence, all six are needed for runoff. Please remember
that the contest is open book, so the judgers can use both the hydraulic
conductivity and the runoff tables.
3. In the hydraulic conductivity section, it is stated that the “presence of a natric horizon
at or above the specified judging depth will move the hydraulic conductivity class to
the next lower class." Does this apply to the six hydraulic conductivity classes or to the
three grouped classes?
a. It applies to the six classes.
4. Regarding Table 10, it is specified in several places that hydraulic conductivity class is
influenced by the organic matter content of the soil, referencing "high" or "moderate"
or "low" organic matter content. However, the thresholds for these three classes are
not specified. Similarly, the Moderately Low HC class refers to "high clay content" but
does not specify how much clay is considered "high". Would it be more appropriate to
use specific class limits based on organic carbon and clay contents?
5.
6.
7.
8.
a. These descriptions are meant to be general enough to be used for a wide range
of soil properties. We think it is a better learning experience for students if they
see how the official judges handle these situations. Then, they can use their best
judgement and make their own interpretations about organic matter and clay
contents. We do not want to define arbitrary class limits based on organic
carbon and clay contents. However, we will add site notes for the practice sites
explaining the reasons when the official judges make adjustments in the
hydraulic conductivity class because of clay or organic matter contents or shrinkswell potential.
Regarding the description of Table 11, it is stated that "If the profile is not visible to a
depth of 150 cm, or if you are requested to describe a soil only to a shallower depth,
then you may assume that the conditions present in the last horizon described extend
to 150 cm." While it would be highly unlikely, what if the pit is 160 cm deep, the depth
of description is 110 cm, and there is observable bedrock at 130 cm? Would the visible
root restrictive layer be ignored because it is below the depth of description?
a. For the scenario mentioned above, we would have made sure that the depth of
description included the observable bedrock. For example, we would have given
the profile depth as 135 cm (not 110 cm), and we would instruct the pit monitor
to make sure that all judgers could see that bedrock was exposed within the
profile depth. We should also mention that the depth to bedrock can be quite
variable within the pit. In addition, there can be much variation between depth
to bedrock from one control section to the other. We will make sure that each
profile has the same number of horizons to describe so that each profile has the
same number of points possible. Judgers should take the depth measurements
from the tape measure anchored to the pit face within the control area.
If redox concentrations are present, would they be identified as such and also
recognized as Fe-Mn matrix concentrations?
a. Redox concentrations would be recognized with a Y in the RMF Conc. column
and with an FE-MN in the Matrix Conc. column.
I am assuming that marking a Y for RMF Concentrations does not automatically
require listing FE-MN under Matrix Concentrations?
a. No, this is not our intent. If a Y is marked for RMF, the type of Matrix
Concentration must also be given. Soils occur in the contest area that have
multiple Matrix Concentrations in the same horizon. For example, we have soil
horizons where Fe-Mn matrix accumulations occur with calcium carbonate
accumulations. In this case, Y should be marked for RMF, and FE-MN and K
should be marked under Matrix Concentration. 1 point would be awarded for
the FE-MN and 1 point for the K.
Is there ever a time when you would put a k, y, or z on the horizon name but not list
them under Matrix Concentrations?
a. We intend for the students to make two separate decisions in regard to the
horizon suffix symbol k, y, or z and the type of Matrix Concentration. In our
professional work, those two decisions are not linked. For example, it is possible
to have a horizon with disseminated pedogenic carbonate in which the Bk
designation should be used. However, the disseminated carbonate would not be
considered as a concentration of pedogenic carbonate that occurs in the matrix.
Also, coatings of pedogenic carbonate can occur along peds. These features are
ped coatings and not concentrations occurring in the matrix. It is up to the
coaches to decide how they want to teach this to students. If coaches teach their
students to link them, this would be correct most of the time for the soils in the
contest area. However, these two decisions will be made separately and not
linked by the official judges.
9. Is there ever a time when you would mark Y for redox concentrations but not put FEMN under Matrix Concentrations?
a. We also intend for the students to make two separate decisions in regard to
marking a Y (yes) for RMF concentrations and for marking FE-MN as a Matrix
Concentration. Please note that RMF concentrations can include pore linings or
ped coatings of Fe and/or Mn. These features are coatings (cutans) and not
concentrations that occur in the matrix. In this case, if no other forms of RMF
concentrations were present, we would mark Y for RMF concentrations and
mark a "-" for matrix concentrations. Again, coaches can decide how to teach
this to their students. If coaches teach their students to link these two decisions,
this would give the correct answer most of the time for the soils in the contest
area. However, the official judges will make two separate decisions.
10. What is your interpretation on carbonate 'masses', do you consider them significant
for pedogenesis (B vs C horizon nomenclature)?
a. We generally do not have carbonate masses in the contest area. The carbonate
forms in the contest area typically include nodules, ped coatings, and/or
filaments (which are probably ped coatings). We believe these forms are
pedogenic. The soils exhibiting these features in the contest area usually have
soil structure. We generally would describe these horizons as some type of a Bk
such as a Btk, Bkss, Bk, etc. Also, we do have Cr horizons with pedogenic
carbonate forms. These will be described as Crk or Crtk.
11. How common is gypsum accumulation in this area? Are there series that have "y"
suffixes mapped in the area? (I didn’t find any in the OSD's).
a. We didn’t recognize gypsum accumulation in the contest area until we started
soil micromorphology for research projects. Gypsum tends to occur in
association with pedogenic carbonate in soils in the contest area that also have
elevated Na contents. It is difficult to recognize the gypsum in field examination,
except it occurs as white accumulations that do not react with 10% HCl. Gypsum
commonly occurs in soils with a parent material sequence of loess over
colluvium over residuum. Dwight and Konza often contain gypsum
accumulations. We have posted a guidebook for a field trip to the Rannells
Prairie on the website. The Konza pedon in the guidebook contains gypsum, and
the horizon nomenclature includes a y suffix. We will post % gypsum for any soil
horizon where gypsum occurs and if the gypsum content is needed for
classification purposes.
12. "k" horizons seem pretty common, but according to the NRCS OSD site, there are no
Calciustolls or Calciudolls mapped in the contest area. What part of the "calcic"
definition in the Taxonomy is usually NOT met in these Bk's (>15% CCE or one of the
following: >5% more CaCO3 compared to C horizon, OR >5% pedogenic carbonates)?
(for example: Benefield).
a. We will post CCE for soils where the data are needed for classification. In most
cases, the soils in the contest area, which have a k designation, will not have the
15% CCE required for a calcic horizon. Many of the soils in the contest area will
have >5% pedogenic carbonate accumulations. Hence, we use a k designation,
but the classification for a calcic is not met. We could find inclusions in a
mapping unit of a soil like Clime that could make the criteria to classify with a
calcic horizon.
13. There are a few redundancies on the scorecard. For example, marking a “k” under
horizon subscript and then marking “K” under Matrix Concentrations while using the
same criteria. What is the meaning for this?
a. We do not view this as a redundancy because these are separate
determinations. The horizon subscript k should be used when appropriate
according to the definition found in Chapter 18 of the 2014 Keys to Soil
Taxonomy. K should be marked as a Matrix Concentration whenever matrix
accumulations of calcium carbonate occurs. Please note to follow this same
procedure for a y horizon subscript and a Y matrix accumulation of gypsum. We
have soil horizons in the contest area that may have matrix accumulations of
both calcium carbonate and gypsum.
14. Many BC horizons underneath argillics would qualify as cambics, but there is no point
in recognizing them. Also, we may find a Bw horizon that qualifies for cambic above a
Bk horizon that qualifies for calcic. Should we mark cambic if it is not the diagnostic
horizon that determines class placement?
a. Although it is open to interpretation, the intent of Keys to Soil Taxonomy is
probably to not recognize a cambic if it occurs above or below another
diagnostic horizon. For this contest, we will not mark cambic if a horizon with
cambic properties occurs above or below an argillic or calcic horizon.
15. Are the disseminated carbonates in the contest area visible with a hand lens?
a. Yes, disseminated carbonates in the contest area are visible with a hand lens.
16. If a Cr horizon is cemented by finely disseminated carbonates, with no visible coatings
or masses in the horizon, are those carbonates considered pedogenic?
a. In the contest area, the Cr (or Crk) horizons that contain carbonates will exhibit
carbonate nodules, masses, and threads (films) of carbonate between mudstone
layers that are clearly visible. At least one practice pit will provide an excellent
example of pedogenic carbonate forms that occur in Crk horizons in the contest
area. Most of the Cr horizons in the contest area have clearly visible pedogenic
carbonate forms such as nodules, masses, and threads. Such horizons will be
designated Crk. Although rare, Cr horizons can occur in the contest area that lack
visible forms of pedogenic carbonate. We will designate such horizons as Cr.
17. The handbook says that if a soil has measureable gypsum content, that data will be
given. But for carbonates, it will be given only if needed for classification. Could there
be a soil where there are detectible or visible carbonates but where no lab data will be
given?
a. If a soil horizon has measureable gypsum content, we will provide % gyspum
because of the difficulty in identifying the gypsum and distinguishing it from
pedogenic carbonate. Some soil horizons in the contest area will have pedogenic
carbonates, but the soil matrix is non-calcareous, and the quantity of pedogenic
carbonate is low enough so that it is obvious that the CCE is less than 15%. CCE
data will be given only if the official judges believe that the data are needed for
classification.
18. If lab data reveals any measureable content of gypsum or carbonates or sodium in an
A or B horizon, is that enough to warrant use of the lowercase letters for naming the
horizon?
a. Since gypsum will be difficult for the judgers to identify and separate from
pedogenic carbonate accumulations, we will designate any horizon in which the
gypsum content is reported with the suffix y. We tend to put a k on any horizon
with visible pedogenic carbonate. Many soils in the contest area will have
measureable amounts of Na. We will provide SAR data only if needed for soil
classification. We tend not to use the n suffix unless the SAR is approaching 13,
and the soil morphology is typical for a natric horizon.
b. Added 3-28-17
c. After describing the practice and contest pits, we have decided to provide
specific criteria on when the n suffix will be used in horizon nomenclature. The
primary reasons for the change is that the morphology typical for soils with an
elevated sodium contest is most apparent during dry conditions. We described
the practice and contest sites following an abnormally dry fall and winter.
Considering the weather forecast for the next two weeks, there is a good
possibility that the contest will be held in wetter conditions. Therefore, we have
decided to make an arbitrary decision to describe any Bt horizon with an SAR ≥
10 or ESP ≥ 12 with the suffix n, e.g., Btn. Please note that some of these soils
that will be described with a Btn designation do not necessarily meet the criteria
for classification with a natric horizon. For additional information about soils in
the contest area with elevated sodium contents or paranatric properties, see
Presley et al., 2011 (Soil Horizons 51:95-101). This paper is included in the NACTA
Soils Contest Materials and Resources web page.
19. Can you give more details about when “Lithological discontinuities” would be checked
as a diagnostic feature?
a. We have decided to simplify, and the judges will check Lithological
discontinuities anytime a prefix of 2 is used in the horizon nomenclature. Please
note that many of the soils in the contest are have multiple parent materials or
multiple ages of the same parent material, e.g., two ages of colluvium.
20. What is the Rangeland Ecological Site for a soil that occurs on a summit in MLRA76
(Bluestem Hills) that lacks the elevated Na characteristics of a Claypan?
a. The simplified key for determining the Rangeland Ecological Site for this situation
is incomplete. Summit should be added to item 2.f.
21. Do Vertisols occur in the contest area?
a. We have soils in the contest area that will classify as Vertisols. However, soils in a
vertic subgroup are more typical for soils in the contest area that exhibit
slickensides. Because of recent heavy rain, soil conditions will not be dried out
enough for cracking characteristics to be visible that could be used to determine
classification as a Vertisol. Therefore, we have decided to provide information on
the data sheet for cracking characteristics for any soil that is close to meeting the
classification criteria for a Vertisol.