Hosted by the School of Agriculture University of Arkansas at Monticello Monticello, Arkansas

Transcription

1 APRIL 19-24, 2015 Hosted by the School of Agriculture University of Arkansas at Monticello Monticello, Arkansas

2 Table of Contents Welcome, Introduction... 1 Conduct of the Contest... 2 Scoring... 3 Scorecard Instructions... 5 Soil Profile Characteristics Site Characteristics Soil Classification Soil Interpretations Appendix 1 Example of Site Card Appendix 2 Official Abbreviations and USDA Texture Triangle Appendix 3 Simplified Key to Soil Sub-Order and Great Group Appendix 4 Rating Guide For Soil Interpretations Appendix 5 Seasonal Water Table (SWT) Classes Appendix 6 Loading Rates (gpd/ft 2 ) For On-Site Wastewater Disposal Appendix 7 Scorecard Illustrated Guide to Soil Taxonomy, version i

3 WELCOME, INTRODUCTION It is a great honor to host the 2015 American Society of Agronomy National Soils Contest here at the University of Arkansas at Monticello, home of the Boll Weevils. We are excited to welcome the best and brightest soil science students from across the U.S. to our region of the world and hope that your experience will be educational, inspirational, and filled with fond memories and new friends who will soon be fellow colleagues. Collegiate soil judging is sponsored by the Students of Agronomy, Soils, and Environmental Sciences (SASES), which is an undergraduate student organization of the American Society of Agronomy (ASA), Crop Science Society of America (CSSA), and Soil Science Society of America (SSSA). Information on eligibility, membership, contest procedures, conduct, and qualification for the International Soil Judging Competition can be found at This handbook provides detailed information on conduct of the contest, scorecard instructions, and other relevant information. Much of the material comes from previous ASA National Soils Contests, but some minor modifications were made based upon regional interpretations, and input from students, coaches, and NRCS Soil Scientists. Other references used to develop this handbook include: Chapter 3 of the Soil Survey Manual (Soil Survey Division Staff, 1993), Field Book for Describing and Sampling Soils, version 3.0 (Schoeneberger et al., 2012), Soil Taxonomy (Soil Survey Staff, 1999), Keys to Soil Taxonomy 12th Edition (Soil Survey Staff, 2010), and the National Soil Survey Handbook (Soil Survey Staff, 1996). We are appreciative for the technical support provided by the soils team of soil scientists from the Arkansas USDA-NRCS and Arkansas Association of Professional Soil Classifiers, the many volunteers and landowners, and the financial assistance from the Soil Science Society of America and American Society of Agronomy, Drew County Farm Bureau, Drew County Conservation District, the University of Arkansas at Monticello, and local businesses. This contest would not be possible without the unselfish efforts of these individuals, businesses, and organizations. Paul B. Francis, Professor Plant and Soil Science School of Agriculture, Univ. Arkansas at Monticello Monticello, AR francis@uamont.edu 1

4 CONDUCT OF THE CONTEST 1. Contest Sites The contest will consist of two sites for group judging and three sites for individual judging with additional sites available for practice prior to the competition. At each site, a pit will be excavated exposing a profile. One or two area(s) will be selected in each pit and clearly designated as the control section by the contest officials. These areas are no pick zones but are used for measurement of horizon depths and boundaries. The selected areas will constitute the officially scored profiles and must remain undisturbed and unblocked by contestants. All measurements should be made within these designated areas. Measuring tapes will be placed in all contest pits and will be maintained by official pit monitors. Contestants will be told which profile they are to evaluate if more than one is selected in a pit. The contestants will describe up to six horizons within a given depth. A card at each site will give the profile depth to be considered, the number of horizons to be described, the depth of a nail within the third horizon, and chemical or physical data that may be required for classification. An example of the site card is included in Appendix 1. A topographic map and/or aerial imagery of the area with the sites located may be provided to help contestants orient themselves to the landscape. Changes to the group/individual contest schedule and the time in and out of pits may be made prior to the coaches meeting depending on the number of participants and pit and weather conditions. 2. Equipment and Reference Materials The equipment and reference materials listed below will be permitted during the contest. Any contestant found in possession of equipment or reference materials other than those listed below will be disqualified. Allowed equipment: clipboard Munsell Soil Color Chart soil knife or other digging tool small pencil sharpener water bottle hand towel tape measure Abney level or clineometer non-programmable calculator pencils (No. 2 suggested) hand lens hydrogen peroxide (2%), HCl (10%) dropper bottle containers for soil samples 2 mm sieve Allowed reference materials: List of accepted abbreviations and texture triangle (Appendix 2) provided during contest. 2

5 Rating guide for soil interpretations (Appendix 4) provided during contest. Seasonal water table (SWT) classes (Appendix 5) provided during contest. Loading rates (gpd/ft 2 ) for on-site wastewater disposal (Appendix 6) provided during contest. 3. Individual Competition Sixty minutes will be allowed for evaluating each site for individual judging. Contestants will be assigned by team number to one of two groups at each site. One group will follow this schedule: 10 minutes in the pit, 10 minutes out, 10 minutes in, 10 minutes out, and 20 minutes free-for-all. The other group will follow the opposite in-and-out schedule. At alternating sites the contestants will switch the in-and-out schedule. Contestants may obtain a sample from the surface horizon while out of the pit, provided they do not enter the pit or disturb those already in the pit. Individual contestants will be assigned a number that will be used to identify their scorecard and the rotation schedule. The procedures for student rotation and time in and out of the pit may be altered prior to the contest to meet unanticipated difficulties at the site. 4. Group Competition Forty five to 50 minutes will be allowed for groups to evaluate each of the two sites. The time will be divided into 10-minute segments similar to the individual competition. Universities will be randomly assigned a group number at registration. All students from a university may participate in the group contest. The start time(s) of the group contest will be announced at the coaches meeting. SCORING 1. General All contestants will use the standard scorecard depicted in Appendix 7. It will consist of five sections. All boxes on the scorecard will be scored for the number of horizons required. If no entry is needed, then the contestant must enter a dash (---). Boxes left blank will be marked wrong. A list of acceptable abbreviations can be found in Appendix 2; each contestant will receive a copy for use during the contest. Illegible entries, as determined by multiple graders, or any abbreviations other than those listed in Appendix 2 will be marked wrong. Input from coaches on scoring decisions is welcome, but decisions of the contest officials will be final. If a pedon has more than one parent material or diagnostic subsurface horizon/feature, 5 points will be awarded for each correct answer. In these sections of the scorecard, negative credit (minus 5 points for each extra answer, with a minimum score of zero for any section) will 3

6 be used to discourage guessing. More than one entry in other areas of the scorecard that require one answer will be considered incorrect, and will result in no credit for that item. For example, if loess and alluvium are the correct parent materials, then 5 points will be awarded for each. If a contestant checks loess (+5) and colluvium (0), the score would be 5; and if the contestant checked loess (+5), alluvium (+5), and colluvium (-5 extra answer) the score would be five because of the excessive answer. Omissions will not be given any points. In all other situations, points will be awarded as indicated on the scorecard. 2. Score Tabulation The overall team score will be the sum of the top three individual scores achieved by the four members selected to participate in the individual competition plus the scores from the group competition. In this manner, all four team members may contribute to the overall team score. An example of the scoring for the individual portion of the contest is shown below: INDIVIDUAL SITE 1 SITE 2 SITE 3 TOTAL A B C 208* * 736 D * Total = Team score * Lowest score is not used to determine team score. Scores used for individual ranking The team score from is then added to the scores for the two group sites to determine the overall team score. Only one official team is permitted from a university. Alternates not on the official team can judge practice sites and participate in the group competition, but only four students from each university will be allowed to participate in the individual competition. These members must be designated by Weds., April 22, Tie Breaker Overall Team In case of a tie, the percent clay content of the third horizon at site #1 will be used. The mean clay content will be calculated from the estimates provided by all members of a given team. The team with the mean estimate closest to the actual value will win. For example: Actual clay content of tie breaker horizon = 33% 4

7 Team estimates: TEAM #5 TEAM #7 Individual A = 38% Individual E = 33% Individual B = 34% Individual F = 29% Individual C = 30% Individual G = 22% Individual D = 39% Individual H = 30% Mean = 35% Mean = 29% Clay Content = 33% Clay Content = 33% Difference = 2% Difference = 4% In this example, TEAM #5 is the winner. If a tie still exists, the clay content of the third horizon at site #2 will be compared, followed by the third horizon at site #3 if necessary. If this does not break the tie, the next (lower) horizon(s) will be used in the same manner and order. 4. Tie Breaker Individual and Group The actual clay content of the third horizon at site #1 will be compared to that estimated by each individual or group tied. If a tie still exists, the clay content of the third horizon at site #2 will be compared, followed by the third horizon at sites #3 and #4 if necessary. If this does not break the tie, the next (lower) horizon(s) will be used in the same manner and order. 5. Awards At minimum, plaques or trophies will be awarded to top ten overall individuals, the top five universities in the group contest, and top five overall teams. The travelling National Collegiate Soils Contest Trophy goes to the team with the highest overall team score. Scorecard Instructions The scorecard consists of five parts: I. Soil Morphology, II. Soil Profile Characteristics, III. Site Characteristics, IV. Soil Classification and V. Soil Interpretation. The points for each item are indicated on the score card. The Soil Survey Manual (USDA Handbook no. 18, 1993 edition) and Keys to Soil Taxonomy, 12 th edition (2014), will be used as guides whenever possible. SECTION I: SOIL MORPHOLOGY A. Horizonation (1) Master 5

8 a. Prefix In mineral soils, Arabic numerals are used as prefixes to indicate that a soil has not formed entirely in one kind of material, which is referred to as a lithologic discontinuity, or just a discontinuity. Wherever needed, the numerals precede the master or transitional horizon designation. A discontinuity is recognized by a significant change in particle-size distribution or mineralogy that typically indicates the horizons formed in different parent materials or have a significant difference in age (unless already denoted with the suffix b). Stratification common to soils formed in alluvium is typically not designated as a discontinuity, unless particle-size distribution differs markedly from layer to layer (is strongly contrasting), even if genetic horizons have formed in the contrasting layers. When a discontinuity is identified, prefix numbering starts in the underlying (second) deposit. The material underlying the surficial deposit is designated by adding a prefix of 2 to all horizons and layers that formed in the second material underlying the discontinuity. There is no minimum number of horizons and layers needed in materials that underlie the surficial deposit. If another discontinuity is found below material with prefix 2, the horizons and layers formed in the third material are designated by a prefix of 3. For example, Ap, E, Bt1, 2Bt2, 2Bt3, 3BC. The number suffixes designating subdivisions of the Bt horizon continue in consecutive order across the discontinuity. A discontinuity prefix is not used to distinguish material of buried (b) horizons that formed in material similar to that of the overlying deposit (no discontinuity). For example, A, Bw, C, Ab, Bwb1, Bwb2. However, if the material in which a horizon of a buried soil is in a discontinuity below the overlying material, the discontinuity is designated by number prefixes and the symbol for a buried horizon is used as well, e.g., Ap, Bw, C, 2Ab, 2Bwb, 2C. If a pedon contains two or more horizons of the same kind which are separated by one or more horizons of a different kind, identical letter and number symbols can be used for those horizons that have the same characteristics, for example, the sequence A-E-Bt-E-Btx-C. The prime ( ), when appropriate, is applied to the capital-letter horizon designation, and any lower-case letter symbols that follow it, e.g. A-E-Bt-E -Btx-C. It is used only when the letter designations of the two layers in question are completely identical. b. Master. The second column is to indicate the appropriate master horizon designations (i.e., A, E, B, C, or R) and combinations of these letters (e.g., AB, E/B, etc.). The prime ( ), used for horizons having otherwise identical designations, should also be included in this column 6

9 after the master horizon designation. O horizons or layers will not be described in this contest. All depth measurements should be taken from the marker in the third horizon. R horizons should be identified in the Master column, if within the judging depth. However, they will not otherwise be described, so all other columns in that row should be marked with a dash. This is also true for Cr horizons except that the C is in the master horizon and the r in the subordinate distinction, which follows. (2) Sub. Subordinate Distinctions. Enter lower case letters to designate specific kinds of master horizons if needed. If none, enter a dash. Students should be familiar with applications of the following subordinate distinctions: b (buried genetic horizon), c (concretions or nodules), k (accumulation of carbonates, commonly calcium carbonate), g (strong gleying), n (pedogenic, exchangeable sodium accumulation), p (tillage or other disturbance), r (weathered or soft bedrock), ss (slickensides), t (accumulation of silicate clay), v (plinthite), w (development of color or structure), x (fragipan characteristics) and y (pedogenic accumulation of gypsum). If used in combination, the suffixes must be written in the proper order. NOTE: a subordinate distinction always follows the B master horizon. Subordinate distinctions on transitional horizons will be used when the horizon is transitioning from or to a B horizon (i.e. AB, BA, BC). The subordinate distinction will reflect the subordinate distinction(s) used with the B horizon (i.e. BCt). Contest officials will communicate the use of subordinate distinctions on transitional horizons to coaches through their use at practice sites. The suffix b will be used only when a buried solum, including an A horizon, is clearly expressed. The suffix c will only be used for concretions or nodules that are cemented, but not with silica. It is not used if the concretions or nodules consist of dolomite or calcite or more soluble salts, but it is used if the concretions or nodules are enriched with minerals that contain iron, aluminum, manganese, or titanium. A Bw is not used to indicate a transitional horizon or a horizon that would be transitional if the entire pedon were present. 7

10 (3) No. Numerical Subdivisions Enter Arabic numerals whenever a horizon identified by the same combination of letters needs to be subdivided. If a subordinate distinction or a numerical subdivision is not used with a given master horizon, enter a dash in the appropriate space on the scorecard. (4) Lower Depth Up to six horizons will be described within a specified depth noted on the site card. The depth provided on the site card is not used for any other purpose than describing horizon morphology in Section I. Determine the depth (in cm) from the mineral soil surface to the lower boundary of each horizon except the last horizon. For example, a Bt1 horizon that occurs between 23 and 37 cm below the soil surface, enter "37." The last horizon boundary should be the specified judging depth with a "+" added, unless the specified depth is at a very evident horizon boundary, such as a lithic or paralithic contact, then the "+" is not used. If a lithic or paralithic contact occurs at or above the specified depth on the site card, the contact should be considered in evaluating the available water holding capacity, effective soil depth, and limiting hydraulic conductivity. Otherwise, the last horizon should be assumed to extend to 150 cm for making all relevant evaluations. If a lithic or paralithic contact occurs within the specified depth, the contact should be considered as one of the horizons to be included in the description, and the appropriate horizon nomenclature should be applied (i.e., Cr or R). However, morphological features need not be provided and dashes should be used on the scorecard. If the contestant gives morphological information, it will be ignored by the graders and will not count against the total score. If in doubt concerning the nature of the horizon, the contestant would is advised to provide all of the information for that horizon. In the contest, horizons less than 8 cm thick (no matter how contrasting) will not be described, although thinner horizons may be described in the practice pits. If a horizon less than 8 cm thick occurs, combine it for depth measurement purposes with the adjoining horizon that is more similar (e.g., a thin, discontinuous E horizon might be combined with an adjoining BE). When two horizons are combined to give a total thickness of 8 cm or more, always describe the properties of the thicker horizon. All depth measurements should be taken from the nail in the no pick zone. The allowed range to be considered correct will depend upon the distinctness of the boundary as detailed below. 8

11 (5) Dist. Distinctness of Boundary The distinctness of lower horizon boundaries is to be evaluated as per the Soil Survey Manual (p 133). The distinctness of the lower boundary of the last horizon is not to be determined unless it is at a lithic or paralithic contact. If the lower depth to be judged is at a lithic or paralithic contact, indicate the distinctness, if there is no lithic or paralithic contact, place a dash (---) in the box. The topography or shape of the boundaries will not be recorded. Distinctness of Boundary Abrupt (A) Clear (C) Gradual (G) Diffuse (D) Range For Grading ±1 cm ±3 cm ±8 cm ±15 cm B. Texture (1) Clay Estimates of percent clay should be made for each horizon and entered in the appropriate columns. Answers within plus or minus 10% of the actual values will be given full credit. Actual content of clay was determined by the hydrometer method (2 hrs 40 min). (2) Percentage Coarse Fragments Estimates of the volume percentage coarse fragment should be made for each horizon and entered in the appropriate column, rounded to the nearest 1.0%. Estimates should be made only within the no-pick zone. If no coarse fragments are observed, enter a 0 on the scorecard. For horizons having 1-100% coarse fragments, credit will be given within plus or minus 10% of the official values. (3) Coarse Fragment Modifer. Modification of textural class is made, if needed, in the coarse fragment column, when the soil contains more than 15% by volume coarse fragments. For the purposes of this contest, the following modifiers will be used when the volume of rock fragments is between 15 and 35%. 9

12 a. Gravelly [GR] (2-76 mm diameter) b. Cobbly (includes stones and boulders) [CB] (> 76 mm diameter) If the volume of coarse fragments is between 35 and 60%, prefix the appropriate modifier with the word very [V]. If the volume is greater than 60%, use the prefix "extremely" [E]. Enter the correct abbreviation for the coarse fragment modifier in the Coarse Frag. column, not in the texture class column. If coarse fragments do not exceed 15% enter a dash in the space on the scorecard. If a relatively equal mixture of sizes occurs within a horizon, the total percentage of coarse fragments (all sizes) is used to determine the modifier prefix and the largest size class (most mechanically restrictive) is named. The smaller size class is named only if the quantity (vol.%) is 2 times the quantity of the larger size class. For example, a horizon with 30% gravels and 10% cobbles would be very gravelly (VGR), but a horizon with 15% gravels and 10% cobbles would be cobbly (CB). (4) Class The textural class for the less than 2 mm fraction of each horizon is to be entered in the column labeled Class; the only acceptable abbreviations are given in Appendix 2. For sand, loamy sand, and sandy loam texture classes, modifiers will be used if needed [i.e., very fine (VF), fine (F), or coarse (CO)]. Enter the abbreviation for only one class. More than one may be considered correct by the official judges, but if a contestant enters more than one class, the entire entry is wrong. C. Color Munsell soil color charts must be used to determine the moist color of each horizon described. Colors must be designated by Hue, Value, and Chroma. Color names such as "pale brown" will not be accepted as correct answers. Partial or full credit may be given for colors close to the official evaluation, either in hue, value, or chroma. In the case of surface horizons, color is to be determined on crushed samples. The color recorded for soil material from any other horizon, including a mottled horizon, should be the dominant, unrubbed color of the ped interior, not a ped surface or cutan. The dominant color may or may not be the matrix color. Blue-cover Munsell color charts are used by the official judges. 10

13 D. Structure Grade and Shape 163). If different kinds of structure occur in different parts of the horizon, give the shape and grade of the structure that is most common. If the most common structure is compound (one kind breaking to another), describe the one having the stronger grade. If they are of equal grade, give the one with the larger peds. Numerical notations will be utilized for grade of structure. If the soil materials are structureless (massive or single-grained), enter "0" under grade E. Consistence Determine Moist Strength at approximately field capacity for each horizon. It is considered impractical to use the definitions in the 1993 Soil Survey Manual for contest purposes and therefore the following definition from the 1951 Soil Survey Manual will be used (p ): Consistence when moist is determined at a moisture content approximately midway between air-dry and field capacity. At this moisture content most soil materials exhibit a form of consistence characterized by (a) tendency to break into small masses rather than into powder; (b) some deformation prior to rupture; (c) absence of brittleness; and (d) ability of the material after disturbance to cohere again when pressed together. The resistance decreases with moisture content, and accuracy of field descriptions of this consistence is limited by the accuracy of estimating moisture content. To evaluate this consistence, select and attempt to crush in the hand a mass that appears slightly moist. Record the dominant Grade and Shape of structure as defined in the Soil Survey Manual (p Abbreviation Moist consistence Criteria L Loose non-coherent VFR FR FI VFI EFI Very friable Friable Firm Very firm Extremely firm crushes under very gentle pressure but coheres when pressed together crushes easily under gentle to moderate pressure between thumb and forefinger, and coheres when pressed together crushes under moderate pressure between thumb and forefinger but resistance is distinctly noticeable crushes under strong pressure; barely crushable between thumb and forefinger Crushes only under very strong pressure; cannot be crushed between thumb and forefinger and must be broken apart bit by bit 11

14 F. Soil Features Redox (RMF Depletions and Concentrations): Soils that have impeded drainage or high water tables during certain times of the year usually exhibit redoximorphic (redox) features (RMF) as a result of the movement of reduced iron and manganese. Redox features to be considered for contest purposes include redox depletions (generally seen as gray zones) and redox concentrations (generally seen as red zones of Fe accumulation or black zones of Mn accumulation), which are a result of seasonal or permanent saturation. These do not include colors inherited from parent materials. Depletions: The presence or absence of redoximorphic depletions should be indicated for each horizon. These are zones inside aggregates, along or inside root channels, or on aggregate surfaces with high value ( 4) and low chroma ( 2) where either iron-manganese oxides alone or both iron and manganese oxides have been reduced including: (1) Iron and manganese depletions (zones which are depleted of oxidized forms of iron and manganese due to reduction processes), and (2) Clay depletions (zones which contain lower than their original amounts of clay due to reduction and removal processes) If the horizon is gleyed (meets the definition of g subordinate distinction), Y should be indicated for RMF depletions. For determination of a seasonal high water table, depletions of chroma 2 or less and value of 4 or more must be present. Presence: Yes (Y) RMF depletions are present. No (---) RMF depletions are not present. Concentrations: Redox concentrations may consist of zones of high chroma color, or the Fe and Mn can accumulate into masses (concretions or nodules). Colors associated with the following features will not be considered redoximorphic features: clay coatings (unless their color results from reduction/oxidation), carbonates, krotovina, rock colors, roots, or mechanical mixtures of horizons such as E or B horizon materials within an Ap horizon. Presence: Yes (Y) RMF concentrations are present. No (---) RMF concentrations are not present. 12

15 II. SOIL PROFILE CHARACTERISTICS A. Hydraulic Conductivity (HC) Estimate the saturated hydraulic conductivity of the surface horizon (Hydraulic Conductivity/ Surface) and the most limiting horizon (Hydraulic Conductivity/Limiting) within the depth specified on the site card. If a lithic or paralithic contact occurs at or above the specified depth, it should also be considered in evaluating conductivity. Although unlikely, it is possible for the surface horizon to be the limiting horizon with respect to saturated hydraulic conductivity. In this event, the surface conductivity would be indicated as both the surface and limiting layer hydraulic conductivity. Three general hydraulic conductivity classes are used: High: Includes sands and loamy sands textures. Sandy loam, sandy clay loam, silt loam, and loam textures that are especially "loose" because of very high organic matter content (>5% organic carbon) also fall into this category. Loamy soils in this category are typically not cultivated and are directly below an O horizon (not described). Horizons containing >60% of coarse fragments with insufficient fines to fill voids between fragments are also considered to have high hydraulic conductivity. Moderate: This includes those materials excluded from the "low" and "high" classes. Low: Low hydraulic conductivity should be indicated with the following: 1) Clays, silty clays, or sandy clays having structure grade of 0, 1 or 2. 2) Silty clay loams and clay loams that have structure grade of 0 or 1. 3) Bedrock layers (Cr or R horizons) where the horizon directly above contains redoximorphic depletions or a depleted matrix due to prolonged wetness (value 4 with chroma 2). 4) Massive, silt and silt loam E horizons, and all root-limiting horizons (including fragipans, natric, and duripans) have low hyrdraulic conductivity. 13

16 B. Effective Soil Depth Soil depth classes as defined as the depth from the soil surface to the upper boundary of a root restricting layer. Restrictive layers include: (i) horizons with coarse sand or rock fragment modified coarse sand textures with some unfilled voids located directly underneath a horizon of finer-textured soil materials (i.e., very fine sand, loamy very fine sand or finer texture); (ii) bedrock (lithic or paralithic materials); (iii) root-limiting horizons as defined in section A above; and (iv) very firm or extremely firm SiC, C, or SC textures that are structureless and massive. If the lower depth of judging is less than 150 cm, and there is no restricting layer within or at the judging depth, the horizon encountered at the bottom of the judged profile may be assumed to continue to at least 150 cm and very deep should be selected. Effective soil depth classes are: Very Shallow Shallow Moderately deep Deep Very deep root restricting layer within 25 cm of soil surface root restricting layer from 25 to 49 cm root restricting layer from 50 to 99 cm root restricting layer from 100 to 149 cm root restricting layer at 150 cm or deeper C. Water Retention Difference The water retention difference is approximately the water held between field capacity and permanent wilting point. The approximate amount of moisture stored in the soil is calculated for the top 150 cm of the soil. This soil thickness may or may not be the same as that designated for purposes of profile descriptions. The total water is calculated by summing the amount of water held in each horizon or portion of horizon, if the horizon extends beyond 150 cm. If a horizon or layer is unfavorable for roots (as defined under effective soil depth), this and all horizons below should be excluded in calculating the available moisture. For water retention difference calculations, the properties of the lowest horizon designated for description can be assumed to extend to 150 cm, if no restrictive layer is present. If a restrictive layer is present between the lowest described horizon and the 150 cm depth, the depth to the restrictive layer should be considered for water retention difference estimations. Four retention classes listed will be used: 14

17 Very low: Low: Moderate: High: < 7.5 cm 7.5 to < 15.0 cm 15.0 to < 22.5 cm 22.5 cm The relationship between water retention difference per centimeter of soil and the textures is given in the table below. Coarse fragments are considered to have negligible (assume zero) water retention, and estimates must be adjusted to reflect the coarse fragment content. If a soil contains coarse fragments, the volume occupied by the rock fragments must be estimated and the water retention difference corrected accordingly. For example, if a silt loam A horizon is 25 cm thick and contains rock fragments which occupy 10% of its volume, the water retention difference of the horizon would be 25 cm x 0.20 cm/cm x [(100-10)/100] = 4.50 cm of water. Calculate the water retention difference for each horizon to the nearest hundredth, sum all horizons, then round the grand total to the nearest tenth. For example, would round to 14.9 in the low class; would round to 15.2 in the moderate class. Texture is an important factor influencing water retention difference. The following estimated relationships are used: Water retention difference (cm water per cm soil) Textures 0.05 All sands, loamy coarse sand, and loamy sand 0.10 Loamy fine sand, loamy very fine sand, and coarse sandy loam Sandy loam, fine sandy loam, sandy clay loam, sandy clay, clay, and silty clay Very fine sandy loam, loam, silt loam, silt, silty clay loam, and clay loam F. Soil Wetness Class Soil wetness classes as defined in the Soil Survey Manual will be used. Soil wetness is a reflection of the rate at which water is removed from the soil by both runoff and 15

18 percolation. Landscape position, slope gradient, infiltration rate, surface runoff, and permeability, are significant factors influencing the soil wetness class. Redoximorphic features, including concentrations, depletions and depleted matrix, are the common indicators of prolonged soil saturation and reduction (wet state), and are used to assess soil wetness class. The following determines the depth of the wet state : (1) The top of an A horizon with: (a) Matrix chroma 2, and (b) Redoximorphic depletions or redoximorphic concentrations as soft masses or pore linings, and (c) Redoximorphic depletions or a depleted matrix due to prolonged saturation and reduction in the horizon directly below the A horizon, or (2) The shallowest observed depth of value 4 with chroma 2 redoximorphic depletions or depleted matrix due to prolonged saturation and reduction. The wetness classes utilized in this contest are those which define a "depth to the wet state." Class Description 1 Not wet above 150 cm 2 Wet in some part between 101 and 150 cm 3 Wet in some part between 51 and 100 cm 4 Wet in some part between 26 and 50 cm 5 Wet at 25 cm or shallower If no evidence of wetness is present above a lithic or paralithic contact that is shallower than 150 cm, assume Class 1: not wet above 150 cm. If no evidence of wetness exists within the specified depth for judging and that depth is less than 150 cm, then assume Class 1: not wet above 150 cm. SECTION III: SITE CHARACTERISTICS A. Parent Material 16

19 Contestants must identify the parent material(s) within each profile. If more than one parent material is present, all should be recorded. Parent material classifications in this region can sometimes be difficult to interpret in transition areas. Landscape position and associations, the soil profile, presence or absence of polished sedimentary rock, percent slope, and proximity to large streams should all be considered in determining parent material classification. (1) Alluvium: Alluvium is material transported and deposited by flowing water or in ponded depressions. It includes material on flood plains, stream terraces, alluvial fans, and at the base of slopes, drainage ways and depressions. Water is the primary mechanism of transport. Evidence of sorting by flowing water (stratification) may occur in several forms, including irregular variability of particle size with depth, especially of sand and rock fragment sizes. For example, thin strata (layers) of sandy textures alternating with silty textures, or a change from non-gravelly to extremely gravelly textures indicate irregular deposition due to variation in the velocity of flowing water. Rounded rock fragments sorted by size are also clues of movement by flowing water. In flooded areas, the soil may contain buried horizons and is coarser-textured nearest the active channel, becoming finer-textured away from the channel. For the purposes of this contest, alluvium refers to soils that are excessively drained to poorly drained, loamy and clayey soils that formed on natural levees and in back swamps in sediment chiefly from the Arkansas and Mississippi Rivers and associated tributaries. (2) Colluvium: Colluvium is poorly sorted material accumulated on, and especially at the base of, hill slopes. Typically, colluvium in the region is found on hill slopes with grades greater than 8% and lengths greater than 100 m. Colluvium results from the combined forces of gravity and water in the local movement and deposition of materials. Colluvium may contain a mixture of rock fragment types with variable size and orientation within a horizon, or it may contain a mismatch between rock fragments in upper horizons with those of horizons below that retain rock-controlled structure or in-place rock fragments below. Recently transported colluvium is typically found on backslope, footslope or toeslope slope profiles. 17

20 (3) Loess: Fine-grained, wind-deposited materials that are dominantly of silt size. Textures are usually silt loam, silt, or silty clay loam. Where loess mantles are thin (< 75 cm), there may be some coarser mineral particles particularly toward the base of the loess deposit. Larger particles (including coarse fragments) may be incorporated the loess mantle through bioturbation. (4) Marine: Soils that formed in sediments of marine origin; laid down in the waters of an ocean. For this contest, marine parent materials are typically soils that formed in uplands in sediment deposited in old coastal embayments and in local sediment washed from these uplands. They are typically moderately well to poorly drained loamy soils that formed in stratified sediment deposited on the bottom of shallow coastal embayment that covered the region many thousands of years ago, and in recent alluvium washed from this material. (5) Residuum: The unconsolidated and partially weathered mineral materials accumulated by disintegration of bedrock in place. B. Landform (1) Depression: For the purpose of this contest, a depression is considered to be shallow depressions less than 0.5 ha in area showing no visible signs of developed surface outlets for runoff. (2) Floodplain: The lowest geomorphic surface which is adjacent to the stream bed and which floods first when the stream goes into flood stage. It is formed by the deposition of alluvium. Each stream has only one floodplain. (3) Stream Terrace: These are geomorphic surfaces of varying age formed by the deposition of alluvium and are higher in elevation than the flood plain. A stream may have more one or more terraces. (4) Mound: A low, rounded natural hill of unspecified origin. Found on flat lying geomorphic surfaces older than late Holocene, usually old fluvial terraces and normally between m in height and 10 and 30 m in diameter. The origin of these pimple mounds is uncertain. Hypotheses suggested include erosion, 18

21 gophers, coppice dunes formed in past droughts, seismic, and others. For the purpose of this contest, mound/intermound areas will contain many obvious mounds. (5) Inter-Mounds: The concave to relatively flat-bottomed, irregularly shaped depressions that separate pimple mounds in mounded landscapes. (6) Uplands: Areas dominated by residual and colluvial parent material which usually are found above floodplains and stream terraces. The bulk of soil material found in uplands is produced by physical and chemical weathering of parent material in place and mass wasting such as soil creep, debris and mud-flows, slumps, landslides, and other erosional depositions. C. Slope Slope classes used in this contest are listed on the scorecard. The slope should be determined with an Abney level or clinometer between two stakes at each site. The stakes may be of unequal height. Stakes are provided to assist contestants to measure the actual slope of the land between the stakes, not the slope at the top of the stakes. The height of the stakes should be compared and the actual soil slope measured. D. Slope Profile The slope profile components are shown graphically by hill slope cross-sections in Figures 1 and 2. Not all profile elements may be present on a given hill slope. When possible slope stakes will be positioned to define the slope profile, but in some cases the slope profile may extend beyond the slope stakes. Contestants should consider the area that includes the soil pit and slope stakes when evaluating slope profile. (1) Summit: a topographic high such as a hilltop or ridge top. Summits can be linear or slightly convex in shape. (2) Shoulder: a slope adjacent to the summit that is convexly rounded. (3) Backslope: a mostly linear surface that extends downward from a summit or shoulder position. 19

22 (4) Footslope: a concave slope segment at the base of a hill slope. If located in a closed depression center that is concave in shape, footslope should be marked. (5) Toeslope: the lowest component that extends away from the base of the hill slope. Toeslopes are typically linear in shape. If located in a closed depression center that is linear in shape, toeslope should be marked. (6) None: This designation will be used when the slope at the site is < 2% AND the site is not in a well-defined example of one of the slope positions given above (e.g., within a nearly level, terrace, or floodplain). Figure 1. Landscape designations for landscapes with a defined drainageway. Figure 2. Landscape designations for closed depression landscapes. E. Surface Runoff Runoff is the water that flows away from the soil over the surface without infiltrating. Soil characteristics, management practices, climatic factors (e.g., rainfall intensity), vegetative cover, and topography determine the rate and amount of runoff. The scorecard includes the six runoff classes and the combined effects of hydraulic conductivity, slope, and vegetation on runoff rate are considered. A guideline for evaluating various slopes and limiting hydraulic conductivity under cultivated conditions follows. If the surface has a dense vegetative or debris cover, the surface runoff class should be assigned one 20

23 lower class rate to a minimum of Very Slow. depression use the closed depression row in the table. If the soil is located in a closed % Slope Closed depression Limiting hydraulic conductivity of the surface horizon High Moderate Low Ponded Ponded Ponded 0 - <1 Very slow Very slow Slow 1 -<2 Very slow Slow Medium 2 - < 6 Slow Medium Rapid 6 - < 12 Medium Rapid Very rapid 12+ Rapid Very rapid Very rapid F. Soil Erosion Potential The erosion potential is dependent on the factors contributing to surface runoff, as well as organic matter content and physical properties of the surface horizon, including texture and structure. For the purposes of this contest, the soil erosion potential will be determined from the surface texture and surface runoff according to the following table. Surface Runoff Surface Horizon Texture S, LS SCL, SC SL, CL, C, SIC L, SI, SIL, Ponded/Neg. Low Low Low Low Very slow Low Low Low Medium Slow Low Low Medium Medium Medium Low Low Medium High Rapid Low Medium High High Very Rapid Medium High High High 21

24 SECTION IV: SOIL CLASSIFICATION A simplified taxonomic key (Appendix 3) should be used for determining the soil Sub- Order and Great Group. This will NOT be provided to the students in competition. Soil Taxonomy, USDA-NRCS Agricultural Handbook 436, 2nd Edition (1999) and the most current edition of Keys to Soil Taxonomy should be referred to for criteria used for other soil details for classification purposes, such as soil Order. The Family Particle Size Class(es) should be determined from the Family Particle Size Control Section as defined in the most current edition of Keys to Soil Taxonomy. Generally, the control section for most soils in the region is between the lower boundary of the Ap horizon or a depth of 25 cm below the mineral soil surface, whichever is deeper, and the shallower of the following: (a) a depth of 100 cm below the mineral soil surface, (b) a fragipan, petrocalcic, petrogypsic, or placic horizon, if between 36 and 100 cm below the mineral soil surface, or (c) the argillic or natric horizon if 50 cm or less thick, or the upper 50 cm of the horizon if >50 cm thick. Should strongly contrasting particle-size classes exist, as defined by the most current edition of Keys to Soil Taxonomy, students should mark a 1 indicating the upper class and a 2 to indicate the lower class. For example, sandy over clayey should have a 1 marked for sandy and a 2 marked for clayey. Partial credit (2 pts) will be awarded if only one of the strongly contrasting particle-size classes is marked. NO points will be awarded if the correct classes are identified but numbered incorrectly! Contestants should list only the diagnostic horizons of the soil to be classified. In the case of buried soils, only the diagnostic horizons (or lack thereof) present above the buried soil should be selected on the scorecard and used to determine taxonomic classification. For example, if a soil contains a horizon sequence of A(ochric)-C1-C2-Ab-Btb(argillic) and the Ab and Btb horizons meet the definition of a buried soil, the correct answers would be "ochric" under epipedon and "none" under subsurface diagnostic feature. If argillic was selected under diagnostic horizons, it would be incorrect. Pertinent laboratory data and other information will be provided for each soil on the pit card. This information will be used to determine the correct epipedon, subsurface horizon or feature, order, suborder, and great group for each soil. For taxonomic decisions, assume that the last horizon extends to 2 m or more unless it is directly underlain by a lithic or paralithic contact, or unless additional 22

25 information is provided on the site card. Assume that saturation, if present, is endo if all the layers from the upper boundary of saturation to a depth of 200 cm or more from the mineral soil surface show evidence of water saturation. If the soil is saturated with water in one or more layers within 200 cm of the mineral soil surface, but also has one or more unsaturated layers, with an upper boundary above a depth of 200 cm, below the saturated layer (eg., the zone of saturation is perched on top of a relatively impermeable layer), the saturation is epi. Dry colors of surface horizons may be provided at some or all sites for help in making taxonomic decisions. If dry colors are not provided, taxonomic decisions should be based solely on moist color. SECTION V: SOIL INTERPRETATIONS A. Interpretations for dwellings with basements, onsite wastewater loading rates, septic tank absorption field, and local roads and streets. Contestants will be expected to recognize soil limitations relative to dwellings with basements, determine onsite wastewater loading rates and suitability for septic tank absorption fields, and limits for local roads and streets. The tables in Appendix 4 have been modified from similar tables in the National Soils Handbook and are guides to making soil interpretations for these uses. A copy will be provided to each contestant. When utilizing the following tables the overall degree of limitation is determined by the most restrictive soil property which is determined first when reading the table from top to bottom. Some instances may occur where the pit does not extend to the necessary depth needed to make the interpretation. In these cases contestants must assume the lowest horizon if the pit extends to the interpretative depth unless a lithic or paralithic contact occurs within the depth to be judged. Special considerations for soil/site interpretations: Fragipans (e.g. Btx horizons) are not considered a cemented pan for interpretations for local roads and streets. 23

26 When rating shrink-swell suitability for houses with basements, consider the continuous thickness of clay textures (SC, SIC, and C). For example, if a profile has an 8cm thick horizon of SIC overlying a 15 cm horizon of C, the continuous thickness of clay is 23 cm, and the site should be rated severe for reason #7, Shrink swell (assuming it was not rated severe by any of the reasons above it in the table). For interpretation of Local Roads and Streets (frost action), consider the texture of the most restrictive horizon within the profile or depth specified. When average texture is specified (Local Roads and Streets-strength), use the weighted average texture based on sand and clay contents of horizons within the depth specified. B. Determination of on-site wastewater loading rates. Contestants will determine the on-site wastewater loading rates using soil criteria established by the Arkansas Health Department with slight modifications for this contest. The method involves estimating the depth to seasonal water tables of three durations for two hydraulic conductivity classes using the guides described in Appendix 5 and modified, if needed, as described below. Hydraulic conductivity class is determined as the most limiting class in the upper 50 cm. Soils with a low HC in the upper 50 cm are not suited for standard on-site disposal systems and are assigned a loading rate of 0 gpd/ft 2. The interpretations relate primarily to redoximorphic features and clay content. All colors are for moist conditions. To determine the on-site wastewater loading rates: 1) determine if the redoximorphic features have dissimilar color patterns on ped surface and ped interiors, or similar color patterns on ped surfaces and ped interiors and horizons without peds. 2) find the depths to the brief, moderate, and long SWT (if present) using the criteria in Appendix 5. A copy of Appendix 5 and 6 will be provided to each contestant. 3) If more than one SWT duration is present, adjust the depths to the moderate SWT and the long SWT as described below. 24

27 To adjust the Moderate SWT, subtract the depth to the brief SWT from the depth to the moderate SWT and divide by 3. Subtract the result from the depth to the moderate SWT to obtain the adjusted moderate SWT. To adjust the long SWT if a moderate SWT is present, subtract the adjusted moderate SWT from the depth to the long SWT and divide by 2. Subtract the result from the depth to the long SWT to obtain the adjusted long SWT. To adjust the long SWT where only a brief SWT and a long SWT is present, subtract the depth to the brief SWT from the long SWT and divide by 6. Subtract the above number from the depth to the long SWT to obtain the adjusted long SWT. 4) Compare the loading rates for the brief, adjusted moderate, and/or adjusted long SWT s using the soil loading charts (Appendix 6). Use the most restrictive (lowest) loading rate to determine the on-site wastewater loading rate. Soils that only have one duration of seasonal water table are loaded by using the loading rate given in the soil loading charts for the duration of seasonal water table observed. Examples of typical scenarios are below. Example 1. The soil has a brief SWT at 45 cm, moderate SWT at 61 cm, long SWT at 84 cm, and a moderate HC at 50 cm. Adjusted moderate SWT = 61 - ((61-45)/3) = 61- (16/3) = 61 5 = 56 cm. Adjusted long SWT = 84 ((85-56)/2) = 84 (29/2) = = 69 cm. The loading rates (Appendix 6) for this soil are: brief SWT = 0.75 gpd/ft 2, adjusted moderate SWT = 0.44 gpd/ft 2, and adjusted long SWT = 0.34 gpd/ft 2. The most restrictive loading rate is 0.34 gpd/ft 2 and therefore the correct answer on the score card is gpd/ft 2. Example 2. The soil has a brief SWT at 56 cm, no moderate SWT is observed, a long SWT at 95 cm, and a moderate HC at 50 cm. The adjusted long SWT = 95 ((95-56)/6) = 95 (39/6) = 95 7 = 88 cm. The loading rates (Appendix 6) for this soil are brief SWT = 0.75 gpd/ft 2, adjusted long SWT = 0.53 gpd/ft 2. The most restrictive loading rate is 0.53 gpd/ft 2 and therefore the correct answer on the score card is gpd/ft 2. Example 3. No brief SWT is observed, a moderate SWT is at 71 cm, a long SWT at 102 cm, and a moderate HC at 50 cm. It will not be necessary to adjust the moderate SWT since no brief SWT is present, however the adjusted long SWT = 102 ((102-71)/2) = 102 (31/2) 25

28 = = 86 cm. The loading rates (Appendix 6) for this soil are moderate SWT = 0.73, adjusted long SWT = 0.50 gpd/ft 2. Therefore, the correct answer on the score card is gpd/ft 2. Example 4. The soil has a clay content >35% at 50 cm. The HC of this soil therefore is LOW in the loading zone of 51 cm and a loading rate of 0 gpd/ft 2 is used (see footnote, Appendix 6). Therefore, the correct answer on the score card would be 0-10 gpd/ft 2. 26

29 Appendix 1 Example of the Site Card Site No. 1 Describe horizons to a depth of cm. The marker is somewhere in the third horizon at cm. Horizon % B.S. % Organic C %CaCO 3 E.S.P. ŧŧ Dry Color These values may or may not be included depending upon the site and conditions. ŧ E.S.P = Exchangeable Sodium Percentage. This value may or may not be included depending upon the site and conditions. Vicinity Map 27