2/10/2011. Arizona FFA Soil CDE Reference

Transcription

1 Arizona FFA Soil CDE Reference 1

2 Soil On the first soils in the first season of the Earth, individualization began. Separated now by solid matrix instead of by the shifting waters of the sea, organisms found it possible to wave without moving away. Things could stay in one place. Soil. William Logan 2

3 Rob Wilson NRCS Primary Authors 3

4 Primary Authors Karen Geldmacher Central Arizona College Dr. Donald Post The University of Arizona 4

5 Contributing Authors Dr. Tom Wilson University of Arizona Dr. Craig Rasmussen University of Arizona Dr. Jeff Silvertooth University of Arizona 5

6 Technical Review Team Ms. Davida Molina FFA Advisor Ms. April White FFA Advisor Ms. Katy Groseta FFA Advisor Mr. Pat Wellert FFA Advisor Mr. Curt Willems FFA Advisor Ms. Cathy McGuire NRCS State Soil Scientist Mr. Bill Johnson NRCS Soil Scientist 6

7 Arizona FFA The authors wish to thank the Arizona FFA for their contributions to this project. 7

8 The Arizona FFA Soil Judging CDE consists of two parts: 1. A WRITTEN EXAM that concentrates on general knowledge of soils from this PowerPoint and the UA Soil Reference Unit. 2. A FIELD PIT TEST that evaluates the soil physical and chemical properties. 8

9 Arizona FFA Soils CDE Contestant Information Contestants are allowed to bring the following to the CDE: Clipboard No. 2 Pencils Knife or Putty Knife Drinking Water Spray bottle to moisten soil for texturing (bottles will be provided by the test hosts) Clean up cloth or towel. 9

10 At Each Pit Site: A soil pit will be opened to a depth of more than three feet when possible. Buckets of soil from each horizon will be provided at each judging site for the students to use for texturing. Hydrochloric acid will be provided to test for effervescence. #10 sieves will be provided. Measuring tape will be present. Spray bottles of water for texturing. The slope stakes will be set by the site host. Site Condition Sheet. 10

11 A Good Site Layout Spray bottle Hydrochloric acid Condition Sheet #10 Sieve for texturing required at each site Boundary markers no touching between the ribbons Tape in inches required at each site 11

12 FFA Contestants Evaluating a Site 12

13 Site Condition Sheets Each Site will have a Condition Sheet. The following two slides are examples of Site Condition Sheets 13

14 Site Number Value for Erosion Calculation Value for Erosion Calculation Optimal ph Reference Range Optimal Nitrogen Reference Range Optimal Phosphorous Reference Range Optimal Potassium Reference Range 14

15 Site number Value for Erosion Calculation Value for Erosion Calculation Optimal ph Reference Range Optimal Nitrogen Reference Range Optimal Phosphorous Reference Range Optimal Potassium Reference Range 15

16 PowerPoint Contents Part I General Soil Information: 5 Soil Forming Factors The Soil Profile Soil Textural Triangle Soil Color Soil Geomorphic Landform 16

17 PowerPoint Contents Part II Arizona Soil Pit Evaluation Score Card Soil Structure Percent Rock Fragments Soil Texture Effervescence Stickiness Plasticity Thickness of the Surface Soil Total Depth of the Soil Slope Soil Parent Material Erosion Surface Runoff Potential Cont 17

18 PowerPoint Contents Part II cont. Ai Arizona Soil Pit Evaluation Score Card cont. ph Nitrogen (N) Phosphorus (P) Potassium (K) Soil Water Holding Capacity Soil Permeability Land Capability Class 18

19 General Soil Information Part I 19

20 The Five Soil Forming Factors Soil is a three dimensional, dynamic natural body, a product of the environment in which it is developing. 20

21 Five Factors of Soil Formation Soils are defined as having properties derived from the combined effects of: Climate Organisms (Biota) Parent Material Relief (Topography) Time These are the Five major factors controlling the formation of soil, or THE 5 SOIL FORMING FACTORS. 21

22 Climate Climate is the long term pattern of temperature and precipitation for a region. Climate is a major factor in determining the kind of plant and animal life lf on and in the soil. It determines the amount of water available for weathering minerals, transporting the minerals and releasing elements. Climate, through its influence on soil temperature, determines the rate of chemical weathering. 22

23 Arizona enjoys a great variety of climatic environments 23

24 Climate affects the Mechanical & Chemical breakdown of Soil Parent Materials wind rain hail ice Heat and cold mechanical weathering chemical weathering parent material sand silt clay 24

25 Plants affect soil development by supplying upper layers with organic matter as the plants die or lose leaves. Leaves, twigs, and bark from large plants fall onto the soil and are broken down by fungi, g, bacteria, insects, earthworms, and burrowing animals. Organisms 25

26 Organisms Deep rooted plants, such as grasses, contribute more to soil development than shallow rooted plants. 26

27 Organisms Grass roots hold soil in place and are very effective in controlling soil loss by wind or water. 27

28 Microorganisms Microorganisms eat and break kdown organic matter releasing plant nutrients They recycle nutrients from lower to upper layers, and help prevent erosion by wind or water. Some organisms change elements such as sulfur and nitrogen into usable forms for plants. 28

29 Microbiotic Crusts Stabilize the Soil Surface: Surface protected by microbotic crust Eroded surface 29

30 Organisms Microscopic organisms and the humus they produce act as a kind of glue to hold soil particles together in aggregates. Well aggregated soil is ideal for providing the right combination of air and water to plant roots. 30

31 Organisms Burrowing animals such as foxes, moles, badgers and so on affect decomposition of waste materials and how soil materials are moved around in the soil profile. 31

32 Organisms Burrows open the soil to air and water movement and mix in organic matter. 32

33 Parent Material Parent Material refers to that great variety of unconsolidated rock and organic matter in which soil formation begins. 33

34 Topography Landscape position has a great deal of influence on soil development. Topography includes the degree and direction of slope. A hillside will erode during rainstorms and the soil will be thinner. The soil at the base of the hill will be thicker because it receives material from the side slope. A river bottom will receive some material after flood events and portions of the bottom may have material removed by swift flowing water. 34

35 Time Time is required for horizon formation. The longer a surface has been exposed to soil forming agents like rain and growing plants, the greater the development of the soil profile. Soils in recent alluvial materials or soils on steep slopes where erosion has been active may show little horizon development. Soils on older, stable surfaces generally have well defined horizons because the rate of soil formation is greater than the rate of erosion. 35

36 5 Soil Forming Factors Review 36

37 The Soil Profile A soil profile is a cross section sample of a soil body. It has horizons (layers) that are approximately parallel to the earth s surface. 37

38 Soil Profiles 38

39 Soil Profiles 39

40 Soil Horizons Soil material is arrayed in layers that are roughly parallel to the surface. These layers are called horizons and each soil pit may express several horizons. A typical soil profile consists of three master horizons: A B and C 40

41 Master Soil Horizons The soil horizons are designated with alphabetic characters from the surface down: HORIZON O A E B C R DEFINITION Organic Horizon Topsoil. Surface Mineral Horizon. Horizon of Eluviation or Leaching. Horizon of Accumulation of Clay Parent Material Bedrock 41

42 The O Horizon O is the Organic Horizon. The O horizon consists of decomposed or partially decomposed organic matter that is being added to the underlying A horizon over time. It may be leaves, grass blades, twigs, etc. In many parts of Arizona the O horizon never forms due to high heat and relative lack of dead organic material. 42

43 The A Horizon The A horizon is known as the 'topsoil' and it is the uppermost layer of the mineral soil. The A horizon is mainly mineral material. It is generally somewhat darker than the lower horizons because of greater amounts of decomposed organic matter. This horizon is where much root activity occurs and is usually the most productive layer of the soil. It may be referred to as a surface horizon. 43

44 The E Horizon The E Horizon is the horizon of eluviation, or exiting. The main feature of the E horizon is loss of clay, iron and aluminum leaving a light colored layer dominated by silt and sand. These are present only in older, well developed soils, and generally occur between the A and B Horizons. In Arizona they are usually not very thick and the horizon below E is high h in clay. 44

45 The B Horizon B Horizons are commonly referred to as subsoil, and consist of mineral layers which may contain concentrations of clay or minerals such as iron or aluminum. In addition, they are defined by having a distinctly different structure or consistence to the A horizon above and the horizons below. 45

46 The B Horizon In general the B horizon displays the maximum structural development and maximum clay content. Structure tends to be angular or sub angular blocky, prismatic or columnar. 46

47 The C Horizon The C horizon includes parent material. 47

48 The R Horizon The R horizon is the layer of bedrock at the base of the soil profile. Unlike the above layers, R horizons largely comprise continuous layers of hard rock that cannot easily be excavated by hand. 48

49 O horizon A horizon E horizon B horizon C Horizon 49

50 Soil Horizons Review 50

51 The Surface Soil The surface soil consists of the total thickness of the A horizon, and the E horizon if it is present. For example; the A horizon thickness is 7 thick and the E horizon is 2 thick then the thickness of the surface soil is 7 +2 =9 51

52 Characteristics of the Surface and Subsurface Horizons Soil Texture size and relative abundance of the soil separates (sand, silt and clay) Soil Stickiness how strongly particles adhere to each other and your fingers Soil Plasticity how well wet soil can be molded and rolled into wires. Think of making pottery. 52

53 Characteristics of the Surface and Subsurface Horizons Soil Structure how soil particles form aggregates with different shapes Rock Fragments presence of particles > 2mm Soil Color dry and moist conditions Soil Effervescence how a soil reacts or forms bubbles with 10% hydrochloric acid HCl 53

54 Soil Texture Soil Texture refers to the relative proportion of the sand, silt and clay in the fine earth fraction of the soil. Texture has a major influence on the productivity and use and management of the soil resource. Texture influences root penetration, water holding capacity, aeration, and erosion potential

55 Soil Texture Texture is a very important soil characteristic. It influences other properties significant to use and management such as soil water holding capacity. Texture is a measure of a soils potential to transmit water downward through the profile. Texture is also an important component in a soils potential to hold plant nutrients. 55

56 Soil Texture An important soil property is the size of the particles, and the relative proportion, or percent of these particles in the soil. A particle size category is called a soil separate. The three main soil separates are called: sand, silt and clay

57 Soil Texture Particle Sizes Sand 2.0 mm to 0.05 mm Silt 0.05 mm to Clay >0.002 mm 57

58 Soil Texture Sand and Silt develop from broken down rock fragments consisting of quartz, feldspar, mica and other minerals. Clay particles are very small, plate lt shaped, crystal tl structures consisting of oxygen, silica and aluminum

59 Soil Texture A textural class has a defined range of particle sizes (sand, silt, and clay) The NRCS recognizes 12 textural classes: Sand Silt loam Silt Loamy sand Silty clay loam Sandy loam Silty clay Sandy clay loam Clay loam Sandy clay Clay Loam 59 59

60 The USDA Soil Textural Triangle 60

61 USDA Soil Textural Triangle The USDA textural triangle estimates the relative amounts of sand, silt and clay in a soil sample. These components make up 100% of your soil sample. 61

62 USDA Soil Textural Triangle The triangle consists of the intersections of 3 separate sets of lines. One set of lines represent sand One represents clay And one represents silt 62

63 USDA Textural Triangle The left side leg represents the percent of clay in the soil sample and that line is read straight across or level and parallel with the bottom. The right side leg represents the percent of silt in the soil sample. That line is read from the leg down and to the left. The bottom of the triangle represents the percent of sand in the sample and is read from the bottom and up and to the left 63

64 For the percent of silt follow these lines For the percent of clay follow these lines Clay Silt For the percent of sand follow these lines Sand 64

65 USDA Textural Triangle The block on the triangle where the lines intersect is the textural class for that soil. Since there are only three components and they must add up to 100% you need to find the intersection of any two of the components and they define the percent of the other component. 65

66 66

67 Soil Color The color of the soil is an important indication of soil conditions and properties that help to determine the various uses of soil. 67

68 Soil Color Soil color gives clues to the organic matter content, the surface drainage, the salt content, the general fertility of the soil. Soil color is used to help classify soils. 68

69 Soil Color Light colored desert soils are normally low in fertility and have <1% organic matter. These soils can be highly productive when properly irrigated and fertilized. Dark brown to black soils indicate high organic matter content (>5%) and good fertility. 69

70 Soil Color Some soils are red to yellow which is indicative of high iron content. 70

71 Geomorphic Landforms This illustrates t the geologic setting or the landscape where the soil occurs. Upland or Mountains Colluvium Foothills or Alluvial Fan Flood plain, stream, terrace or basin floor 71 71

72 Gullies formed by water erosion Bottomland subject to flooding Stable upland 72

73 mountains fan terrace basin floor 73

74 End of Part 1 General Soil Information 74

75 Arizona Soil Pit Evaluation Score Card PowerPoint P tpart tii 75

76 PowerPoint Contents Part II Arizona Soil Pit Evaluation Score Card Soil Structure Percent Rock Fragments Soil Texture Effervescence Stickiness Plasticity Thickness of the Surface Soil Total Depth of the Soil Slope Soil Parent Material Erosion Surface Runoff Potential Cont 76

77 PowerPoint Contents Part II cont. Ai Arizona Soil Pit Evaluation Score Card cont. ph Nitrogen (N) Phosphorus (P) Potassium (K) Soil Water Holding Capacity Soil Permeability Land Capability Class 77

78 Field Pit Question: Soil Structure 78

79 Soil Structure Soil Structure is the arrangement of soil particles, (sand, silt and clay) to form natural aggregates. 79

80 Soil Structure is best observed while it is in place in the soil wall of the pit. 80

81 Soil Structure in a Soil Profile Soil texture and organic matter content are the two most important soil characteristics that determine the structure formed. Clayey soils often exhibit blocky or massive structure whereas soils high h in organic matter may exhibit granular structure. Granular 81 81

82 Soil structure is important because structure influences air and water movement. 82

83 Soil Structure Typically in the surface horizon of cultivated fields the structure will be granular. However if the field is muddy the structure will appear massive. In a range setting the surface structure may typically be a very weak platy or granular. Structure is influenced by clay content. Structure in the subsurface horizon of a profile that p has high clay may typically be blocky and prismatic. 83

84 Soil Structure Soil structure is important because, to a great degree, it helps determine availability of soil nutrients, movement of air and water in the soil profile, and ease of plant root establishment and growth. There are six categories of soil structure to select from in both the surface and subsurface soil horizons. 84

85 Soil Structure 6 types: Granular Platy Prismatic or Columnar Blocky Massive Single Grained 85

86 Soil Structure Granular If soil particles are arranged in small aggregates with round edges the soil structure is termed granular. Commonly found in the A horizons that are enriched with organic matter. This type of structure is very desirable for plant growth because it provides a combination of large and small pores

87 Granular Structure 87

88 Soil Structure Platy Platy structure units are thin, flat and plate like. Soils may develop a platy structure naturally or through the action of man. Thin layers of platy structure can effectively seal the soil against air and water movement. Therefore, platy structure is usually indicative of very slow permeability and infiltration

89 Platy Structure 89 89

90 Soil Structure Prismatic and Columnar Prismatic structure units resemble blocky structure except that they are longer than they are wide. Prismatic aggregates are flat on the top whereas columnar aggregates have rounded tops. This structural type usually indicates a higher clay content than the horizons above

91 Prismatic Structure Prisms can be different sizes, but have the same shape

92 PRISMATIC STRUCTURE in the soil wall 92

93 Prismatic Structure 93

94 Soil Structure Blocky When particles cling together in nearly square cube like units the structure is termed blocky. 94

95 Note: The mass of soil readily breaks into aggregates when manipulated. Blocky 95

96 Blocky Structure in the Soil Wall 96

97 Soil Structure Massive Massive soil is when the soil particles are stuck together in a mass and there are no individual aggregates

98 Soil Structure Single Grain In single grained structure the particles will not stick together, and no aggregates are formed

99 Soil Structure 99 99

100 Field Pit Question: Percent Rock Fragments 100

101 Examples of Rock Fragments on the Surface Horizon

102 Example of Rock Fragments within the Sub Surface Horizon 102

103 Percent Rock Fragments Rock fragments are commonly present in Arizona soil horizons. Percent Rock Fragments are expressed as: Less than 15% by volume 15 35% by volume Greater than 35% by volume

104 Percent Rock Fragments In the field you can estimate the percent rock fragments by completely sieving a measured sample and then comparing the amounts of material left on the screen and that which passed through the screen. For example the entire sample represents 100% and if you estimate that 30% passed through the screen then that leaves 70% rock fragments

105 A #10, 2mm sieve is used to separate the fine earth fraction, or portion of the soil sample that is <2.0 mm from the rock fragments

106 The fine earth portion of the soil sample passes through the 2.0mm screen The coarse fragments are retained on the mesh Fine earth passes through the mesh

107 Estimating percent of rock fragments in a soil sample: To get a frame of reference take a hand full of soil and that will represent 100% of your sample. 107

108 Or you may fill the sieve pan. Reference what 100% of the sample looks like. 108

109 Sieve the material completely and compare the volume of the material that passed through the mesh against what you remember as 100% of the total. The scorecard choices are <15%, 15 35% or >35% based on volume. 109

110 Place the material side by side and make an estimate of fine and coarse material by comparing them. <15% coarse fragments: 110

111 15 35% coarse fragments: 111

112 >35% coarse fragments: 112

113 Field Pit Question: Soil Texture 113

114 The scorecard groups the 12 USDA textural classes into 5 options: Coarse Sand/ Loamy Sand Moderately Coarse Sandy Loam/ Fine Sandy Loam Medium Loam/Silt Loam/Silt Moderately Fine Clay Loam/Sandy Clay Loam/Silty Clay Loam Fine Clay/Silty Clay/Sandy Clay The following triangle illustrates the 12 USDA classes consolidated into the 5 field pit test textural classes. 114

115 Fine Moderately Fine Coarse Moderately Coarse Medium 115

116 Soil Texture by Feel Method Texture by feel is the physical skill set developed, through practice, to determine the approximate percentage of sand, silt and clay in a sample by rubbing the moistened soil between your finger and thumb. 116

117 117

118 The Feel Method Moisten the soil in your palm to the consistency of putty. Push your thumb gradually forward to form the soil into a ribbon. 118

119 Texture by Feel Coarse (Sand/Loamy Sand) Air and water move readily through sandy soils. Sand feels gritty. When sand is wetted, formed into a ball and tossed into the air, it will not remain in the form of a ball when it lands back in your hand. 119

120 Texture by Feel Moderately Coarse (Sandy Loam/Fine Sandy Loam) A sandy loam contains much sand but has enough silt and clay to make it stick together more than the loamy sand or sand. The individual sand grains can be seen and felt. A short ribbon can be formed (< 2 cm) A sandy loam soil contains 43 85% sand, 0 50% silt, and 0 20% clay. 120

121 Soil Texture by Feel Medium (Loam/Silt Loam/Silt) These textural classes can be molded in your hand when moistened. They form short ribbons. They are typically slightly sticky and slightly yplastic. 121

122 Loam Loam is a soil that t feels and behaves like it has about equal proportion of sand, silt, and clay. It is mellow, with a somewhat gritty feel, yet fairly smooth and slightly plastic. Squeezed when moist, the ball can be handled without breaking, and it will form a short ribbon. Soils termed Loam contain 23 52% sand, 28 50% silt, and 8 27% clay

123 Silt A soil high in silt feels floury, smooth, or like velvet cloth. Silt particles stain the fingers and will leave a fingerprint. Silty soils hold more water for plans than sandy soils. Silt sticks together better than sand

124 Silt Loam A silt loam soil has a moderate amount of the fine grades of sand and only a small amount of clay; over half the particles are silt size. Squeezed when moist, it will form a ball, but will form only a short ribbon. It can be molded into a thin wire, and is plastic and sticky. This soil contains 0 50% sand, 50 88% silt, and 0 27% clay

125 Texture by Feel Moderately Fine (Clay Loam/Sandy Clay Loam/Silty Clay Loam) The moist soil is plastic and will form a ball which will bear much handling. When the moist soil is pinched between the thumb and forefinger, it will form a thin ribbon (2 5 cm in length). Clay Loams contain 20 45% sand, 15 23% silt and 27 40% clay. 125

126 Texture by Feel Fine (Clay, Silty Clay, Sandy Clay) Very sticky and very plastic. Forms a long ribbon (> 5 cm) when pressed between the thumb and forefinger

127 Clay Clay textured soils feel sticky when moist. A soil high in clay will form a tight ball when tossed in the air and caught. When moist, clay textured soils will form a long ribbon (> 5 cm) and stain your fingers with shiny color. 127

128 Field Pit Question: Effervescence 128

129 Soil Effervescence This test uses 10% hydrochloric acid (HCl) dropped on soil to determine if carbonates are present. The reaction or effervescence indicates the presence of carbonates. There are four classifications of Soil Effervescence: None Slight Strong Violent 129

130 Soil Effervescence None A drop of 10% HCl is added to the soil. The bubbling reaction is observed. If there is no reaction, none is recorded. 130

131 Soil Effervescence Slight or Strong Slight bubbles readily seen Strong bubbles form low foam

132 Soil Effervescence Violent Violent thick foam forms quickly

133 Field Test Question: Stickiness 133

134 Soil Stickiness Stickiness refers to the capacity of a soil to adhere to other objects. The determination is made on soil <2mm in diameter. Stickiness is estimated at the moisture content that displays the greatest adherence when pressure is pressed between thumb and forefinger

135 Soil Stickiness There are four classes of stickiness: Non Sticky Slightly Sticky Moderately Sticky Very Sticky

136 Soil Stickiness: Non Sticky After release of pressure, practically no soil material adheres to thumb or forefinger

137 Soil Stickiness: Slightly Sticky After release of pressure soil material sticks to both fingers. As the fingers are separated the material tends to come off cleanly and the material does not stretch

138 Soil Stickiness: Moderately Sticky After release of pressure, soil material adheres to both fingers and tends to stretch slightly rather than pull completely free from either finger

139 Soil Stickiness: Very Sticky After release of pressure, soil material adheres so strongly to both fingers that it stretches decidedly when the fingers are separated. Soil material remains on both fingers

140 Field Pit Question: Field Pit Question: Plasticity 140

141 Soil Plasticity Plasticity is the pliability and the capacity of soil to be molded to form a wire (or worm orm ) ). Soils containing more than about 15% clay exhibit plasticity. Plasticity is determined on material smaller than 2mm and the soil is very moist

142 Soil Plasticity There are four plasticity classes: Non Plastic Slightly Plastic Moderately Plastic Very Plastic

143 Plasticity: Non Plastic Make a wire 4 cm long. Will not form a 6 mm diameter wire; or if formed, cannot support itself if held on end. Sandy soils are nonplastic

144 Plasticity: Slightly Plastic Make a wire 4 cm long. 6 mm diameter wire supports itself; 4 mm diameter roll does not support itself

145 Plasticity: Moderately Plastic Make a wire 4 cm long. 4 mm diameter wire supports itself, 2 mm diameter wire does not support itself

146 Plasticity: Very Plastic Make a wire 4 cm long. 2 mm diameter wire supports its weight

147 Field Pit Questions: Observable Characteristics of the Site 147

148 Field Pit Question: Thickness of the Surface Soil 148

149 Thickness of thesurface Soil Observe the thickness of the surface in the soil wall of the pit. Select from the following choices: 0 No surface soil >4 149

150 Field Pit Question: Total Depth of the Soil 150

151 Total Soil Depth This is the thickness of the soil horizons to bedrock or a layer which restricts the growth of plant roots. The categories are: Very Deep: Deep: Moderately Deep: Shallow: > 60 inches to Limiting Layer 40 to 60 inches to Limiting Layer 20 to 40 inches to Limiting Layer 10 to 20 inches to Limiting Layer Very Shallow: < 10 inches to Limiting Layer This dimension will be posted in inches on the Site Condition Sheet

152 Deep Soil > 40 inches

153 Very shallow soil <10 inches Root restrictive layer

154 Field Pit Question: Soil Slope 154

155 155

156 Slope of Soil Landscape The setting of the soil must be observed and the percent slope measured. <1% Nearly level 1 3% Gently sloping 3 5% Moderately sloping 5 8% Strongly sloping 8 15% Steeply sloping >15% Very steeply sloping

157 Soil Slope Slope is measured as the difference in elevation over a distance of 100 If the fall (difference in elevation) is 1 foot then the slope is 1%. If the fall is 5 feet then the slope is 5% and so on

158 Soil Slope Basic Instructions Students who are determining slope may want to pair up with another student of nearly the same height. This way you know that your eyes are about the same distance from the ground giving ii you a zero baseline. 158

159 Hold the clipboard level with your eyes and use it as a sighting device to establish a leve sight line 159

160 When you are on the high or up slope side your sight line could be above your partners head My partner is almost 6 tall. I estimate there is 1 more of him above the base line and a couple of feet extra so I estimate 8 or 8%. Sight line Base line: 0% slope 160

161 When you are on the low or down slope side your sightline could be lower than your part Sight line Estimate 2 feet from the sight line to base 161

162 The ribbons on the stakes are the same distance from the ground. (Stakes are closer than 100 for purposes of illustration) 162

163 Soil Slope Working alone you can determine the slope by using the clipboard and the opposite stake. If and you ll need to ask the site host to confirm this, the ribbons are the same distance from the ground then set the clipboard as a level from one of the ribbons and then estimate the rise or fall from that sight line. 163

164 Setting a level sightline from the down slope stake: 164

165 View from the downslope stake (stakes are closer than 100 for illustration purposes) Estimate vertical distance Sight line 165

166 View from the upslope stake Estimate difference from level clipboard to top of ribbon on the downslope stake 166

167 Field Pit Question: Field Pit Question: Soil Parent Material 167

168 Soil Parent Material Parent material is the rock or mineral material from which soil is formed. The parent material determines the elemental, mineralogical, and particle size properties of soil. Soil parent material occurs in place, through weathering, or it can be transported by various geologic agents, such as water, wind and gravity

169 Parent Material Alluvium material deposited by water Colluvium material moved by gravity Eolian wind blown sands or silts Residuum formed in place through the physical and chemical process of weathering rock 169

170 Landscapes and potential soil parent materials Alluvium Bottomland subject to flooding Colluvial position Side slope subject to erosion upland

171 Alluvium Alluvial soils are deposited by water. They can be recognized by stratification of material of contrasting sizes which represent different flood events. Depending on the intensity of the flood event, material may be added or removed from a specific point on the landscape

172 Colluvium Colluvial soils are deposited by gravity. Colluvial landscape position 172

173 Colluvial landscape position Energy

174 Eolian soils can be recognized by being composed of material Eolian of uniform size because eolian material has been moved from another location by the wind

175 Residuum Residual soils formed in place. 175

176 Field Pit Question: Erosion by Wind or Water 176

177 Soil Erosion Soil erosion is the detachment and removal of soil particles through the effects of wind or water. This question speaks to the observable effect of erosion. Major factors include percent slope, length of slope, ground cover and duration and intensity of rainfall There are four erosion classes: None to Slight Moderate Severe Very Severe 177

178 Soil Erosion None to Slight More than 75% of the surface soil is present and no gullies are present. Moderate 25 to 75% of the original soil surface is still present however there may be some mixing of the A and B horizons. Small rills and a few crossable gullies may be present. Severe Less than 75% of the original soil surface is present. Frequent crossable and occasional uncrossable gullies are present.* V S L th % f th i i l il f i Very Severe Less than 75% of the original soil surface is present. Frequent uncrossable gullies are present.* 178

179 Example of a crossable gully 179

180 Example of a non crossable gully 180

181 Soil Erosion To answer the erosion question measure the thickness of the topsoil of the soil profile in the soil wall. Read the original i thickness of the topsoil on the site condition sheet. Following are examples of the process: 181

182 Soil Erosion Example #1 The site condition sheet lists the original i top soil thickness as 13. While in the soil pit you measure 5 of top soil = 8 of topsoil removed by erosion 8 / 13 = 61% of top soil removed. 100% 61% = 39% topsoil still present. 39% topsoil present = Moderate Erosion 182

183 Soil Erosion Example #2 The site condition sheet lists the original top soil thickness as 7. While in the soil pit you measure 2 of top soil. 7 2 = 5 of topsoil removed by erosion 5 / 7 = 71% of top soil removed. 100% 71% = 29%. 29% topsoil still present = Moderate Erosion 183

184 Soil Erosion Example #3 The site condition sheet lists the original top soil thickness as 14. While in the soil pit you measure 12 of top soil = 2 of topsoil removed by erosion 2 / 14 = 14% of top soil removed. 100% 14% = 86% 86% still present = None or Slight Erosion 184

185 Field Pit Question: Field Pit Question: Surface Runoff Potential 185

186 Surface Runoff Potential Surface runoff is the rate in which water is removed by flowing over the soil surface. Rainfall, irrigation water and water from adjacent upland slopes are considered. 186

187 Surface Runoff Potential Surface runoff is the combination of slope and permeability. Four classes of runoff are recognized: Rapid Moderate Slow Very Slow 187

188 Surface Runoff Potential Rapid Rapid water movement has the potential to erode soil at an accelerated rate. The amount of water entering the soil profile is influenced by: Slopes are greater than 3% Low Permeability 188

189 Surface Runoff Potential Moderate surface runoff Water drains away readily but allows water to enter the soil profile freely. Slopes can range from 1 up to 3%. Permeability is moderately low 189

190 Surface Runoff Potential Slow water flows away slowly and water stands on the surface. The downside is it may interfere with farming operations. Slopes range from 0 to 1%. Permeability is slow. 190

191 Surface Runoff Potential Very Slow Water stands on the surface for very long periods of time. Much of the water is lost through evaporation. Slope is 0% or concave Permeability is very slow. 191

192 Soil Pit Questions: Recommended Fertilizer and Soil Amendments 192

193 Information for Fertilizer & Soil Amendment Pit Questions will be posted on the Condition Sheet at each site. 193

194 Fertilizer & Soil Amendments The purpose of this section is to make the students aware of the ranges of soil amendments needed to produce crops in Arizona. Awareness is a necessary step in cost effective fertilizer application as a Best Management Practice (BMP.) It is difficult, if not impossible, to make blanket nutrient recommendations due to Arizona having such a variety of soils, climates and crops. 194

195 Fertilizer & Soil Amendments Nutrient availability is dependent on many factors such as soil ph, soil moisture, method of application, and soil texture. The questions will relate to recommendations for upland cotton grown on a moderately coarse textured soil in Maricopa, Pinal & Pima Counties. 195

196 Fertilizer & Soil Amendments Soil ph Optimum soil ph for plant growth ranges from 6.5 to 7.5 but many soils in Arizona have a ph of greater than 8.0 Consider ph to be an issue for cotton if the level is greater than 7.5 or less than 6.5 If the ph shown on the site condition card is outside this range then farmers traditionally add an amendment to adjust the ph. 196

197 Fertilizer & Soil Amendments Soil Nitrogen (N) Soil Nitrogen (N) nitrogen levels of 80 lbs/acre to 300 lbs/acre are sufficient for irrigated, continuous cotton in central Arizona. If the N level on the site is less than 80 lbs/ac or greater than 300 lbs/acre, N is outside the optimum range for cotton. 197

198 Fertilizer & Soil Amendments Soil Phosphorus (P) Phosphorus availability to the plants is very dependent on soil ph. The higher the ph the less plant available phosphorus h becomes. P levels of 80 to 100 pounds per acre are considered sufficient for cotton production. If the P level on the site condition card is lower than 80 lbs/ac or greater than 150 lbs/ac, P is outside the optimum range for cotton. 198

199 Fertilizer & Soil Amendments Soil Potassium (K) 150 pounds of potassium (K) per acre is considered the base critical level for the production of cotton. If the amount of K is less or greater than 150 lbs/ac, K is outside the optimum range for cotton. 199

200 Fertilizer & Soil Amendments Nutrient trientavailability Both phosphorus (P) and potassium (K) are insoluble nutrients in soil. The level of these nutrients in the soil does not change rapidly and does not depend on weather conditions. A fundamental point to consider is that there is usually a rather poor relationship between the total amount of a given nutrient found in the soil (i.e. P or K) and the amount actually available to the plant for uptake and utilization. 200

201 Soil Pit Questions: Interpretations Based on Your Observations 201

202 Soil Pit Question: Water Holding Capacity of the Soil 202

203 Soil Water Holding Capacity Soil Water Holding Capacity is important in agriculture because it is the soil property that holds water against the pull of gravity. For the purposes of the contest the soil water holding capacity is evaluated using the soil in the bucket marked subsoil

204 Soil Water Holding Capacity The water holding capacity of a soil refers to the portion of water in a soil that can be readily absorbed by plant roots. 204

205 Soil Water Holding Capacity Water Holding Capacity has 4 ranges and is expressed as: High Moderately high Moderately low Low

206 Soil Water Holding Capacity Subsoil Texture COARSE MODERATELY COARSE MEDIUM MODERATELY FINE FINE Water Holding Capacity LOW MODERATELY LOW MODERATELY HIGH MODERATELY HIGH HIGH 206

207 Soil Pit Question: Soil Water Permeability 207

208 Permeability Introduction Permeability refers to the movement of water and air in the soil. This is very important in agriculture because it is the property p that affects the supply of nutrients, air and water to the root zone. Permeability is directly related to soil texture in that the coarser the soil texture the easier it is for water to move through the soil profile. 208

209 Permeability Introduction Soils that have rapid permeability will transmit water downward through the soil profile very quickly, removing water needed for plant growth. Such soils will require more frequent irrigation for less duration than soils with slower permeability. This increases the cost of growing ga crop. 209

210 Permeability Introduction Soils that are slowly permeable will transmit water slowly and if irrigation water is not managed carefully the saturated subsoil condition may cause root rot in crops. Each soil textural group has a permeability rating, but, for contest purposes, the soil s permeability rating is determined using the soil in the bucket marked Subsoil. 210

211 Guide for Determining Permeability Subsoil Texture Permeability Class COARSE MODERATELY COARSE MEDIUM MODERATELY FINE FINE RAPID MODERATE SLOW SLOW VERY SLOW 211

212 Soil Pit Question: Soil Pit Question: Land Capability Classification 212

213 Land Capability Classes LCC Land Capability Classes, LCC, are designated by Roman Numerals I through VIII. The increasing numerals indicate progressively greater limitations and narrower choices for practical use in production agriculture. 213

214 Land Capability Classification Land Capability Classes (LCC) are arrayed from Class I thru Class VIII. By definition Class I is the best for cultivated crops while Class VIII is primarily used for recreational activities. In Arizona, we are combining Classes VI and VII, and eliminating Class V for the purposes of this CDE. There are differences and the NRCS recognizes them, but it takes a professional to recognize the differences in the field. This decision simplifies the test and eliminates guesswork on the students part. 214

215 Land Capability Classification Cultivated Land Class: Non Cultivated Land Class: I VI / VII II VIII III IV So if you are evaluating a crop field you have 4 choices to make Class I, II, III or IV In a rangeland situation you have only 2 choices to make, Class VI / VII or VIII 215

216 LCC Irrigated Arizona Farmland 216

217 LCC Arizona Rangeland 217

218 LCC Class I Class I represents agricultural land that has no limitations for use. This class represents Arizona s best soil for cropland. Class I land has water available in a working irrigation system, nearly level or gently sloping, and medium or moderately fine dominant texture. 218

219 LCC Class II Class II soils have moderate limitations that reduce the choice of plants or that require moderate conservation practices. These soils are moderately sloping and have moderately coarse dominant texture. 219

220 LCC Class III Class III soils have severe limitations that reduce the choice of plants or that require special conservation practices, or both. These soils are moderately sloping and have a dominant texture of fine 220

221 LCC Class IV Class IV soils have very severe limitations that reduce the choice of plants or that require very careful management, or both. These moderately sloping soils have a coarse dominant texture. 221

222 LCC Class VI/VII Class VI/VII soils have severe limitations that make them generally unsuitable for cultivation. These soils are nearly level to strongly sloping and may These soils are nearly level to strongly sloping and may display all dominant textures. 222

223 LCC Class VIII Class VIII soils have limitations that nearly preclude their use for any production and are often just used for recreation. They are steeply and very steeply sloping. 223

224 Class VIII Class VI/VII 224

225 Land Capability Classification In order to place a site in the correct Land Capability Class (LCC), evaluate the soil and the site using four observations: 1. Irrigation water does the site have an irrigation water delivery system in place? 2. Dominate texture observe the depth of the surface soil and its texture and the thickness and texture of the subsoil. 3. Depth to contrasting texture this very important concept because contrasting textures will impede downward water movement in a soil. 4. Slope Influences cropping limitations. 225

226 Land Capability Classification Irrigation Dominant Depth to Water Texture Contrasting Texture YES Medium or Moderately Fine Very deep Slope Nearly level or gently sloping YES Moderately Coarse Deep Moderately sloping YES Fine Moderately deep Moderately sloping YES Coarse Shallow Moderately sloping NO All All Nearly level to strongly sloping NO All All Steeply and very steeply sloping LCC Class I II III IV VI/VII VIII 226

227 Land Capability Classification Use the previous table. Follow each example from irrigation water on the left side through LCC Class on the right side. Answering the questions in order: Does it have irrigation water? What is the dominate texture? What is the depth to a contrasting texture? What is the slope? Answering these questions will lead you to the LCC Class. 227

228 Evaluate the Site: Does it have Irrigation Water? 228

229 Land Capability Classification Irrigation In Arizona, as in most western states, LCC is dependent on irrigation water. A specific site can be classified as class I, irrigated or class VI, non irrigated as illustrated in the following photograph from southeast Arizona. The soil and site conditions are the same. If field 1 were not irrigated it would be classed as class VI, non irrigated. but because it is irrigated is becomes class I, irrigated. Remove the water, the LCC changes. 229

230 Land Capability Classification Irrigation Bothfields are nearly level, have moderately fine textures, are very deep to contrasting textures and are deeper than 60 Field 1 Class I if irrigated Field 2 class VI non irrigated 230

231 Land Capability Classification Dominant Texture The dominant texture is that textural class that makes up the bulk of a profile. For example if you observe a moderately fine surface soil that t is 10 thick and a subsurface soil that is 30 thick and is also moderately fine then the dominant texture is moderately fine. If the subsurface texture in this example is coarse, a common occurrence, thenthedominate texture is coarse. 10 of moderately fine texture and 30 of coarse texture. 231

232 Land Capability Classification Dominant Texture Caution! When applying this thickness rule be aware of the texture and thickness of subsequent horizons. If the surface is moderately fine and you encounter a horizon that is coarse but is only 4 thick the rule is not met, but if the next horizon is moderately coarse and is 11 thick thetwo two combined are 15 andthey are more than one class apart from moderately fine. The rule is met. 232

233 Land Capability Classification Dominant Texture In this example the dominant texture is moderately coarse and depth to contrasting texture is of moderately coarse material 16 fine textured material 16 of coarse material 233

234 Land Capability Class Depth to Contrasting Texture Depth to contrasting texture The following 3 slides address how contrasting soil textures are to be taken into account in a soil contest. In a best case scenario the texture remains the same throughout 60 inches of the soil profile. For example if the texture is moderate throughout the 60 inch profile then the computation tti 234

235 Land Capability Class Depth to Contrasting Texture Requirements In order to be considered a contrasting texture the textural class must be at least two classes different. For example if one horizon has a moderately fine texture and the other horizon(s) have fine textures the requirement is not met as these classes are only one apart. If the other horizon were moderately coarse the condition is met. For the purposes of this contest the contrasting horizon must be at least 1 foot thick. This will rule out thin lenses of sand or gravel that you may encounter. 235

236 Land Capability Class Depth to Contrasting Texture The soil profiles in Arizona may display one of the following characteristics: uniform texture throughout the total depth a moderately fine or fine cap over a coarse substratum a coarse cap over a fine or moderately fine substratum 236

237 Land Capability Class Depth to Contrasting Texture This illustrates a horizon 35 thick that is medium texture overlying a horizon of coarse material. loam Sand and gravel 237

238 Land Capability Class Depth to Contrasting Texture This illustrates >40 inches of medium textured soil. Water will move through this profile at a consistent rate. Water can be stored in the whole profile. 238

239 LCC Depth to Contrasting Texture 30 of medium textured cap over coarse textured soil. Water storage is limited to the surface cap. Once water reaches the coarse material it will move stack up until the overlying material is completely saturatedand and them move downward rapidly and be lost to the plants. 239

240 LCC Depth to Contrasting Texture Sand over clay. Clay starts t at 2 6. Water will move rapidly through the upper 2 6 of the profile effectively reducing the storage capacity of the soil by that amount. 240

241 Land Capability Class Slope Refer back to Question 15 on the Pit Scorecard. 0th through h 3% slopes may fall in classes I through h IV. Slopes above 4% will fall into classes VI-VIII 241

242 Examples of the LCC Matrix When using the matrix to place a site in the correct land capability class remember the most limiting property will determine the class placement. For example if a site meets all the requirements for Class IV but is very steeply sloping then it is class VIII, with Slope being the one property that is in a lower class. The following three slides are further examples. 242

243 Land Capability Classification Irrigation Water Dominant Texture Depth to Contrasting Texture YES Medium or Moderately Very deep Fine Slope Nearly level or gently sloping YES Moderately Coarse Deep Moderately sloping YES Fine Moderately deep Moderately sloping YES Coarse Shallow Moderately sloping NO All All Nearly level to strongly sloping NO All All Steeply and very steeply sloping Class I II III IV VI/VII VIII 243

244 Land Capability Classification Irrigation Water Dominate Texture Depth to Contrasting Texture YES Medium or Moderately Very deep Fine Slope Nearly level or gently sloping YES Moderately Coarse Deep Moderately sloping YES Fine Moderately deep Moderately sloping YES Coarse Shallow Moderately sloping NO All All Nearly level to strongly sloping NO All All Steeply and very steeply sloping Class I II III IV VI/VII VIII 244

245 Land Capability Classification Irrigation Water Dominant Texture Depth to Contrasting Texture YES Medium or Moderately Very deep Fine Slope Nearly level or gently sloping YES Moderately Coarse Deep Moderately sloping YES Fine Moderately deep Moderately sloping YES Coarse Shallow Moderately sloping NO All All Nearly level to strongly sloping NO All All Steeply and very steeply sloping Class I II III IV VI/VII VIII 245

246 References Resource unit on Soils for Core Curriculum Resource Unit #10, Agricultural Education Section, Department of vocational Education, Phoenix and Department of Agricultural Education, Uof A, Tucson structure 246

247 Soil If we take the time to learn the language of the land, the soil will speak to us. 247