1. Soil Physical Properties Used to Assess Soil Quality Field Exercise

2. Two Ways to Assess Soil Quality 1.Measurements over time. 2.Comparing management systems. Examples: 1.Side-by-side comparisons of management systems. 2.Measurements in the same field over time. 3.Problem areas versus non-problem areas. 4.Compare measured values to a reference soil condition or to the natural ecosystem.

3. Soil quality is assessed by measuring a number of soil properties to evaluate the soil’s ability to perform basic functions. Physical Property: Bulk Density Porosity Macroporosity Microporosity Air-Filled Porosity Hydraulic Conductivity Field Capacity Plant Available Water Aggregate Stability Infiltration Penetration Resistance Condition: Compaction Aeration Percolation Infiltration Drainage Aggregation Waterlogging Erodibility Crusting Root Growth Plant Growth

4. Bulk Density The ratio of oven-dried soil (mass) to its bulk volume (g/cm 3 ). Range: 1.0 to 1.7 g/cm 3. Used to convert soil water content in percent by weight to percent by volume. Used to calculate porosity. Calculation: BD = Oven-Dry Soil Weight/Core Sample Volume Indicator of: Compaction, aeration, root growth, microbial activity, infiltration, and drainage.

5. Porosity That portion (%) of the soil not occupied by solid material. The ratio of the soil pore volume to its bulk volume. Calculation: Porosity (%) = 100 – 100(BD/PD) where, PD = Particle density. Indicator: Compaction, aeration, aggregation, root growth, microbial activity, water movement and storage.

6. Macroporosity That portion (%) of the soil occupied by pores of large size. Because of their large size, they are not able to retain water against gravity by capillary action. The ratio of large pore volume to the soil bulk volume. Calculation: % Water by volume at saturation - % Water by volume at field capacity. Indicator: Compaction, aeration, aggregation, root growth, microbial activity, water movement and storage.

7. Microporosity That portion (%) of the soil occupied by pores of small size –also called capillary pores. Because of their small size, they are able to retain water against gravity by capillary action. The ratio of small pore volume to the soil bulk volume. Calculation: % Total Porosity - % Macroporosity. Indicator: Compaction, aeration, aggregation, root growth, microbial activity, water movement and storage.

8. Air-Filled Porosity That portion (%) of the soil occupied by air- filled pores. The ratio of air-filled pore volume to the soil bulk volume. Calculation: % Water by Volume at Saturation - % Water by Volume at Sampling. Indicator: Aeration, excessively wet conditions, microbial activity, drainage.

9. Saturated Hydraulic Conductivity Indicator of the soil ability to conduct water (in/hr) in saturated conditions. The ratio of the flow density or “flux” per unit hydraulic gradient. Estimation: Soil Water Characteristics Calculator (http://www.pedosphere.com/resources/texture/triangl e_us.cfmhttp://www.pedosphere.com/resources/texture/triangl e_us.cfm Indicator: Water movement, compaction, aggregation.

10. Field Capacity The water content (in/ft) of soil after free drainage from a saturated condition. The amount of water (in/ft) that a soil is able to retain after free drainage. Calculation: (% Water Content by Volume)/100 x (12in/ft). Indicator: Water retention, plant growth, rooting, microbial activity, compaction, aggregation.

11. Permanent Wilting Point The water content (in/ft) below which plants are generally unable to extract water from the soil. Calculation: (% Water Content by Volume)/100 x (12in/ft). Estimation: Soil Water Characteristics Calculator (http://www.pedosphere.com/resources/texture/triangl e_us.cfm).http://www.pedosphere.com/resources/texture/triangl e_us.cfm

12. Plant Available Water Holding Capacity The quantity of water (in/ft) that a plant is able to extract from a soil at field capacity. Calculation: Field Capacity (in/ft) – Permanent Wilting Point (in/ft). Indicator: Available water retention, plant growth, rooting, microbial activity, compaction, aggregation.

13. Water Stable Aggregates (Aggregate Stability) Measures the amount of stable aggregates (%) against flowing water. Calculation: % Water Stable Aggregates = 100 [(Weight of Stable Aggregates)/(Weight of Aggregate Sample Used)]. Indicator: Soil erodibility.

14. Infiltration The entry of water into the soil (in/hr). The height (in) of water entering the soil surface per unit time (hr). Calculation: Water Height (in)/Time (hr). Indicator: Water runoff, erosion.

15. Penetration Resistance (Soil Strength) Soil resistance (kg/cm 2 ) to penetration by a metal rod. Calculation: Cone Index = force applied (kg)/cone tip basal area (cm 2 ). Indicator: Compaction, root proliferation, infiltration, drainage, microbial activity.

16. Measurement of Soil Physical Properties for Soil Quality Assessment ParameterEquationResult 1% Organic Matter 2Soil Structure 3Soil Color 4% Sand 5% Silt 6% Clay 7Textural Class

17. Soil Water Content at Sampling ParameterEquationResult 8 Soil Moisture Sample Weight, g 9 Hydroscout Reading 10 Mass Wetness, g#9 / (#8 - #9)

18. Collecting an Undisturbed Soil Core

19. Data From Undisturbed Core Sample ParameterEquationResult 11Ring Weight, g 12Ring Diameter, cm 13Ring Height, cm 14Ring Volume, cm3 15Weight Rubber Band + Dry Cloth, g 16Weight Rubber Band + Cloth + Metal Core + Field Moist Soil, g 17Weight Rubber Band + Cloth + Metal Core + Saturated Soil, g

20. Data From Undisturbed Core Sample ParameterEquationResult 18Weight Rubber Band + Cloth + + Metal Core + Drained Soil, g 19Weight Rubber Band + Cloth After Drainage, g 20Weight Rubber Band + Cloth Saturated, g 21Core Sample Field Moist Weight, g 22Core Sample Dry Weight, g 23Bulk Density, g/cm3

21. Data From Undisturbed Core Sample ParameterEquationResult 24Weight of Water at Sampling, g 25% Water at Sampling 26Weight of Water at Saturation, g 27% Water at Saturation 28Weight of Water at Field Capacity, g 29% Water at Field Capacity

22. Particle Density Determination ParameterEquationResult 30Weight of Moist Soil, g 31Weight of Dry Soil, g 32Weight of Flask Full of Water, g 33Weight of Flask Full of Water + Soil, g 34Particle Density, g/cm3

23. Calculation of Soil Physical Parameters ParameterEquationResult 35% Porosity 36% Macropores 37% Micropores 38% Air-Filled Porosity 39Hydraulic Conductivity, in/hr 40% Water PWP 41% PAW

24. Calculation of Soil Physical Parameters ParameterEquationResult 42Depth of Water at Saturation, in/ft 43Depth of Water at Field Capacity, in/ft 44Depth of Water at Sampling, in/ft 45Depth of Water at PWP, in/ft 46Depth of PAW, in/ft

25. Aggregate Stability Determination ParameterEquationResult 47Volume of Initial Aggregates + Gravel, cc 48Volume of Stable Aggregates + Gravel, cc 49Volume of Gravel, cc 50Volume of Initial Aggregates, cc 51Volume of Stable Aggregates, cc 52% Water Stable Aggregates

26. Infiltration ParameterEquationResult 53Infiltration Time, minutes 54Infiltration, in/hr Soil Respiration 55Soil Temp., o F 56Soil Temp., o C 57Draeger Tube Reading 58Respiration, lbs CO2-C/acre/day 59Penetration Resistance, kg/cm2

27. Property Conventional Tillage Strip Tillage Textural ClassSandy loamSandy clay loam % Sand, Silt, Clay60 – 22 - 1856 – 20 - 24 Soil StructureFine Moderate Blocky Organic Matter, %1.72.5 Soil Color7.5 YR 4/67.5YR 3/4 Bulk Density, g/cm31.321.47 Total Porosity, %47.441.4 Macroporosity, %16.213.8 Microporosity, %31.227.6

28. Property Conventional Tillage Strip Tillage Air-Filled Porosity, %26.89.2 Hydraulic Conductivity, in/hr 2.051.20 Field Capacity, in/ft3.13.5 Permanent Wilting Point 1.51.9 Plant Available Water, in/ft 1.6 Water Stable Aggregates, % 64.062.7 Infiltration, in/hr Penetration Resistance, kg/cm 2

29. Question 1: Based on the soil water content obtained from the core sample, determine the depth of water (inches) needed so that the upper foot of soil reaches field capacity. Conventional Tillage: Water Content at Sampling= 20.6% or 2.47 in/ft Field Capacity = 3.1 in/ft Answer: 3.1 – 2.47 = 0.63 in/ft Strip Tillage: Water Content at Sampling= 32.2% or 3.86 in/ft Field Capacity = 3.5 in/ft Answer: 0 in/ft

30. Question 2: Calculate the soil water content (in/ft) at 50% plant available water depletion. Next, calculate how much water (inches) needs to be added to the upper foot of soil to reach field capacity. Conventional Tillage: Soil Water Content @ 50% Depletion = PAW/2 + PWP = (1.6/2) + 1.5 = 2.3 in/ft (19.1 %) To reach FC add the amount depleted = 1.6/2 = 0.8 inches

31. Question 3: Use the soil water characteristic calculator to estimate the soil properties listed below. Compare the estimations with the results obtained from your samples. Conventional TillageStrip Tillage ActualEstimatedActualEstimated Bulk Density, g/cm 3 1.321.181.471.15 FC, in/ft3.13.03.53.4 PAW1.61.5 1.6

32. Question 4: Using the soil water characteristic calculator determine the effect of a two-fold increase in organic matter in each soil environment. Any improvements? Conventional TillageStrip Tillage ActualTwo-fold OMActualTwo-fold OM Bulk Density, g/cm 3 1.321.181.471.12 FC, in/ft3.13.5 3.9 PAW1.61.81.51.9