Download
estimating soil moisture by appearance and feel n.
Skip this Video
Loading SlideShow in 5 Seconds..
Estimating Soil Moisture by Appearance and Feel PowerPoint Presentation
Download Presentation
Estimating Soil Moisture by Appearance and Feel

Estimating Soil Moisture by Appearance and Feel

214 Vues Download Presentation
Télécharger la présentation

Estimating Soil Moisture by Appearance and Feel

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Estimating Soil Moisture by Appearance and Feel By N. Klocke and P. Fishbach http://www.p2pays.org/ref/20/19761.htm

  2. Evaluate soil moisture • Important management tools • How much to irrigate • When to irrigate • “appearance and feel” method • Where moisture is located in the profile • Depth of water penetration from irrigation or rainfall • ID problem areas soil compacted layers that restrict water penetration

  3. Soil Texture • Relative amount of sand, silt and clay • Indicates amount of water soil will hold • Available water capacity is max water the soil holds that plants can use

  4. Available water capacity for soils Soil texture available water inches/foot Fine sand or loamy sand 1.0 to 1.1 Sandy loam 1.4 Loam or silt loam 2.0 to 2.5 Silty clay or clay loam 1.8

  5. Knowing water potential • Different soil types respond differently to method described • Key is texture • County soil survey • Cooperative Extension Office or Natural Resource Conservation Service office

  6. Sampling and Evaluation Procedures • Extract sample. Probe, auger, spade • One foot intervals • Surface to bottom of active root zone • Most crop – 3 feet • Start early in spring – 1 to 2 days after a heavy rain • Soil near field capacity • End of growing season • Soil is dry • Use photo descriptions

  7. Guides for estimating soil moisture • Soil probe extract the sample • Scrape clean before inserting probe • Pull sample back to surface • Inspect soils, remove all soil • Clean probe after each use

  8. Procedure using description • Determine texture • Squeeze firmly • Observe condition of soil ball • Attempt to form a ribbon • Observe what happens • Compare your observations with photos and descriptions in guides

  9. Use photo descriptions • From http://mt.nrcs.usda.gov/technical/ecs/agronomy/soilmoisture/sandyclay.html • Sandy clay, loam and silt loam soils • Available water capacity = 1.5 to 2.1 inches per foot • % available : current available soil moisture as % of available water capacity • Inches per foot depleted: inches of water currently needed to refill a foot of soil to field capacity

  10. 0 to 25% available 2.1 to 1.1 inches per foot depleted • Dry, • soil aggregations breaks away easily, • no staining on fingers, • clods crumble with pressures

  11. 25% to 50% available 1.6 to 0.8 inches per foot depleted • Slightly moist • Forms a weak ball with rough surfaces • No water staining on fingers • Few aggregated soil grains break away

  12. 50% to 75% available 1.1 to 0.4 inches per foot depleted • Moist • Forms a ball • Very light staining on fingers • Darkened color • Pliable • Forms a weak ribbon between thumb and forefinger

  13. 75% to 100% available 0.5 to 0.0 inches per foot depleted • Wet • Forms a ball with well defined finger marks • Light to heavy soil/Water coating on fingers • Ribbons between thumb and forefinger

  14. 100% available 0.0 inches per foot depleted (field capacity) • Wet • Forms a soft ball • Free water appears briefly on soils surface after squeezing or shaking • Medium to heavy soil/water coating on fingers

  15. Use photo descriptions • From http://mt.nrcs.usda.gov/technical/ecs/agronomy/soilmoisture/clay.html • Clay, clay, loam and silt clay loam soils • Available water capacity = 1.6 to 2.4 inches per foot • % available : current available soil moisture as % of available water capacity • Inches per foot depleted: inches of water currently needed to refill a foot of soil to field capacity

  16. 0 to 25% available 2.4 to 1.2 inches per foot depleted • Dry, • soil aggregations separate easily, • Clods are hard to crumble with applied pressure

  17. 25% to 50% available 1.8 to 0.8 inches per foot depleted • Slightly moist • Forms a weak ball • Very few soil aggregations break away • No water stains • Clods flatten with applied pressure

  18. 50% to 75% available 1.2 to 0.4 inches per foot depleted • Moist • Forms a smooth ball with defined finger marks • Light soil/water staining on fingers • ribbon between thumb and forefinger

  19. 75% to 100% available 0.6 to 0.0 inches per foot depleted • Wet • Forms a ball • Uneven medium to heavy soil/water coating on fingers • Ribbons easily between thumb and forefinger

  20. 100% available 0.0 inches per foot depleted (field capacity) • Wet • Forms a soft ball • Free water appears on soil surface after squeezing or shaking • Thick soil/water coating on fingers • Slick and sticky

  21. Calculating soil moisture status • After estimating soil moisture, water can be calculated using table values • Example: silt loam • Available water at FC = 2.4 inches / foot • Current status = 50% available soil moisture remaining • Amount of soil in sample = 1 foot • Available moisture remaining = 50* 2.4 in/ ft * 1 ft = 1.2 inches

  22. Other sitesHow to estimate soil moisture by feel • Why know available soil water? • Management decisions • Favorable moisture, plant population, nutrients applied • Large acreages • Several day to cover area • Most crops start irrigation when 50% available moisture in root zone is depleted

  23. Chart below from http://sanangelo.tamu.edu/agronomy/sorghum/moisfeel.htm Degree Percent Appearance of soils of soil useful soil moisture moisture __________________ Dry 0 powdery, hard, baked, slightly crusted cracked__ Fair 50-75% forms a ball, forms a ball, somewhat will ribbon plastic_________________ Ideal at FC squeezing, no free water appears, wet outline of ball left on hand

  24. Knowing the texture and topsoil depth • Estimate available water • Soil texture is silt or clay loam • 1.5 to 2 inches of available water per foot • Soil texture is clay • 2-2.5 inches of available water per foot of topsoil