QUIZ 6_AnswersQUIZ 6_Answers

1. Explain how a brush fire might lead to subsequent mudslides, as often occurs in California. (2)1. Explain how a brush fire might lead to subsequent mudslides, as often occurs in California. (2) Fire can significantly increase surface soil temperatureFire can significantly increase surface soil temperature Volatilize soil organic matterVolatilize soil organic matter These org compounds move down through profile and condense on soil These org compounds move down through profile and condense on soil

particlesparticles Creates hydrophobic layerCreates hydrophobic layer Rain cannot infiltrate past layer, causes saturation of surface with water, Rain cannot infiltrate past layer, causes saturation of surface with water,

increase chance for mudslide.increase chance for mudslide.2. What are the major components of soil water potential? (2)2. What are the major components of soil water potential? (2) gravitational, matric, osmosticgravitational, matric, osmostic 3. Describe the gravimetric method of measuring soil water content. (2)3. Describe the gravimetric method of measuring soil water content. (2) 1. weigh wet soil1. weigh wet soil 2. dry the soil2. dry the soil 3. reweigh the dry soil3. reweigh the dry soil 4. subtract dry soil wt from wet soil wt to obtain mass of water4. subtract dry soil wt from wet soil wt to obtain mass of water 5. mass water content (Өm) = mass water/mass dry soil5. mass water content (Өm) = mass water/mass dry soil4. The Waddell study used a tensiometer to measure the horizontal and vertical distribution of soil 4. The Waddell study used a tensiometer to measure the horizontal and vertical distribution of soil

water pressures in both the ridge-till and the no-till system. Figures 4 and 5 showed the difference water pressures in both the ridge-till and the no-till system. Figures 4 and 5 showed the difference in water potentials between 1) right after a rain (Fig. 4) and 2) after seven days of drying (Fig. 5). in water potentials between 1) right after a rain (Fig. 4) and 2) after seven days of drying (Fig. 5). The no-till plots showed level horizontal distribution of soil water pressures in both figures The no-till plots showed level horizontal distribution of soil water pressures in both figures (decreasing with depth), but the ridge-till figures indicated that after seven days of drying water (decreasing with depth), but the ridge-till figures indicated that after seven days of drying water pressure was highest in the ridge and lowest in the furrows. pressure was highest in the ridge and lowest in the furrows.

a. What was the direction of water movement in the ridge-till plot over that seven day period? (2)a. What was the direction of water movement in the ridge-till plot over that seven day period? (2) away from ridge (water moves from high potential to low potential)away from ridge (water moves from high potential to low potential)b. What potential implications does this have for soil temperature in the spring? (2)b. What potential implications does this have for soil temperature in the spring? (2) If ridges are dryer than the surrounding soil, they will be able to warm If ridges are dryer than the surrounding soil, they will be able to warm

more quickly. This gives an advantage to ridge-till systems in northern more quickly. This gives an advantage to ridge-till systems in northern climates while maintaining overall high surface residue cover. climates while maintaining overall high surface residue cover.

Soil Water continued…Soil Water continued…

Chapter 5Chapter 5

Chapter 5 OutlineChapter 5 Outline

I. ReviewI. Review

II. Journal Articles – General ConceptsII. Journal Articles – General Concepts

III. Waddell ArticleIII. Waddell Article

IV. Infiltration/PercolationIV. Infiltration/Percolation

V. Field Capacity/Permanent Wilting %V. Field Capacity/Permanent Wilting %

Table 5.3

Fig 5.28Fig 5.28

Stratified Soils

Michael J. Singer and Donald N. MunnsMichael J. Singer and Donald N. MunnsSoils: An Introduction, 6eSoils: An Introduction, 6e

wetting front vs preferential flowwetting front vs preferential flow

Michael J. Singer and Donald N. MunnsMichael J. Singer and Donald N. MunnsSoils: An Introduction, 6eSoils: An Introduction, 6e

Fig 5.35Fig 5.35

Classification of Soil Waterhttp://www.pedosphere.com/volume01/pdf/section_08_03.pdf