PLSS-201: Soil Science: Quiz 10.19

8. A soil pH of 5.0 means that the H+ ion concentration (activity) is a. 5 moles/L of H+ ions on the average b. 0.00005 moles/L of H+ ions in the water films c. 0.00001 moles /L of H+ in the soil solution d. 0.00001 moles/L of H+ ions on the exchange sites

0.00001 moles /L of H+ in the soil solution

11. A soil with a pH of 7 would contain a. 100 times MORE hydrogen ions per liter than one at pH 9 b. 2 times as many hydrogen ions per liter than one at pH 9 c 100 times LESS hydrogen ions per liter than one at pH 9 d. None of the above

100 times MORE hydrogen ions per liter than one at pH 9

15. Soils are limed to a pH of a. 5.5 b. 6.5 c. 7.5 d. 8.5

6.5

10. If the sum of all the exchangeable basic ions in a soil equals 22.0 meq/100 g. of soil and the CEC is 25.9 meq/100g soil, the percent base saturation is a. 25.9 meq. /100 g. of soil b. 22.0 meq/100 g. of soil c. 85% d. 100%

85%

9. In calcareous soils the dominant compounds in the soil responsible for the soil's pH is a. CaSO4 b. CaCO3 c. Na2 (CO3) d. Al(OH)3

CaCO3

Agricultural lime is *a. CaCO3 b. CaO c. Ca (OH)2 d. CaSO4

CaCO3

14. The pH of a sodic soil can be lowered by adding a. CaCO3 b. MgO c. CaSO4.2H2O d. None of the above

CaSO4.2H2O

The exchange sites at a pH of 4.0 are occupied predominantly be Mg and K ions. a. True b. False

False

At pH of 5.5 Al precipitates out of the soil solution because it is neutral. a. True b. False

True

Soil acidity is due to the dissociation of the aluminum-hexahydrate ion. a. True b. False

True

12. Humid soils become acid due a. leaching of soluble basic cations b. replacement of soluble basic cations by H+ and Al3+ions c. a and b d. None of the above

a and b

7. Which group of soil organisms would be least favored in acid soils: a. fungi b. bacteria c. actinomycetes d. none of these

actinomycetes

Soil pH is the a. negative log of the reciprocal of hydrogen ion concentration b. hydrogen ion concentration c. the log of the reciprocal of the hydrogen ion concentration d. none of these

c. the log of the reciprocal of the hydrogen ion concentration

16. Acid soils are normally limed 5 months prior to cultivation for a period of a. one year b. five years c. ten years d. none of the above

five years

13. When we measure active acidity we are measuring Al3+ and H+ ions a. on the exchange sites b. in the soil solution c. on both the exchange sites and in the soil solution d. none of the above

in the soil solution

6. pH of sodic soil is ___ a. pH 4.5 b. pH 6.5 c. pH 7.8 d. pH 9.0

pH 9.0