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