Humus is an important soil colloid. It differs from 2:1 type minerals in all but one of the following characteristics. Select the one.
A) influence on soil aggregate stability
B) structural framework of the particles
C) capable of adsorbing cations
D) CEC dependence on soil pH
E) influence of isomorphous substitution
Question 2In an alkaline soil, much of the iron in most iron chelates is rapidly replaced in the chelate complex by which other metallic nutrient?
A) Zn B) Mn C) K D) Cu E) Ca
Question 3When soil pH is between 4.5 and 5.5, which micronutrient most commonly causes plant toxicity?
A) Zn B) Mo C) Cu D) Fe E) Mn
Question 4As biotite weathers in soils, which of the following would not likely develop by mere alteration of this mineral?
A) kaolinite
B) smectite
C) fine-grained mica
D) chlorite
E) vermiculite
Question 5Molybdenum toxicity is most likely to occur under which soil conditions?
A) excessively well-drained humid region loamy sand with pH 5.0
B) poorly drained calcareous soil with pH 8.0
C) well-drained calcareous soil with pH 8.0
D) muck soil (Saprist) with pH 5.5
E) soil with pH 4.3 and subject to frequent flooding
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