When the same amount of fertilizer is applied into sandy soil and clayey soil, the fertilizer efficiency is higher in sandy soil. One of the reason for this phenomena is that ( ).
A. The cation exchange capacity of sandy soil is larger, so that the cation saturation and availability are lower
B. The cation exchange capacity of sandy soil is lower, so that the cation saturation and availability are higher
C. The cation exchange capacity of sandy soil is lower, so that the cation saturation and availability are lower
D. The cation exchange capacity of sandy soil is larger, so that the cation saturation and availability are higher
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When the pH of kaolinite suspension is increased, the absolute number of variable charges ( ).
A. does not change
B. decreases
C. increase or decrease
D. increases
Soil mineral is the main component of soil, and it accounts for ( ) of the total solid weight.
A. above 95%
B. above 80%
C. 85%
D. 75%
The average carbon content of humic substances is ( ).
A. 45％
B. 38%
C. 58％
D. 65％
Which of the following does not belong to transported parent material?
A. Slope deposits
B. Residual deposits
C. Alluvial deposits
D. Colluvial deposits
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