In agricultural soils, soil profile can be divided into ______ , subsurface layer and bottom layer from top to bottom.
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The main pathways of soil available nitrogen loss are ______ and denitrification.
Soil water potential is usually ( ).
A. Less than zero
B. Equal to zero
C. Larger than zero
D. Larger than zero or equal to zero
Forest workers and researchers use ______ to judge the soil acidity or alkalinity.
The hydroxyl ions in soil solution mainly come from calcium, magnesium and sodium carbonates or bicarbonates, as well as the hydrolysis of ______ adsorbed by soil colloids.