Which layer of soil is least likely to be penetrated by plant roots?
a.
o (organic matter)
b.
a (topsoil)
c.
b (subsoil)
d.
c (parent rock)

The correct answer is Parent rock.

Parent rock can also be defined as the substratum which refers to the original rock from which soil is formed. The nature of soil formed is decided by the parent rock. The roots of the plant cannot reach this layer. This layer is deep inside that the roots of the plant cannot reach upto this extent.

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.