Complex sentence: Unlike cosmogenic isotopes produced in the atmosphere, 41 Ca is produced by neutron activation of 40 Ca, primarily in the top metre of the soil column, where the cosmogenic neutron flux is still sufficiently strong.
Split into simpler sentences: Unlike cosmogenic isotopes that are produced in the atmosphere, 41 Ca is produced by neutron activation of 40 Ca. Most of its production is in the upper metre or so of the soil column, where the cosmogenic neutron flux is still sufficiently strong.