Agriculture has no impact on the levels of organic content in soil because organic matter is plowed back into the soil every year true or false

The statement is false.

The agriculture usually makes the soil poorer and poorer with each year, a nice proof for this is the usage of the chemical fertilizers to allow the plants to grow. Also, not every branch in the agriculture uses plowing, there's multiple cultures that do not require that or it's just not possible to perform plowing. 
There are exceptions of course, like for example the wheat, which is after the plowing is a great fertilizer of the soil, but in general, the agriculture has a bad effect on the organic content and quality of the soil.

Ithink is a i believe