Answer:
seeds require light in order to germinate
Step-by-step explanation:
The most likely reason some seeds are to be covered with only 1/4 inch of soil is that such seeds require light for germination to occur.
Some seeds require light in order to germinate and if such seeds are deeply buried in the soil, they might not germinate.
According to some research, light is needed primarily to break the (photo) dormancy of some seeds. Some other research just consider light as one of the environmental factors such as water, air, etc. needed for germination.