Many primal ~agricultural deities tended to be female.
By primal I mean more rudimentary natural life oriented concepts like plants, fertility, growing. This is in contrast to more sophisticated agricultural gods associated more with technological advancements and or harnessing of natural forces. The latter group tended to have higher populations of men.
One obvious biological difference between men and women is women's ability to bare and produce life. In the absence of scientific knowledge, it would be logical to associate life bringing natural aspects with feminine traits. Because it takes two copulate, is why male gods are not completely removed from agricultural deities. This cannot explain exactly the gender assignments of gods across societies because social traits very respective to the region tended to influence it heavily.
These guys are difficult but if you look at it with respect to their geography my point remains:
Anuket - Goddess of the Nile
Qetesh - Goddess of nature, beauty, sacred ecstasy , and sexual pleasure
Isis - Major Goddess of healing, there's also some pretty relevant tales in their too.
Tefnut - was the ancient Egyptian goddess of water and fertility.
Here is where my point may seem to break down at face value:
Geb - Prominent God of Earth.
First thing to note is the Egyptians were a desert civilization where the majority of known land is dead, lifeless. Geb is also commonly associated with Earthquakes. This suggests that Geb is associated with a more crudely fundamental aspect of Earth like "all land". Since "all land" from their perspective is mostly dead its no wonder ,with respect to my point, that he is a man. Notice how the majority of "life oriented" aspects are represented by female goddesses. Notice how a lot of water oriented aspects also tended to represented by female gods. In a desert civilization water would be the obvious life bringing force and since it takes two it again is no wonder the earth is a man.
Now some wiki may claim that Geb is the god of vegetation, I think this is a misconception. Geb is portrayed in many ways. Some depictions of Geb color him green representing vegetation. Some depictions of Geb color him deep brown like fertile soil. Some depictions of Geb depict him sprouting flowers. It would be easy to assume he is a god of vegetation.
If you consider the many life bringing goddesses, if you think about Geb's depictions temporally, and you consider the possibility that Geb simply represents 'all land'; Geb isn't god of vegetation, vegetation is growing on Geb with the seasons. Since it is the water that is bringing life you could imagine the vegetation to be like kids climbing on daddy.
As a Bonus
Then there is Hapi. Who is this confused god of birds, fishes, marshes and "river bringing vegetation". He is clearly semi associated with life bringing properties. He is always depicted with feminine features (breasts). In my opinion, one way to interpret his gender confusion is that it stems from the fact that he is bridging the divide between the feminine life bringing aquatic forces with the male land forces resulting in his gender confusion.
Now why this is relevant to the OPs question
When you ask about mother earth vs father earth, in what way do you mean mother earth? Most commonly mother earth is synonymous with mother nature again binding female reproduction with life oriented aspects. For instance to say "Mother Earth is dead" isnt to say the Earth no longer exists only that all life on it has ceased. Following the common meaning of mother earth then mother earth for the Egyptians would be someone like Anuket, Quetesh, or most likely Tefnut and not Geb.