Apples

This is pretty good work. I like the expression, as well as the details in the hair.

There are some structural issues that I'd have a mind to raise for a picture like this, such as that her legs have no visible joints, and end in abnormally large hooves, and that her right eye is sticking way out beyond her head, but I suppose all these things can be attributed to stylistic choices.

You may have made her a little bit too big. Your Rarity picture has a great representation of Rarity's mane, but here it looks like you didn't leave enough room to do justice to Applejack's stetson. It seems a bit small.

Another thing I can mention is the shading. I like how intense it is in her hindquarters, and at the back of her head. It helps to give the character 3D definition. However, when doing colored images, it's often good policy to look for colors other than straight-up black to do your shading. Choose a darker color, yes, but try to mix it up a bit by bringing maybe a different shade of orange or brown. It would give your color palette a bit of a more interesting look to it.

That's all I got. Overall, great work. Can't wait to see what you do with Rainbow Dash.