Open the images you want to blend in Photoshop
Choose file>automate>photomerge
Photoshop will merge the images.
Select the white areas around the outside and press backspace on the keyboard.
Press ok to the conten aware fill option and Photoshop will create more sky or grass so you dont have to crop the image.
Photoshop CS5 Photomerge and Content aware fill demo from Leopard Rock Media on Vimeo.