According to a couple of dictionary sources (since the question stumped me), there is a difference in these two words.
"Allocate" means to set aside for a specific purpose, to fix the place of, to locate. "Allot" means to divide or distribute by share, to appropriate for a specific purpose, to set apart or dedicate.
Very close, but to me the difference is in this sentence. "The Parks Council has allocated 10 hectares of XXX Park for community gardens. The garden was divided into 10 plots which were each allotted to a specific local charity."