TL;DR - No... well, yes you can, but it won't decompose in your lifetime.
Addressing this question fully - from the point of composting, rather than landfill:
From Wikipedia - PLA - End of life:
Composting: PLA is biodegradable under industrial composting conditions, starting with chemical hydrolysis process, followed by microbial digestion, to ultimately degrade the PLA. Under industrial composting conditions (58 °C), PLA can partly (about half) decompose into water and carbon dioxide in 60 days, after which the remainder decomposes much more slowly, with the rate depending on the material's degree of crystallinity. Environments without the necessary conditions will see very slow decomposition akin to that of non-bioplastics, not fully decomposing for hundreds or thousands of years.
According to Is PLA filament actually biodegradable?:
It takes 80 years to biodegrade naturally. Although, how they actually know that for sure, seeing as PLA (for 3D Printing at least) hasn't been around for 80 years yet, is unclear.
In addition, PLA can only be recycled at plants that have separate facilities that deal with PLA (as bio-plastics interfere with the recycling of other plastics if combined), and (as an aside) the fumes from PLA are not as harmless as many people think, due to the (up to 40%) additives.
So, PLA is not such a "happy" plastic as many people are led to believe by the marketing folks...