The minimum track length you can submit on an album is 2 seconds.
Though, please be aware that track lengths that are extremely short are often times submitted by nefarious users who wish to attempt to exploit or engage in fraudulent streaming activity in the music platforms and thus they are subject to closer scrutiny by the stores (And Catapult) as they try to weed out fraudulent streaming activity. Catapult has a zero tolerance policy for fraudulent streaming activity and will pull all content from an account and cancel the account if this activity is suspected.
Further, all content is reviewed by Catapult staff and if the majority of your tracks are extremely short, we may, in our sole discretion, decline distribution of your content to protect our relationships with the music stores.