Yes you can use only SPF with DMARC, however this will greatly reduce email deliverability.


DMARC relies on (aligned) authenticated identifiers from both SPF and DKIM, if one fails but the other passes then DMARC will pass. 


If you're using both SPF and DKIM, this increases the chances of emails being delivered. Further SPF does not survive forwarding of emails which means that DMARC will always fail if only SPF is used and the email is forwarded. 


Therefore, it is highly recommended to implement DKIM as well, as it survives forwarding and DMARC will pass. 


Most email providers does support both SPF and DKIM and there should be no reason only using SPF.