Is there any benefit to only having sex once in cycle on the day of ovulation when trying to concieve if partner has low sperm count .

No: I wouldn't think so. I would still recommend daily or every-other-day intercourse during the ovulation cycle to maximize your chances of conception.

Every other day: Is a good regimen as it allows sperm counts to remain as normal as they can be. Bracket the predicted time of ovulation. Talk w/your gyn about other techniques and suggestions.

Not really: Your partner needs to go and have a sperm count and assessment of sperm mobility by giving a sample. It might help to have not ejaculated for 24-48 hrs prior to producing a specimen.