My father and me are in different places because of my work. He is older and alone in the farm.....

having some health issues. By God's blessings, His daily needs are taken care of my brother and neighbors. Sometimes I feel guilty not able to take care of him in this time.

is it because of his karma or my karma? what can do better in this situation?

Visit him once in a while, be in touch with him over phone/skype, support him as much as possible financially. Once in while when you go there, you can take him to the doctor. Spend time with him in the farm house. Organize a picnic and satsang in the farmhouse and have a potluck dinner. Put a tape in the farm house that repeatedly keeps chanting om namah shivaya and other mantras. Do as much as possible. Don’t worry about karma and feel guilty. Your intentions matter. Even if you stay far from him, send your prayers and blessings to him after your sadhana everyday.