There are regular composts and there are super composts. To make up a compost you will need items like weeds, produce, flowers, and other grown items and put them in a compost bin. Close it up once it is full and wait an hour. Then you will need to get it out of the bin with 15 empty buckets. This compost will net you 4.5 experience for removing it per bucket.
Super Compost will allow your crops to grow better and faster. It will also make your crops be more abundant. It will depend what you put in your compost bin as to what type of compost you will get out of there. Super Compost is made from pineapples or better fruits, avantoe or better herbs, Jangerberry or better berries, tree roots, and watermelon. You need to put any combination of 15 of these items to make a Super Compost. Adding anything else will net you regular compost.