Minecraft wiki entry for Hay_Bale, associated text: Placing a hay bale into a composter has an 85% chance of raising the compost level by 1. Composting with hay bales is very inefficient, as the hay bale's chance to be composted is only slightly higher than wheat. For example, 900 wheat could be composted to yield 834⁄7 bone meal on average, but if crafted into 100 hay bales, they would only yield 121⁄7 bone meal on average