Turning organic matter into compost is a process that involves the natural breakdown of organic material through the action of bacteria, fungi, and other organisms. This process is known as ROT or DECAY, which are two of the solutions to the crossword puzzle term 'turn to compost'. ROT is the process of decomposition caused by microorganisms, while DECAY is the gradual deterioration of organic matter due to age or environmental factors. Both processes are essential for the production of compost, which is a nutrient-rich soil amendment used in gardening and agriculture.