Introducing organic matter in the soil can be achieved with a variety of different materials including peat moss, manure, and kitchen scraps, generally in the form of compost.
Organic matter will improve the soil tilth, thus improving the feeding of the life within the soil. Good tilth refers to soil that has the proper structure and nutrients to grow healthy crops and plants.
The tilth is improved with organic matter because it gives the soil a clumping property which holds water and nutrients more effectively and prevents cracking and water runoff.
In addition, organic matter improves soil by stimulating or feeding the life of the soil. It provides nutrients to bacteria, fungi, earthworms, and other organisms in the soil, which in turn recycle the nutrients into forms that are readily available for plants to absorb through their roots.