Additions of plant debris to soils will initiate the build up of organisms that will decompose the plant debris. After decomposition the organic material will be called organic matter or soil humus. This decomposed plant debris will be in the form of very small particles and will coat the sand, silt, and clay particles making up the mineral soil particles, thus making the soil black. The more organic matter accumulating in a soil, the darker the soil will become. Continued additions of organic matter are important to create a soft, tillable soil that is conducive to plant growth. Organic matter is important in soils because it will add nutrients, store nitrogen and other positive cations, and create a stronger soil aggregate that will withstand the impact of raindrops and thus prevent water erosion.