Soil fertilizer is a material that is added to soil to improve its fertility and promote plant growth. Two common types of soil fertilizer are MARL and COMPOST. MARL is a type of sedimentary rock composed of clay, silt, and calcium carbonate, which is used to increase the soil's ability to retain water and nutrients. COMPOST is a mixture of organic matter such as leaves, grass clippings, and food scraps that has been decomposed and can be used to add nutrients to the soil. Both MARL and COMPOST can be used to improve the fertility of soil and promote healthy plant growth.