Fertiliser is a material that is added to soil to improve its fertility and promote plant growth. It can be made up of a variety of materials, including GUANO (5 letters), COMPOST (7 letters), MANURE (6 letters), NITRATE (7 letters), urea (4 letters), MARL (4 letters) and DUNG (4 letters). GUANO is the excrement of seabirds and bats, COMPOST is organic matter that has been decomposed, MANURE is animal waste, NITRATE is a form of nitrogen found in soil, urea is a synthetic compound, MARL is a type of clay, and DUNG is animal excrement.