Work out compost requirement instantly with clear inputs, formula shown and shareable results.
Compost is ordered by weight but hauled and spread by volume, so the tonnage (area x rate) is converted through bulk density to cubic metres. Dividing that volume by the area gives the spread depth in millimetres, which is the figure to check against what a spreader can lay down in one pass.
Compost quantity
Tonnes = area (ha) x rate (t/ha); volume (m3) = tonnes x 1000 / bulk density
Spread depth
Depth (mm) = volume (m3) / area (m2) x 1000
5-10 t/ha annually is a maintenance rate for arable soils; 20-40 t/ha is used to build organic matter on degraded land or in horticulture. Match it to a compost analysis so nutrients are not over-applied.
Not immediately. Compost releases nutrients slowly and its nitrogen availability in year one is often under 15%. Use it to build soil and reduce mineral rates gradually as organic matter rises.