A biogeochemist investigated the rate of decomposition of different agricultural crop residues to assess their suitability as green manure.

• Samples of dried barley straw and clover shoots of equal mass were placed into separate mesh litterbags.
• Each bag was buried in an identical container filled with standardized sandy loam soil.
• The containers were maintained under controlled laboratory conditions for 60 days.
• The litterbags were then retrieved, cleared of soil, dried, and reweighed to calculate the percentage mass loss.