(a) Putrefying bacteria
(b) Nitrogen-fixing bacteria
(c) Nitrifying bacteria
(d) Earthworm
(a) The role of putrefying bacteria in maintaining soil fertility.
1. Causes decay: decompose organic remains thereby adding humus/plant nutrients to the soil, making soil to retain water/moisture. OR
(b) Nitrogen-fixing bacteria:
i. fix atmospheric nitrogen in the roots of legumes.
ii. change nitrogen to nitrites, in the soil.
(c) Nitrifying bacteria change nitrites, in the soil
(d) Earthworms
i. burrow/make channels in the soil which improve drainage aeration and soil texture.
ii. drag leaves into the soil when leaves decay humus is added to the soil.
iii. Form worm caste which improves soil texture
iv. dead worm in the burrow add humus to soil
