Q.(a) What is soil profile ? Explain about the different soil horizons. OR

(a) A soil profile has horizons O, A, E, B, C, R from surface to bedrock; (b) seeds are stored longer by drying, cold/airtight storage and cryopreservation.

(a) Soil profile and its horizons

A soil profile is a vertical (cross-sectional) view of the soil, from the ground surface down to the underlying unweathered parent (bed) rock, revealing distinct horizontal layers called horizons, each differing in composition, colour, and texture. The main horizons, from top to bottom, are:

1. O horizon: the uppermost organic layer, composed of leaf litter and partly decomposed organic matter (humus) at the surface.
2. A horizon (topsoil): dark-coloured, rich in humus and organic matter, and the zone of maximum biological activity (roots, microorganisms); it is the most important horizon for plant growth and nutrient supply.
3. E horizon: a pale, leached (eluviated) zone present in some soils, from which minerals and clay have been washed downward.
4. B horizon (subsoil): where minerals, clay, and organic material leached from the horizons above accumulate; generally less fertile and lower in organic content than the A horizon.
5. C horizon: consists of weathered parent material (regolith) -- partially broken-down rock that has not yet developed into true soil.
6. R horizon: the unweathered, solid bedrock at the very base of the profile, from which the soil above was ultimately derived.

(b) Ways to store seeds for longer duration

Seed viability can be extended by several storage practices:

1. Drying: reducing the seed's moisture content before storage, since high moisture is the single biggest factor shortening seed life.
2. Cool/cold storage: storing seeds at low temperature (refrigeration) slows down metabolic deterioration. …