Give reasons.
1 Topsoil is dark in colour.
2 Clayey soils have maximum capacity for holding water
3. Red soil is red in colour.
Alluvial soil is found in plains of Punjab.
Answers
Answer:
1. The topsoil is usually darker than lower layers (or horizons) because this is where organic matter accumulates. Soil colour is usually due to 3 main pigments: black—from organic matter. red—from iron and aluminium oxides.
2. The clay soil had the highest water holding capacity and the sand soil had the least; clay>silt>sand. Clay particles are so tiny and have many small pore spaces that make water move slower (the highest water holding capacity). Sandy soils have good drainage but low water and nutrient holding capacities.
3. Their colour is mainly due to ferric oxides occurring as thin coatings on the soil particles while the iron oxide occurs as haematite or as hydrous ferric oxide, the color is red and when it occurs in the hydrate form as limonite the soil gets a yellow colour.
4. The soil of central Punjab ranges from sandy loam to clayey with pH value from 7.8 to 8.5 making alkalinity and salinity problematic for this place. The alluvial soil of this zone can be widely described as arid and brown soil or tropical arid brown soil. The soil in Eastern Punjab is loamy to clayey.
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