Discuss any two physical properties of soils.
Answers
1. Sand: Sand particles are large with very little surface area exposed (0.1 m2/g specific area). These are fragments of quartz, insoluble; nutrients supplying ability are practically nil. Pre space are bigger (macro pores) which facilitates rapid movement of air and water. Sand does not absorb water; do not exhibit properties swelling and shrinkages, stickiness and plasticity. Unless coated with clay or silt, they do not exhibit properties as Cohesions, moisture and nutrient retention, etc. Soils having high percent of sand can be easily cultivated with little or light draft requirements, low water holding capacity, less fertile, dry out quickly. As sand grains are large and coarse, soils dominated by sand are called as coarse textured or light soils.
2. Silt: These particles are intermediate in size to sand and clay. Because of adhering film of clay, they exhibit some plasticity, cohesions adhesion and absorption and can hold more amount of water than sand but less than clay. Soils dominated by silts armid way in properties, workability and productivity between sandy and clayey soils. The average specific area of silt particles is 1 sp. m/g.