Soil Science - Study Mode
[#776] When organic matter is > 1.5% in soil, rated as
Correct Answer
(A) High
Explanation
Solution: When organic matter is greater than 1.5% in soil, rated as High . Organic matter makes up just 2 - 10% of most soil's mass and has an important role in the physical, chemical and biological functions of agricultural soils. The portion made of fresh organic material and living organisms, as well as partially decomposed material that is slowly decomposing, is called active organic matter.
[#777] Who proposed the criteria of essentiality of plant nutrients?
Correct Answer
(A) D. I. Arnor
Explanation
Solution: D. I. Arnor and Stout proposed the criteria of essentiality of plant nutrients in 1939. The elements that are considered essential elements in deficiency of which the plant must be unable to complete its life cycle. There are 17 elements classified as essential elements and these are carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, Sulphur, calcium, magnesium, boron, chlorine, copper, iron, manganese, molybdenum, nickel and zinc.
[#778] Thermal conductivity is highest in
Correct Answer
(C) Sand
Explanation
Solution: The thermal conductivity of a material is a measure of its ability to conduct heat. Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. The thermal conductivity of sand is highest in comparison to other soil particles given in the options. The thermal conductivity of dry coarse sand is 2.05 W/m/oC at steady state conditions.
[#779] Which rock having specific gravity lower than water & sponge like?
Correct Answer
(B) Pumice
Explanation
Solution: Pumice is a rock having a specific gravity lower than water and sponge. Specific gravity refers to the ratio of a solid or liquid to the density of water at 4 degrees Celcius. Pumice is a pyroclastic igneous rock. It is extremely porous, with a foamy appearance. The specific gravity of pumice is found to be 0.95.
[#780] After submergence how Specific Conductance of a soil changes
Correct Answer
(C) First increases then decreases
Explanation
Solution: After submergence specific conductance of soil changes first increases then decreases. Submerged soils are soils that are saturated with water for a sufficiently long time in a year. Water fills the pore spaces and replaces the air. Specific conductance refers to electrical conductivity i.e. water-quality property whose value is proportional to the collective concentration of ions in solution.