Soil Science MCQ Question and Answer | Agriculture MCQ Question

Thermal conductivity can be defined as the rate at which heat is transferred by conduction through a unit cross-section area of a material when a temperature gradient exits perpendicular to the area.
Its value depends on factors like soil type, composition, structure, bulk density, porosity, moisture content, and temperature.
Thermal conductivity follows the order for different soil types that is: Sand > loam > clay > peat.
It refers that sand has the highest thermal conductivity whereas peat has the lowest.

The dual salt process is associated with Ammonium Chloride.
Ammonium chloride is a nitrogenous fertilizer that usually contains 25% N and most of it is produced by the dual-salt process, in which NH₄Cl and (Na)₂CO₃ are formed simultaneously.
The double salt process is when two or more simple salts in stoichiometric proportions are attracted to each other, resulting in the formation of a molecular salt that exists only in a solid crystal state but dissociates into their constituent compound in water or any other solvents.

Tectosilicate is the silicate class that has a 3-D structure.
These are framework silicates that have a three-dimensional framework of silicate tetrahedral with SiO₂ or a 1 : 2 ratio.
Any member of a group of compounds with structures that have silicate tetrahedrons (each of which consists of a central silicon atom surrounded by four oxygen atoms at the corners of the tetrahedron) arranged in a three-dimensional lattice.

The rate of water absorption is decreased due to deficiency of Potassium. Potassium is needed for controlling both water uptake and the process of allowing plants to harness energy from the sun.
The deficiency of potassium might have reduced aquaporin activity, consequently suppressing root hydraulic conductance and water supply to the growing stem for diameter expansion and leaf for transpiration, thus it ultimately affects the rate of absorption of water from roots.

Nitrogen is lost in the greatest amount by allowing exposure of manure pile to rain as manure nitrogen is highly vulnerable to volatilization when ammonium is transformed to ammonia.
The efficiency of retention of nutrient elements during manure collection and storage is most critical and causes loss of nutrients.

Water stable aggregates in soil increase by the addition of P-fertilizers.
Soil aggregation could reduce the loss of organic P in aggregates and increase the absorption of inorganic P by silt and clay particles.
Aggregate stability refers to the ability of soil aggregates to resist disruption when outside forces usually associated with water are applied.
Wet aggregate stability suggests how well a soil can resist raindrop impact and water erosion, while the size distribution of dry aggregates can be used to predict resistance to abrasion and wind erosion.

Clay mineral with the limited expansion is Vermiculite.
Vermiculites expand more than Kaolinite but much less than smectite. The cation exchange capacity (CEC) of vermiculite is higher than all other silicate clays because of the very high negative charge in the tetrahedral sheet.

SAR is the Sodium adsorption ratio and is a measure of the amount of sodium (Na) relative to calcium (Ca) and magnesium (Mg) in the water extract from saturated soil paste. It is the ratio of the Na concentration divided by the square root of one-half of the Ca + Mg concentration.
SAR is measured by: $${\text{SAR}} = \frac{{\frac{{{\text{N}}{{\text{a}}^ + }}}{{\sqrt {{\text{C}}{{\text{a}}^{2 + }}} + {\text{M}}{{\text{g}}^{2 + }}}}}}{2}$$

The readily available form of K in soil ranges from 0.1 - 2.0% of total potassium in the soil. It consists of potassium dissolved in the soil solution and held on the exchange positions of the clay and organic matter.
A readily available form of phosphorus is dissolved in soil water and held on clay particle's exchange sites, which are found on the surface of clay particles.

Humus fraction lightest in colour is Fulvic acid. Fulvic acids are a mixture of weak aliphatic and aromatic organic acids which are soluble in water at all pH conditions. It is lowest in molecular weight, lightest in colour, soluble in both acid and alkali and most susceptible to microbial attack.
A fulvic acid is a group of chemicals formed when plants and animals break down. It is found in the humus part of soil and peat and is also found in streams and lakes.