Soil Science MCQ Question and Answer | Agriculture MCQ Question

The rate of weathering of rocks depends on the composition of the rock, the climate of the area, the topography of the land and the activities of humans, animals and plants.
The rate of weathering is generally high in a humid tropical climate, because of the combination of high heat and heavy rainfall.
Generally, hot wet climates accelerate chemical weathering while cold dry climates accelerate physical weathering.

Phosphorus fixation refers to the conversion of the phosphorus element into a fixed compound or absorbed by plants that are further unavailable for use. It occurs in soil using:

Intercrystalline adsorption- adsorption of phosphate takes place on the surface of constant charge which interacts with phosphorus mainly through the cations held tightly to their plate-like surfaces and on the surfaces of variable charge.

Isomorphous substitution- through this process the mechanism of the phosphate fixation is by the replacement with hydroxyl or silicate anions up to a certain amount of silicate released from the tetrahedrons.

Double decomposition- based on the solubility product principles, a variety of reactions is significant in the fixation of soluble phosphates. However, the formation of insoluble precipitates of the phosphatic compound will depend on the pH of the system.

Molybdenosis, a disease in cattle, is caused by an imbalance of Mo and Cu in the diet when the Mo content of the forage is greater than 5 ppm.
Molybdenosis is a disease of ruminants, especially cattle, caused by dietary intake of excessive molybdenum with resultant copper deficiency characterized by persistent diarrhea and, especially around the eyes, a fading of coat pigment.

Soil moisture is defined as force per unit area that must be exerted to extract water from the soil. Soil moisture tension is usually expressed in terms of atmosphere.
For a given soil, soil moisture tension is inversely proportional to water content in the soil.
In soil, water is available between the 15 atm and $$\frac{1}{3}$$ atm.

Nitrogen is a major nutrient because it is required in large quantities by plants for proper functioning and growth.
Nitrogen is a major component of the chlorophyll molecule, which enables the plants to capture sunlight and synthesize food by the process of photosynthesis, driving plant growth and grain yield. It is also a key element in the nucleic acids DNA and RNA.

Plant roots come under the Macro flora group.
Macroflora is a term used for all the plants occurring in a particular area that are large enough to be seen with naked eyes.
Soil macro flora creates voids and macropores in the soil so that air and water can move through the soil.

Red soils are mainly confined to Tamil Nadu.
It is a type of soil that typically develops in warm, temperate and humid climates and comprises approximately 13% of the Earth's soils.
It contains thin organic-mineral layers of highly leached soil resting on a red layer of alluvium. Red soils contain a large amount of clay and are generally derived from the weathering of ancient crystalline and metamorphic rock.

Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. It quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical and matrix effects such as capillary action.
In terms of plants, water potential is the measure of potential energy in water and drives the movement of water through plants.
Among all the parts of plants, water potential is maximum in Leaves.

Carbonaceous material is a ubiquitous component of atmospheric aerosols. From combustion processes, carbon-containing compounds are emitted directly into the atmosphere in particulate form.
Critical C : S for carbonaceous materials is 50 : 1.

The common method of determining soluble sodium in the soil is Flame photometric.
Flame photometry is also known as Flame emission spectrometry (FES) and it is an atomic optical emission spectroscopy technique that uses the flame as the source of atoms excitation.
Flame photometry is highly empirical, in comparison to an absolute, method of analysis such as gravimetry. Sodium gives yellow flame in flame photometry.