Soil Science MCQ Question and Answer | Agriculture MCQ Question

Black soil is an expansive type of soil, mainly consisting of montmorillonite type clay minerals.
Black soils are mineral soils that have a black surface horizon, enriched with organic carbon that is at least 25 cm deep.
It is fine textured and clayey which makes it highly retentive of water. It has high amounts of lime, iron, magnesium and generally low quantities of phosphorus, nitrogen and organic matter.

Gypsum is a soft sulphate mineral composed of calcium sulphate dehydrated with the chemical formula CaSO₄·2H₂O. It is widely mined and is used as a miraculous fertilizer. It is moderately soluble in water.
Pure gypsum contains 29.2% of calcium (Ca) and 18.6% of Sulphur (S).

Azospirillum is a microaerobic organism, that free fixers or survives in association with grasses.
These are gram-negative, microaerophilic, non-fermentative, and nitrogen-fixing bacterial genus from the family of Rhodospitillaceae.
This bacteria helps in promoting plant growth by mechanisms of tolerance of abiotic stresses named as induced systemic tolerance, mediated by antioxidants, osmotic adjustment, production of phytohormones, and defense strategies.

Calcium is the most immobile element in the plant out of the given options.
This is because the upward movement of calcium takes place in the transpiration stream through the xylem vessels. The calcium ions do not move by mass flow but by a series of exchange reactions along negatively charged sites on the walls of xylem tissues, thus it keeps on moving and immobile.

A soil with a high cation exchange capacity can hold more Potassium.
Cation exchange capacity is a measure of soil’s ability to hold positively charged ions, thus the soil with high cation exchange capacity can hold more positively charged ions and potassium is a positively charged ion. And that is why soil with high cation exchange capacity is considered more fertile as it can hold good ions which add nutrients to the soil.

The average content of silica in the soil is around 27%, whereas sandy soil is rich in silica.
Silica is an oxide of silicon, the most complex and abundant family of materials. It is most commonly found in nature as quartz, which comprises more than 10% of the mass of the earth's crust.

The moisture equivalent was introduced by Lyman Brigg and McLane in 1910 as a measure of field capacity for fine-textured soil materials.
Moisture capacity is defined as the percentage of water that a soil can retain in opposition to a centrifugal force 1000 times that of gravity.
It is measured by saturating a sample of soil 1 cm thick, and subjecting it to a centrifugal force of 1000 times gravity for 30 min. the gravimetric water content after this treatment is its moisture equivalent.

C : N ratio is a ratio of the mass of carbon to the mass of nitrogen in a substance.
FYM (Farmyard manure) is an important organic resource for agricultural production in live-stock-based farming systems in the semi-arid tropics of India.
The C : N ratio of farmyard manure is 40 : 1.

Super digested compost is called so because Super phosphate is added to the compost during its preparation, thus the prefix Super is added to differentiate it from the normal one.
Compost is a mixture of ingredients used to fertilize and improve the soil, prepared by decomposing plant and food waste and recycling organic waste. And on the addition of superphosphate fertilizer make it more nutritive and effective to be used.

Flocculation refers to a state when primary soil particles (sand, silt and clay) are drawn to each other by inter-particle forces to create microscopic floccules or clumps.
The reason for soil flocculation is the Lowering of Zeta potential. Zeta potential is a property of charged interfaces within the soil solution. Thus, when it is lowered, the soil particles clump and floccules are formed.