Soil Science MCQ Question and Answer | Agriculture MCQ Question

Among the following options, Citric acid is an example of a natural chelate.
The natural chelates are very small molecules and consequently pass through the plant's barriers including the cuticle, cell walls and cell membranes maximizing absorption and assimilation.
Citric acid had typically been used to control free iron cations in spent HCl solutions by chelating to iron and preventing the precipitation of iron hydroxide or iron sulphide.

Calcium and magnesium can be deficient in Acidic soils.
Acid soils are those that have a pH value of less than 5.5 for most of the year.
Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Acidification also occurs when base cations such as calcium, magnesium, potassium, and sodium are leached from the soil.

In New Zealand, most of the N is required for crop production through Nitrogen fixation by legumes.
Fertilizer usage in New Zealand grassland farming is almost entirely confined to the application of non-nitrogenous fertilizers and lime to grass or clover pastures. Once established and effectively nodulated, with satisfactory mineral nutrition clovers can obtain their nitrogen for growth through symbiosis with rhizobial bacteria.

The cation exchange capacity of a mineral soil containing pre-dominantly kaolinitic clay minerals generally ranges between 3 - 15 meq per 100 gm soil.
Cation exchange capacity is the amount of a cation that can be exchanged by another cation on the surface of a clay mineral. It is expressed in cmol (+) per kg which is numerical to meq per 100g, where mol (+) represents moles of electrical charge.

The most efficient method of fertility evaluation is field trial. Soil testing is the most accurate and convenient method for evaluating a soil’s fertility.
For soil survey work, samples are collected from a soil profile representative of the soil of the surrounding area. And field trials are real-life experiments that test directly whether proposed interventions work.

Base saturation is calculated as the percentage of CEC occupied by base cations. Base saturation is closely related to pH, as base saturation increases, pH increases. Soils with high percent base saturation have a higher pH, therefore they are more buffered against acid cations from plant roots and soil processes that acidify the soil.
Base saturation can be calculated by: $$\frac{{{\text{Total bases}}}}{{{\text{CEC}}}} \times 100$$
CEC is Cation exchange capacity.

Principle factors governing K fixation in clay lattice are Both Ionic radii as well as Hydration energy. Potassium ions and other cations are readily fixed because they have relatively low energies of hydration.
Fixation occurs when K is held in highly charged sites in the interlayer region of vermiculite and mica minerals. This differs from exchangeable K which is held at lower charged sites, on the surface and edges of clay minerals.

The amount of gypsum required by soil is known as the gypsum requirement. Gypsum is a soft sulphate mineral composed of calcium sulphate dihydrate.
Gypsum is one of the earliest forms of fertilizer. Gypsum is a moderately soluble source of the essential plant nutrients, calcium and Sulphur, and can improve overall plant growth.
Gypsum Requirement of Gypsum is 1.

The B horizon is generally absent in Black soils. Black soils are young soils or soils highly resistant to weathering and it usually lacks a B horizon.
Black soils are mineral soils that have a black surface horizon, enriched with organic carbon that is at least 25 cm deep. It is very fertile soil rich in humus and nutrients.

A soil, which has a pH of more than 8.5 and ESP of more than 15 and EC is greater than 4 m mhos/cm, the soil is called saline-alkaline soil.
ESP is Exchangeable sodium percentage and it measures the proportion of cation exchange sites occupied by sodium.
Soil Electrical Conductivity (EC) is a measure of the number of salts in the soil. it is an excellent indicator of nutrient availability and loss, soil texture and available water capacity.