Soil Science MCQ Question and Answer | Agriculture MCQ Question

Igneous rock is formed through the cooling and solidification of magma or lava. These rocks occur in a wide range of geological settings, shields, platforms, orogens, basins, large igneous provinces, extended crust and metallic crust.
Syenite, Trachite and Andesite are examples of igneous rock.

Bioavailability is the term that refers to the subcategory of absorption and is the fraction of an administered drug that reaches the systemic circulation. It is used to describe the percentage of an administered dose of a xenobiotic that reaches the systemic circulation.
The term ‘Bioavailable’ was coined by Barber. It is denoted by the letter f.

Clay soil must contain at least 35% clay separate, to be designated clay.
Clay soil is comprised of very fine mineral particles and not much organic material, which makes it quite sticky and it does not drain well at all.
Clay develops plasticity when wet, due to a molecular film of water surrounding the clay particles, but becomes hard, brittle and non-plastic upon drying or firing.

Out of the 17 essential nutrients, a few of them are major nutrients and these are N (Nitrogen), P (Phosphorus) and K (Potassium). These are also termed as “Big 3” primary nutrients in commercial fertilizers.
Plants need significant amounts of nitrogen, phosphorus and potassium to grow and develop. These help in vegetative growth in stems and roots particularly during the early stages, root growth, seed and flower formation, bud growth and ripening of fruits.

Plasticity of the soil is the ability of a material to undergo permanent deformation under stress without cracking. Fine-grained soils become plastic as their moisture content is increased, leading to a loss in shear strength and stability.
The plasticity of soil can be determined by using Atterberg’s Apparatus. it helps in determining with a series of laboratory tests that classify the properties of silt and clay soils at different moisture contents.

Cation exchange in the soil is the capacity of the particles to attract and absorb cations (positively charged ions).
Cation exchange of soil colloidal clay is due to isomorphous substitution and broken edges of clay lattices. Isomorphous substitution in a clay mineral is the process of replacing one structural cation for another of similar size.

Soils developed in hilly areas are susceptible to erosion. The agricultural potential of hill soils is mainly low for field crops, but it ranges between low and high for tree crops. Nutrients especially nitrogen are lost from the soils with runoff water.
Hill soils are generally acidic, which means their pH ranges from less than 5.5 for most of the year.

Ammonium nitrate is a salt of ammonia and nitric acid with chemical formula, (NH₄NO₃). It is widely used in fertilizers and explosives.
The commercial-grade of ammonium nitrate contains 33 - 35% of Nitrogen. It is a greyish white solid in the form of prills and is soluble in water. It produces toxic oxides of nitrogen during combustion.

Rhizobium is a genus of gram-negative soil bacteria that fix nitrogen for plants.
Alfa alfa is an important leguminous forage crop, which is hypothesized to select compatible rhizobial partners from the rhizosphere to form nitrogen-fixing nodules.
Rhizobium of alfalfa group is Melilolti. Meliloti are motile and possess a cluster of peritrichous flagella. It fixes atmospheric nitrogen into ammonia for their legume symbionts.

Straw is an agricultural byproduct consisting of dry stalks of cereal plants after the grain and chaff have been removed. It has several different uses, including fuel, livestock bedding, fodder, thatching and basket making.
Straw may be fed as part of the roughage component of the diet to cattle or horses. It has a low digestible energy and nutrient content. It is a particularly rich source of Potash.