Soil Science MCQ Question and Answer | Agriculture MCQ Question

Rhizobia are heterotrophic soil bacteria with diverse lifestyles. These are aerobic bacteria and are a genus of gram-negative, rod-shaped, nitrogen-fixing bacteria.
It can form nodules on legume roots and fix atmospheric nitrogen for the host plant.

Entropy is the measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work. The amount of entropy is also a measure of the molecular disorder, or randomness, of a system.
Entropy is highest for Gas as because the gas particles move freely, therefore the degree of randomness is the highest.

Night soil is nothing but Human excreta, collected from cesspools, privies, pail closets, pit latrines, and septic tanks. It was produced as a result of a sanitation system in areas without sewer systems or septic tanks and sold as a fertilizer.
Night soil is very rich in essential plant nutrients. It contains about 5.5% Nitrogen, along with other compounds like phosphorus, potassium, etc.

The concept of 'Leaching requirement' was first developed by the US Salinity Laboratory, California. It has been defined as the fraction of the irrigation water that must be percolated out of the bottom of the root zone to prevent average soil salinity from rising above some level.
It can be expressed as EC_DW/EC_IW as well as Depth of DW/depth of IW.
Where, EC = salinity of the soil
             EC_IW = salinity of Irrigation water

Crickle leaf of cotton is a disease of cotton crop caused by the toxicity of Manganese. Its toxicity mostly occurs in acidic soils, below pH 5.2. However, sufficient acidity develops in those soils that have a high potential to supply the power of soluble manganese.
In this disease, the leaves appear crinkled and cupped, with stunted growth.

Serpentine is a rock composed of one or more serpentine group minerals. Serpentine (1 : 1) mineral is rich in Magnesium.
Minerals in this group which are rich in magnesium and water, light to dark green, greasy looking, and slippery feeling, are formed by the serpentinization process. It is a form of low-temperature metamorphism of ultramafic rocks.

DAP stands for Diammonium Phosphate, which is water soluble ammonium phosphate salts. It contains 46% Phosphorus and 18% Nitrogen. It is manufactured by reacting Ammonia with Phosphoric acid under controlled conditions in fertilizer plants.
It is used as fertilizer, and it temporarily increases the soil pH.

Bulk density is defined as the mass of the many particles of the material divided by the total volume they occupy. It can be defined as the Bulk density of soil is the dry weight of soil per unit volume of the soil.
Most of the rocks have a bulk density of 2.65 gm/cm³ and a medium textured normal soil with about 50% of pore space will have a bulk density of 1.33 gm/cm³.

Potato scab is caused by Streptomyces scabies, which can survive indefinitely in slightly alkaline soils.
Pox in sweet potatoes is caused by a soil-borne filamentous bacterium, Streptomyces ipomoea and can persist in neutral to alkaline soil for many years.
Black root rot of tobacco is caused by the fungus Thielaviopsis basicola. This disease is less severe in soil with a pH below 6.5, but as the pH moves to the alkaline side, its severity increases.
Thus, all these three diseases are caused by different microbes but are favoured by Neutral to alkaline conditions.