Soil Science MCQ Question and Answer | Agriculture MCQ Question

L-value was first suggested by Larsen in 1952. L-value also known as ‘Labile form’ is the amount of phosphorus in the soil and in the soil solution which is exchangeable with added orthophosphate to the soil as measured by a plant growing in the system.

Colwell in 1967 emphasized the importance of soil testing through an integrated soil test approach to crop yield response to provide information on fertilizer requirements.

Desai and Biswas in India first demonstrated the production of combustible gas from cow dung i.e. Biogas by anaerobic fermentation in 1975.

The Law of limiting factors is given by Blackmann, not Lundegardh.

The organic colloids consist of convoluted chains and rings of carbon atoms bonded to hydrogen, oxygen and nitrogen.
For organic colloids and ^Fe/_Al hydrous oxides, ZPC = isoelectric point.
ZPC is the point of zero charges and is described as the pH at which the net charge of the total particle surface is equal to zero. And the isoelectric charge is the pH at which a particular molecule carries no net electrical charge.

Most salt tolerant grass is Kamal Grass (Diplachne fusca).
It is widespread species of grass in the genus Diplachne, native to North America, Africa, Asia, etc. all other places. It prefers to live in salty, wet conditions, such as in salt marshes and shallow depressions.

The soil erodibility factor (K) indicates the inherent erodibility of soil indicates the soil loss from a unit plot 22 m long with a 9% slope under continuous fallow culture.
K factor represents both susceptibility of soil to erosion and the rate of runoff as measured under the standard unit plot condition.

Cellulose decomposing bacteria are Cytophaga, Angiococcus and Polyngium.
Microorganisms that can produce cellulase enzymes for the degradation of cellulose are cellulose decomposing organisms.
Cytophaga is a genus of gram-negative, gliding, rod-shaped bacteria and it rapidly digests crystalline cellulose C.

Potassium is the nutrient element responsible for resistance to plant disease.
Disease resistance is the ability to prevent or reduce the presence of diseases in otherwise susceptible hosts. And potassium is an essential element for plant growth it is important to food crops. It helps use water and resist drought and enhances fruits and vegetable production.

The correct stages of a sequence of weathering stages in soil formation are:
Initial - Juvenile - virile - senile - final.
Mohr and Van Baren have differentiated soil formation into 5 stages.
Initial - The un-weathered parent rock.
Juvenile - weathering just started.
Virile - Easily weatherable minerals have been decomposed for the greater part and the clay content has increased.
Senile - decomposition is on the verge of completion.
Final - soil formation has been completed, the parent material is completely weathered.

The liquid limit (LL) or upper plastic limit is the e-water content at which the soil changes from a liquid state to an aplastic state.
The pF value is a quantity that indicates the quality of water contained in the soil. A pF value near 0 indicates that the soil is filled with water.
For the upper plastic limit or liquid limit, the pF value is 0.5.

The salt index is a numeric ratio of the increase in osmotic pressure produced by a selected fertilizer product compared to that produced by the same weight of sodium nitrate, where sodium nitrate is assigned a relative value of 100.
The salt index is given by Puri.

Phosphorus is drilled in upland crops to put it near roots.
Phosphorus is important in cell division and the development of new tissue. Adding phosphorus to soil low in available phosphorus promotes root growth and winter hardiness, stimulates tillering and often hastens maturity.