Soil Science MCQ Question and Answer | Agriculture MCQ Question

Five soil forming factors are further divided into active and passive factors and this is done by Joffe.
Active factors refer to the agent that supply energies that act upon the mass for the process of soil formation and these are climate and biotic organisms.
Passive factors refer to the source of the soil-forming mass and conditions affecting it. And these are parent material, relief and time.

The availability of Molybdenum increases with an increase in soil pH.
It is found that there is a positive relationship between soil pH and the availability of soil Molybdenum. It is most available to the crop at a pH of 7 and above.
Molybdenum is a trace element found in the soil and is required for the synthesis and activity of the enzyme nitrate reductase, thus playing a vital role in the process of symbiotic fixation of nitrogen by rhizobium bacteria in root nodules of legumes.

On the functional basis Fe, Zn, Mn and Cu have been classified as Catalysts and activators.
These are micronutrients required by the plant in very small amounts and they usually act as catalysts or enzyme activators for most of the biochemical reactions in the plant cell.

Sugarbeet is an indicator plant for Sodium. It is sensitive to sodium elements. Sugarbeet is used as a bioindicator plant for the detection of various herbicides also in the soil.
Indicator plants are those plants that can react to any abnormality in the soil and water whether it is nutrient deficiency, excess of any nutrient element or indication of any pest infection or disease.

Among the families of crop plants, the Sulphur requirement increases in the order of Graminae < Leguminosae < Cruciferae.
The plants of the Graminae family which are monocotyledonous flowering plants commonly known as grasses need the least amount of sulphur for their functioning and growth followed by Leguminosae which need a little more amount of sulphur. All the pulses belong to this family.
Cruciferae is a medium-sized and economically important family of flowering plants commonly known for oil seeds such as mustard, which require sulphur in the highest amount and that can be observed with a pungency in the oil that reflects the highest ratio of sulphur content in the seeds.

A soil having Bulk density = 1.3
article density = 2.65
The space between the soil particles in the pore space.
The formulas for calculating the pore space percentage: $${\text{PS}} = \left( {1 - \frac{{{\text{BD}}}}{{{\text{PD}}}}} \right) \times 100$$
Where PS is Pore Space, BD is Bulk Density and PD is Particle Density.
Putting all the values in the above formula
$$\eqalign{ & {\text{PS}} = \left( {1 - \frac{{1.3}}{{2.65}}} \right) \times 100 \cr & = 0.5094 \times 100 \cr & = 50.94 \cr} $$

The lowest category of soil classification includes Series. The levels from top to bottom are Order, suborder, great group, subgroup, family and series respectively.
Soil classification is a dynamic subject, from the structure of the system itself to the definitions of classes, and finally in the application in the field. Soil classification can be approached from the perspective of soil as a material and soil as a resource.

Nitrate nitrogen status in drinking water according to WHO is 10mg/L.
The term “nitrate nitrogen” is used to refer to the nitrogen present which is combined in the nitrate ion.
Nitrates are essential to plant nutrients, but in excess amounts they can cause significant water quality problems, it can accelerate eutrophication and increases the risk of colon cancer. Drinking water with a nitrate level above 10 mg/L is unsafe.

CH₃Hg⁺ is the fat-soluble form of mercury, thus most harmful to the ecosystem.
Methyl mercury (CH₃Hg⁺) is the deadly form of mercury due to its higher membrane permeability and greater tissue fixation.
It affects the immune system, alters genetic and enzyme systems, and damages the nervous system, including coordination and the senses of touch, taste and sight.

Diamine Putrescine accumulates due to deficiency of Potassium (K).
Putrescine has the potential to be a useful biomarker to reveal potassium deficiency. It is an organic compound containing a primary aliphatic amine group. Its chemical formula is C₄H₁₂N₂ and is classified as a diamine.
Putrescine is found in all organisms. It play role in stress responses in plants, both to biotic and abiotic stressors.