Soil Science MCQ Question and Answer | Agriculture MCQ Question

Legumes fail to develop nodules as the soil has a pH of < 5.
Legumes can form a symbiotic relationship with nitrogen-fixing soil bacteria called rhizobia.
At low pH (<5), dry matter production, seed yield and nitrogen fixation were significantly lower than at higher pH levels. Low pH delayed the development of nitrogenase activity.

New alluvial soil is known as Khadar.
Khadar soils are more fertile as they are below the flood level, composed of fine silt and clay. It is fertile land as it contains alluvial soil deposited by rivers and gets replenished with each flooding cycle.
It is usually seen near the rivers, the Indo-Gangetic Plains and Yamuna khadar flood plains.

Specific heat is the quantity of heat required to raise the temperature of one gram of a substance by one Celsius degree.
Specific heat is higher in Humus as the organic matter present in humus can retain more water in it and to make it cooler, the heat energy gets spent in evaporation of soil moisture.

Hysteresis is the dependence of the state of a system on its history.
Hysteresis is related to the Sorption - desorption curve, which means the equilibrium moisture content is different in desorption and adsorption processes.
The hysteresis between the adsorption isotherm and desorption isotherm is thought to be caused by the gradual desorption mechanism (percolation theory) due to the different size pores being combined.

The acidic igneous rocks contain silica > 65%.
Acidic rock or acid rock refers to the chemical composition of igneous rocks that has 63% of SiO₂ content. Rocks described as acidic usually contain more than 20% of free quartz. Typical acidic rocks are granite or rhyolite.
It was based on the idea that high silica rocks are acidic and on the contrary the rocks with low silica content are basic.

Langbeinite process is associated with the manufacturing of K₂SO₄ (Potassium Sulphate) fertilize.
Langbeinite is a potassium magnesium sulfate mineral with the chemical formula K₂Mg₂(SO₄)₃. Langbeinite crystallizes in the isometric-tetartoidal (cubic) system as transparent colorless or white with pale tints of yellow to green and violet crystalline masses.
Langbeinite is treated with a concentrated solution of potassium chloride to yield precipitates of potassium sulfate. The precipitates of potassium sulphate are separated from the solution by decantation.

Feldspar is a group of rock-forming aluminum tectosilicate minerals, containing sodium, calcium, potassium, or barium.

Micas are a group of phyllosilicate minerals, not iron and aluminium silicates.

Gibbsite is a hydrous oxide of aluminium. it is an important ore of aluminium.

Goethite is hydrous iron oxide. It is a widespread soil mineral and a major component of many ores, sediments, and soils and it is one of the most thermodynamically stable iron oxides.

Potentially acid sulphate soils are also known as cat clays. Cat clay minerals are Alunite and Jarosite.
Cat clays are planted with rice so that the soil can be kept wet preventing oxidation. Subsurface drainage of these soils is normally not advisable.
Alunite is hydrated aluminium potassium, sulphate mineral. It is usually mined for the manufacture of alum.
Jarosite is a basic hydrous sulphate of potassium and ferric ion. This sulphate mineral is formed in ore deposits by the oxidation of iron sulphides.

The number 32 in 12-32-16 represents P₂O₅ content. This number represents the proportion of nutrients in complex fertilizer NPK which means Nitrogen is 12%, Phosphorous is 32% and potassium is 16%.
NPK should be applied to the soil considering important factors such as placement, proportion and time of crop cycle.

Diagnosis and recommendation integrated system (DRIS) is a mathematical technique to apply plant analysis information (Nutrient concentration) for diagnosing the most limiting nutrient in a production system.
DRIS is a widely used statistical approach for interpretation of the plant tissue analysis data and diagnosing the plant nutrient needs much earlier than the reduction of crop yield with greater accuracy. It is applicable for long-duration crops.