Soil Science - Study Mode

[#411] The water holding capacity (WHC) of humus on a mass basis is . . . . . . . . times that of the silicate clays
Correct Answer

(B) 4 - 5

Explanation

Solution: The water holding capacity (WHC) of humus on a mass basis is 4 - 5 times that of the silicate clays. The water holding capacity of a soil is calculated by summing the capacity of each layer in the root zone. Humus can hold the equivalent of 80 - 90% of its weight in moisture, thus it increases the soil’s capacity to withstand drought.

[#412] The total nutrients in 100 kg of 17-17-17 are
Correct Answer

(B) 51 kg

Explanation

Solution: The total nutrients in 100 kg of 17-17-17 are 51 kg i.e. summing up all 17% of Nitrogen, 17% of phosphorus, and 17% of potassium, makes it 17 kg + 17 kg + 17 kg = 51 kg. NPK is the complex fertilizer that provides the nutrients for the overall growth of the plant.

[#413] Chlorite are basically silicates of
Correct Answer

(A) Magnesium with some iron and aluminum

Explanation

Solution: Chlorites are silicates of Magnesium with some iron and aluminum. Chlorite minerals show a wide variety of compositions, in which magnesium, iron, aluminium and silicon substitute for each other in the crystal structure. Chlorites are a group of phyllosilicate minerals common in low-grade metamorphic rocks and altered igneous rocks.

[#414] Which one is most resistant to decomposition by microbes in soil?
Correct Answer

(B) Lignin

Explanation

Solution: Lignin is the most resistant to decomposition by microbes in the soil. lignin after cellulose is the most abundant organic material on Earth, it decomposes very slowly. The slow rate of lignin decomposition by fungi, actinomycetes, and bacteria is thought to be due to the complexity of its bonds and cross-linkages and because it has a relatively low nitrogen content.
Soils with a loose structure allow for ample spaces between soil particles for oxygen to collect and in such soils, organic matter will decompose faster.

[#415] The nutrient with a key role in biological N-fixation is
Correct Answer

(D) Mo

Explanation

Solution: The nutrient with a key role in Biological nitrogen fixation is Molybdenum . Molybdenum, an essential micronutrient, plays an important role in nitrogen fixation, metabolism and protein synthesis in plants. During symbiotic nitrogen fixation, Mo acts as a cofactor for nitrogenase enzymes to catalyze the redox reaction to convert elemental N to ammonium ions.