Soil Science MCQ Question and Answer | Agriculture MCQ Question

Guano is the accumulated excrement of sea birds and bats. It is a highly effective fertilizer due to its exceptionally high content of nitrogen, phosphate and potassium.
Bird guano has high levels of nutrients like nitrate and ammonium.
It contains about 11 - 14% P₂O₅, 8 - 21% nitrogen, 10% protein, 7% ammonia and 0.5% nitrate.

A fertilizer is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers can be either natural or industrially produced. Fertilizers enhance the growth of the plants and the effectiveness of the soil by modifying its water retention and aeration.
Fertilizers contain one or more plant nutrients.

Epipedons are a horizon that has developed at the soil surface. It is a horizon in which rock structure has been destroyed and which has either been darkened by organic matter or eluviated.
There are eight important epipedons anthropic, folistic, histic, melanic, mollic, orchric, plaggen and umbric epipedons. However, Folistic epipedon is not common in India.

The DTPA (Diethylene triamine pentaacetic acid) micronutrient extraction method is a non-equilibrium extraction for estimating the potential soil availability of Zinc, Copper, Manganese and Iron.
The critical concentration (ppm) of Zinc in the case of DTPA extract is 6.

Urea is an organic compound with the chemical formula CO(NH₂)₂. This amide has two NH₂ groups joined by a carbonyl (C = O) functional group. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals.

The decline in the yield of citrus fruits is commonly known as ‘dieback’ or chlorosis.
It is a syndrome expressing many disorders in the plant that leads to a decline in productivity, reduced productive life and poor fruit quality.
The deficiency of copper in the soil is responsible for the cause of the 'dieback’ of citrus fruits. It leads to poor growth, delayed flowering and plant sterility in citrus.

Base saturation is the sum of the base cations held onto the soil exchange sites divided by the total CEC and expressed as a percentage. Base saturation is calculated as the percentage of CEC occupied by base cations.
Depending on soil pH, the soil's base saturation may be a fraction of CEC or approximately equal to CEC (Cation Exchange Capacity). With an increase in base saturation, soil pH increases.

To determine a fertilizer ratio for a recommendation, divide the weight of each of the nutrients by the nutrient with the lowest weight.
Thus here, A fertilizer is having 20-10-10 fertilizer grade, dividing the weight of each of the nutrients by 10 (lowest one), the fertilizer ratio will be 2-1-1.

The vertical section of soil, which shows different horizons is called the Soil profile. It extends from the soil surface to the parent rock material.
A soil horizon is a layer parallel to the soil surface whose physical, chemical and biological characteristics differ from the layers above and beneath.

A soil layer of maximum leaching is indicated by the symbol of A₂.
Leaching is the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. It is the practice of applying a small amount of excess irrigation where the water has a high salt content to avoid salts from building up in the soil.