Soil Science - Study Mode

[#206] Water stable aggregates in soil increase by addition of
Correct Answer

(B) P-fertilizers

Explanation

Solution: Water stable aggregates in soil increase by the addition of P-fertilizers . Soil aggregation could reduce the loss of organic P in aggregates and increase the absorption of inorganic P by silt and clay particles. Aggregate stability refers to the ability of soil aggregates to resist disruption when outside forces usually associated with water are applied. Wet aggregate stability suggests how well a soil can resist raindrop impact and water erosion, while the size distribution of dry aggregates can be used to predict resistance to abrasion and wind erosion.

[#207] Clay mineral with limited expansion
Correct Answer

(A) Vermiculite

Explanation

Solution: Clay mineral with the limited expansion is Vermiculite. Vermiculites expand more than Kaolinite but much less than smectite. The cation exchange capacity (CEC) of vermiculite is higher than all other silicate clays because of the very high negative charge in the tetrahedral sheet.

[#208] SAR is measured by
Correct Answer

(C) $$frac{{frac{{{ ext{N}}{{ ext{a}}^ + }}}{{sqrt {{ ext{C}}{{ ext{a}}^{2 + }}} + { ext{M}}{{ ext{g}}^{2 + }}}}}}{2}$$

Explanation

Solution: SAR is the Sodium adsorption ratio and is a measure of the amount of sodium (Na) relative to calcium (Ca) and magnesium (Mg) in the water extract from saturated soil paste. It is the ratio of the Na concentration divided by the square root of one-half of the Ca + Mg concentration. SAR is measured by: $${ ext{SAR}} = frac{{frac{{{ ext{N}}{{ ext{a}}^ + }}}{{sqrt {{ ext{C}}{{ ext{a}}^{2 + }}} + { ext{M}}{{ ext{g}}^{2 + }}}}}}{2}$$

[#209] The readily available form of K in soil ranges from
Correct Answer

(A) 0.1 - 2.0%

Explanation

Solution: The readily available form of K in soil ranges from 0.1 - 2.0% of total potassium in the soil. It consists of potassium dissolved in the soil solution and held on the exchange positions of the clay and organic matter. A readily available form of phosphorus is dissolved in soil water and held on clay particle's exchange sites, which are found on the surface of clay particles.

[#210] Humus fraction lightest in colour is
Correct Answer

(A) Fulvic acid

Explanation

Solution: Humus fraction lightest in colour is Fulvic acid . Fulvic acids are a mixture of weak aliphatic and aromatic organic acids which are soluble in water at all pH conditions. It is lowest in molecular weight, lightest in colour, soluble in both acid and alkali and most susceptible to microbial attack. A fulvic acid is a group of chemicals formed when plants and animals break down. It is found in the humus part of soil and peat and is also found in streams and lakes.