Soil Science - Study Mode
[#876] Calcium and magnesium can be deficient in
Correct Answer
(A) Acidic soils
Explanation
Solution: Calcium and magnesium can be deficient in Acidic soils. Acid soils are those that have a pH value of less than 5.5 for most of the year. Soil acidification is the buildup of hydrogen cations, which reduces the soil pH. Acidification also occurs when base cations such as calcium, magnesium, potassium, and sodium are leached from the soil.
[#877] In which country most of the N required for crop production through N 2 fixation by legumes
Correct Answer
(D) New Zealand
Explanation
Solution: In New Zealand, most of the N is required for crop production through Nitrogen fixation by legumes. Fertilizer usage in New Zealand grassland farming is almost entirely confined to the application of non-nitrogenous fertilizers and lime to grass or clover pastures. Once established and effectively nodulated, with satisfactory mineral nutrition clovers can obtain their nitrogen for growth through symbiosis with rhizobial bacteria.
[#878] The cation exchange capacity of a mineral soil containing pre-dominately kaolinitic clay minerals generally ranges between
Correct Answer
(A) 3 - 15 meq per 100 gm soil
Explanation
Solution: The cation exchange capacity of a mineral soil containing pre-dominantly kaolinitic clay minerals generally ranges between 3 - 15 meq per 100 gm soil. Cation exchange capacity is the amount of a cation that can be exchanged by another cation on the surface of a clay mineral. It is expressed in cmol (+) per kg which is numerical to meq per 100g, where mol (+) represents moles of electrical charge.
[#879] Most efficient method of fertility evaluation is
Correct Answer
(A) Field trial
Explanation
Solution: The most efficient method of fertility evaluation is field trial. Soil testing is the most accurate and convenient method for evaluating a soil’s fertility. For soil survey work, samples are collected from a soil profile representative of the soil of the surrounding area. And field trials are real-life experiments that test directly whether proposed interventions work.
[#880] Which one of the following formula is used for calculation of base saturation
Correct Answer
(A) $$frac{{{ ext{Total}},{ ext{bases}}}}{{{ ext{CEC}}}} imes 100$$
Explanation
Solution: Base saturation is calculated as the percentage of CEC occupied by base cations. Base saturation is closely related to pH, as base saturation increases, pH increases. Soils with high percent base saturation have a higher pH, therefore they are more buffered against acid cations from plant roots and soil processes that acidify the soil. Base saturation can be calculated by: $$frac{{{ ext{Total bases}}}}{{{ ext{CEC}}}} imes 100$$ CEC is Cation exchange capacity.