Soil Science - Study Mode
[#896] Sources of negative charges on silicate clays is/are
Correct Answer
(D) All of these
Explanation
Solution: Silicate clay is the electro-microscopic clay mineral, which a diameter of fewer than 2 microns. The sources of negative charges on silicate clays are due to exposed crystal edges, Isomorphus substitution and anion exchange.
[#897] The most important nutrient for oil production is
Correct Answer
(A) N
Explanation
Solution: Nitrogen (N) is the most important nutrient for oil production in oilseed crops because it plays a fundamental role in plant metabolism, growth, and seed development. Why is nitrogen essential for oil production? Protein and enzyme synthesis: Nitrogen is a key component of amino acids, which form proteins. These proteins regulate metabolic pathways involved in oil biosynthesis. Chlorophyll formation: Nitrogen is essential for chlorophyll production, which supports photosynthesis —the process that provides energy for oil accumulation. Enhanced seed development: Oilseeds such as soybeans, canola, and sunflower require high nitrogen availability to maximize oil content in seeds . How does nitrogen impact oilseed crops? In soybeans and canola, nitrogen increases seed oil content by improving lipid metabolism . In sunflower crops, nitrogen improves both seed yield and oil percentage by supporting the synthesis of fatty acids. Adequate nitrogen supply ensures better seed filling , which directly influences oil quantity and quality . Comparison with other nutrients: Sulfur (S) is important for certain enzyme functions but is not the primary driver of oil synthesis. Magnesium (Mg) supports photosynthesis but has an indirect role in oil production. Zinc (Zn) helps enzyme activation but does not directly influence oil yield. Conclusion: Nitrogen has the most significant impact on oilseed crops because it directly influences the metabolic processes required for oil formation. A proper nitrogen supply enhances oil yield, seed quality, and overall crop productivity.
[#898] The most conspicuous chemical change that take place when soil is flooded is reduction of
Correct Answer
(A) Fe
Explanation
Solution: Flooded soils are a condition in which an area of soil is oversaturated with water, often due to natural occurrence or with the intended purpose of agricultural reasons like the cultivation of rice. The most conspicuous chemical change that takes place in the flooded soil is the reduction of iron (Fe). Competition generally limits the use of weaker electron acceptors, iron reducers may exist in the soil but will be dominated by the presence of denitrifiers, who will grow faster with access to their stronger electron acceptor.
[#899] Olivine is the good source of
Correct Answer
(B) Mg
Explanation
Solution: Magnesium (Mg) : Magnesium is an essential nutrient for plant growth and development. It is a central component of the chlorophyll molecule, which is vital for photosynthesis. Magnesium also influences various metabolic processes in plants, including nutrient uptake and enzyme activation. In soils with magnesium deficiencies, adding olivine can help enhance magnesium levels, thereby improving soil fertility and ensuring healthy plant growth.
[#900] A soil with 20 me/100g CEC and 5 me/100g exchangeable H will have a base saturation of
Correct Answer
(A) 25%
Explanation
Solution: To calculate the percent base saturation, divide the sum of the K, Mg, Ca, and Na (the bases) in meq/100g soil by the CEC. Multiply the result by 100%. Based on the formula A soil with 20 me/100g CEC and % me/100g exchangeable H will have a base saturation of 25%.