Final answer:
The decision between magnesium (Mg) and potassium (K) as a replacement for calcium depends on the soil type and specific crop needs. Magnesium is a closer substitute for calcium's role in structure and pH regulation, while potassium serves other functional roles in plant nutrition.Hence, the correct answer is option D.
Step-by-step explanation:
If a farmer is looking for an alternative to calcium (Ca) to help maintain chemical balance in the soil, the choice between magnesium (Mg) and potassium (K) should be based on the specific needs of the soil and crops. Magnesium plays a crucial role in photosynthesis due to its presence at the center of the chlorophyll molecule. Potassium is essential for various plant functions including protein synthesis, chlorophyll synthesis, enzyme reactions, and homeostasis. Both of these elements can alter the pH of the soil upon addition, with magnesium typically raising pH levels similar to calcium.
It is important to consider that the soil type and its nutritional requirements will largely determine whether Mg or K would be more beneficial. Specific soil tests can provide information about nutrient deficiencies. If the goal is to replace calcium specifically for its role in pH regulation and structural support in plants, magnesium might be a closer substitute compared to potassium, which fulfills different roles in plant nutrition.
Choosing the best soil nutrient to replace calcium should be informed by soil tests to identify what the soil and crops need. If the replacement is solely based on chemical balance and pH regulation, magnesium could be a more suitable alternative to calcium than potassium. However, if there are particular nutritional needs to be addressed in the soil, potassium might be necessary as well.