In Ca and S deficient soils, gypsum placement should be done at
Show Hint
Gypsum is applied to groundnut at 30-40 days after sowing (flowering/pegging stage).
This ensures soluble calcium is present in the shallow "pegging zone" where the developing pods can absorb it directly.
Step 1: Understanding the Concept:
Gypsum (\(\text{CaSO}_4 \cdot 2\text{H}_2\text{O}\)) is a valuable soil amendment and fertilizer.
It provides two essential secondary nutrients: Calcium (\(\text{Ca}\)) and Sulfur (\(\text{S}\)).
The timing of gypsum application is critical to ensure these nutrients are available when the crop needs them most. Detailed Explanation:
The timing of gypsum application is particularly important for groundnut (Arachis hypogaea):
- Groundnut produces flowers above ground, but the fertilized ovaries (pegs) must grow downward and enter the soil to develop pods.
- The developing pods absorb calcium directly from the surrounding soil, rather than receiving it from the roots.
- A calcium deficiency during this "pegging" stage leads to empty pods, a condition known as "pops."
- Pegging begins around 30 to 45 days after sowing.
- Applying gypsum around 30 days after sowing ensures that soluble calcium and sulfur are available in the topsoil (the pegging zone) just as the pegs begin to enter the ground.
- This timing also provides sulfur when the plant is actively synthesizing oil and proteins, maximizing both pod filling and oil yield. Step 2: Final Answer:
In calcium and sulfur deficient soils, gypsum placement should be done 30 days after sowing.
