Question

For determining the seed moisture content in the pigeon pea seeds, the seed sample is dried in an oven at a temperature and for a duration of -

• A. $103^{\circ}$C for 7 hours
• B. $103^{\circ}$C for 4 hours
• C. $130^{\circ}$C for 2 hours
• D. $130^{\circ}$C for 1 hour

Hint:

Remember the ISTA high constant temperature oven drying rules:
- Maize: 4 hours
- Other Cereals: 2 hours
- Other Species (including pulses like pigeon pea): 1 hour
This simple three-tier rule is highly useful for agricultural competitive exams.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Seed moisture content is a key parameter in seed testing as it directly determines seed viability, longevity, and storage potential.
The International Seed Testing Association (ISTA) prescribes standard air-oven drying methods to estimate seed moisture content.
These include the low constant temperature oven method ($103 \pm 2^{\circ}$C) and the high constant temperature oven method ($130^{\circ}$C to $133^{\circ}$C).

Step 2: Detailed Explanation:
Under the high constant temperature oven method, the sample is dried at $130^{\circ}$C to $133^{\circ}$C.
The duration of exposure at this high temperature varies according to the crop group:
- For Zea mays (maize), the drying period is 4 hours.
- For other cereals (such as wheat, barley, oats, and rice), the drying period is 2 hours.
- For other agricultural and horticultural species, including most grain legumes/pulses like pigeon pea (Cajanus cajan), the drying period is 1 hour.
Pigeon pea seeds are relatively large but contain less oil, making them highly suitable for the high constant temperature method without risking chemical degradation of oils.
Drying them for 1 hour at $130^{\circ}$C ensures complete moisture evaporation from the seeds.
The low constant temperature method ($103^{\circ}$C for 17 hours) is reserved for oily seeds to prevent oxidation and volatile loss.
Options (A) and (B) do not represent standard ISTA drying protocols for any crop group.
Option (C) ($130^{\circ}$C for 2 hours) is specifically designated for cereals.

Step 3: Final Answer:
The standard drying requirement for pigeon pea seed moisture estimation is $130^{\circ}$C for 1 hour.
Therefore, the correct option is (D).