Supervisor of the field:

Ramalingam's wife is the supervisor of the field.

Explanation:

- Ramalingam's wife: In many traditional agricultural families, especially in rural areas, the role of overseeing field operations is often taken on by the wife of the head of the household. This includes tasks such as managing the farm workers, ensuring proper cultivation practices are followed, and making important decisions regarding the crops.

- Ramalingam: While Ramalingam may be the head of the household and the main decision-maker in the family, it is common for his wife to take charge of the day-to-day operations in the field. This division of labor allows for a more efficient running of the farm, as each person can focus on their respective roles.

- Supervisory duties: Ramalingam's wife would be responsible for overseeing the planting, watering, weeding, and harvesting of crops. She would also need to ensure that the farm workers are performing their tasks correctly and efficiently.

- Experience and knowledge: It is likely that Ramalingam's wife has gained experience and knowledge about farming practices over the years, making her well-equipped to handle the responsibilities of field supervision. Her expertise in agricultural matters would be invaluable in ensuring the success of the crops grown on the farm.

In conclusion, Ramalingam's wife is the supervisor of the field due to her experience, knowledge, and the traditional division of labor in their agricultural family.