Organic farming is known to require more labor input compared to conventional farming because it avoids the use of synthetic chemicals, pesticides, and fertilizers. This means that farmers need to rely more on manual labor, crop rotation, and other natural methods to manage pests and maintain soil health.
Option (3) "Organic farming requires more labour input than conventional farming" is correct because it is indeed one of the known disadvantages of organic farming.
Option (1) "Organic farming yields lesser crops compared to modern agricultural farming" is often true in the initial years of organic farming, though it can improve over time.
Option (2) "Organic farming generates marginal returns on investment" is incorrect. Organic farming can sometimes generate good returns by reducing input costs such as synthetic fertilizers and pesticides, though returns can vary based on location and market demand.
Option (4) "Organic farming produces are blemished with shorter shelf life" is another disadvantage as organic products often have a shorter shelf life and may have visible imperfections.
Conclusion:
The statement "Organic farming requires more labour input than conventional farming" is indeed a disadvantage of organic farming, and this makes option (3) the correct choice.